mirror of
https://github.com/torvalds/linux.git
synced 2024-11-30 08:01:59 +00:00
bb0bb3b659
This is a patch that I have had in my tree for ages. If init causes an exception that raises a signal, such as a SIGSEGV, SIGILL or SIGFPE, and it hasn't registered a handler for it, we don't deliver the signal, since init doesn't get any signals that it doesn't have a handler for. But that means that we just return to userland and generate the same exception again immediately. With this patch we print a message and kill init in this situation. This is very useful when you have a bug in the kernel that means that init doesn't get as far as executing its first instruction. :) Without this patch the system hangs when it gets to starting the userland init; with it you at least get a message giving you a clue about what has gone wrong. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
437 lines
11 KiB
C
437 lines
11 KiB
C
/*
|
|
* arch/ppc/mm/fault.c
|
|
*
|
|
* 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.
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License
|
|
* as published by the Free Software Foundation; either version
|
|
* 2 of the License, or (at your option) any later version.
|
|
*/
|
|
|
|
#include <linux/config.h>
|
|
#include <linux/signal.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/errno.h>
|
|
#include <linux/string.h>
|
|
#include <linux/types.h>
|
|
#include <linux/ptrace.h>
|
|
#include <linux/mman.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/interrupt.h>
|
|
#include <linux/highmem.h>
|
|
#include <linux/module.h>
|
|
|
|
#include <asm/page.h>
|
|
#include <asm/pgtable.h>
|
|
#include <asm/mmu.h>
|
|
#include <asm/mmu_context.h>
|
|
#include <asm/system.h>
|
|
#include <asm/uaccess.h>
|
|
#include <asm/tlbflush.h>
|
|
|
|
#if defined(CONFIG_XMON) || defined(CONFIG_KGDB)
|
|
extern void (*debugger)(struct pt_regs *);
|
|
extern void (*debugger_fault_handler)(struct pt_regs *);
|
|
extern int (*debugger_dabr_match)(struct pt_regs *);
|
|
int debugger_kernel_faults = 1;
|
|
#endif
|
|
|
|
unsigned long htab_reloads; /* updated by hashtable.S:hash_page() */
|
|
unsigned long htab_evicts; /* updated by hashtable.S:hash_page() */
|
|
unsigned long htab_preloads; /* updated by hashtable.S:add_hash_page() */
|
|
unsigned long pte_misses; /* updated by do_page_fault() */
|
|
unsigned long pte_errors; /* updated by do_page_fault() */
|
|
unsigned int probingmem;
|
|
|
|
/*
|
|
* Check whether the instruction at regs->nip is a store using
|
|
* an update addressing form which will update r1.
|
|
*/
|
|
static int store_updates_sp(struct pt_regs *regs)
|
|
{
|
|
unsigned int inst;
|
|
|
|
if (get_user(inst, (unsigned int __user *)regs->nip))
|
|
return 0;
|
|
/* check for 1 in the rA field */
|
|
if (((inst >> 16) & 0x1f) != 1)
|
|
return 0;
|
|
/* check major opcode */
|
|
switch (inst >> 26) {
|
|
case 37: /* stwu */
|
|
case 39: /* stbu */
|
|
case 45: /* sthu */
|
|
case 53: /* stfsu */
|
|
case 55: /* stfdu */
|
|
return 1;
|
|
case 31:
|
|
/* check minor opcode */
|
|
switch ((inst >> 1) & 0x3ff) {
|
|
case 183: /* stwux */
|
|
case 247: /* stbux */
|
|
case 439: /* sthux */
|
|
case 695: /* stfsux */
|
|
case 759: /* stfdux */
|
|
return 1;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
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;
|
|
siginfo_t info;
|
|
int code = SEGV_MAPERR;
|
|
#if defined(CONFIG_4xx) || defined (CONFIG_BOOKE)
|
|
int is_write = error_code & ESR_DST;
|
|
#else
|
|
int is_write = 0;
|
|
|
|
/*
|
|
* Fortunately the bit assignments in SRR1 for an instruction
|
|
* fault and DSISR for a data fault are mostly the same for the
|
|
* bits we are interested in. But there are some bits which
|
|
* indicate errors in DSISR but can validly be set in SRR1.
