x86, mm: fault.c cleanup
Impact: cleanup, no code changed
Clean up various small details, which can be correctness checked
automatically:
- tidy up the include file section
- eliminate unnecessary includes
- introduce show_signal_msg() to clean up code flow
- standardize the code flow
- standardize comments and other style details
- more cleanups, pointed out by checkpatch
No code changed on either 32-bit nor 64-bit:
arch/x86/mm/fault.o:
text data bss dec hex filename
4632 32 24 4688 1250 fault.o.before
4632 32 24 4688 1250 fault.o.after
the md5 changed due to a change in a single instruction:
2e8a8241e7f0d69706776a5a26c90bc0 fault.o.before.asm
c5c3d36e725586eb74f0e10692f0193e fault.o.after.asm
Because a __LINE__ reference in a WARN_ONCE() has changed.
On 32-bit a few stack offsets changed - no code size difference
nor any functionality difference.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e4b9fc5..351d679 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1,56 +1,59 @@
/*
* Copyright (C) 1995 Linus Torvalds
- * Copyright (C) 2001,2002 Andi Kleen, SuSE Labs.
+ * Copyright (C) 2001, 2002 Andi Kleen, SuSE Labs.
*/
-
-#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/mmiotrace.h>
-#include <linux/mman.h>
-#include <linux/mm.h>
-#include <linux/smp.h>
#include <linux/interrupt.h>
-#include <linux/init.h>
-#include <linux/tty.h>
-#include <linux/vt_kern.h> /* For unblank_screen() */
+#include <linux/mmiotrace.h>
+#include <linux/bootmem.h>
#include <linux/compiler.h>
#include <linux/highmem.h>
-#include <linux/bootmem.h> /* for max_low_pfn */
-#include <linux/vmalloc.h>
-#include <linux/module.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+#include <linux/vt_kern.h>
+#include <linux/signal.h>
+#include <linux/kernel.h>
+#include <linux/ptrace.h>
+#include <linux/string.h>
+#include <linux/module.h>
#include <linux/kdebug.h>
+#include <linux/errno.h>
#include <linux/magic.h>
+#include <linux/sched.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/mman.h>
+#include <linux/tty.h>
+#include <linux/smp.h>
+#include <linux/mm.h>
-#include <asm/system.h>
-#include <asm/desc.h>
-#include <asm/segment.h>
-#include <asm/pgalloc.h>
-#include <asm/smp.h>
-#include <asm/tlbflush.h>
-#include <asm/proto.h>
#include <asm-generic/sections.h>
+
+#include <asm/tlbflush.h>
+#include <asm/pgalloc.h>
+#include <asm/segment.h>
+#include <asm/system.h>
+#include <asm/proto.h>
#include <asm/traps.h>
+#include <asm/desc.h>
/*
- * Page fault error code bits
- * bit 0 == 0 means no page found, 1 means protection fault
- * bit 1 == 0 means read, 1 means write
- * bit 2 == 0 means kernel, 1 means user-mode
- * bit 3 == 1 means use of reserved bit detected
- * bit 4 == 1 means fault was an instruction fetch
+ * Page fault error code bits:
+ *
+ * bit 0 == 0: no page found 1: protection fault
+ * bit 1 == 0: read access 1: write access
+ * bit 2 == 0: kernel-mode access 1: user-mode access
+ * bit 3 == 1: use of reserved bit detected
+ * bit 4 == 1: fault was an instruction fetch
*/
-#define PF_PROT (1<<0)
-#define PF_WRITE (1<<1)
-#define PF_USER (1<<2)
-#define PF_RSVD (1<<3)
-#define PF_INSTR (1<<4)
+enum x86_pf_error_code {
+
+ PF_PROT = 1 << 0,
+ PF_WRITE = 1 << 1,
+ PF_USER = 1 << 2,
+ PF_RSVD = 1 << 3,
+ PF_INSTR = 1 << 4,
+};
static inline int kmmio_fault(struct pt_regs *regs, unsigned long addr)
{
@@ -82,23 +85,27 @@
}
/*
- * X86_32
- * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
- * Check that here and ignore it.
