davidlt/kernel-ark
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
61f77eda9b
kernel-ark/arch/sparc/mm/fault_32.c
Linus Torvalds 33692f2759 vm: add VM_FAULT_SIGSEGV handling support 
The core VM already knows about VM_FAULT_SIGBUS, but cannot return a
"you should SIGSEGV" error, because the SIGSEGV case was generally
handled by the caller - usually the architecture fault handler.

That results in lots of duplication - all the architecture fault
handlers end up doing very similar "look up vma, check permissions, do
retries etc" - but it generally works.  However, there are cases where
the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV.

In particular, when accessing the stack guard page, libsigsegv expects a
SIGSEGV.  And it usually got one, because the stack growth is handled by
that duplicated architecture fault handler.

However, when the generic VM layer started propagating the error return
from the stack expansion in commit fee7e49d45 ("mm: propagate error
from stack expansion even for guard page"), that now exposed the
existing VM_FAULT_SIGBUS result to user space.  And user space really
expected SIGSEGV, not SIGBUS.

To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those
duplicate architecture fault handlers about it.  They all already have
the code to handle SIGSEGV, so it's about just tying that new return
value to the existing code, but it's all a bit annoying.

This is the mindless minimal patch to do this.  A more extensive patch
would be to try to gather up the mostly shared fault handling logic into
one generic helper routine, and long-term we really should do that
cleanup.

Just from this patch, you can generally see that most architectures just
copied (directly or indirectly) the old x86 way of doing things, but in
the meantime that original x86 model has been improved to hold the VM
semaphore for shorter times etc and to handle VM_FAULT_RETRY and other
"newer" things, so it would be a good idea to bring all those
improvements to the generic case and teach other architectures about
them too.

Reported-and-tested-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Jan Engelhardt <jengelh@inai.de>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com> # "s390 still compiles and boots"
Cc: linux-arch@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-01-29 10:51:32 -08:00