|
|
*/
|
|
if (TRAP(regs) == 0x400)
|
|
error_code &= 0x48200000;
|
|
else
|
|
is_write = error_code & 0x02000000;
|
|
#endif /* CONFIG_4xx || CONFIG_BOOKE */
|
|
|
|
#if defined(CONFIG_XMON) || defined(CONFIG_KGDB)
|
|
if (debugger_fault_handler && TRAP(regs) == 0x300) {
|
|
debugger_fault_handler(regs);
|
|
return 0;
|
|
}
|
|
#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
|
|
if (error_code & 0x00400000) {
|
|
/* DABR match */
|
|
if (debugger_dabr_match(regs))
|
|
return 0;
|
|
}
|
|
#endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/
|
|
#endif /* CONFIG_XMON || CONFIG_KGDB */
|
|
|
|
if (in_atomic() || mm == NULL)
|
|
return SIGSEGV;
|
|
|
|
down_read(&mm->mmap_sem);
|
|
vma = find_vma(mm, address);
|
|
if (!vma)
|
|
goto bad_area;
|
|
if (vma->vm_start <= address)
|
|
goto good_area;
|
|
if (!(vma->vm_flags & VM_GROWSDOWN))
|
|
goto bad_area;
|
|
if (!is_write)
|
|
goto bad_area;
|
|
|
|
/*
|
|
* N.B. The rs6000/xcoff ABI allows programs to access up to
|
|
* a few hundred 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) {
|
|
/* get user regs even if this fault is in kernel mode */
|
|
struct pt_regs *uregs = current->thread.regs;
|
|
if (uregs == NULL)
|
|
goto bad_area;
|
|
|
|
/*
|
|
* 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]
|
|
&& (!user_mode(regs) || !store_updates_sp(regs)))
|
|
goto bad_area;
|
|
}
|
|
if (expand_stack(vma, address))
|
|
goto bad_area;
|
|
|
|
good_area:
|
|
code = SEGV_ACCERR;
|
|
#if defined(CONFIG_6xx)
|
|
if (error_code & 0x95700000)
|
|
/* an error such as lwarx to I/O controller space,
|
|
address matching DABR, eciwx, etc. */
|
|
goto bad_area;
|
|
#endif /* CONFIG_6xx */
|
|
#if defined(CONFIG_8xx)
|
|
/* The MPC8xx seems to always set 0x80000000, which is
|
|
* "undefined". Of those that can be set, this is the only
|
|
* one which seems bad.
|
|
*/
|
|
if (error_code & 0x10000000)
|
|
/* Guarded storage error. */
|
|
goto bad_area;
|
|
#endif /* CONFIG_8xx */
|
|
|
|
/* a write */
|
|
if (is_write) {
|
|
if (!(vma->vm_flags & VM_WRITE))
|
|
goto bad_area;
|
|
#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
|
|
/* an exec - 4xx/Book-E allows for per-page execute permission */
|
|
} else if (TRAP(regs) == 0x400) {
|
|
pte_t *ptep;
|
|
|
|
#if 0
|
|
/* It would be nice to actually enforce the VM execute
|
|
permission on CPUs which can do so, but far too
|
|
much stuff in userspace doesn't get the permissions
|
|
right, so we let any page be executed for now. */
|
|
if (! (vma->vm_flags & VM_EXEC))
|
|
goto bad_area;
|
|
#endif
|
|
|
|
/* Since 4xx/Book-E supports per-page execute permission,
|
|
* we lazily flush dcache to icache. */
|
|
ptep = NULL;
|
|
if (get_pteptr(mm, address, &ptep) && pte_present(*ptep)) {
|
|
struct page *page = pte_page(*ptep);
|
|
|
|
if (! test_bit(PG_arch_1, &page->flags)) {
|
|
flush_dcache_icache_page(page);
|
|
set_bit(PG_arch_1, &page->flags);
|
|
}
|
|
pte_update(ptep, 0, _PAGE_HWEXEC);
|
|
_tlbie(address);
|
|
pte_unmap(ptep);
|
|
up_read(&mm->mmap_sem);
|
|
return 0;
|
|
}
|
|
if (ptep != NULL)
|
|
pte_unmap(ptep);
|
|
#endif
|
|
/* a read */
|
|
} else {
|
|
/* protection fault */
|
|
if (error_code & 0x08000000)
|
|
goto bad_area;
|
|
if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
|
|
goto bad_area;
|
|
}
|
|
|
|
/*
|
|
* If for any reason at all we couldn't handle the fault,
|
|
* make sure we exit gracefully rather than endlessly redo
|
|
* the fault.
|
|
*/
|
|
survive:
|
|
switch (handle_mm_fault(mm, vma, address, is_write)) {
|
|
case VM_FAULT_MINOR:
|
|
current->min_flt++;
|
|
break;
|
|
case VM_FAULT_MAJOR:
|
|
current->maj_flt++;
|
|
break;
|
|
case VM_FAULT_SIGBUS:
|
|
goto do_sigbus;
|
|
case VM_FAULT_OOM:
|
|
goto out_of_memory;
|
|
default:
|
|
BUG();
|
|
}
|
|
|
|
up_read(&mm->mmap_sem);
|
|
/*
|
|
* keep track of tlb+htab misses that are good addrs but
|
|
* just need pte's created via handle_mm_fault()
|
|
* -- Cort
|
|
*/
|
|
pte_misses++;
|
|
return 0;
|
|
|
|
bad_area:
|
|
up_read(&mm->mmap_sem);
|
|
pte_errors++;
|
|
|
|
/* User mode accesses cause a SIGSEGV */
|
|
if (user_mode(regs)) {
|
|
_exception(SIGSEGV, regs, code, address);
|
|
return 0;
|
|
}
|
|
|
|
return SIGSEGV;
|
|
|
|
/*
|
|
* We ran out of memory, or some other thing happened to us that made
|
|
* us unable to handle the page fault gracefully.