+ * Prefetch quirks:
*
- * X86_64
- * Sometimes the CPU reports invalid exceptions on prefetch.
- * Check that here and ignore it.
+ * 32-bit mode:
*
- * Opcode checker based on code by Richard Brunner
+ * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
+ * Check that here and ignore it.
+ *
+ * 64-bit mode:
+ *
+ * Sometimes the CPU reports invalid exceptions on prefetch.
+ * Check that here and ignore it.
+ *
+ * Opcode checker based on code by Richard Brunner.
*/
-static int is_prefetch(struct pt_regs *regs, unsigned long error_code,
- unsigned long addr)
+static int
+is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
{
+ unsigned char *max_instr;
unsigned char *instr;
int scan_more = 1;
int prefetch = 0;
- unsigned char *max_instr;
/*
* If it was a exec (instruction fetch) fault on NX page, then
@@ -114,9 +121,9 @@
return 0;
while (scan_more && instr < max_instr) {
- unsigned char opcode;
unsigned char instr_hi;
unsigned char instr_lo;
+ unsigned char opcode;
if (probe_kernel_address(instr, opcode))
break;
@@ -173,15 +180,17 @@
return prefetch;
}
-static void force_sig_info_fault(int si_signo, int si_code,
- unsigned long address, struct task_struct *tsk)
+static void
+force_sig_info_fault(int si_signo, int si_code, unsigned long address,
+ struct task_struct *tsk)
{
siginfo_t info;
- info.si_signo = si_signo;
- info.si_errno = 0;
- info.si_code = si_code;
- info.si_addr = (void __user *)address;
+ info.si_signo = si_signo;
+ info.si_errno = 0;
+ info.si_code = si_code;
+ info.si_addr = (void __user *)address;
+
force_sig_info(si_signo, &info, tsk);
}
@@ -189,6 +198,7 @@
static int bad_address(void *p)
{
unsigned long dummy;
+
return probe_kernel_address((unsigned long *)p, dummy);
}
#endif
@@ -200,13 +210,14 @@
page = read_cr3();
page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
+
#ifdef CONFIG_X86_PAE
printk("*pdpt = %016Lx ", page);
if ((page >> PAGE_SHIFT) < max_low_pfn
&& page & _PAGE_PRESENT) {
page &= PAGE_MASK;
page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT)
- & (PTRS_PER_PMD - 1)];
+ & (PTRS_PER_PMD - 1)];
printk(KERN_CONT "*pde = %016Lx ", page);
page &= ~_PAGE_NX;
}
@@ -218,14 +229,15 @@
* We must not directly access the pte in the highpte
* case if the page table is located in highmem.
* And let's rather not kmap-atomic the pte, just in case
- * it's allocated already.
+ * it's allocated already:
*/
if ((page >> PAGE_SHIFT) < max_low_pfn
&& (page & _PAGE_PRESENT)
&& !(page & _PAGE_PSE)) {
+
page &= PAGE_MASK;
page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
- & (PTRS_PER_PTE - 1)];
+ & (PTRS_PER_PTE - 1)];
printk("*pte = %0*Lx ", sizeof(page)*2, (u64)page);
}
@@ -239,26 +251,38 @@
pgd = (pgd_t *)read_cr3();
pgd = __va((unsigned long)pgd & PHYSICAL_PAGE_MASK);
+
pgd += pgd_index(address);
- if (bad_address(pgd)) goto bad;
+ if (bad_address(pgd))
+ goto bad;
+
printk("PGD %lx ", pgd_val(*pgd));
- if (!pgd_present(*pgd)) goto ret;
+
+ if (!pgd_present(*pgd))
+ goto out;
pud = pud_offset(pgd, address);
- if (bad_address(pud)) goto bad;
+ if (bad_address(pud))
+ goto bad;
+
printk("PUD %lx ", pud_val(*pud));
if (!pud_present(*pud) || pud_large(*pud))
- goto ret;
+ goto out;
pmd = pmd_offset(pud, address);
- if (bad_address(pmd)) goto bad;
+ if (bad_address(pmd))
+ goto bad;
+
printk("PMD %lx ", pmd_val(*pmd));
- if (!pmd_present(*pmd) || pmd_large(*pmd)) goto ret;
+ if (!pmd_present(*pmd) || pmd_large(*pmd))
+ goto out;
pte = pte_offset_kernel(pmd, address);
- if (bad_address(pte)) goto bad;
+ if (bad_address(pte))
+ goto bad;
+
printk("PTE %lx", pte_val(*pte));
-ret:
+out:
printk("\n");
return;
bad:
@@ -285,7 +309,6 @@
* and redundant with the set_pmd() on non-PAE. As would
* set_pud.
