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Diffstat (limited to 'arch/x86/mm/fault_32.c')
-rw-r--r--arch/x86/mm/fault_32.c148
1 files changed, 83 insertions, 65 deletions
diff --git a/arch/x86/mm/fault_32.c b/arch/x86/mm/fault_32.c
index db8d748814e..bfb0917d699 100644
--- a/arch/x86/mm/fault_32.c
+++ b/arch/x86/mm/fault_32.c
@@ -1,6 +1,4 @@
/*
- * linux/arch/i386/mm/fault.c
- *
* Copyright (C) 1995 Linus Torvalds
*/
@@ -30,11 +28,25 @@
#include <asm/desc.h>
#include <asm/segment.h>
-extern void die(const char *,struct pt_regs *,long);
+/*
+ * 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
+ */
+#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)
+
+extern void die(const char *, struct pt_regs *, long);
-#ifdef CONFIG_KPROBES
static inline int notify_page_fault(struct pt_regs *regs)
{
+#ifdef CONFIG_KPROBES
int ret = 0;
/* kprobe_running() needs smp_processor_id() */
@@ -46,13 +58,10 @@ static inline int notify_page_fault(struct pt_regs *regs)
}
return ret;
-}
#else
-static inline int notify_page_fault(struct pt_regs *regs)
-{
return 0;
-}
#endif
+}
/*
* Return EIP plus the CS segment base. The segment limit is also
@@ -65,7 +74,7 @@ static inline int notify_page_fault(struct pt_regs *regs)
* If CS is no longer a valid code segment, or if EIP is beyond the
* limit, or if it is a kernel address when CS is not a kernel segment,
* then the returned value will be greater than *eip_limit.
- *
+ *
* This is slow, but is very rarely executed.
*/
static inline unsigned long get_segment_eip(struct pt_regs *regs,
@@ -84,7 +93,7 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
/* The standard kernel/user address space limit. */
*eip_limit = user_mode(regs) ? USER_DS.seg : KERNEL_DS.seg;
-
+
/* By far the most common cases. */
if (likely(SEGMENT_IS_FLAT_CODE(seg)))
return ip;
@@ -99,7 +108,7 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
return 1; /* So that returned ip > *eip_limit. */
}
- /* Get the GDT/LDT descriptor base.
+ /* Get the GDT/LDT descriptor base.
When you look for races in this code remember that
LDT and other horrors are only used in user space. */
if (seg & (1<<2)) {
@@ -109,16 +118,16 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
desc = (void *)desc + (seg & ~7);
} else {
/* Must disable preemption while reading the GDT. */
- desc = (u32 *)get_cpu_gdt_table(get_cpu());
+ desc = (u32 *)get_cpu_gdt_table(get_cpu());
desc = (void *)desc + (seg & ~7);
}
/* Decode the code segment base from the descriptor */
base = get_desc_base((struct desc_struct *)desc);
- if (seg & (1<<2)) {
+ if (seg & (1<<2))
mutex_unlock(&current->mm->context.lock);
- } else
+ else
put_cpu();
/* Adjust EIP and segment limit, and clamp at the kernel limit.
@@ -129,19 +138,19 @@ static inline unsigned long get_segment_eip(struct pt_regs *regs,
return ip + base;
}
-/*
+/*
* Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
* Check that here and ignore it.
*/
static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
-{
+{
unsigned long limit;
- unsigned char *instr = (unsigned char *)get_segment_eip (regs, &limit);
+ unsigned char *instr = (unsigned char *)get_segment_eip(regs, &limit);
int scan_more = 1;
- int prefetch = 0;
+ int prefetch = 0;
int i;
- for (i = 0; scan_more && i < 15; i++) {
+ for (i = 0; scan_more && i < 15; i++) {
unsigned char opcode;
unsigned char instr_hi;
unsigned char instr_lo;
@@ -149,27 +158,43 @@ static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
if (instr > (unsigned char *)limit)
break;
if (probe_kernel_address(instr, opcode))
- break;
+ break;
- instr_hi = opcode & 0xf0;
- instr_lo = opcode & 0x0f;
+ instr_hi = opcode & 0xf0;
+ instr_lo = opcode & 0x0f;
instr++;
- switch (instr_hi) {
+ switch (instr_hi) {
case 0x20:
case 0x30:
- /* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */
+ /*
+ * Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes.
+ * In X86_64 long mode, the CPU will signal invalid
+ * opcode if some of these prefixes are present so
+ * X86_64 will never get here anyway
+ */
scan_more = ((instr_lo & 7) == 0x6);
break;
-
+#ifdef CONFIG_X86_64
+ case 0x40:
+ /*
+ * In AMD64 long mode 0x40..0x4F are valid REX prefixes
+ * Need to figure out under what instruction mode the
+ * instruction was issued. Could check the LDT for lm,
+ * but for now it's good enough to assume that long
+ * mode only uses well known segments or kernel.
