[PATCH v10 01/18] x86/mm: Relocate page fault error codes to traps.h

Ricardo Neri
2017-10-27T20:32:19Z

Up to this point, only fault.c used the definitions of the page fault error
codes. Thus, it made sense to keep them within such file. Other portions of
code might be interested in those definitions too. For instance, the User-
Mode Instruction Prevention emulation code will use such definitions to
emulate a page fault when it is unable to successfully copy the results
of the emulated instructions to user space.

While relocating the error code enumeration, the prefix X86_ is used to
make it consistent with the rest of the definitions in traps.h. Of course,
code using the enumeration had to be updated as well. No functional changes
were performed.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: x86@kernel.org
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
arch/x86/include/asm/traps.h | 18 +++++++++
arch/x86/mm/fault.c | 88 +++++++++++++++++---------------------------
2 files changed, 52 insertions(+), 54 deletions(-)

diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 5545f64..da3c3a3 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -144,4 +144,22 @@ enum {
X86_TRAP_IRET = 32, /* 32, IRET Exception */
};

+/*
+ * 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
+ * bit 5 == 1: protection keys block access
+ */
+enum x86_pf_error_code {
+ X86_PF_PROT = 1 << 0,
+ X86_PF_WRITE = 1 << 1,
+ X86_PF_USER = 1 << 2,
+ X86_PF_RSVD = 1 << 3,
+ X86_PF_INSTR = 1 << 4,
+ X86_PF_PK = 1 << 5,
+};
#endif /* _ASM_X86_TRAPS_H */
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e2baeaa..db71c73 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -29,26 +29,6 @@
#include <asm/trace/exceptions.h>

/*
- * 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
- * bit 5 == 1: protection keys block access
- */
-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,
- PF_PK = 1 << 5,
-};
-
-/*
* Returns 0 if mmiotrace is disabled, or if the fault is not
* handled by mmiotrace:
*/
@@ -149,7 +129,7 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
* If it was a exec (instruction fetch) fault on NX page, then
* do not ignore the fault:
*/
- if (error_code & PF_INSTR)
+ if (error_code & X86_PF_INSTR)
return 0;

instr = (void *)convert_ip_to_linear(current, regs);
@@ -179,7 +159,7 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
* siginfo so userspace can discover which protection key was set
* on the PTE.
*
- * If we get here, we know that the hardware signaled a PF_PK
+ * If we get here, we know that the hardware signaled a X86_PF_PK
* fault and that there was a VMA once we got in the fault
* handler. It does *not* guarantee that the VMA we find here
* was the one that we faulted on.
@@ -204,7 +184,7 @@ static void fill_sig_info_pkey(int si_code, siginfo_t *info, u32 *pkey)
/*
* force_sig_info_fault() is called from a number of
* contexts, some of which have a VMA and some of which
- * do not. The PF_PK handing happens after we have a
+ * do not. The X86_PF_PK handing happens after we have a
* valid VMA, so we should never reach this without a
* valid VMA.
*/
@@ -697,7 +677,7 @@ show_fault_oops(struct pt_regs *regs, unsigned long error_code,
if (!oops_may_print())
return;

- if (error_code & PF_INSTR) {
+ if (error_code & X86_PF_INSTR) {
unsigned int level;
pgd_t *pgd;
pte_t *pte;
@@ -779,7 +759,7 @@ no_context(struct pt_regs *regs, unsigned long error_code,
*/
if (current->thread.sig_on_uaccess_err && signal) {
tsk->thread.trap_nr = X86_TRAP_PF;
- tsk->thread.error_code = error_code | PF_USER;
+ tsk->thread.error_code = error_code | X86_PF_USER;
tsk->thread.cr2 = address;

/* XXX: hwpoison faults will set the wrong code. */
@@ -897,7 +877,7 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
struct task_struct *tsk = current;

/* User mode accesses just cause a SIGSEGV */
- if (error_code & PF_USER) {
+ if (error_code & X86_PF_USER) {
/*
* It's possible to have interrupts off here:
*/
@@ -918,7 +898,7 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
* Instruction fetch faults in the vsyscall page might need
* emulation.
*/
- if (unlikely((error_code & PF_INSTR) &&
+ if (unlikely((error_code & X86_PF_INSTR) &&
((address & ~0xfff) == VSYSCALL_ADDR))) {
if (emulate_vsyscall(regs, address))
return;
@@ -931,7 +911,7 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code,
* are always protection faults.
*/
if (address >= TASK_SIZE_MAX)
- error_code |= PF_PROT;
+ error_code |= X86_PF_PROT;

if (likely(show_unhandled_signals))
show_signal_msg(regs, error_code, address, tsk);
@@ -992,11 +972,11 @@ static inline bool bad_area_access_from_pkeys(unsigned long error_code,

if (!boot_cpu_has(X86_FEATURE_OSPKE))
return false;
- if (error_code & PF_PK)
+ if (error_code & X86_PF_PK)
return true;
/* this checks permission keys on the VMA: */
- if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
- (error_code & PF_INSTR), foreign))
+ if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
+ (error_code & X86_PF_INSTR), foreign))
return true;
return false;
}
@@ -1024,7 +1004,7 @@ do_sigbus(struct pt_regs *regs, unsigned long error_code, unsigned long address,
int code = BUS_ADRERR;

