linux/arch/powerpc/mm/fault.c

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* PowerPC version
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
*
* Derived from "arch/i386/mm/fault.c"
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
*
* Modified by Cort Dougan and Paul Mackerras.
*
* Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
*/
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/pagemap.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/highmem.h>
#include <linux/extable.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
perf: Do the big rename: Performance Counters -> Performance Events Bye-bye Performance Counters, welcome Performance Events! In the past few months the perfcounters subsystem has grown out its initial role of counting hardware events, and has become (and is becoming) a much broader generic event enumeration, reporting, logging, monitoring, analysis facility. Naming its core object 'perf_counter' and naming the subsystem 'perfcounters' has become more and more of a misnomer. With pending code like hw-breakpoints support the 'counter' name is less and less appropriate. All in one, we've decided to rename the subsystem to 'performance events' and to propagate this rename through all fields, variables and API names. (in an ABI compatible fashion) The word 'event' is also a bit shorter than 'counter' - which makes it slightly more convenient to write/handle as well. Thanks goes to Stephane Eranian who first observed this misnomer and suggested a rename. User-space tooling and ABI compatibility is not affected - this patch should be function-invariant. (Also, defconfigs were not touched to keep the size down.) This patch has been generated via the following script: FILES=$(find * -type f | grep -vE 'oprofile|[^K]config') sed -i \ -e 's/PERF_EVENT_/PERF_RECORD_/g' \ -e 's/PERF_COUNTER/PERF_EVENT/g' \ -e 's/perf_counter/perf_event/g' \ -e 's/nb_counters/nb_events/g' \ -e 's/swcounter/swevent/g' \ -e 's/tpcounter_event/tp_event/g' \ $FILES for N in $(find . -name perf_counter.[ch]); do M=$(echo $N | sed 's/perf_counter/perf_event/g') mv $N $M done FILES=$(find . -name perf_event.*) sed -i \ -e 's/COUNTER_MASK/REG_MASK/g' \ -e 's/COUNTER/EVENT/g' \ -e 's/\<event\>/event_id/g' \ -e 's/counter/event/g' \ -e 's/Counter/Event/g' \ $FILES ... to keep it as correct as possible. This script can also be used by anyone who has pending perfcounters patches - it converts a Linux kernel tree over to the new naming. We tried to time this change to the point in time where the amount of pending patches is the smallest: the end of the merge window. Namespace clashes were fixed up in a preparatory patch - and some stylistic fallout will be fixed up in a subsequent patch. ( NOTE: 'counters' are still the proper terminology when we deal with hardware registers - and these sed scripts are a bit over-eager in renaming them. I've undone some of that, but in case there's something left where 'counter' would be better than 'event' we can undo that on an individual basis instead of touching an otherwise nicely automated patch. ) Suggested-by: Stephane Eranian <eranian@google.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Paul Mackerras <paulus@samba.org> Reviewed-by: Arjan van de Ven <arjan@linux.intel.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: David Howells <dhowells@redhat.com> Cc: Kyle McMartin <kyle@mcmartin.ca> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: <linux-arch@vger.kernel.org> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-09-21 10:02:48 +00:00
#include <linux/perf_event.h>
#include <linux/ratelimit.h>
#include <linux/context_tracking.h>
#include <linux/hugetlb.h>
mm/fault, arch: Use pagefault_disable() to check for disabled pagefaults in the handler Introduce faulthandler_disabled() and use it to check for irq context and disabled pagefaults (via pagefault_disable()) in the pagefault handlers. Please note that we keep the in_atomic() checks in place - to detect whether in irq context (in which case preemption is always properly disabled). In contrast, preempt_disable() should never be used to disable pagefaults. With !CONFIG_PREEMPT_COUNT, preempt_disable() doesn't modify the preempt counter, and therefore the result of in_atomic() differs. We validate that condition by using might_fault() checks when calling might_sleep(). Therefore, add a comment to faulthandler_disabled(), describing why this is needed. faulthandler_disabled() and pagefault_disable() are defined in linux/uaccess.h, so let's properly add that include to all relevant files. This patch is based on a patch from Thomas Gleixner. Reviewed-and-tested-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: David.Laight@ACULAB.COM Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: airlied@linux.ie Cc: akpm@linux-foundation.org Cc: benh@kernel.crashing.org Cc: bigeasy@linutronix.de Cc: borntraeger@de.ibm.com Cc: daniel.vetter@intel.com Cc: heiko.carstens@de.ibm.com Cc: herbert@gondor.apana.org.au Cc: hocko@suse.cz Cc: hughd@google.com Cc: mst@redhat.com Cc: paulus@samba.org Cc: ralf@linux-mips.org Cc: schwidefsky@de.ibm.com Cc: yang.shi@windriver.com Link: http://lkml.kernel.org/r/1431359540-32227-7-git-send-email-dahi@linux.vnet.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2015-05-11 15:52:11 +00:00
#include <linux/uaccess.h>
#include <asm/firmware.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/siginfo.h>
#include <asm/debug.h>
#include <asm/kup.h>
/*
* Check whether the instruction inst is a store using
* an update addressing form which will update r1.
*/
static bool store_updates_sp(unsigned int inst)
{
/* check for 1 in the rA field */
if (((inst >> 16) & 0x1f) != 1)
return false;
/* check major opcode */
switch (inst >> 26) {
case OP_STWU:
case OP_STBU:
case OP_STHU:
case OP_STFSU:
case OP_STFDU:
return true;
case OP_STD: /* std or stdu */
return (inst & 3) == 1;
case OP_31:
/* check minor opcode */
switch ((inst >> 1) & 0x3ff) {
case OP_31_XOP_STDUX:
case OP_31_XOP_STWUX:
case OP_31_XOP_STBUX:
case OP_31_XOP_STHUX:
case OP_31_XOP_STFSUX:
case OP_31_XOP_STFDUX:
return true;
}
}
return false;
}
/*
* do_page_fault error handling helpers
*/
static int
__bad_area_nosemaphore(struct pt_regs *regs, unsigned long address, int si_code)
{
/*
* If we are in kernel mode, bail out with a SEGV, this will
* be caught by the assembly which will restore the non-volatile
* registers before calling bad_page_fault()
*/
if (!user_mode(regs))
return SIGSEGV;
_exception(SIGSEGV, regs, si_code, address);
return 0;
}
static noinline int bad_area_nosemaphore(struct pt_regs *regs, unsigned long address)
{
return __bad_area_nosemaphore(regs, address, SEGV_MAPERR);
}
static int __bad_area(struct pt_regs *regs, unsigned long address, int si_code)
{
struct mm_struct *mm = current->mm;
/*
* Something tried to access memory that isn't in our memory map..