*/
-
pud = pud_offset(pgd, address);
pud_k = pud_offset(pgd_k, address);
if (!pud_present(*pud_k))
@@ -295,11 +318,14 @@
pmd_k = pmd_offset(pud_k, address);
if (!pmd_present(*pmd_k))
return NULL;
+
if (!pmd_present(*pmd)) {
set_pmd(pmd, *pmd_k);
arch_flush_lazy_mmu_mode();
- } else
+ } else {
BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
+ }
+
return pmd_k;
}
#endif
@@ -312,29 +338,37 @@
KERN_ERR "******* Disabling USB legacy in the BIOS may also help.\n";
#endif
-/* Workaround for K8 erratum #93 & buggy BIOS.
- BIOS SMM functions are required to use a specific workaround
- to avoid corruption of the 64bit RIP register on C stepping K8.
- A lot of BIOS that didn't get tested properly miss this.
- The OS sees this as a page fault with the upper 32bits of RIP cleared.
- Try to work around it here.
- Note we only handle faults in kernel here.
- Does nothing for X86_32
+/*
+ * Workaround for K8 erratum #93 & buggy BIOS.
+ *
+ * BIOS SMM functions are required to use a specific workaround
+ * to avoid corruption of the 64bit RIP register on C stepping K8.
+ *
+ * A lot of BIOS that didn't get tested properly miss this.
+ *
+ * The OS sees this as a page fault with the upper 32bits of RIP cleared.
+ * Try to work around it here.
+ *
+ * Note we only handle faults in kernel here.
+ * Does nothing on 32-bit.
*/
static int is_errata93(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_64
- static int warned;
+ static int once;
+
if (address != regs->ip)
return 0;
+
if ((address >> 32) != 0)
return 0;
+
address |= 0xffffffffUL << 32;
if ((address >= (u64)_stext && address <= (u64)_etext) ||
(address >= MODULES_VADDR && address <= MODULES_END)) {
- if (!warned) {
+ if (!once) {
printk(errata93_warning);
- warned = 1;
+ once = 1;
}
regs->ip = address;
return 1;
@@ -344,16 +378,17 @@
}
/*
- * Work around K8 erratum #100 K8 in compat mode occasionally jumps to illegal
- * addresses >4GB. We catch this in the page fault handler because these
- * addresses are not reachable. Just detect this case and return. Any code
+ * Work around K8 erratum #100 K8 in compat mode occasionally jumps
+ * to illegal addresses >4GB.
+ *
+ * We catch this in the page fault handler because these addresses
+ * are not reachable. Just detect this case and return. Any code
* segment in LDT is compatibility mode.
*/
static int is_errata100(struct pt_regs *regs, unsigned long address)
{
#ifdef CONFIG_X86_64
- if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) &&
- (address >> 32))
+ if ((regs->cs == __USER32_CS || (regs->cs & (1<<2))) && (address >> 32))
return 1;
#endif
return 0;
@@ -363,8 +398,9 @@
{
#ifdef CONFIG_X86_F00F_BUG
unsigned long nr;
+
/*
- * Pentium F0 0F C7 C8 bug workaround.