/* Kernel mode? Handle exceptions or die: */
- if (!(error_code & PF_USER)) {
+ if (!(error_code & X86_PF_USER)) {
no_context(regs, error_code, address, SIGBUS, BUS_ADRERR);
return;
}
@@ -1052,14 +1032,14 @@ static noinline void
mm_fault_error(struct pt_regs *regs, unsigned long error_code,
unsigned long address, u32 *pkey, unsigned int fault)
{
- if (fatal_signal_pending(current) && !(error_code & PF_USER)) {
+ if (fatal_signal_pending(current) && !(error_code & X86_PF_USER)) {
no_context(regs, error_code, address, 0, 0);
return;
}

if (fault & VM_FAULT_OOM) {
/* Kernel mode? Handle exceptions or die: */
- if (!(error_code & PF_USER)) {
+ if (!(error_code & X86_PF_USER)) {
no_context(regs, error_code, address,
SIGSEGV, SEGV_MAPERR);
return;
@@ -1084,16 +1064,16 @@ mm_fault_error(struct pt_regs *regs, unsigned long error_code,

static int spurious_fault_check(unsigned long error_code, pte_t *pte)
{
- if ((error_code & PF_WRITE) && !pte_write(*pte))
+ if ((error_code & X86_PF_WRITE) && !pte_write(*pte))
return 0;

- if ((error_code & PF_INSTR) && !pte_exec(*pte))
+ if ((error_code & X86_PF_INSTR) && !pte_exec(*pte))
return 0;
/*
* Note: We do not do lazy flushing on protection key
- * changes, so no spurious fault will ever set PF_PK.
+ * changes, so no spurious fault will ever set X86_PF_PK.
*/
- if ((error_code & PF_PK))
+ if ((error_code & X86_PF_PK))
return 1;

return 1;
@@ -1139,8 +1119,8 @@ spurious_fault(unsigned long error_code, unsigned long address)
* change, so user accesses are not expected to cause spurious
* faults.
*/
- if (error_code != (PF_WRITE | PF_PROT)
- && error_code != (PF_INSTR | PF_PROT))
+ if (error_code != (X86_PF_WRITE | X86_PF_PROT) &&
+ error_code != (X86_PF_INSTR | X86_PF_PROT))
return 0;

pgd = init_mm.pgd + pgd_index(address);
@@ -1200,19 +1180,19 @@ access_error(unsigned long error_code, struct vm_area_struct *vma)
* always an unconditional error and can never result in
* a follow-up action to resolve the fault, like a COW.
*/
- if (error_code & PF_PK)
+ if (error_code & X86_PF_PK)
return 1;

/*
* Make sure to check the VMA so that we do not perform
- * faults just to hit a PF_PK as soon as we fill in a
+ * faults just to hit a X86_PF_PK as soon as we fill in a
* page.
*/
- if (!arch_vma_access_permitted(vma, (error_code & PF_WRITE),
- (error_code & PF_INSTR), foreign))
+ if (!arch_vma_access_permitted(vma, (error_code & X86_PF_WRITE),
+ (error_code & X86_PF_INSTR), foreign))
return 1;

- if (error_code & PF_WRITE) {
+ if (error_code & X86_PF_WRITE) {
/* write, present and write, not present: */
if (unlikely(!(vma->vm_flags & VM_WRITE)))
return 1;
@@ -1220,7 +1200,7 @@ access_error(unsigned long error_code, struct vm_area_struct *vma)
}

/* read, present: */
- if (unlikely(error_code & PF_PROT))
+ if (unlikely(error_code & X86_PF_PROT))
return 1;

/* read, not present: */
@@ -1243,7 +1223,7 @@ static inline bool smap_violation(int error_code, struct pt_regs *regs)
if (!static_cpu_has(X86_FEATURE_SMAP))
return false;

- if (error_code & PF_USER)
+ if (error_code & X86_PF_USER)
return false;

if (!user_mode(regs) && (regs->flags & X86_EFLAGS_AC))
@@ -1296,7 +1276,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
* protection error (error_code & 9) == 0.
*/
if (unlikely(fault_in_kernel_space(address))) {
- if (!(error_code & (PF_RSVD | PF_USER | PF_PROT))) {
+ if (!(error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
if (vmalloc_fault(address) >= 0)
return;

@@ -1324,7 +1304,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
if (unlikely(kprobes_fault(regs)))
return;

- if (unlikely(error_code & PF_RSVD))
+ if (unlikely(error_code & X86_PF_RSVD))
pgtable_bad(regs, error_code, address);

if (unlikely(smap_violation(error_code, regs))) {
@@ -1350,7 +1330,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
*/
if (user_mode(regs)) {
local_irq_enable();
- error_code |= PF_USER;
+ error_code |= X86_PF_USER;
flags |= FAULT_FLAG_USER;
} else {
if (regs->flags & X86_EFLAGS_IF)
@@ -1359,9 +1339,9 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,

perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);

- if (error_code & PF_WRITE)
+ if (error_code & X86_PF_WRITE)
flags |= FAULT_FLAG_WRITE;
- if (error_code & PF_INSTR)
+ if (error_code & X86_PF_INSTR)
flags |= FAULT_FLAG_INSTRUCTION;

/*
@@ -1381,7 +1361,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
* space check, thus avoiding the deadlock:
*/
if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
- if ((error_code & PF_USER) == 0 &&
+ if (!(error_code & X86_PF_USER) &&
!search_exception_tables(regs->ip)) {
bad_area_nosemaphore(regs, error_code, address, NULL);
return;
@@ -1408,7 +1388,7 @@ __do_page_fault(struct pt_regs *regs, unsigned long error_code,
bad_area(regs, error_code, address);
return;
}
- if (error_code & PF_USER) {
+ if (error_code & X86_PF_USER) {
/*
* Accessing the stack below %sp is always a bug.
* The large cushion allows instructions like enter
--
2.7.4