* Fix it, but check if it's kernel or user first..
*/
up_read(&mm->mmap_sem);
return __bad_area_nosemaphore(regs, address, si_code);
}
static noinline int bad_area(struct pt_regs *regs, unsigned long address)
{
return __bad_area(regs, address, SEGV_MAPERR);
}
#ifdef CONFIG_PPC_MEM_KEYS
static noinline int bad_access_pkey(struct pt_regs *regs, unsigned long address,
struct vm_area_struct *vma)
{
struct mm_struct *mm = current->mm;
int pkey;
/*
* We don't try to fetch the pkey from page table because reading
* page table without locking doesn't guarantee stable pte value.
* Hence the pkey value that we return to userspace can be different
* from the pkey that actually caused access error.
*
* It does *not* guarantee that the VMA we find here
* was the one that we faulted on.
*
* 1. T1 : mprotect_key(foo, PAGE_SIZE, pkey=4);
* 2. T1 : set AMR to deny access to pkey=4, touches, page
* 3. T1 : faults...
* 4. T2: mprotect_key(foo, PAGE_SIZE, pkey=5);
* 5. T1 : enters fault handler, takes mmap_sem, etc...
* 6. T1 : reaches here, sees vma_pkey(vma)=5, when we really
* faulted on a pte with its pkey=4.
*/
pkey = vma_pkey(vma);
up_read(&mm->mmap_sem);
/*
* If we are in kernel mode, bail out with a SEGV, this will
* be caught by the assembly which will restore the non-volatile
* registers before calling bad_page_fault()
*/
if (!user_mode(regs))
return SIGSEGV;
_exception_pkey(regs, address, pkey);
return 0;
}
#endif
powerpc/mm: Fix SEGV on mapped region to return SEGV_ACCERR The recent refactoring of the powerpc page fault handler in commit c3350602e876 ("powerpc/mm: Make bad_area* helper functions") caused access to protected memory regions to indicate SEGV_MAPERR instead of the traditional SEGV_ACCERR in the si_code field of a user-space signal handler. This can confuse debug libraries that temporarily change the protection of memory regions, and expect to use SEGV_ACCERR as an indication to restore access to a region. This commit restores the previous behavior. The following program exhibits the issue: $ ./repro read || echo "FAILED" $ ./repro write || echo "FAILED" $ ./repro exec || echo "FAILED" #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <signal.h> #include <sys/mman.h> #include <assert.h> static void segv_handler(int n, siginfo_t *info, void *arg) { _exit(info->si_code == SEGV_ACCERR ? 0 : 1); } int main(int argc, char **argv) { void *p = NULL; struct sigaction act = { .sa_sigaction = segv_handler, .sa_flags = SA_SIGINFO, }; assert(argc == 2); p = mmap(NULL, getpagesize(), (strcmp(argv[1], "write") == 0) ? PROT_READ : 0, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); assert(p != MAP_FAILED); assert(sigaction(SIGSEGV, &act, NULL) == 0); if (strcmp(argv[1], "read") == 0) printf("%c", *(unsigned char *)p); else if (strcmp(argv[1], "write") == 0) *(unsigned char *)p = 0; else if (strcmp(argv[1], "exec") == 0) ((void (*)(void))p)(); return 1; /* failed to generate SEGV */ } Fixes: c3350602e876 ("powerpc/mm: Make bad_area* helper functions") Cc: stable@vger.kernel.org # v4.14+ Signed-off-by: John Sperbeck <jsperbeck@google.com> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [mpe: Add commit references in change log] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2018-01-01 05:24:58 +00:00
static noinline int bad_access(struct pt_regs *regs, unsigned long address)
{
return __bad_area(regs, address, SEGV_ACCERR);
powerpc/mm: Fix SEGV on mapped region to return SEGV_ACCERR The recent refactoring of the powerpc page fault handler in commit c3350602e876 ("powerpc/mm: Make bad_area* helper functions") caused access to protected memory regions to indicate SEGV_MAPERR instead of the traditional SEGV_ACCERR in the si_code field of a user-space signal handler. This can confuse debug libraries that temporarily change the protection of memory regions, and expect to use SEGV_ACCERR as an indication to restore access to a region. This commit restores the previous behavior. The following program exhibits the issue: $ ./repro read || echo "FAILED" $ ./repro write || echo "FAILED" $ ./repro exec || echo "FAILED" #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <signal.h> #include <sys/mman.h> #include <assert.h> static void segv_handler(int n, siginfo_t *info, void *arg) { _exit(info->si_code == SEGV_ACCERR ? 0 : 1); } int main(int argc, char **argv) { void *p = NULL; struct sigaction act = { .sa_sigaction = segv_handler, .sa_flags = SA_SIGINFO, }; assert(argc == 2); p = mmap(NULL, getpagesize(), (strcmp(argv[1], "write") == 0) ? PROT_READ : 0, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); assert(p != MAP_FAILED); assert(sigaction(SIGSEGV, &act, NULL) == 0); if (strcmp(argv[1], "read") == 0) printf("%c", *(unsigned char *)p); else if (strcmp(argv[1], "write") == 0) *(unsigned char *)p = 0; else if (strcmp(argv[1], "exec") == 0) ((void (*)(void))p)(); return 1; /* failed to generate SEGV */ } Fixes: c3350602e876 ("powerpc/mm: Make bad_area* helper functions") Cc: stable@vger.kernel.org # v4.14+ Signed-off-by: John Sperbeck <jsperbeck@google.com> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [mpe: Add commit references in change log] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2018-01-01 05:24:58 +00:00
}
static int do_sigbus(struct pt_regs *regs, unsigned long address,
