diff options
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/include/asm/cpufeature.h | 86 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 6 |
2 files changed, 91 insertions, 1 deletions
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 252b28f1176a..47538a61c91b 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -357,6 +357,7 @@ extern const char * const x86_power_flags[32]; #if __GNUC__ >= 4 extern void warn_pre_alternatives(void); +extern bool __static_cpu_has_safe(u16 bit); /* * Static testing of CPU features. Used the same as boot_cpu_has(). @@ -437,11 +438,94 @@ static __always_inline __pure bool __static_cpu_has(u16 bit) __static_cpu_has(bit) : \ boot_cpu_has(bit) \ ) + +static __always_inline __pure bool _static_cpu_has_safe(u16 bit) +{ +#if __GNUC__ > 4 || __GNUC_MINOR__ >= 5 +/* + * We need to spell the jumps to the compiler because, depending on the offset, + * the replacement jump can be bigger than the original jump, and this we cannot + * have. Thus, we force the jump to the widest, 4-byte, signed relative + * offset even though the last would often fit in less bytes. + */ + asm goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n" + "2:\n" + ".section .altinstructions,\"a\"\n" + " .long 1b - .\n" /* src offset */ + " .long 3f - .\n" /* repl offset */ + " .word %P1\n" /* always replace */ + " .byte 2b - 1b\n" /* src len */ + " .byte 4f - 3f\n" /* repl len */ + ".previous\n" + ".section .altinstr_replacement,\"ax\"\n" + "3: .byte 0xe9\n .long %l[t_no] - 2b\n" + "4:\n" + ".previous\n" + ".section .altinstructions,\"a\"\n" + " .long 1b - .\n" /* src offset */ + " .long 0\n" /* no replacement */ + " .word %P0\n" /* feature bit */ + " .byte 2b - 1b\n" /* src len */ + " .byte 0\n" /* repl len */ + ".previous\n" + : : "i" (bit), "i" (X86_FEATURE_ALWAYS) + : : t_dynamic, t_no); + return true; + t_no: + return false; + t_dynamic: + return __static_cpu_has_safe(bit); +#else /* GCC_VERSION >= 40500 */ + u8 flag; + /* Open-coded due to __stringify() in ALTERNATIVE() */ + asm volatile("1: movb $2,%0\n" + "2:\n" + ".section .altinstructions,\"a\"\n" + " .long 1b - .\n" /* src offset */ + " .long 3f - .\n" /* repl offset */ + " .word %P2\n" /* always replace */ + " .byte 2b - 1b\n" /* source len */ + " .byte 4f - 3f\n" /* replacement len */ + ".previous\n" + ".section .discard,\"aw\",@progbits\n" + " .byte 0xff + (4f-3f) - (2b-1b)\n" /* size check */ + ".previous\n" + ".section .altinstr_replacement,\"ax\"\n" + "3: movb $0,%0\n" + "4:\n" + ".previous\n" + ".section .altinstructions,\"a\"\n" + " .long 1b - .\n" /* src offset */ + " .long 5f - .\n" /* repl offset */ + " .word %P1\n" /* feature bit */ + " .byte 4b - 3b\n" /* src len */ + " .byte 6f - 5f\n" /* repl len */ + ".previous\n" + ".section .discard,\"aw\",@progbits\n" + " .byte 0xff + (6f-5f) - (4b-3b)\n" /* size check */ + ".previous\n" + ".section .altinstr_replacement,\"ax\"\n" + "5: movb $1,%0\n" + "6:\n" + ".previous\n" + : "=qm" (flag) + : "i" (bit), "i" (X86_FEATURE_ALWAYS)); + return (flag == 2 ? __static_cpu_has_safe(bit) : flag); +#endif +} + +#define static_cpu_has_safe(bit) \ +( \ + __builtin_constant_p(boot_cpu_has(bit)) ? \ + boot_cpu_has(bit) : \ + _static_cpu_has_safe(bit) \ +) #else /* * gcc 3.x is too stupid to do the static test; fall back to dynamic. */ -#define static_cpu_has(bit) boot_cpu_has(bit) +#define static_cpu_has(bit) boot_cpu_has(bit) +#define static_cpu_has_safe(bit) boot_cpu_has(bit) #endif #define cpu_has_bug(c, bit) cpu_has(c, (bit)) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 59adaa17e220..a4a07c0acb1f 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1372,3 +1372,9 @@ void warn_pre_alternatives(void) } EXPORT_SYMBOL_GPL(warn_pre_alternatives); #endif + +inline bool __static_cpu_has_safe(u16 bit) +{ + return boot_cpu_has(bit); +} +EXPORT_SYMBOL_GPL(__static_cpu_has_safe); |