+ * Pentium F0 0F C7 C8 bug workaround:
*/
if (boot_cpu_data.f00f_bug) {
nr = (address - idt_descr.address) >> 3;
@@ -378,8 +414,9 @@
return 0;
}
-static void show_fault_oops(struct pt_regs *regs, unsigned long error_code,
- unsigned long address)
+static void
+show_fault_oops(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
{
#ifdef CONFIG_X86_32
if (!oops_may_print())
@@ -389,12 +426,14 @@
#ifdef CONFIG_X86_PAE
if (error_code & PF_INSTR) {
unsigned int level;
+
pte_t *pte = lookup_address(address, &level);
- if (pte && pte_present(*pte) && !pte_exec(*pte))
+ if (pte && pte_present(*pte) && !pte_exec(*pte)) {
printk(KERN_CRIT "kernel tried to execute "
"NX-protected page - exploit attempt? "
"(uid: %d)\n", current_uid());
+ }
}
#endif
@@ -403,34 +442,45 @@
printk(KERN_CONT "NULL pointer dereference");
else
printk(KERN_CONT "paging request");
+
printk(KERN_CONT " at %p\n", (void *) address);
printk(KERN_ALERT "IP:");
printk_address(regs->ip, 1);
+
dump_pagetable(address);
}
#ifdef CONFIG_X86_64
-static noinline void pgtable_bad(struct pt_regs *regs,
- unsigned long error_code, unsigned long address)
+static noinline void
+pgtable_bad(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
{
- unsigned long flags = oops_begin();
- int sig = SIGKILL;
- struct task_struct *tsk = current;
+ struct task_struct *tsk;
+ unsigned long flags;
+ int sig;
+
+ flags = oops_begin();
+ tsk = current;
+ sig = SIGKILL;
printk(KERN_ALERT "%s: Corrupted page table at address %lx\n",
tsk->comm, address);
dump_pagetable(address);
- tsk->thread.cr2 = address;
- tsk->thread.trap_no = 14;
- tsk->thread.error_code = error_code;
+
+ tsk->thread.cr2 = address;
+ tsk->thread.trap_no = 14;
+ tsk->thread.error_code = error_code;
+
if (__die("Bad pagetable", regs, error_code))
sig = 0;
+
oops_end(flags, regs, sig);
}
#endif
-static noinline void no_context(struct pt_regs *regs,
- unsigned long error_code, unsigned long address)
+static noinline void
+no_context(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
{
struct task_struct *tsk = current;
unsigned long *stackend;
@@ -440,18 +490,20 @@
int sig;
#endif
- /* Are we prepared to handle this kernel fault? */
+ /* Are we prepared to handle this kernel fault? */
if (fixup_exception(regs))
return;
/*
- * X86_32
- * Valid to do another page fault here, because if this fault
- * had been triggered by is_prefetch fixup_exception would have
- * handled it.
+ * 32-bit:
*
- * X86_64
- * Hall of shame of CPU/BIOS bugs.
+ * Valid to do another page fault here, because if this fault
+ * had been triggered by is_prefetch fixup_exception would have
+ * handled it.
+ *
+ * 64-bit:
+ *
+ * Hall of shame of CPU/BIOS bugs.
*/
if (is_prefetch(regs, error_code, address))
return;
@@ -461,7 +513,7 @@
/*
* Oops. The kernel tried to access some bad page. We'll have to
- * terminate things with extreme prejudice.