+ */
+ scan_more = (!user_mode(regs)) || (regs->cs == __USER_CS);
+ break;
+#endif
case 0x60:
/* 0x64 thru 0x67 are valid prefixes in all modes. */
scan_more = (instr_lo & 0xC) == 0x4;
- break;
+ break;
case 0xF0:
- /* 0xF0, 0xF2, and 0xF3 are valid prefixes */
+ /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
scan_more = !instr_lo || (instr_lo>>1) == 1;
- break;
+ break;
case 0x00:
/* Prefetch instruction is 0x0F0D or 0x0F18 */
scan_more = 0;
@@ -179,11 +204,11 @@ static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
break;
prefetch = (instr_lo == 0xF) &&
(opcode == 0x0D || opcode == 0x18);
- break;
+ break;
default:
scan_more = 0;
break;
- }
+ }
}
return prefetch;
}
@@ -199,7 +224,7 @@ static inline int is_prefetch(struct pt_regs *regs, unsigned long addr,
return __is_prefetch(regs, addr);
}
return 0;
-}
+}
static noinline void force_sig_info_fault(int si_signo, int si_code,
unsigned long address, struct task_struct *tsk)
@@ -284,19 +309,12 @@ int show_unhandled_signals = 1;
* This routine handles page faults. It determines the address,
* and the problem, and then passes it off to one of the appropriate
* routines.
- *
- * error_code:
- * 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
*/
void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
{
struct task_struct *tsk;
struct mm_struct *mm;
- struct vm_area_struct * vma;
+ struct vm_area_struct *vma;
unsigned long address;
int write, si_code;
int fault;
@@ -307,7 +325,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
trace_hardirqs_fixup();
/* get the address */
- address = read_cr2();
+ address = read_cr2();
tsk = current;
@@ -350,7 +368,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
/*
* If we're in an interrupt, have no user context or are running in an
- * atomic region then we must not take the fault..
+ * atomic region then we must not take the fault.
*/
if (in_atomic() || !mm)
goto bad_area_nosemaphore;
@@ -371,7 +389,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
* thus avoiding the deadlock.
*/
if (!down_read_trylock(&mm->mmap_sem)) {
- if ((error_code & 4) == 0 &&
+ if ((error_code & PF_USER) == 0 &&
!search_exception_tables(regs->ip))
goto bad_area_nosemaphore;
down_read(&mm->mmap_sem);
@@ -384,7 +402,7 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
goto good_area;
if (!(vma->vm_flags & VM_GROWSDOWN))
goto bad_area;
- if (error_code & 4) {
+ if (error_code & PF_USER) {
/*
* Accessing the stack below %sp is always a bug.
* The large cushion allows instructions like enter
@@ -403,19 +421,19 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
good_area:
si_code = SEGV_ACCERR;
write = 0;
- switch (error_code & 3) {
- default: /* 3: write, present */
- /* fall through */
- case 2: /* write, not present */
- if (!(vma->vm_flags & VM_WRITE))
- goto bad_area;
- write++;
- break;
- case 1: /* read, present */
+ switch (error_code & (PF_PROT|PF_WRITE)) {
+ default: /* 3: write, present */
+ /* fall through */
+ case PF_WRITE: /* write, not present */
+ if (!(vma->vm_flags & VM_WRITE))
+ goto bad_area;
+ write++;
+ break;
+ case PF_PROT: /* read, present */
+ goto bad_area;
+ case 0: /* read, not present */
+ if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
goto bad_area;
- case 0: /* read, not present */
- if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
- goto bad_area;
}
survive:
@@ -457,14 +475,14 @@ bad_area:
bad_area_nosemaphore:
/* User mode accesses just cause a SIGSEGV */
- if (error_code & 4) {
+ if (error_code & PF_USER) {
/*
* It's possible to have interrupts off here.
*/
local_irq_enable();
- /*
- * Valid to do another page fault here because this one came
+ /*
+ * Valid to do another page fault here because this one came
* from user space.
*/
if (is_prefetch(regs, address, error_code))
@@ -492,7 +510,7 @@ bad_area_nosemaphore:
*/
if (boot_cpu_data.f00f_bug) {
unsigned long nr;
-
+
nr = (address - idt_descr.address) >> 3;
if (nr == 6) {
@@ -507,13 +525,13 @@ no_context:
if (fixup_exception(regs))
return;
- /*
+ /*
* Valid to do another page fault here, because if this fault
- * had been triggered by is_prefetch fixup_exception would have
+ * had been triggered by is_prefetch fixup_exception would have
* handled it.
*/
- if (is_prefetch(regs, address, error_code))
- return;
+ if (is_prefetch(regs, address, error_code))
+ return;
/*
* Oops. The kernel tried to access some bad page. We'll have to
@@ -541,7 +559,7 @@ no_context:
else
printk(KERN_ALERT "BUG: unable to handle kernel paging"
" request");
- printk(" at virtual address %08lx\n",address);
+ printk(" at virtual address %08lx\n", address);
printk(KERN_ALERT "printing ip: %08lx ", regs->ip);
page = read_cr3();
@@ -605,7 +623,7 @@ do_sigbus:
up_read(&mm->mmap_sem);
/* Kernel mode? Handle exceptions or die */
- if (!(error_code & 4))
+ if (!(error_code & PF_USER))
goto no_context;
/* User space => ok to do another page fault */
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-12-19 22:27:13 +0000