mm: convert return type of handle_mm_fault() caller to vm_fault_t Use new return type vm_fault_t for fault handler. For now, this is just documenting that the function returns a VM_FAULT value rather than an errno. Once all instances are converted, vm_fault_t will become a distinct type. Ref-> commit 1c8f422059ae ("mm: change return type to vm_fault_t") In this patch all the caller of handle_mm_fault() are changed to return vm_fault_t type. Link: http://lkml.kernel.org/r/20180617084810.GA6730@jordon-HP-15-Notebook-PC Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Richard Henderson <rth@twiddle.net> Cc: Tony Luck <tony.luck@intel.com> Cc: Matt Turner <mattst88@gmail.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Russell King <linux@armlinux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Michal Simek <monstr@monstr.eu> Cc: James Hogan <jhogan@kernel.org> Cc: Ley Foon Tan <lftan@altera.com> Cc: Jonas Bonn <jonas@southpole.se> Cc: James E.J. Bottomley <jejb@parisc-linux.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Palmer Dabbelt <palmer@sifive.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: David S. Miller <davem@davemloft.net> Cc: Richard Weinberger <richard@nod.at> Cc: Guan Xuetao <gxt@pku.edu.cn> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-17 22:44:47 +00:00
vm_fault_t fault)
{
if (!user_mode(regs))
return SIGBUS;
current->thread.trap_nr = BUS_ADRERR;
#ifdef CONFIG_MEMORY_FAILURE
if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
unsigned int lsb = 0; /* shutup gcc */
pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
current->comm, current->pid, address);
if (fault & VM_FAULT_HWPOISON_LARGE)
lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
if (fault & VM_FAULT_HWPOISON)
lsb = PAGE_SHIFT;
force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);
return 0;
}
#endif
force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
return 0;
}
mm: convert return type of handle_mm_fault() caller to vm_fault_t Use new return type vm_fault_t for fault handler. For now, this is just documenting that the function returns a VM_FAULT value rather than an errno. Once all instances are converted, vm_fault_t will become a distinct type. Ref-> commit 1c8f422059ae ("mm: change return type to vm_fault_t") In this patch all the caller of handle_mm_fault() are changed to return vm_fault_t type. Link: http://lkml.kernel.org/r/20180617084810.GA6730@jordon-HP-15-Notebook-PC Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Richard Henderson <rth@twiddle.net> Cc: Tony Luck <tony.luck@intel.com> Cc: Matt Turner <mattst88@gmail.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Russell King <linux@armlinux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Michal Simek <monstr@monstr.eu> Cc: James Hogan <jhogan@kernel.org> Cc: Ley Foon Tan <lftan@altera.com> Cc: Jonas Bonn <jonas@southpole.se> Cc: James E.J. Bottomley <jejb@parisc-linux.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Palmer Dabbelt <palmer@sifive.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: David S. Miller <davem@davemloft.net> Cc: Richard Weinberger <richard@nod.at> Cc: Guan Xuetao <gxt@pku.edu.cn> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-17 22:44:47 +00:00
static int mm_fault_error(struct pt_regs *regs, unsigned long addr,
vm_fault_t fault)
{
/*
* Kernel page fault interrupted by SIGKILL. We have no reason to
* continue processing.
*/
if (fatal_signal_pending(current) && !user_mode(regs))
return SIGKILL;
/* Out of memory */
if (fault & VM_FAULT_OOM) {
/*
* We ran out of memory, or some other thing happened to us that
* made us unable to handle the page fault gracefully.
*/
if (!user_mode(regs))
return SIGSEGV;
pagefault_out_of_memory();
} else {
if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|
VM_FAULT_HWPOISON_LARGE))
return do_sigbus(regs, addr, fault);
else if (fault & VM_FAULT_SIGSEGV)
return bad_area_nosemaphore(regs, addr);
else
BUG();
}
return 0;
}
/* Is this a bad kernel fault ? */
static bool bad_kernel_fault(struct pt_regs *regs, unsigned long error_code,
unsigned long address, bool is_write)
{
int is_exec = TRAP(regs) == 0x400;
/* NX faults set DSISR_PROTFAULT on the 8xx, DSISR_NOEXEC_OR_G on others */
if (is_exec && (error_code & (DSISR_NOEXEC_OR_G | DSISR_KEYFAULT |
DSISR_PROTFAULT))) {
pr_crit_ratelimited("kernel tried to execute %s page (%lx) - exploit attempt? (uid: %d)\n",
address >= TASK_SIZE ? "exec-protected" : "user",
address,
from_kuid(&init_user_ns, current_uid()));
// Kernel exec fault is always bad
return true;
}
if (!is_exec && address < TASK_SIZE && (error_code & DSISR_PROTFAULT) &&
!search_exception_tables(regs->nip)) {
pr_crit_ratelimited("Kernel attempted to access user page (%lx) - exploit attempt? (uid: %d)\n",
address,
from_kuid(&init_user_ns, current_uid()));
}
// Kernel fault on kernel address is bad
if (address >= TASK_SIZE)
return true;
// Fault on user outside of certain regions (eg. copy_tofrom_user()) is bad
if (!search_exception_tables(regs->nip))
return true;
// Read/write fault in a valid region (the exception table search passed
// above), but blocked by KUAP is bad, it can never succeed.
if (bad_kuap_fault(regs, address, is_write))
return true;
// What's left? Kernel fault on user in well defined regions (extable
// matched), and allowed by KUAP in the faulting context.
return false;
}
static bool bad_stack_expansion(struct pt_regs *regs, unsigned long address,
struct vm_area_struct *vma, unsigned int flags,
bool *must_retry)
{
/*
* N.B. The POWER/Open ABI allows programs to access up to
* 288 bytes below the stack pointer.
* The kernel signal delivery code writes up to about 1.5kB
* below the stack pointer (r1) before decrementing it.
* The exec code can write slightly over 640kB to the stack
* before setting the user r1. Thus we allow the stack to
* expand to 1MB without further checks.
*/
if (address + 0x100000 < vma->vm_end) {
unsigned int __user *nip = (unsigned int __user *)regs->nip;
/* get user regs even if this fault is in kernel mode */
struct pt_regs *uregs = current->thread.regs;
if (uregs == NULL)
return true;
/*
* A user-mode access to an address a long way below
* the stack pointer is only valid if the instruction
* is one which would update the stack pointer to the
* address accessed if the instruction completed,
* i.e. either stwu rs,n(r1) or stwux rs,r1,rb
* (or the byte, halfword, float or double forms).
*
* If we don't check this then any write to the area
* between the last mapped region and the stack will
* expand the stack rather than segfaulting.