+ * terminate things with extreme prejudice:
*/
#ifdef CONFIG_X86_32
bust_spinlocks(1);
@@ -471,7 +523,7 @@
show_fault_oops(regs, error_code, address);
- stackend = end_of_stack(tsk);
+ stackend = end_of_stack(tsk);
if (*stackend != STACK_END_MAGIC)
printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
@@ -487,28 +539,54 @@
sig = SIGKILL;
if (__die("Oops", regs, error_code))
sig = 0;
+
/* Executive summary in case the body of the oops scrolled away */
printk(KERN_EMERG "CR2: %016lx\n", address);
+
oops_end(flags, regs, sig);
#endif
}
-static void __bad_area_nosemaphore(struct pt_regs *regs,
- unsigned long error_code, unsigned long address,
- int si_code)
+/*
+ * Print out info about fatal segfaults, if the show_unhandled_signals
+ * sysctl is set:
+ */
+static inline void
+show_signal_msg(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, struct task_struct *tsk)
+{
+ if (!unhandled_signal(tsk, SIGSEGV))
+ return;
+
+ if (!printk_ratelimit())
+ return;
+
+ printk(KERN_CONT "%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
+ task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
+ tsk->comm, task_pid_nr(tsk), address,
+ (void *)regs->ip, (void *)regs->sp, error_code);
+
+ print_vma_addr(KERN_CONT " in ", regs->ip);
+
+ printk(KERN_CONT "\n");
+}
+
+static void
+__bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, int si_code)
{
struct task_struct *tsk = current;
/* User mode accesses just cause a SIGSEGV */
if (error_code & PF_USER) {
/*
- * It's possible to have interrupts off here.
+ * It's possible to have interrupts off here:
*/
local_irq_enable();
/*
* Valid to do another page fault here because this one came
- * from user space.
+ * from user space:
*/
if (is_prefetch(regs, error_code, address))
return;
@@ -516,22 +594,16 @@
if (is_errata100(regs, address))
return;
- if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
- printk_ratelimit()) {
- printk(
- "%s%s[%d]: segfault at %lx ip %p sp %p error %lx",
- task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
- tsk->comm, task_pid_nr(tsk), address,
- (void *) regs->ip, (void *) regs->sp, error_code);
- print_vma_addr(" in ", regs->ip);
- printk("\n");
- }
+ if (unlikely(show_unhandled_signals))
+ show_signal_msg(regs, error_code, address, tsk);
- tsk->thread.cr2 = address;
- /* Kernel addresses are always protection faults */
- tsk->thread.error_code = error_code | (address >= TASK_SIZE);
- tsk->thread.trap_no = 14;
+ /* Kernel addresses are always protection faults: */
+ tsk->thread.cr2 = address;
+ tsk->thread.error_code = error_code | (address >= TASK_SIZE);
+ tsk->thread.trap_no = 14;
+
force_sig_info_fault(SIGSEGV, si_code, address, tsk);
+
return;
}
@@ -541,15 +613,16 @@
no_context(regs, error_code, address);
}
-static noinline void bad_area_nosemaphore(struct pt_regs *regs,
- unsigned long error_code, unsigned long address)
+static noinline void
+bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
{
__bad_area_nosemaphore(regs, error_code, address, SEGV_MAPERR);
}
-static void __bad_area(struct pt_regs *regs,
- unsigned long error_code, unsigned long address,
- int si_code)
+static void
+__bad_area(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, int si_code)
{
struct mm_struct *mm = current->mm;
@@ -562,67 +635,77 @@
__bad_area_nosemaphore(regs, error_code, address, si_code);
}
-static noinline void bad_area(struct pt_regs *regs,
- unsigned long error_code, unsigned long address)
+static noinline void
+bad_area(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
__bad_area(regs, error_code, address, SEGV_MAPERR);
}
-static noinline void bad_area_access_error(struct pt_regs *regs,
- unsigned long error_code, unsigned long address)
+static noinline void
+bad_area_access_error(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
{
__bad_area(regs, error_code, address, SEGV_ACCERR);
}
/* TODO: fixup for "mm-invoke-oom-killer-from-page-fault.patch" */
-static void out_of_memory(struct pt_regs *regs,
- unsigned long error_code, unsigned long address)
+static void
+out_of_memory(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address)
{
/*
* We ran out of memory, call the OOM killer, and return the userspace
- * (which will retry the fault, or kill us if we got oom-killed).
