From 60e019eb37a8d989031ad47ae9810453536f3127 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 29 Apr 2013 16:04:20 +0200 Subject: x86: Get rid of ->hard_math and all the FPU asm fu Reimplement FPU detection code in C and drop old, not-so-recommended detection method in asm. Move all the relevant stuff into i387.c where it conceptually belongs. Finally drop cpuinfo_x86.hard_math. [ hpa: huge thanks to Borislav for taking my original concept patch and productizing it ] [ Boris, note to self: do not use static_cpu_has before alternatives! ] Signed-off-by: H. Peter Anvin Link: http://lkml.kernel.org/r/1367244262-29511-2-git-send-email-bp@alien8.de Link: http://lkml.kernel.org/r/1365436666-9837-2-git-send-email-bp@alien8.de Signed-off-by: Borislav Petkov Signed-off-by: H. Peter Anvin diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h index e25cc33..fb808d7 100644 --- a/arch/x86/include/asm/fpu-internal.h +++ b/arch/x86/include/asm/fpu-internal.h @@ -62,10 +62,8 @@ extern user_regset_set_fn fpregs_set, xfpregs_set, fpregs_soft_set, #define xstateregs_active fpregs_active #ifdef CONFIG_MATH_EMULATION -# define HAVE_HWFP (boot_cpu_data.hard_math) extern void finit_soft_fpu(struct i387_soft_struct *soft); #else -# define HAVE_HWFP 1 static inline void finit_soft_fpu(struct i387_soft_struct *soft) {} #endif diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 22224b3..578f8b1 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -89,9 +89,9 @@ struct cpuinfo_x86 { char wp_works_ok; /* It doesn't on 386's */ /* Problems on some 486Dx4's and old 386's: */ - char hard_math; char rfu; char pad0; + char pad1; #else /* Number of 4K pages in DTLB/ITLB combined(in pages): */ int x86_tlbsize; @@ -164,6 +164,7 @@ extern const struct seq_operations cpuinfo_op; #define cache_line_size() (boot_cpu_data.x86_cache_alignment) extern void cpu_detect(struct cpuinfo_x86 *c); +extern void __cpuinit fpu_detect(struct cpuinfo_x86 *c); extern void early_cpu_init(void); extern void identify_boot_cpu(void); diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c index 0ef4bba..d67c4be 100644 --- a/arch/x86/kernel/asm-offsets_32.c +++ b/arch/x86/kernel/asm-offsets_32.c @@ -28,7 +28,6 @@ void foo(void) OFFSET(CPUINFO_x86_vendor, cpuinfo_x86, x86_vendor); OFFSET(CPUINFO_x86_model, cpuinfo_x86, x86_model); OFFSET(CPUINFO_x86_mask, cpuinfo_x86, x86_mask); - OFFSET(CPUINFO_hard_math, cpuinfo_x86, hard_math); OFFSET(CPUINFO_cpuid_level, cpuinfo_x86, cpuid_level); OFFSET(CPUINFO_x86_capability, cpuinfo_x86, x86_capability); OFFSET(CPUINFO_x86_vendor_id, cpuinfo_x86, x86_vendor_id); diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 4112be9..0344534 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -17,15 +17,6 @@ #include #include -static int __init no_387(char *s) -{ - boot_cpu_data.hard_math = 0; - write_cr0(X86_CR0_TS | X86_CR0_EM | X86_CR0_MP | read_cr0()); - return 1; -} - -__setup("no387", no_387); - static double __initdata x = 4195835.0; static double __initdata y = 3145727.0; @@ -44,15 +35,6 @@ static void __init check_fpu(void) { s32 fdiv_bug; - if (!boot_cpu_data.hard_math) { -#ifndef CONFIG_MATH_EMULATION - pr_emerg("No coprocessor found and no math emulation present\n"); - pr_emerg("Giving up\n"); - for (;;) ; -#endif - return; - } - kernel_fpu_begin(); /* @@ -107,5 +89,6 @@ void __init check_bugs(void) * kernel_fpu_begin/end() in check_fpu() relies on the patched * alternative instructions. */ - check_fpu(); + if (cpu_has_fpu) + check_fpu(); } diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 22018f7..d4dd993 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -711,10 +711,9 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) return; cpu_detect(c); - get_cpu_vendor(c); - get_cpu_cap(c); + fpu_detect(c); if (this_cpu->c_early_init) this_cpu->c_early_init(c); diff --git a/arch/x86/kernel/cpu/cyrix.c b/arch/x86/kernel/cpu/cyrix.c index d048d5c..7582f47 100644 --- a/arch/x86/kernel/cpu/cyrix.c +++ b/arch/x86/kernel/cpu/cyrix.c @@ -333,7 +333,7 @@ static void __cpuinit init_cyrix(struct cpuinfo_x86 *c) switch (dir0_lsn) { case 0xd: /* either a 486SLC or DLC w/o DEVID */ dir0_msn = 0; - p = Cx486_name[(c->hard_math) ? 1 : 0]; + p = Cx486_name[(cpu_has_fpu ? 1 : 0)]; break; case 0xe: /* a 486S A step */ diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c index 37a198b..aee6317 100644 --- a/arch/x86/kernel/cpu/proc.c +++ b/arch/x86/kernel/cpu/proc.c @@ -37,8 +37,8 @@ static void show_cpuinfo_misc(struct seq_file *m, struct cpuinfo_x86 *c) static_cpu_has_bug(X86_BUG_FDIV) ? "yes" : "no", static_cpu_has_bug(X86_BUG_F00F) ? "yes" : "no", static_cpu_has_bug(X86_BUG_COMA) ? "yes" : "no", - c->hard_math ? "yes" : "no", - c->hard_math ? "yes" : "no", + static_cpu_has(X86_FEATURE_FPU) ? "yes" : "no", + static_cpu_has(X86_FEATURE_FPU) ? "yes" : "no", c->cpuid_level, c->wp_works_ok ? "yes" : "no"); } diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 73afd11..e65ddc6 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -444,7 +444,6 @@ is486: orl %ecx,%eax movl %eax,%cr0 - call check_x87 lgdt early_gdt_descr lidt idt_descr ljmp $(__KERNEL_CS),$1f @@ -467,26 +466,6 @@ is486: pushl $0 # fake return address for unwinder jmp *(initial_code) -/* - * We depend on ET to be correct. This checks for 287/387. - */ -check_x87: - movb $0,X86_HARD_MATH - clts - fninit - fstsw %ax - cmpb $0,%al - je 1f - movl %cr0,%eax /* no coprocessor: have to set bits */ - xorl $4,%eax /* set EM */ - movl %eax,%cr0 - ret - ALIGN -1: movb $1,X86_HARD_MATH - .byte 0xDB,0xE4 /* fsetpm for 287, ignored by 387 */ - ret - - #include "verify_cpu.S" /* diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index cb33909..b627746 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -131,7 +131,7 @@ static void __cpuinit init_thread_xstate(void) * xsave_init(). */ - if (!HAVE_HWFP) { + if (!cpu_has_fpu) { /* * Disable xsave as we do not support it if i387 * emulation is enabled. @@ -158,6 +158,14 @@ void __cpuinit fpu_init(void) unsigned long cr0; unsigned long cr4_mask = 0; +#ifndef CONFIG_MATH_EMULATION + if (!cpu_has_fpu) { + pr_emerg("No FPU found and no math emulation present\n"); + pr_emerg("Giving up\n"); + for (;;) + asm volatile("hlt"); + } +#endif if (cpu_has_fxsr) cr4_mask |= X86_CR4_OSFXSR; if (cpu_has_xmm) @@ -167,7 +175,7 @@ void __cpuinit fpu_init(void) cr0 = read_cr0(); cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */ - if (!HAVE_HWFP) + if (!cpu_has_fpu) cr0 |= X86_CR0_EM; write_cr0(cr0); @@ -185,7 +193,7 @@ void __cpuinit fpu_init(void) void fpu_finit(struct fpu *fpu) { - if (!HAVE_HWFP) { + if (!cpu_has_fpu) { finit_soft_fpu(&fpu->state->soft); return; } @@ -214,7 +222,7 @@ int init_fpu(struct task_struct *tsk) int ret; if (tsk_used_math(tsk)) { - if (HAVE_HWFP && tsk == current) + if (cpu_has_fpu && tsk == current) unlazy_fpu(tsk); tsk->thread.fpu.last_cpu = ~0; return 0; @@ -511,14 +519,13 @@ int fpregs_get(struct task_struct *target, const struct user_regset *regset, if (ret) return ret; - if (!HAVE_HWFP) + if (!static_cpu_has(X86_FEATURE_FPU)) return fpregs_soft_get(target, regset, pos, count, kbuf, ubuf); - if (!cpu_has_fxsr) { + if (!cpu_has_fxsr) return user_regset_copyout(&pos, &count, &kbuf, &ubuf, &target->thread.fpu.state->fsave, 0, -1); - } sanitize_i387_state(target); @@ -545,13 +552,13 @@ int fpregs_set(struct task_struct *target, const struct user_regset *regset, sanitize_i387_state(target); - if (!HAVE_HWFP) + if (!static_cpu_has(X86_FEATURE_FPU)) return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf); - if (!cpu_has_fxsr) { + if (!cpu_has_fxsr) return user_regset_copyin(&pos, &count, &kbuf, &ubuf, - &target->thread.fpu.state->fsave, 0, -1); - } + &target->thread.fpu.state->fsave, 0, + -1); if (pos > 0 || count < sizeof(env)) convert_from_fxsr(&env, target); @@ -592,3 +599,33 @@ int dump_fpu(struct pt_regs *regs, struct user_i387_struct *fpu) EXPORT_SYMBOL(dump_fpu); #endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */ + +static int __init no_387(char *s) +{ + setup_clear_cpu_cap(X86_FEATURE_FPU); + return 1; +} + +__setup("no387", no_387); + +void __cpuinit fpu_detect(struct cpuinfo_x86 *c) +{ + unsigned long cr0; + u16 fsw, fcw; + + fsw = fcw = 0xffff; + + cr0 = read_cr0(); + cr0 &= ~(X86_CR0_TS | X86_CR0_EM); + write_cr0(cr0); + + asm volatile("fninit ; fnstsw %0 ; fnstcw %1" + : "+m" (fsw), "+m" (fcw)); + + if (fsw == 0 && (fcw & 0x103f) == 0x003f) + set_cpu_cap(c, X86_FEATURE_FPU); + else + clear_cpu_cap(c, X86_FEATURE_FPU); + + /* The final cr0 value is set in fpu_init() */ +} diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c index ada87a3..d6c28ac 100644 --- a/arch/x86/kernel/xsave.c +++ b/arch/x86/kernel/xsave.c @@ -243,7 +243,7 @@ int save_xstate_sig(void __user *buf, void __user *buf_fx, int size) if (!access_ok(VERIFY_WRITE, buf, size)) return -EACCES; - if (!HAVE_HWFP) + if (!static_cpu_has(X86_FEATURE_FPU)) return fpregs_soft_get(current, NULL, 0, sizeof(struct user_i387_ia32_struct), NULL, (struct _fpstate_ia32 __user *) buf) ? -1 : 1; @@ -350,11 +350,10 @@ int __restore_xstate_sig(void __user *buf, void __user *buf_fx, int size) if (!used_math() && init_fpu(tsk)) return -1; - if (!HAVE_HWFP) { + if (!static_cpu_has(X86_FEATURE_FPU)) return fpregs_soft_set(current, NULL, 0, sizeof(struct user_i387_ia32_struct), NULL, buf) != 0; - } if (use_xsave()) { struct _fpx_sw_bytes fx_sw_user; diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index 7114c63..d482bca 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -1410,7 +1410,7 @@ __init void lguest_init(void) new_cpu_data.x86_capability[0] = cpuid_edx(1); /* Math is always hard! */ - new_cpu_data.hard_math = 1; + set_cpu_cap(&new_cpu_data, X86_FEATURE_FPU); /* We don't have features. We have puppies! Puppies! */ #ifdef CONFIG_X86_MCE diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index a492be2..2fa02bc 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -1557,7 +1557,7 @@ asmlinkage void __init xen_start_kernel(void) #ifdef CONFIG_X86_32 /* set up basic CPUID stuff */ cpu_detect(&new_cpu_data); - new_cpu_data.hard_math = 1; + set_cpu_cap(&new_cpu_data, X86_FEATURE_FPU); new_cpu_data.wp_works_ok = 1; new_cpu_data.x86_capability[0] = cpuid_edx(1); #endif -- cgit v0.10.2 From c3b83598c1eeb1507603b461f5843ec2a49e3033 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Sun, 9 Jun 2013 12:07:30 +0200 Subject: x86, cpu: Add a synthetic, always true, cpu feature This will be used in alternatives later as an always-replace