*/
if (address + 2048 >= uregs->gpr[1])
return false;
if ((flags & FAULT_FLAG_WRITE) && (flags & FAULT_FLAG_USER) &&
Remove 'type' argument from access_ok() function Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument of the user address range verification function since we got rid of the old racy i386-only code to walk page tables by hand. It existed because the original 80386 would not honor the write protect bit when in kernel mode, so you had to do COW by hand before doing any user access. But we haven't supported that in a long time, and these days the 'type' argument is a purely historical artifact. A discussion about extending 'user_access_begin()' to do the range checking resulted this patch, because there is no way we're going to move the old VERIFY_xyz interface to that model. And it's best done at the end of the merge window when I've done most of my merges, so let's just get this done once and for all. This patch was mostly done with a sed-script, with manual fix-ups for the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form. There were a couple of notable cases: - csky still had the old "verify_area()" name as an alias. - the iter_iov code had magical hardcoded knowledge of the actual values of VERIFY_{READ,WRITE} (not that they mattered, since nothing really used it) - microblaze used the type argument for a debug printout but other than those oddities this should be a total no-op patch. I tried to fix up all architectures, did fairly extensive grepping for access_ok() uses, and the changes are trivial, but I may have missed something. Any missed conversion should be trivially fixable, though. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-01-04 02:57:57 +00:00
access_ok(nip, sizeof(*nip))) {
unsigned int inst;
if (!probe_user_read(&inst, nip, sizeof(inst)))
return !store_updates_sp(inst);
*must_retry = true;
}
return true;
}
return false;
}
#ifdef CONFIG_PPC_MEM_KEYS
static bool access_pkey_error(bool is_write, bool is_exec, bool is_pkey,
struct vm_area_struct *vma)
{
/*
* Make sure to check the VMA so that we do not perform
* faults just to hit a pkey fault as soon as we fill in a
* page. Only called for current mm, hence foreign == 0
*/
if (!arch_vma_access_permitted(vma, is_write, is_exec, 0))
return true;
return false;
}
#endif
static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma)
{
/*
* Allow execution from readable areas if the MMU does not
* provide separate controls over reading and executing.
*
* Note: That code used to not be enabled for 4xx/BookE.
* It is now as I/D cache coherency for these is done at
* set_pte_at() time and I see no reason why the test
* below wouldn't be valid on those processors. This -may-
* break programs compiled with a really old ABI though.
*/
if (is_exec) {
return !(vma->vm_flags & VM_EXEC) &&
(cpu_has_feature(CPU_FTR_NOEXECUTE) ||
!(vma->vm_flags & (VM_READ | VM_WRITE)));
}
if (is_write) {
if (unlikely(!(vma->vm_flags & VM_WRITE)))
return true;
return false;
}
mm/vma: make vma_is_accessible() available for general use Lets move vma_is_accessible() helper to include/linux/mm.h which makes it available for general use. While here, this replaces all remaining open encodings for VMA access check with vma_is_accessible(). Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> Acked-by: Guo Ren <guoren@kernel.org> Acked-by: Vlastimil Babka <vbabka@suse.cz> Cc: Guo Ren <guoren@kernel.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Paul Burton <paulburton@kernel.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: Rich Felker <dalias@libc.org> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Nick Piggin <npiggin@gmail.com> Cc: Paul Mackerras <paulus@ozlabs.org> Cc: Will Deacon <will@kernel.org> Link: http://lkml.kernel.org/r/1582520593-30704-3-git-send-email-anshuman.khandual@arm.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-04-07 03:03:47 +00:00
if (unlikely(!vma_is_accessible(vma)))
return true;
/*
* We should ideally do the vma pkey access check here. But in the
* fault path, handle_mm_fault() also does the same check. To avoid
* these multiple checks, we skip it here and handle access error due
* to pkeys later.
*/
return false;
}
#ifdef CONFIG_PPC_SMLPAR
static inline void cmo_account_page_fault(void)
{
if (firmware_has_feature(FW_FEATURE_CMO)) {
u32 page_ins;
preempt_disable();
page_ins = be32_to_cpu(get_lppaca()->page_ins);
page_ins += 1 << PAGE_FACTOR;
get_lppaca()->page_ins = cpu_to_be32(page_ins);
preempt_enable();
}
}
#else
static inline void cmo_account_page_fault(void) { }
#endif /* CONFIG_PPC_SMLPAR */
#ifdef CONFIG_PPC_BOOK3S
static void sanity_check_fault(bool is_write, bool is_user,
unsigned long error_code, unsigned long address)
{
/*
* Userspace trying to access kernel address, we get PROTFAULT for that.
*/
if (is_user && address >= TASK_SIZE) {
if ((long)address == -1)
return;
pr_crit_ratelimited("%s[%d]: User access of kernel address (%lx) - exploit attempt? (uid: %d)\n",
current->comm, current->pid, address,
from_kuid(&init_user_ns, current_uid()));
return;
}
/*
* For hash translation mode, we should never get a
* PROTFAULT. Any update to pte to reduce access will result in us
* removing the hash page table entry, thus resulting in a DSISR_NOHPTE
* fault instead of DSISR_PROTFAULT.
*
* A pte update to relax the access will not result in a hash page table
* entry invalidate and hence can result in DSISR_PROTFAULT.
* ptep_set_access_flags() doesn't do a hpte flush. This is why we have
* the special !is_write in the below conditional.
*
* For platforms that doesn't supports coherent icache and do support
* per page noexec bit, we do setup things such that we do the
* sync between D/I cache via fault. But that is handled via low level
* hash fault code (hash_page_do_lazy_icache()) and we should not reach
* here in such case.
*
* For wrong access that can result in PROTFAULT, the above vma->vm_flags
* check should handle those and hence we should fall to the bad_area
* handling correctly.
*
* For embedded with per page exec support that doesn't support coherent
* icache we do get PROTFAULT and we handle that D/I cache sync in
* set_pte_at while taking the noexec/prot fault. Hence this is WARN_ON
* is conditional for server MMU.
*
* For radix, we can get prot fault for autonuma case, because radix
* page table will have them marked noaccess for user.
*/
if (radix_enabled() || is_write)
return;
WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
}
#else
static void sanity_check_fault(bool is_write, bool is_user,
unsigned long error_code, unsigned long address) { }
#endif /* CONFIG_PPC_BOOK3S */
/*
* Define the correct "is_write" bit in error_code based
* on the processor family
*/
#if (defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
#define page_fault_is_write(__err) ((__err) & ESR_DST)
#define page_fault_is_bad(__err) (0)
#else
#define page_fault_is_write(__err) ((__err) & DSISR_ISSTORE)
#if defined(CONFIG_PPC_8xx)
#define page_fault_is_bad(__err) ((__err) & DSISR_NOEXEC_OR_G)
#elif defined(CONFIG_PPC64)
#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_64S)
#else
#define page_fault_is_bad(__err) ((__err) & DSISR_BAD_FAULT_32S)
#endif
#endif
/*
* For 600- and 800-family processors, the error_code parameter is DSISR
* for a data fault, SRR1 for an instruction fault. For 400-family processors
* the error_code parameter is ESR for a data fault, 0 for an instruction
* fault.