+ * (which will retry the fault, or kill us if we got oom-killed):
*/
up_read(¤t->mm->mmap_sem);
+
pagefault_out_of_memory();
}
-static void do_sigbus(struct pt_regs *regs,
- unsigned long error_code, unsigned long address)
+static void
+do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;
up_read(&mm->mmap_sem);
- /* Kernel mode? Handle exceptions or die */
+ /* Kernel mode? Handle exceptions or die: */
if (!(error_code & PF_USER))
no_context(regs, error_code, address);
+
#ifdef CONFIG_X86_32
- /* User space => ok to do another page fault */
+ /* User space => ok to do another page fault: */
if (is_prefetch(regs, error_code, address))
return;
#endif
- tsk->thread.cr2 = address;
- tsk->thread.error_code = error_code;
- tsk->thread.trap_no = 14;
+
+ tsk->thread.cr2 = address;
+ tsk->thread.error_code = error_code;
+ tsk->thread.trap_no = 14;
+
force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
}
-static noinline void mm_fault_error(struct pt_regs *regs,
- unsigned long error_code, unsigned long address, unsigned int fault)
+static noinline void
+mm_fault_error(struct pt_regs *regs, unsigned long error_code,
+ unsigned long address, unsigned int fault)
{
- if (fault & VM_FAULT_OOM)
+ if (fault & VM_FAULT_OOM) {
out_of_memory(regs, error_code, address);
- else if (fault & VM_FAULT_SIGBUS)
- do_sigbus(regs, error_code, address);
- else
- BUG();
+ } else {
+ if (fault & VM_FAULT_SIGBUS)
+ do_sigbus(regs, error_code, address);
+ else
+ BUG();
+ }
}
static int spurious_fault_check(unsigned long error_code, pte_t *pte)
{
if ((error_code & PF_WRITE) && !pte_write(*pte))
return 0;
+
if ((error_code & PF_INSTR) && !pte_exec(*pte))
return 0;
@@ -630,16 +713,19 @@
}
/*
- * Handle a spurious fault caused by a stale TLB entry. This allows
- * us to lazily refresh the TLB when increasing the permissions of a
- * kernel page (RO -> RW or NX -> X). Doing it eagerly is very
- * expensive since that implies doing a full cross-processor TLB
- * flush, even if no stale TLB entries exist on other processors.
+ * Handle a spurious fault caused by a stale TLB entry.
+ *
+ * This allows us to lazily refresh the TLB when increasing the
+ * permissions of a kernel page (RO -> RW or NX -> X). Doing it
+ * eagerly is very expensive since that implies doing a full
+ * cross-processor TLB flush, even if no stale TLB entries exist
+ * on other processors.
+ *
* There are no security implications to leaving a stale TLB when
* increasing the permissions on a page.
*/
-static noinline int spurious_fault(unsigned long error_code,
- unsigned long address)
+static noinline int
+spurious_fault(unsigned long error_code, unsigned long address)
{
pgd_t *pgd;
pud_t *pud;
@@ -678,20 +764,23 @@
return 0;
/*
- * Make sure we have permissions in PMD
- * If not, then there's a bug in the page tables.
+ * Make sure we have permissions in PMD.
+ * If not, then there's a bug in the page tables:
*/
ret = spurious_fault_check(error_code, (pte_t *) pmd);
WARN_ONCE(!ret, "PMD has incorrect permission bits\n");
+
return ret;
}
/*
- * X86_32
- * Handle a fault on the vmalloc or module mapping area
+ * 32-bit:
*
- * X86_64
- * Handle a fault on the vmalloc area
+ * Handle a fault on the vmalloc or module mapping area
+ *
+ * 64-bit:
+ *
+ * Handle a fault on the vmalloc area
*
* This assumes no large pages in there.
