#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
-#include <asm/hardirq.h>
#include <asm/smp.h>
#include <asm/tlbflush.h>
#include <asm/proto.h>
/* Sometimes the CPU reports invalid exceptions on prefetch.
Check that here and ignore.
Opcode checker based on code by Richard Brunner */
-static int is_prefetch(struct pt_regs *regs, unsigned long addr)
+static noinline int is_prefetch(struct pt_regs *regs, unsigned long addr,
+ unsigned long error_code)
{
unsigned char *instr = (unsigned char *)(regs->rip);
int scan_more = 1;
int prefetch = 0;
unsigned char *max_instr = instr + 15;
- /* Avoid recursive faults for this common case */
- if (regs->rip == addr)
- return 0;
+ /* If it was a exec fault ignore */
+ if (error_code & (1<<4))
+ return 0;
/* Code segments in LDT could have a non zero base. Don't check
when that's possible */
(tsk->sighand->action[sig-1].sa.sa_handler == SIG_DFL);
}
+static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs,
+ unsigned long error_code)
+{
+ oops_begin();
+ printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
+ current->comm, address);
+ dump_pagetable(address);
+ __die("Bad pagetable", regs, error_code);
+ oops_end();
+ do_exit(SIGKILL);
+}
+
int page_fault_trace;
int exception_trace = 1;
mm = tsk->mm;
info.si_code = SEGV_MAPERR;
- /* 5 => page not present and from supervisor mode */
- if (unlikely(!(error_code & 5) &&
- ((address >= VMALLOC_START && address <= VMALLOC_END) ||
- (address >= MODULES_VADDR && address <= MODULES_END))))
- goto vmalloc_fault;
+
+ /*
+ * 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.
+ *
+ * This verifies that the fault happens in kernel space
+ * (error_code & 4) == 0, and that the fault was not a
+ * protection error (error_code & 1) == 0.
+ */
+ if (unlikely(address >= TASK_SIZE)) {
+ if (!(error_code & 5))
+ goto vmalloc_fault;
+ /*
+ * Don't take the mm semaphore here. If we fixup a prefetch
+ * fault we could otherwise deadlock.
+ */
+ goto bad_area_nosemaphore;
+ }
+
+ if (unlikely(error_code & (1 << 3)))
+ goto page_table_corruption;
/*
* If we're in an interrupt or have no user
goto bad_area_nosemaphore;
again:
- down_read(&mm->mmap_sem);
+ /* 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. Unfortunatly, in the case of an
+ * erroneous fault occuring 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 possibilty 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 (!down_read_trylock(&mm->mmap_sem)) {
+ if ((error_code & 4) == 0 &&
+ !search_exception_tables(regs->rip))
+ goto bad_area_nosemaphore;
+ down_read(&mm->mmap_sem);
+ }
vma = find_vma(mm, address);
if (!vma)
bad_area_nosemaphore:
#ifdef CONFIG_IA32_EMULATION
- /* 32bit vsyscall. map on demand. */
- if (test_thread_flag(TIF_IA32) &&
+ /* 32bit vsyscall. map on demand. */
+ if (test_thread_flag(TIF_IA32) &&
address >= 0xffffe000 && address < 0xffffe000 + PAGE_SIZE) {
- if (map_syscall32(mm, address) < 0)
- goto out_of_memory2;
- return;
- }
+ if (map_syscall32(mm, address) < 0)
+ goto out_of_memory2;
+ return;
+ }
#endif
/* User mode accesses just cause a SIGSEGV */
if (error_code & 4) {
- if (is_prefetch(regs, address))
+ if (is_prefetch(regs, address, error_code))
return;
/* Work around K8 erratum #100 K8 in compat mode
return;
if (exception_trace && unhandled_signal(tsk, SIGSEGV)) {
- printk(KERN_INFO
+ printk(KERN_INFO
"%s[%d]: segfault at %016lx rip %016lx rsp %016lx error %lx\n",
tsk->comm, tsk->pid, address, regs->rip,
regs->rsp, error_code);
* Hall of shame of CPU/BIOS bugs.
*/
- if (is_prefetch(regs, address))
+ if (is_prefetch(regs, address, error_code))
return;
if (is_errata93(regs, address))
* is really there and when yes flush the local TLB.
*/
pgd = pgd_offset_k(address);
- if (pgd != current_pgd_offset_k(address))
- BUG();
if (!pgd_present(*pgd))
- goto bad_area_nosemaphore;
+ goto bad_area_nosemaphore;
pmd = pmd_offset(pgd, address);
if (!pmd_present(*pmd))
goto bad_area_nosemaphore;
__flush_tlb_all();
return;
}
+
+page_table_corruption:
+ pgtable_bad(address, regs, error_code);
}
git://git.onelab.eu / linux-2.6.git / blobdiff