* For 64-bit processors, the error_code parameter is
* - DSISR for a non-SLB data access fault,
* - SRR1 & 0x08000000 for a non-SLB instruction access fault
* - 0 any SLB fault.
*
* The return value is 0 if the fault was handled, or the signal
* number if this is a kernel fault that can't be handled here.
*/
static int __do_page_fault(struct pt_regs *regs, unsigned long address,
unsigned long error_code)
{
struct vm_area_struct * vma;
struct mm_struct *mm = current->mm;
mm: introduce FAULT_FLAG_DEFAULT Although there're tons of arch-specific page fault handlers, most of them are still sharing the same initial value of the page fault flags. Say, merely all of the page fault handlers would allow the fault to be retried, and they also allow the fault to respond to SIGKILL. Let's define a default value for the fault flags to replace those initial page fault flags that were copied over. With this, it'll be far easier to introduce new fault flag that can be used by all the architectures instead of touching all the archs. Signed-off-by: Peter Xu <peterx@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Brian Geffon <bgeffon@google.com> Reviewed-by: David Hildenbrand <david@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Bobby Powers <bobbypowers@gmail.com> Cc: Denis Plotnikov <dplotnikov@virtuozzo.com> Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jerome Glisse <jglisse@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: "Kirill A . Shutemov" <kirill@shutemov.name> Cc: Martin Cracauer <cracauer@cons.org> Cc: Marty McFadden <mcfadden8@llnl.gov> Cc: Matthew Wilcox <willy@infradead.org> Cc: Maya Gokhale <gokhale2@llnl.gov> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Mike Rapoport <rppt@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Link: http://lkml.kernel.org/r/20200220160238.9694-1-peterx@redhat.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-04-02 04:08:37 +00:00
unsigned int flags = FAULT_FLAG_DEFAULT;
int is_exec = TRAP(regs) == 0x400;
powerpc/mm: Evaluate user_mode(regs) only once in do_page_fault() Analysis of the assembly code shows that when using user_mode(regs), at least the 'andi.' is redone all the time, and also the 'lwz ,132(r31)' most of the time. With the new form, the 'is_user' is mapped to cr4, then all further use of is_user results in just things like 'beq cr4,218 <do_page_fault+0x218>' Without the patch: 50: 81 1e 00 84 lwz r8,132(r30) 54: 71 09 40 00 andi. r9,r8,16384 58: 40 82 00 0c bne 64 <do_page_fault+0x64> 84: 81 3e 00 84 lwz r9,132(r30) 8c: 71 2a 40 00 andi. r10,r9,16384 90: 41 a2 01 64 beq 1f4 <do_page_fault+0x1f4> d4: 81 3e 00 84 lwz r9,132(r30) dc: 71 28 40 00 andi. r8,r9,16384 e0: 41 82 02 08 beq 2e8 <do_page_fault+0x2e8> 108: 81 3e 00 84 lwz r9,132(r30) 110: 71 28 40 00 andi. r8,r9,16384 118: 41 82 02 28 beq 340 <do_page_fault+0x340> 1e4: 81 3e 00 84 lwz r9,132(r30) 1e8: 71 2a 40 00 andi. r10,r9,16384 1ec: 40 82 01 68 bne 354 <do_page_fault+0x354> 228: 81 3e 00 84 lwz r9,132(r30) 22c: 71 28 40 00 andi. r8,r9,16384 230: 41 82 ff c4 beq 1f4 <do_page_fault+0x1f4> 288: 71 2a 40 00 andi. r10,r9,16384 294: 41 a2 fe 60 beq f4 <do_page_fault+0xf4> 50c: 81 3e 00 84 lwz r9,132(r30) 514: 71 2a 40 00 andi. r10,r9,16384 518: 40 a2 fc e0 bne 1f8 <do_page_fault+0x1f8> 534: 81 3e 00 84 lwz r9,132(r30) 53c: 71 2a 40 00 andi. r10,r9,16384 540: 41 82 fc b8 beq 1f8 <do_page_fault+0x1f8> This patch creates a local var called 'is_user' which contains the result of user_mode(regs) With the patch: 20: 81 03 00 84 lwz r8,132(r3) 48: 55 09 97 fe rlwinm r9,r8,18,31,31 58: 2e 09 00 00 cmpwi cr4,r9,0 5c: 40 92 00 0c bne cr4,68 <do_page_fault+0x68> 88: 41 b2 01 90 beq cr4,218 <do_page_fault+0x218> d4: 40 92 01 d0 bne cr4,2a4 <do_page_fault+0x2a4> 120: 41 b2 00 f8 beq cr4,218 <do_page_fault+0x218> 138: 41 b2 ff a0 beq cr4,d8 <do_page_fault+0xd8> 1d4: 40 92 00 e0 bne cr4,2b4 <do_page_fault+0x2b4> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-04-19 12:56:30 +00:00
int is_user = user_mode(regs);
int is_write = page_fault_is_write(error_code);
mm: convert return type of handle_mm_fault() caller to vm_fault_t Use new return type vm_fault_t for fault handler. For now, this is just documenting that the function returns a VM_FAULT value rather than an errno. Once all instances are converted, vm_fault_t will become a distinct type. Ref-> commit 1c8f422059ae ("mm: change return type to vm_fault_t") In this patch all the caller of handle_mm_fault() are changed to return vm_fault_t type. Link: http://lkml.kernel.org/r/20180617084810.GA6730@jordon-HP-15-Notebook-PC Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Richard Henderson <rth@twiddle.net> Cc: Tony Luck <tony.luck@intel.com> Cc: Matt Turner <mattst88@gmail.com> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: Russell King <linux@armlinux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Richard Kuo <rkuo@codeaurora.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Michal Simek <monstr@monstr.eu> Cc: James Hogan <jhogan@kernel.org> Cc: Ley Foon Tan <lftan@altera.com> Cc: Jonas Bonn <jonas@southpole.se> Cc: James E.J. Bottomley <jejb@parisc-linux.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Palmer Dabbelt <palmer@sifive.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: David S. Miller <davem@davemloft.net> Cc: Richard Weinberger <richard@nod.at> Cc: Guan Xuetao <gxt@pku.edu.cn> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: "Levin, Alexander (Sasha Levin)" <alexander.levin@verizon.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-08-17 22:44:47 +00:00
vm_fault_t fault, major = 0;
bool must_retry = false;