flag. Signed-off-by: Borislav Petkov Link: http://lkml.kernel.org/r/1370772454-6106-2-git-send-email-bp@alien8.de Signed-off-by: H. Peter Anvin diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index e99ac27..043d61e 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -92,7 +92,7 @@ #define X86_FEATURE_LFENCE_RDTSC (3*32+18) /* "" Lfence synchronizes RDTSC */ #define X86_FEATURE_11AP (3*32+19) /* "" Bad local APIC aka 11AP */ #define X86_FEATURE_NOPL (3*32+20) /* The NOPL (0F 1F) instructions */ - /* 21 available, was AMD_C1E */ +#define X86_FEATURE_ALWAYS (3*32+21) /* "" Always-present feature */ #define X86_FEATURE_XTOPOLOGY (3*32+22) /* cpu topology enum extensions */ #define X86_FEATURE_TSC_RELIABLE (3*32+23) /* TSC is known to be reliable */ #define X86_FEATURE_NONSTOP_TSC (3*32+24) /* TSC does not stop in C states */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index d4dd993..d388ce1 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -723,6 +723,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) if (this_cpu->c_bsp_init) this_cpu->c_bsp_init(c); + + setup_force_cpu_cap(X86_FEATURE_ALWAYS); } void __init early_cpu_init(void) -- cgit v0.10.2 From 5700f743b597951743da9c7d891d3989aac0486e Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Sun, 9 Jun 2013 12:07:32 +0200 Subject: x86: Sanity-check static_cpu_has usage static_cpu_has may be used only after alternatives have run. Before that it always returns false if constant folding with __builtin_constant_p() doesn't happen. And you don't want that. This patch is the result of me debugging an issue where I overzealously put static_cpu_has in code which executed before alternatives have run and had to spend some time with scratching head and cursing at the monitor. So add a jump to a warning which screams loudly when we use this function too early. The alternatives patch that check away in conjunction with patching the rest of the kernel image. [ hpa: factored this into its own configuration option. If we want to have an overarching option, it should be an option which selects other options, not as a group option in the source code. ] Signed-off-by: Borislav Petkov Link: http://lkml.kernel.org/r/1370772454-6106-4-git-send-email-bp@alien8.de Signed-off-by: H. Peter Anvin diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug index c198b7e..c6acdf7 100644 --- a/arch/x86/Kconfig.debug +++ b/arch/x86/Kconfig.debug @@ -304,4 +304,14 @@ config DEBUG_NMI_SELFTEST If unsure, say N. +config X86_DEBUG_STATIC_CPU_HAS + bool "Debug alternatives" + depends on DEBUG_KERNEL + ---help--- + This option causes additional code to be generated which + fails if static_cpu_has() is used before alternatives have + run. + + If unsure, say N. + endmenu diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 043d61e..252b28f 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -356,15 +356,35 @@ extern const char * const x86_power_flags[32]; #endif /* CONFIG_X86_64 */ #if __GNUC__ >= 4 +extern void warn_pre_alternatives(void); + /* * Static testing of CPU features. Used the same as boot_cpu_has(). * These are only valid after alternatives have run, but will statically * patch the target code for additional performance. - * */ static __always_inline __pure bool __static_cpu_has(u16 bit) { #if __GNUC__ > 4 || __GNUC_MINOR__ >= 5 + +#ifdef CONFIG_X86_DEBUG_STATIC_CPU_HAS + /* + * Catch too early usage of this before alternatives + * have run. + */ + asm goto("1: jmp %l[t_warn]\n" + "2:\n" + ".section .altinstructions,\"a\"\n" + " .long 1b - .