*/
@@ -702,7 +791,7 @@
pmd_t *pmd_k;
pte_t *pte_k;
- /* Make sure we are in vmalloc area */
+ /* Make sure we are in vmalloc area: */
if (!(address >= VMALLOC_START && address < VMALLOC_END))
return -1;
@@ -717,9 +806,11 @@
pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
if (!pmd_k)
return -1;
+
pte_k = pte_offset_kernel(pmd_k, address);
if (!pte_present(*pte_k))
return -1;
+
return 0;
#else
pgd_t *pgd, *pgd_ref;
@@ -727,69 +818,84 @@
pmd_t *pmd, *pmd_ref;
pte_t *pte, *pte_ref;
- /* Make sure we are in vmalloc area */
+ /* Make sure we are in vmalloc area: */
if (!(address >= VMALLOC_START && address < VMALLOC_END))
return -1;
- /* Copy kernel mappings over when needed. This can also
- happen within a race in page table update. In the later
- case just flush. */
-
+ /*
+ * Copy kernel mappings over when needed. This can also
+ * happen within a race in page table update. In the later
+ * case just flush:
+ */
pgd = pgd_offset(current->active_mm, address);
pgd_ref = pgd_offset_k(address);
if (pgd_none(*pgd_ref))
return -1;
+
if (pgd_none(*pgd))
set_pgd(pgd, *pgd_ref);
else
BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_ref));
- /* Below here mismatches are bugs because these lower tables
- are shared */
+ /*
+ * Below here mismatches are bugs because these lower tables
+ * are shared:
+ */
pud = pud_offset(pgd, address);
pud_ref = pud_offset(pgd_ref, address);
if (pud_none(*pud_ref))
return -1;
+
if (pud_none(*pud) || pud_page_vaddr(*pud) != pud_page_vaddr(*pud_ref))
BUG();
+
pmd = pmd_offset(pud, address);
pmd_ref = pmd_offset(pud_ref, address);
if (pmd_none(*pmd_ref))
return -1;
+
if (pmd_none(*pmd) || pmd_page(*pmd) != pmd_page(*pmd_ref))
BUG();
+
pte_ref = pte_offset_kernel(pmd_ref, address);
if (!pte_present(*pte_ref))
return -1;
+
pte = pte_offset_kernel(pmd, address);
- /* Don't use pte_page here, because the mappings can point
- outside mem_map, and the NUMA hash lookup cannot handle
- that. */
+
+ /*
+ * Don't use pte_page here, because the mappings can point
+ * outside mem_map, and the NUMA hash lookup cannot handle
+ * that:
+ */
if (!pte_present(*pte) || pte_pfn(*pte) != pte_pfn(*pte_ref))
BUG();
+
return 0;
#endif
}
int show_unhandled_signals = 1;
-static inline int access_error(unsigned long error_code, int write,
- struct vm_area_struct *vma)
+static inline int
+access_error(unsigned long error_code, int write, struct vm_area_struct *vma)
{
if (write) {
- /* write, present and write, not present */
+ /* write, present and write, not present: */
if (unlikely(!(vma->vm_flags & VM_WRITE)))
return 1;
- } else if (unlikely(error_code & PF_PROT)) {
- /* read, present */
- return 1;
- } else {
- /* read, not present */
- if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
- return 1;
+ return 0;
}
+ /* read, present: */
+ if (unlikely(error_code & PF_PROT))
+ return 1;
+
+ /* read, not present: */
+ if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
+ return 1;
+
return 0;
}
@@ -797,9 +903,9 @@
{
#ifdef CONFIG_X86_32
return address >= TASK_SIZE;
-#else /* !CONFIG_X86_32 */
+#else
return address >= TASK_SIZE64;
-#endif /* CONFIG_X86_32 */
+#endif
}
/*
@@ -812,18 +918,19 @@
#endif
void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
- unsigned long address;
- struct task_struct *tsk;
- struct mm_struct *mm;
struct vm_area_struct *vma;
+ struct task_struct *tsk;
+ unsigned long address;
+ struct mm_struct *mm;
int write;
int fault;
tsk = current;
mm = tsk->mm;
+
prefetchw(&mm->mmap_sem);
- /* get the address */
+ /* Get the faulting address: */
address = read_cr2();
if (unlikely(kmmio_fault(regs, address)))
@@ -847,22 +954,23 @@
vmalloc_fault(address) >= 0)
return;
- /* Can handle a stale RO->RW TLB */
+ /* Can handle a stale RO->RW TLB: */
if (spurious_fault(error_code, address))
return;
- /* kprobes don't want to hook the spurious faults. */
+ /* kprobes don't want to hook the spurious faults: */
if (notify_page_fault(regs))
return;
/*
* Don't take the mm semaphore here. If we fixup a prefetch
- * fault we could otherwise deadlock.