mm, kprobes: generalize and rename notify_page_fault() as kprobe_page_fault() Architectures which support kprobes have very similar boilerplate around calling kprobe_fault_handler(). Use a helper function in kprobes.h to unify them, based on the x86 code. This changes the behaviour for other architectures when preemption is enabled. Previously, they would have disabled preemption while calling the kprobe handler. However, preemption would be disabled if this fault was due to a kprobe, so we know the fault was not due to a kprobe handler and can simply return failure. This behaviour was introduced in commit a980c0ef9f6d ("x86/kprobes: Refactor kprobes_fault() like kprobe_exceptions_notify()") [anshuman.khandual@arm.com: export kprobe_fault_handler()] Link: http://lkml.kernel.org/r/1561133358-8876-1-git-send-email-anshuman.khandual@arm.com Link: http://lkml.kernel.org/r/1560420444-25737-1-git-send-email-anshuman.khandual@arm.com Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Christophe Leroy <christophe.leroy@c-s.fr> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Andrey Konovalov <andreyknvl@google.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: "David S. Miller" <davem@davemloft.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: James Hogan <jhogan@kernel.org> Cc: Paul Burton <paul.burton@mips.com> Cc: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-16 23:28:00 +00:00
bool kprobe_fault = kprobe_page_fault(regs, 11);
mm, kprobes: generalize and rename notify_page_fault() as kprobe_page_fault() Architectures which support kprobes have very similar boilerplate around calling kprobe_fault_handler(). Use a helper function in kprobes.h to unify them, based on the x86 code. This changes the behaviour for other architectures when preemption is enabled. Previously, they would have disabled preemption while calling the kprobe handler. However, preemption would be disabled if this fault was due to a kprobe, so we know the fault was not due to a kprobe handler and can simply return failure. This behaviour was introduced in commit a980c0ef9f6d ("x86/kprobes: Refactor kprobes_fault() like kprobe_exceptions_notify()") [anshuman.khandual@arm.com: export kprobe_fault_handler()] Link: http://lkml.kernel.org/r/1561133358-8876-1-git-send-email-anshuman.khandual@arm.com Link: http://lkml.kernel.org/r/1560420444-25737-1-git-send-email-anshuman.khandual@arm.com Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Christophe Leroy <christophe.leroy@c-s.fr> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Andrey Konovalov <andreyknvl@google.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Paul Mackerras <paulus@samba.org> Cc: Russell King <linux@armlinux.org.uk> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Yoshinori Sato <ysato@users.sourceforge.jp> Cc: "David S. Miller" <davem@davemloft.net> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Vineet Gupta <vgupta@synopsys.com> Cc: James Hogan <jhogan@kernel.org> Cc: Paul Burton <paul.burton@mips.com> Cc: Ralf Baechle <ralf@linux-mips.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-07-16 23:28:00 +00:00
if (unlikely(debugger_fault_handler(regs) || kprobe_fault))
return 0;
if (unlikely(page_fault_is_bad(error_code))) {
if (is_user) {
_exception(SIGBUS, regs, BUS_OBJERR, address);
return 0;
}
return SIGBUS;
}
/* Additional sanity check(s) */
sanity_check_fault(is_write, is_user, error_code, address);
/*
* The kernel should never take an execute fault nor should it
* take a page fault to a kernel address or a page fault to a user
* address outside of dedicated places
*/
if (unlikely(!is_user && bad_kernel_fault(regs, error_code, address, is_write)))
return SIGSEGV;
/*
* If we're in an interrupt, have no user context or are running
* in a region with pagefaults disabled then we must not take the fault
*/
if (unlikely(faulthandler_disabled() || !mm)) {
if (is_user)
printk_ratelimited(KERN_ERR "Page fault in user mode"
" with faulthandler_disabled()=%d"
" mm=%p\n",
faulthandler_disabled(), mm);
return bad_area_nosemaphore(regs, address);
}
/* We restore the interrupt state now */
if (!arch_irq_disabled_regs(regs))
local_irq_enable();
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
/*
* We want to do this outside mmap_sem, because reading code around nip
* can result in fault, which will cause a deadlock when called with
* mmap_sem held
*/
powerpc/mm: Evaluate user_mode(regs) only once in do_page_fault() Analysis of the assembly code shows that when using user_mode(regs), at least the 'andi.' is redone all the time, and also the 'lwz ,132(r31)' most of the time. With the new form, the 'is_user' is mapped to cr4, then all further use of is_user results in just things like 'beq cr4,218 <do_page_fault+0x218>' Without the patch: 50: 81 1e 00 84 lwz r8,132(r30) 54: 71 09 40 00 andi. r9,r8,16384 58: 40 82 00 0c bne 64 <do_page_fault+0x64> 84: 81 3e 00 84 lwz r9,132(r30) 8c: 71 2a 40 00 andi. r10,r9,16384 90: 41 a2 01 64 beq 1f4 <do_page_fault+0x1f4> d4: 81 3e 00 84 lwz r9,132(r30) dc: 71 28 40 00 andi. r8,r9,16384 e0: 41 82 02 08 beq 2e8 <do_page_fault+0x2e8> 108: 81 3e 00 84 lwz r9,132(r30) 110: 71 28 40 00 andi. r8,r9,16384 118: 41 82 02 28 beq 340 <do_page_fault+0x340> 1e4: 81 3e 00 84 lwz r9,132(r30) 1e8: 71 2a 40 00 andi. r10,r9,16384 1ec: 40 82 01 68 bne 354 <do_page_fault+0x354> 228: 81 3e 00 84 lwz r9,132(r30) 22c: 71 28 40 00 andi. r8,r9,16384 230: 41 82 ff c4 beq 1f4 <do_page_fault+0x1f4> 288: 71 2a 40 00 andi. r10,r9,16384 294: 41 a2 fe 60 beq f4 <do_page_fault+0xf4> 50c: 81 3e 00 84 lwz r9,132(r30) 514: 71 2a 40 00 andi. r10,r9,16384 518: 40 a2 fc e0 bne 1f8 <do_page_fault+0x1f8> 534: 81 3e 00 84 lwz r9,132(r30) 53c: 71 2a 40 00 andi. r10,r9,16384 540: 41 82 fc b8 beq 1f8 <do_page_fault+0x1f8> This patch creates a local var called 'is_user' which contains the result of user_mode(regs) With the patch: 20: 81 03 00 84 lwz r8,132(r3) 48: 55 09 97 fe rlwinm r9,r8,18,31,31 58: 2e 09 00 00 cmpwi cr4,r9,0 5c: 40 92 00 0c bne cr4,68 <do_page_fault+0x68> 88: 41 b2 01 90 beq cr4,218 <do_page_fault+0x218> d4: 40 92 01 d0 bne cr4,2a4 <do_page_fault+0x2a4> 120: 41 b2 00 f8 beq cr4,218 <do_page_fault+0x218> 138: 41 b2 ff a0 beq cr4,d8 <do_page_fault+0xd8> 1d4: 40 92 00 e0 bne cr4,2b4 <do_page_fault+0x2b4> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-04-19 12:56:30 +00:00
if (is_user)
flags |= FAULT_FLAG_USER;
if (is_write)
flags |= FAULT_FLAG_WRITE;
if (is_exec)
flags |= FAULT_FLAG_INSTRUCTION;
/* When running in the kernel we expect faults to occur only to
* addresses in user space. All other faults represent errors in the
* kernel and should generate an OOPS. Unfortunately, in the case of an
* erroneous fault occurring in a code path which already holds mmap_sem
* we will deadlock attempting to validate the fault against the
* address space. Luckily the kernel only validly references user
* space from well defined areas of code, which are listed in the
* exceptions table.
