Author: Ingo Molnar <mingo@xxxxxxx>
AuthorDate: Fri, 20 Feb 2009 20:37:05 +0100
Commit: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Sat, 21 Feb 2009 00:09:40 +0100
x86, mm: fault.c, refactor/simplify the is_prefetch() code
Impact: no functionality changed
Factor out the opcode checker into a helper inline.
The code got a tiny bit smaller:
text data bss dec hex filename
4632 32 24 4688 1250 fault.o.before
4618 32 24 4674 1242 fault.o.after
And it got cleaner / easier to review as well.
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
arch/x86/mm/fault.c | 100 +++++++++++++++++++++++++-------------------------
1 files changed, 50 insertions(+), 50 deletions(-)
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 351d679..72973c7 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -99,12 +99,58 @@ static inline int notify_page_fault(struct pt_regs *regs)
*
* Opcode checker based on code by Richard Brunner.
*/
+static inline int
+check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
+ unsigned char opcode, int *prefetch)
+{
+ unsigned char instr_hi = opcode & 0xf0;
+ unsigned char instr_lo = opcode & 0x0f;
+
+ switch (instr_hi) {
+ case 0x20:
+ case 0x30:
+ /*
+ * 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
+ */
+ return ((instr_lo & 7) == 0x6);
+#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.
+ */
+ return (!user_mode(regs)) || (regs->cs == __USER_CS);
+#endif
+ case 0x60:
+ /* 0x64 thru 0x67 are valid prefixes in all modes. */
+ return (instr_lo & 0xC) == 0x4;
+ case 0xF0:
+ /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
+ return !instr_lo || (instr_lo>>1) == 1;
+ case 0x00:
+ /* Prefetch instruction is 0x0F0D or 0x0F18 */
+ if (probe_kernel_address(instr, opcode))
+ return 0;
+
+ *prefetch = (instr_lo == 0xF) &&
+ (opcode == 0x0D || opcode == 0x18);
+ return 0;
+ default:
+ return 0;
+ }
+}
+
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;
/*
@@ -114,68 +160,22 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
if (error_code & PF_INSTR)
return 0;
- instr = (unsigned char *)convert_ip_to_linear(current, regs);
+ instr = (void *)convert_ip_to_linear(current, regs);
max_instr = instr + 15;
if (user_mode(regs) && instr >= (unsigned char *)TASK_SIZE)
return 0;
- while (scan_more && instr < max_instr) {
- unsigned char instr_hi;
- unsigned char instr_lo;
+ while (instr < max_instr) {
unsigned char opcode;
if (probe_kernel_address(instr, opcode))
break;
- instr_hi = opcode & 0xf0;
- instr_lo = opcode & 0x0f;
instr++;
- switch (instr_hi) {
- case 0x20:
- case 0x30:
- /*
- * 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;
+ if (!check_prefetch_opcode(regs, instr, opcode, &prefetch))
break;
- case 0xF0:
- /* 0xF0, 0xF2, 0xF3 are valid prefixes in all modes. */
- scan_more = !instr_lo || (instr_lo>>1) == 1;
- break;
- case 0x00:
- /* Prefetch instruction is 0x0F0D or 0x0F18 */
- scan_more = 0;
-
- if (probe_kernel_address(instr, opcode))
- break;
- prefetch = (instr_lo == 0xF) &&
- (opcode == 0x0D || opcode == 0x18);
- break;
- default:
- scan_more = 0;
- break;
- }
}
return prefetch;
}
--
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