|
|
*/
|
|
out_of_memory:
|
|
up_read(&mm->mmap_sem);
|
|
if (current->pid == 1) {
|
|
yield();
|
|
down_read(&mm->mmap_sem);
|
|
goto survive;
|
|
}
|
|
printk("VM: killing process %s\n", current->comm);
|
|
if (user_mode(regs))
|
|
do_exit(SIGKILL);
|
|
return SIGKILL;
|
|
|
|
do_sigbus:
|
|
up_read(&mm->mmap_sem);
|
|
info.si_signo = SIGBUS;
|
|
info.si_errno = 0;
|
|
info.si_code = BUS_ADRERR;
|
|
info.si_addr = (void __user *)address;
|
|
force_sig_info (SIGBUS, &info, current);
|
|
if (!user_mode(regs))
|
|
return SIGBUS;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
|
|
/* Are we prepared to handle this fault? */
|
|
if ((entry = search_exception_tables(regs->nip)) != NULL) {
|
|
regs->nip = entry->fixup;
|
|
return;
|
|
}
|
|
|
|
/* kernel has accessed a bad area */
|
|
#if defined(CONFIG_XMON) || defined(CONFIG_KGDB)
|
|
if (debugger_kernel_faults)
|
|
debugger(regs);
|
|
#endif
|
|
die("kernel access of bad area", regs, sig);
|
|
}
|
|
|
|
#ifdef CONFIG_8xx
|
|
|
|
/* The pgtable.h claims some functions generically exist, but I
|
|
* can't find them......
|
|
*/
|
|
pte_t *va_to_pte(unsigned long address)
|
|
{
|
|
pgd_t *dir;
|
|
pmd_t *pmd;
|
|
pte_t *pte;
|
|
|
|
if (address < TASK_SIZE)
|
|
return NULL;
|
|
|
|
dir = pgd_offset(&init_mm, address);
|
|
if (dir) {
|
|
pmd = pmd_offset(dir, address & PAGE_MASK);
|
|
if (pmd && pmd_present(*pmd)) {
|
|
pte = pte_offset_kernel(pmd, address & PAGE_MASK);
|
|
if (pte && pte_present(*pte))
|
|
return(pte);
|
|
}
|
|
}
|
|
return NULL;
|
|
}
|
|
|
|
unsigned long va_to_phys(unsigned long address)
|
|
{
|
|
pte_t *pte;
|
|
|
|
pte = va_to_pte(address);
|
|
if (pte)
|
|
return(((unsigned long)(pte_val(*pte)) & PAGE_MASK) | (address & ~(PAGE_MASK)));
|
|
return (0);
|
|
}
|
|
|
|
void
|
|
print_8xx_pte(struct mm_struct *mm, unsigned long addr)
|
|
{
|
|
pgd_t * pgd;
|
|
pmd_t * pmd;
|
|
pte_t * pte;
|
|
|
|
printk(" pte @ 0x%8lx: ", addr);
|
|
pgd = pgd_offset(mm, addr & PAGE_MASK);
|
|
if (pgd) {
|
|
pmd = pmd_offset(pgd, addr & PAGE_MASK);
|
|
if (pmd && pmd_present(*pmd)) {
|
|
pte = pte_offset_kernel(pmd, addr & PAGE_MASK);
|
|
if (pte) {
|
|
printk(" (0x%08lx)->(0x%08lx)->0x%08lx\n",
|
|
(long)pgd, (long)pte, (long)pte_val(*pte));
|
|
#define pp ((long)pte_val(*pte))
|
|
printk(" RPN: %05lx PP: %lx SPS: %lx SH: %lx "
|
|
"CI: %lx v: %lx\n",
|
|
pp>>12, /* rpn */
|
|
(pp>>10)&3, /* pp */
|
|
(pp>>3)&1, /* small */
|
|
(pp>>2)&1, /* shared */
|
|
(pp>>1)&1, /* cache inhibit */
|
|
pp&1 /* valid */
|
|
);
|
|
#undef pp
|
|
}
|
|
else {
|
|
printk("no pte\n");
|
|
}
|
|
}
|
|
else {
|
|
printk("no pmd\n");
|
|
}
|
|
}
|
|
else {
|
|
printk("no pgd\n");
|
|
}
|
|
}
|
|
|
|
int
|
|
get_8xx_pte(struct mm_struct *mm, unsigned long addr)
|
|
{
|
|
pgd_t * pgd;
|
|
pmd_t * pmd;
|
|
pte_t * pte;
|
|
int retval = 0;
|
|
|
|
pgd = pgd_offset(mm, addr & PAGE_MASK);
|
|
if (pgd) {
|
|
pmd = pmd_offset(pgd, addr & PAGE_MASK);
|
|
if (pmd && pmd_present(*pmd)) {
|
|
pte = pte_offset_kernel(pmd, addr & PAGE_MASK);
|
|
if (pte) {
|
|
retval = (int)pte_val(*pte);
|
|
}
|
|
}
|
|
}
|
|
return(retval);
|
|
}
|
|
#endif /* CONFIG_8xx */
|