*
* As the vast majority of faults will be valid we will only perform
* the source reference check when there is a possibility of a deadlock.
* Attempt to lock the address space, if we cannot we then validate the
* source. If this is invalid we can skip the address space check,
* thus avoiding the deadlock.
*/
if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
powerpc/mm: Evaluate user_mode(regs) only once in do_page_fault() Analysis of the assembly code shows that when using user_mode(regs), at least the 'andi.' is redone all the time, and also the 'lwz ,132(r31)' most of the time. With the new form, the 'is_user' is mapped to cr4, then all further use of is_user results in just things like 'beq cr4,218 <do_page_fault+0x218>' Without the patch: 50: 81 1e 00 84 lwz r8,132(r30) 54: 71 09 40 00 andi. r9,r8,16384 58: 40 82 00 0c bne 64 <do_page_fault+0x64> 84: 81 3e 00 84 lwz r9,132(r30) 8c: 71 2a 40 00 andi. r10,r9,16384 90: 41 a2 01 64 beq 1f4 <do_page_fault+0x1f4> d4: 81 3e 00 84 lwz r9,132(r30) dc: 71 28 40 00 andi. r8,r9,16384 e0: 41 82 02 08 beq 2e8 <do_page_fault+0x2e8> 108: 81 3e 00 84 lwz r9,132(r30) 110: 71 28 40 00 andi. r8,r9,16384 118: 41 82 02 28 beq 340 <do_page_fault+0x340> 1e4: 81 3e 00 84 lwz r9,132(r30) 1e8: 71 2a 40 00 andi. r10,r9,16384 1ec: 40 82 01 68 bne 354 <do_page_fault+0x354> 228: 81 3e 00 84 lwz r9,132(r30) 22c: 71 28 40 00 andi. r8,r9,16384 230: 41 82 ff c4 beq 1f4 <do_page_fault+0x1f4> 288: 71 2a 40 00 andi. r10,r9,16384 294: 41 a2 fe 60 beq f4 <do_page_fault+0xf4> 50c: 81 3e 00 84 lwz r9,132(r30) 514: 71 2a 40 00 andi. r10,r9,16384 518: 40 a2 fc e0 bne 1f8 <do_page_fault+0x1f8> 534: 81 3e 00 84 lwz r9,132(r30) 53c: 71 2a 40 00 andi. r10,r9,16384 540: 41 82 fc b8 beq 1f8 <do_page_fault+0x1f8> This patch creates a local var called 'is_user' which contains the result of user_mode(regs) With the patch: 20: 81 03 00 84 lwz r8,132(r3) 48: 55 09 97 fe rlwinm r9,r8,18,31,31 58: 2e 09 00 00 cmpwi cr4,r9,0 5c: 40 92 00 0c bne cr4,68 <do_page_fault+0x68> 88: 41 b2 01 90 beq cr4,218 <do_page_fault+0x218> d4: 40 92 01 d0 bne cr4,2a4 <do_page_fault+0x2a4> 120: 41 b2 00 f8 beq cr4,218 <do_page_fault+0x218> 138: 41 b2 ff a0 beq cr4,d8 <do_page_fault+0xd8> 1d4: 40 92 00 e0 bne cr4,2b4 <do_page_fault+0x2b4> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-04-19 12:56:30 +00:00
if (!is_user && !search_exception_tables(regs->nip))
return bad_area_nosemaphore(regs, address);
retry:
down_read(&mm->mmap_sem);
} else {
/*
* The above down_read_trylock() might have succeeded in
* which case we'll have missed the might_sleep() from
* down_read():
*/
might_sleep();
}
vma = find_vma(mm, address);
if (unlikely(!vma))
return bad_area(regs, address);
if (likely(vma->vm_start <= address))
goto good_area;
if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
return bad_area(regs, address);
/* The stack is being expanded, check if it's valid */
if (unlikely(bad_stack_expansion(regs, address, vma, flags,
&must_retry))) {
if (!must_retry)
return bad_area(regs, address);
up_read(&mm->mmap_sem);
if (fault_in_pages_readable((const char __user *)regs->nip,
sizeof(unsigned int)))
return bad_area_nosemaphore(regs, address);
goto retry;
}
/* Try to expand it */
if (unlikely(expand_stack(vma, address)))
return bad_area(regs, address);
good_area:
#ifdef CONFIG_PPC_MEM_KEYS
if (unlikely(access_pkey_error(is_write, is_exec,
(error_code & DSISR_KEYFAULT), vma)))
return bad_access_pkey(regs, address, vma);
#endif /* CONFIG_PPC_MEM_KEYS */
if (unlikely(access_error(is_write, is_exec, vma)))
powerpc/mm: Fix SEGV on mapped region to return SEGV_ACCERR The recent refactoring of the powerpc page fault handler in commit c3350602e876 ("powerpc/mm: Make bad_area* helper functions") caused access to protected memory regions to indicate SEGV_MAPERR instead of the traditional SEGV_ACCERR in the si_code field of a user-space signal handler. This can confuse debug libraries that temporarily change the protection of memory regions, and expect to use SEGV_ACCERR as an indication to restore access to a region. This commit restores the previous behavior. The following program exhibits the issue: $ ./repro read || echo "FAILED" $ ./repro write || echo "FAILED" $ ./repro exec || echo "FAILED" #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <signal.h> #include <sys/mman.h> #include <assert.h> static void segv_handler(int n, siginfo_t *info, void *arg) { _exit(info->si_code == SEGV_ACCERR ? 0 : 1); } int main(int argc, char **argv) { void *p = NULL; struct sigaction act = { .sa_sigaction = segv_handler, .sa_flags = SA_SIGINFO, }; assert(argc == 2); p = mmap(NULL, getpagesize(), (strcmp(argv[1], "write") == 0) ? PROT_READ : 0, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0); assert(p != MAP_FAILED); assert(sigaction(SIGSEGV, &act, NULL) == 0); if (strcmp(argv[1], "read") == 0) printf("%c", *(unsigned char *)p); else if (strcmp(argv[1], "write") == 0) *(unsigned char *)p = 0; else if (strcmp(argv[1], "exec") == 0) ((void (*)(void))p)(); return 1; /* failed to generate SEGV */ } Fixes: c3350602e876 ("powerpc/mm: Make bad_area* helper functions") Cc: stable@vger.kernel.org # v4.14+ Signed-off-by: John Sperbeck <jsperbeck@google.com> Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> [mpe: Add commit references in change log] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2018-01-01 05:24:58 +00:00
return bad_access(regs, address);
/*
* If for any reason at all we couldn't handle the fault,
* make sure we exit gracefully rather than endlessly redo
* the fault.