+ * fault we could otherwise deadlock:
*/
bad_area_nosemaphore(regs, error_code, address);
+
return;
}
- /* kprobes don't want to hook the spurious faults. */
+ /* kprobes don't want to hook the spurious faults: */
if (unlikely(notify_page_fault(regs)))
return;
/*
@@ -870,13 +978,15 @@
* vmalloc fault has been handled.
*
* User-mode registers count as a user access even for any
- * potential system fault or CPU buglet.
+ * potential system fault or CPU buglet:
*/
if (user_mode_vm(regs)) {
local_irq_enable();
error_code |= PF_USER;
- } else if (regs->flags & X86_EFLAGS_IF)
- local_irq_enable();
+ } else {
+ if (regs->flags & X86_EFLAGS_IF)
+ local_irq_enable();
+ }
#ifdef CONFIG_X86_64
if (unlikely(error_code & PF_RSVD))
@@ -884,8 +994,8 @@
#endif
/*
- * If we're in an interrupt, have no user context or are running in an
- * atomic region then we must not take the fault.
+ * If we're in an interrupt, have no user context or are running
+ * in an atomic region then we must not take the fault:
*/
if (unlikely(in_atomic() || !mm)) {
bad_area_nosemaphore(regs, error_code, address);
@@ -894,19 +1004,19 @@
/*
* 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.
+ * 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.
+ * 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))) {
if ((error_code & PF_USER) == 0 &&
@@ -917,8 +1027,9 @@
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().
+ * The above down_read_trylock() might have succeeded in
+ * which case we'll have missed the might_sleep() from
+ * down_read():
*/
might_sleep();
}
@@ -938,7 +1049,7 @@
/*
* Accessing the stack below %sp is always a bug.
* The large cushion allows instructions like enter
- * and pusha to work. ("enter $65535,$31" pushes
+ * and pusha to work. ("enter $65535, $31" pushes
* 32 pointers and then decrements %sp by 65535.)
*/
if (unlikely(address + 65536 + 32 * sizeof(unsigned long) < regs->sp)) {
@@ -957,6 +1068,7 @@
*/
good_area:
write = error_code & PF_WRITE;
+
if (unlikely(access_error(error_code, write, vma))) {
bad_area_access_error(regs, error_code, address);
return;
@@ -965,13 +1077,15 @@
/*
* If for any reason at all we couldn't handle the fault,
* make sure we exit gracefully rather than endlessly redo
- * the fault.
+ * the fault:
*/
fault = handle_mm_fault(mm, vma, address, write);
+
if (unlikely(fault & VM_FAULT_ERROR)) {
mm_fault_error(regs, error_code, address, fault);
return;
}
+
if (fault & VM_FAULT_MAJOR)
tsk->maj_flt++;
else
@@ -1004,13 +1118,13 @@
for (address = VMALLOC_START & PMD_MASK;
address >= TASK_SIZE && address < FIXADDR_TOP;
address += PMD_SIZE) {
+
unsigned long flags;
struct page *page;
spin_lock_irqsave(&pgd_lock, flags);
list_for_each_entry(page, &pgd_list, lru) {
- if (!vmalloc_sync_one(page_address(page),
- address))
+ if (!vmalloc_sync_one(page_address(page), address))
break;
}
spin_unlock_irqrestore(&pgd_lock, flags);
@@ -1018,12 +1132,14 @@
#else /* CONFIG_X86_64 */
for (address = VMALLOC_START & PGDIR_MASK; address <= VMALLOC_END;
address += PGDIR_SIZE) {
+
const pgd_t *pgd_ref = pgd_offset_k(address);
unsigned long flags;
struct page *page;
if (pgd_none(*pgd_ref))
continue;
+
spin_lock_irqsave(&pgd_lock, flags);
list_for_each_entry(page, &pgd_list, lru) {
pgd_t *pgd;