469 lines
11 KiB
C
Raw Blame History

/*
* fault.c: Page fault handlers for the Sparc.
*
* Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
* Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
* Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
*/
#include <asm/head.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/threads.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/perf_event.h>
#include <linux/interrupt.h>
#include <linux/kdebug.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/openprom.h>
#include <asm/oplib.h>
#include <asm/setup.h>
#include <asm/smp.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
#include "mm_32.h"
int show_unhandled_signals = 1;
static void __noreturn unhandled_fault(unsigned long address,
struct task_struct *tsk,
struct pt_regs *regs)
{
if ((unsigned long) address < PAGE_SIZE) {
printk(KERN_ALERT
"Unable to handle kernel NULL pointer dereference\n");
} else {
printk(KERN_ALERT "Unable to handle kernel paging request at virtual address %08lx\n",
address);
}
printk(KERN_ALERT "tsk->{mm,active_mm}->context = %08lx\n",
(tsk->mm ? tsk->mm->context : tsk->active_mm->context));
printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %08lx\n",
(tsk->mm ? (unsigned long) tsk->mm->pgd :
(unsigned long) tsk->active_mm->pgd));
die_if_kernel("Oops", regs);
}
asmlinkage int lookup_fault(unsigned long pc, unsigned long ret_pc,
unsigned long address)
{
struct pt_regs regs;
unsigned long g2;
unsigned int insn;
int i;
i = search_extables_range(ret_pc, &g2);
switch (i) {
case 3:
/* load & store will be handled by fixup */
return 3;
case 1:
/* store will be handled by fixup, load will bump out */
/* for _to_ macros */
insn = *((unsigned int *) pc);
if ((insn >> 21) & 1)
return 1;
break;
case 2:
/* load will be handled by fixup, store will bump out */
/* for _from_ macros */
insn = *((unsigned int *) pc);
if (!((insn >> 21) & 1) || ((insn>>19)&0x3f) == 15)
return 2;
break;
default:
break;
}
memset(&regs, 0, sizeof(regs));
regs.pc = pc;
regs.npc = pc + 4;
__asm__ __volatile__(
"rd %%psr, %0\n\t"
"nop\n\t"
"nop\n\t"
"nop\n" : "=r" (regs.psr));
unhandled_fault(address, current, &regs);
/* Not reached */
return 0;
}
static inline void
show_signal_msg(struct pt_regs *regs, int sig, int code,
unsigned long address, struct task_struct *tsk)
{
if (!unhandled_signal(tsk, sig))
return;
if (!printk_ratelimit())
return;
printk("%s%s[%d]: segfault at %lx ip %p (rpc %p) sp %p error %x",
task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
tsk->comm, task_pid_nr(tsk), address,
(void *)regs->pc, (void *)regs->u_regs[UREG_I7],
(void *)regs->u_regs[UREG_FP], code);
print_vma_addr(KERN_CONT " in ", regs->pc);
printk(KERN_CONT "\n");
}
static void __do_fault_siginfo(int code, int sig, struct pt_regs *regs,
unsigned long addr)
{
siginfo_t info;
info.si_signo = sig;
info.si_code = code;
info.si_errno = 0;
info.si_addr = (void __user *) addr;
info.si_trapno = 0;
if (unlikely(show_unhandled_signals))
show_signal_msg(regs, sig, info.si_code,
addr, current);
force_sig_info (sig, &info, current);
}
static unsigned long compute_si_addr(struct pt_regs *regs, int text_fault)
{
unsigned int insn;
if (text_fault)
return regs->pc;
if (regs->psr & PSR_PS)
insn = *(unsigned int *) regs->pc;
else
__get_user(insn, (unsigned int *) regs->pc);
return safe_compute_effective_address(regs, insn);
}
static noinline void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
int text_fault)
{
unsigned long addr = compute_si_addr(regs, text_fault);
__do_fault_siginfo(code, sig, regs, addr);
}
asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
unsigned long address)
{
struct vm_area_struct *vma;
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;
unsigned int fixup;
unsigned long g2;
int from_user = !(regs->psr & PSR_PS);
int fault, code;
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
if (text_fault)
address = regs->pc;
/*
* 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.
*/
code = SEGV_MAPERR;
if (address >= TASK_SIZE)
goto vmalloc_fault;
/*
* If we're in an interrupt or have no user
* context, we must not take the fault..
*/
if (in_atomic() || !mm)
goto no_context;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
retry:
down_read(&mm->mmap_sem);
if (!from_user && address >= PAGE_OFFSET)
goto bad_area;
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:
code = SEGV_ACCERR;
if (write) {
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
} else {
/* Allow reads even for write-only mappings */
