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ARC: Page Fault handling

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This includes recent changes to make handler "retry" and/or "killable"

The killable (early exit) logic is loosely based on how SH implements it
	return if SIGKILL + either of VM_FAULT_OOM or VM_FAULT_RETRY
which is different from Hexagon implementation which would NOT early
exit for
	SIGKILL + VM_FAULT_OOM + !VM_FAULT_RETRY

credits: Non executable stack support from Simon Spooner

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta 2013-01-18 15:12:20 +05:30
parent d79e678d74
commit fbd7053a78
1 changed files with 228 additions and 0 deletions
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228
arch/arc/mm/fault.c Normal file
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/* Page Fault Handling for ARC (TLB Miss / ProtV)
*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/signal.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/version.h>
#include <linux/uaccess.h>
#include <linux/kdebug.h>
#include <asm/pgalloc.h>
static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address)
{
/*
* Synchronize this task's top level page-table
* with the 'reference' page table.
*/
pgd_t *pgd, *pgd_k;
pud_t *pud, *pud_k;
pmd_t *pmd, *pmd_k;
pgd = pgd_offset_fast(mm, address);
pgd_k = pgd_offset_k(address);
if (!pgd_present(*pgd_k))
goto bad_area;
pud = pud_offset(pgd, address);
pud_k = pud_offset(pgd_k, address);
if (!pud_present(*pud_k))
goto bad_area;
pmd = pmd_offset(pud, address);
pmd_k = pmd_offset(pud_k, address);
if (!pmd_present(*pmd_k))
goto bad_area;
set_pmd(pmd, *pmd_k);
/* XXX: create the TLB entry here */
return 0;
bad_area:
return 1;
}
void do_page_fault(struct pt_regs *regs, int write, unsigned long address,
unsigned long cause_code)
{
struct vm_area_struct *vma = NULL;
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;
siginfo_t info;
int fault, ret;
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
(write ? FAULT_FLAG_WRITE : 0);
/*
* We fault-in kernel-space virtual memory on-demand. The
* 'reference' page table is init_mm.pgd.
*
* NOTE! We MUST NOT take any locks for this case. We may
* be in an interrupt or a critical region, and should
* only copy the information from the master page table,
* nothing more.
*/
if (address >= VMALLOC_START && address <= VMALLOC_END) {
ret = handle_vmalloc_fault(mm, address);
if (unlikely(ret))
goto bad_area_nosemaphore;
else
return;
}
info.si_code = SEGV_MAPERR;
/*
* If we're in an interrupt or have no user
* context, we must not take the fault..
*/
if (in_atomic() || !mm)
goto no_context;
retry:
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 (expand_stack(vma, address))
goto bad_area;
/*
* Ok, we have a good vm_area for this memory access, so
* we can handle it..
*/
good_area:
info.si_code = SEGV_ACCERR;
/* Handle protection violation, execute on heap or stack */
if (cause_code == ((ECR_V_PROTV << 16) | ECR_C_PROTV_INST_FETCH))
goto bad_area;
if (write) {
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
} else {
if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
goto bad_area;
}
survive:
/*
* 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(mm, vma, address, flags);
/* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
if (unlikely(fatal_signal_pending(current))) {
if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
up_read(&mm->mmap_sem);
if (user_mode(regs))
return;
}
if (likely(!(fault & VM_FAULT_ERROR))) {
if (flags & FAULT_FLAG_ALLOW_RETRY) {
/* To avoid updating stats twice for retry case */
if (fault & VM_FAULT_MAJOR)
tsk->maj_flt++;
else
tsk->min_flt++;
if (fault & VM_FAULT_RETRY) {
flags &= ~FAULT_FLAG_ALLOW_RETRY;
flags |= FAULT_FLAG_TRIED;
goto retry;
}
}
/* Fault Handled Gracefully */
up_read(&mm->mmap_sem);
return;
}
/* TBD: switch to pagefault_out_of_memory() */
if (fault & VM_FAULT_OOM)
goto out_of_memory;
else if (fault & VM_FAULT_SIGBUS)
goto do_sigbus;
/* no man's land */
BUG();
/*
* Something tried to access memory that isn't in our memory map..
* Fix it, but check if it's kernel or user first..
*/
bad_area:
up_read(&mm->mmap_sem);
bad_area_nosemaphore:
/* User mode accesses just cause a SIGSEGV */
if (user_mode(regs)) {
tsk->thread.fault_address = address;
tsk->thread.cause_code = cause_code;
info.si_signo = SIGSEGV;
info.si_errno = 0;
/* info.si_code has been set above */
info.si_addr = (void __user *)address;
force_sig_info(SIGSEGV, &info, tsk);
return;
}
no_context:
/* Are we prepared to handle this kernel fault?
*
* (The kernel has valid exception-points in the source
* when it acesses user-memory. When it fails in one
* of those points, we find it in a table and do a jump
* to some fixup code that loads an appropriate error
* code)
*/
if (fixup_exception(regs))
return;
die("Oops", regs, address, cause_code);
out_of_memory:
if (is_global_init(tsk)) {
yield();
goto survive;
}
up_read(&mm->mmap_sem);
if (user_mode(regs))
do_group_exit(SIGKILL); /* This will never return */
goto no_context;
do_sigbus:
up_read(&mm->mmap_sem);
if (!user_mode(regs))
goto no_context;
tsk->thread.fault_address = address;
tsk->thread.cause_code = cause_code;
info.si_signo = SIGBUS;
info.si_errno = 0;
info.si_code = BUS_ADRERR;
info.si_addr = (void __user *)address;
force_sig_info(SIGBUS, &info, tsk);
}