*/
fault = handle_mm_fault(vma, address, flags);
major |= fault & VM_FAULT_MAJOR;
if (fault_signal_pending(fault, regs))
return user_mode(regs) ? 0 : SIGBUS;
/*
* Handle the retry right now, the mmap_sem has been released in that
* case.
*/
if (unlikely(fault & VM_FAULT_RETRY)) {
if (flags & FAULT_FLAG_ALLOW_RETRY) {
flags |= FAULT_FLAG_TRIED;
goto retry;
}
}
up_read(&current->mm->mmap_sem);
if (unlikely(fault & VM_FAULT_ERROR))
return mm_fault_error(regs, address, fault);
/*
* Major/minor page fault accounting.
*/
if (major) {
current->maj_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
cmo_account_page_fault();
} else {
current->min_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
}
return 0;
}
NOKPROBE_SYMBOL(__do_page_fault);
int do_page_fault(struct pt_regs *regs, unsigned long address,
unsigned long error_code)
{
enum ctx_state prev_state = exception_enter();
int rc = __do_page_fault(regs, address, error_code);
exception_exit(prev_state);
return rc;
}
NOKPROBE_SYMBOL(do_page_fault);
/*
* bad_page_fault is called when we have a bad access from the kernel.
* It is called from the DSI and ISI handlers in head.S and from some
* of the procedures in traps.c.
*/
void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
{
const struct exception_table_entry *entry;
int is_write = page_fault_is_write(regs->dsisr);
/* Are we prepared to handle this fault? */
if ((entry = search_exception_tables(regs->nip)) != NULL) {
regs->nip = extable_fixup(entry);
return;
}
/* kernel has accessed a bad area */
switch (TRAP(regs)) {
case 0x300:
case 0x380:
KVM: PPC: Book3S HV: Implement functions to access quadrants 1 & 2 The POWER9 radix mmu has the concept of quadrants. The quadrant number is the two high bits of the effective address and determines the fully qualified address to be used for the translation. The fully qualified address consists of the effective lpid, the effective pid and the effective address. This gives then 4 possible quadrants 0, 1, 2, and 3. When accessing these quadrants the fully qualified address is obtained as follows: Quadrant | Hypervisor | Guest -------------------------------------------------------------------------- | EA[0:1] = 0b00 | EA[0:1] = 0b00 0 | effLPID = 0 | effLPID = LPIDR | effPID = PIDR | effPID = PIDR -------------------------------------------------------------------------- | EA[0:1] = 0b01 | 1 | effLPID = LPIDR | Invalid Access | effPID = PIDR | -------------------------------------------------------------------------- | EA[0:1] = 0b10 | 2 | effLPID = LPIDR | Invalid Access | effPID = 0 | -------------------------------------------------------------------------- | EA[0:1] = 0b11 | EA[0:1] = 0b11 3 | effLPID = 0 | effLPID = LPIDR | effPID = 0 | effPID = 0 -------------------------------------------------------------------------- In the Guest; Quadrant 3 is normally used to address the operating system since this uses effPID=0 and effLPID=LPIDR, meaning the PID register doesn't need to be switched. Quadrant 0 is normally used to address user space since the effLPID and effPID are taken from the corresponding registers. In the Host; Quadrant 0 and 3 are used as above, however the effLPID is always 0 to address the host. Quadrants 1 and 2 can be used by the host to address guest memory using a guest effective address. Since the effLPID comes from the LPID register, the host loads the LPID of the guest it would like to access (and the PID of the process) and can perform accesses to a guest effective address. This means quadrant 1 can be used to address the guest user space and quadrant 2 can be used to address the guest operating system from the hypervisor, using a guest effective address. Access to the quadrants can cause a Hypervisor Data Storage Interrupt (HDSI) due to being unable to perform partition scoped translation. Previously this could only be generated from a guest and so the code path expects us to take the KVM trampoline in the interrupt handler. This is no longer the case so we modify the handler to call bad_page_fault() to check if we were expecting this fault so we can handle it gracefully and just return with an error code. In the hash mmu case we still raise an unknown exception since quadrants aren't defined for the hash mmu. Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com> Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2018-12-14 05:29:05 +00:00
case 0xe00:
pr_alert("BUG: %s on %s at 0x%08lx\n",
regs->dar < PAGE_SIZE ? "Kernel NULL pointer dereference" :
"Unable to handle kernel data access",
is_write ? "write" : "read", regs->dar);
break;
case 0x400:
case 0x480:
pr_alert("BUG: Unable to handle kernel instruction fetch%s",
regs->nip < PAGE_SIZE ? " (NULL pointer?)\n" : "\n");
break;
case 0x600:
pr_alert("BUG: Unable to handle kernel unaligned access at 0x%08lx\n",
regs->dar);
break;
default:
pr_alert("BUG: Unable to handle unknown paging fault at 0x%08lx\n",
regs->dar);
break;
}
printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
regs->nip);
if (task_stack_end_corrupted(current))
printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
die("Kernel access of bad area", regs, sig);
}