From: Ingo Molnar Date: Fri, 20 Feb 2009 19:37:05 +0000 (+0100) Subject: x86, mm: fault.c, refactor/simplify the is_prefetch() code X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=107a03678cac0dd6cf7095f81442a4fa477e4700;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git 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 Signed-off-by: Ingo Molnar --- diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 351d679bf977..72973c7682ba 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; }