if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
goto bad_area;
}
if (from_user)
flags |= FAULT_FLAG_USER;
if (write)
flags |= FAULT_FLAG_WRITE;
/*
* 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 ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
return;
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM)
goto out_of_memory;
else if (fault & VM_FAULT_SIGSEGV)
goto bad_area;
else if (fault & VM_FAULT_SIGBUS)
goto do_sigbus;
BUG();
}
if (flags & FAULT_FLAG_ALLOW_RETRY) {
if (fault & VM_FAULT_MAJOR) {
current->maj_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
1, regs, address);
} else {
current->min_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
1, regs, address);
}
if (fault & VM_FAULT_RETRY) {
flags &= ~FAULT_FLAG_ALLOW_RETRY;
flags |= FAULT_FLAG_TRIED;
/* No need to up_read(&mm->mmap_sem) as we would
* have already released it in __lock_page_or_retry
* in mm/filemap.c.
*/
goto retry;
}
}
up_read(&mm->mmap_sem);
return;
/*
* 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 (from_user) {
do_fault_siginfo(code, SIGSEGV, regs, text_fault);
return;
}
/* Is this in ex_table? */
no_context:
g2 = regs->u_regs[UREG_G2];
if (!from_user) {
fixup = search_extables_range(regs->pc, &g2);
/* Values below 10 are reserved for other things */
if (fixup > 10) {
extern const unsigned __memset_start[];
extern const unsigned __memset_end[];
extern const unsigned __csum_partial_copy_start[];
extern const unsigned __csum_partial_copy_end[];
#ifdef DEBUG_EXCEPTIONS
printk("Exception: PC<%08lx> faddr<%08lx>\n",
regs->pc, address);
printk("EX_TABLE: insn<%08lx> fixup<%08x> g2<%08lx>\n",
regs->pc, fixup, g2);
#endif
if ((regs->pc >= (unsigned long)__memset_start &&
regs->pc < (unsigned long)__memset_end) ||
(regs->pc >= (unsigned long)__csum_partial_copy_start &&
regs->pc < (unsigned long)__csum_partial_copy_end)) {
regs->u_regs[UREG_I4] = address;
regs->u_regs[UREG_I5] = regs->pc;
}
regs->u_regs[UREG_G2] = g2;
regs->pc = fixup;
regs->npc = regs->pc + 4;
return;
}
}
unhandled_fault(address, tsk, regs);
do_exit(SIGKILL);
/*
* 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 (from_user) {
pagefault_out_of_memory();
return;
}
goto no_context;
do_sigbus:
up_read(&mm->mmap_sem);
do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, text_fault);
if (!from_user)
goto no_context;
vmalloc_fault:
{
/*
* Synchronize this task's top level page-table
* with the 'reference' page table.
*/
int offset = pgd_index(address);
pgd_t *pgd, *pgd_k;
pmd_t *pmd, *pmd_k;
pgd = tsk->active_mm->pgd + offset;
pgd_k = init_mm.pgd + offset;
if (!pgd_present(*pgd)) {
if (!pgd_present(*pgd_k))
goto bad_area_nosemaphore;
pgd_val(*pgd) = pgd_val(*pgd_k);
return;
}
pmd = pmd_offset(pgd, address);
pmd_k = pmd_offset(pgd_k, address);
if (pmd_present(*pmd) || !pmd_present(*pmd_k))
goto bad_area_nosemaphore;
*pmd = *pmd_k;
return;
}
}
/* This always deals with user addresses. */
static void force_user_fault(unsigned long address, int write)
{
struct vm_area_struct *vma;
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;
unsigned int flags = FAULT_FLAG_USER;
int code;
code = SEGV_MAPERR;
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;
good_area:
code = SEGV_ACCERR;
if (write) {
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
flags |= FAULT_FLAG_WRITE;
} else {
if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
goto bad_area;
}
switch (handle_mm_fault(mm, vma, address, flags)) {
case VM_FAULT_SIGBUS:
case VM_FAULT_OOM:
goto do_sigbus;
}
up_read(&mm->mmap_sem);
return;
bad_area:
up_read(&mm->mmap_sem);
__do_fault_siginfo(code, SIGSEGV, tsk->thread.kregs, address);
return;
do_sigbus:
up_read(&mm->mmap_sem);
__do_fault_siginfo(BUS_ADRERR, SIGBUS, tsk->thread.kregs, address);
}
static void check_stack_aligned(unsigned long sp)
{
if (sp & 0x7UL)
force_sig(SIGILL, current);
}
void window_overflow_fault(void)
{
unsigned long sp;
sp = current_thread_info()->rwbuf_stkptrs[0];
if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
force_user_fault(sp + 0x38, 1);
force_user_fault(sp, 1);
check_stack_aligned(sp);
}
void window_underflow_fault(unsigned long sp)
{
if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
force_user_fault(sp + 0x38, 0);
force_user_fault(sp, 0);
check_stack_aligned(sp);
}
void window_ret_fault(struct pt_regs *regs)
{
unsigned long sp;
sp = regs->u_regs[UREG_FP];
if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
force_user_fault(sp + 0x38, 0);
force_user_fault(sp, 0);
check_stack_aligned(sp);
}
Reference in New Issue View Git Blame Copy Permalink