\n" + " .long 0\n" /* no replacement */ + " .word %P0\n" /* 1: do replace */ + " .byte 2b - 1b\n" /* source len */ + " .byte 0\n" /* replacement len */ + ".previous\n" + /* skipping size check since replacement size = 0 */ + : : "i" (X86_FEATURE_ALWAYS) : : t_warn); +#endif + asm goto("1: jmp %l[t_no]\n" "2:\n" ".section .altinstructions,\"a\"\n" @@ -379,7 +399,13 @@ static __always_inline __pure bool __static_cpu_has(u16 bit) return true; t_no: return false; -#else + +#ifdef CONFIG_X86_DEBUG_STATIC_CPU_HAS + t_warn: + warn_pre_alternatives(); + return false; +#endif +#else /* GCC_VERSION >= 40500 */ u8 flag; /* Open-coded due to __stringify() in ALTERNATIVE() */ asm volatile("1: movb $0,%0\n" diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index d388ce1..59adaa1 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1364,3 +1364,11 @@ void __cpuinit cpu_init(void) fpu_init(); } #endif + +#ifdef CONFIG_X86_DEBUG_STATIC_CPU_HAS +void warn_pre_alternatives(void) +{ + WARN(1, "You're using static_cpu_has before alternatives have run!\n"); +} +EXPORT_SYMBOL_GPL(warn_pre_alternatives); +#endif -- cgit v0.10.2 From 4a90a99c4f8002edaa6be11bd756872ebf3f3d97 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Sun, 9 Jun 2013 12:07:33 +0200 Subject: x86: Add a static_cpu_has_safe variant We want to use this in early code where alternatives might not have run yet and for that case we fall back to the dynamic boot_cpu_has. For that, force a 5-byte jump since the compiler could be generating differently sized jumps for each label. Signed-off-by: Borislav Petkov Link: http://lkml.kernel.org/r/1370772454-6106-5-git-send-email-bp@alien8.de Signed-off-by: H. Peter Anvin diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 252b28f..47538a6 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 59adaa1..a4a07c0 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); -- cgit v0.10.2 From 5f8c4218148822fde6eebbeefc34bd0a6061e031 Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Sun, 9 Jun 2013 12:07:34 +0200 Subject: x86, fpu: Use static_cpu_has_safe before alternatives The call stack below shows how this happens: basically eager_fpu_init() calls __thread_fpu_begin(current) which then does if (!use_eager_fpu()), which, in turn, uses static_cpu_has. And we're executing before alternatives so static_cpu_has doesn't work there yet. Use the safe variant in this path which becomes optimal after alternatives have run. WARNING: at arch/x86/kernel/cpu/common.c:1368 warn_pre_alternatives+0x1e/0x20() You're using static_cpu_has before alternatives have run! Modules linked in: Pid: 0, comm: swapper Not tainted 3.9.0-rc8+ #1 Call Trace: warn_slowpath_common warn_slowpath_fmt ? fpu_finit warn_pre_alternatives eager_fpu_init fpu_init cpu_init trap_init start_kernel ? repair_env_string x86_64_start_reservations x86_64_start_kernel Signed-off-by: Borislav Petkov Link: http://lkml.kernel.org/r/1370772454-6106-6-git-send-email-bp@alien8.de Signed-off-by: H. Peter Anvin diff --git a/arch/x86/include/asm/fpu-internal.h b/arch/x86/include/asm/fpu-internal.h index fb808d7..4d0bda7 100644 --- a/arch/x86/include/asm/fpu-internal.h +++ b/arch/x86/include/asm/fpu-internal.h @@ -343,7 +343,7 @@ static inline void __thread_fpu_end(struct task_struct *tsk) static inline void __thread_fpu_begin(struct task_struct *tsk) { - if (!use_eager_fpu()) + if (!static_cpu_has_safe(X86_FEATURE_EAGER_FPU)) clts(); __thread_set_has_fpu(tsk); } -- cgit v0.10.2