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Date: Thu, 07 Mar 2019 12:45:19 +0100 From: Peter Zijlstra <peterz@...radead.org> To: torvalds@...ux-foundation.org, tglx@...utronix.de, hpa@...or.com, julien.thierry@....com, will.deacon@....com, luto@...capital.net, mingo@...nel.org, catalin.marinas@....com, james.morse@....com, valentin.schneider@....com, brgerst@...il.com, jpoimboe@...hat.com, luto@...nel.org, bp@...en8.de, dvlasenk@...hat.com Cc: linux-kernel@...r.kernel.org, peterz@...radead.org, dvyukov@...gle.com, rostedt@...dmis.org Subject: [PATCH 08/20] x86/uaccess: Introduce user_access_{save,restore}() Introduce common helpers for when we need to safely suspend a uaccess section; for instance to generate a {KA,UB}SAN report. Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org> --- arch/x86/include/asm/smap.h | 20 ++++++++++++++++++++ arch/x86/include/asm/uaccess.h | 3 +++ include/linux/uaccess.h | 2 ++ 3 files changed, 25 insertions(+) --- a/arch/x86/include/asm/smap.h +++ b/arch/x86/include/asm/smap.h @@ -58,6 +58,23 @@ static __always_inline void stac(void) alternative("", __stringify(__ASM_STAC), X86_FEATURE_SMAP); } +static __always_inline unsigned long smap_save(void) +{ + unsigned long flags; + + asm volatile (ALTERNATIVE("", "pushf; pop %0; " __stringify(__ASM_CLAC), + X86_FEATURE_SMAP) + : "=rm" (flags) : : "memory", "cc"); + + return flags; +} + +static __always_inline void smap_restore(unsigned long flags) +{ + asm volatile (ALTERNATIVE("", "push %0; popf", X86_FEATURE_SMAP) + : : "g" (flags) : "memory", "cc"); +} + /* These macros can be used in asm() statements */ #define ASM_CLAC \ ALTERNATIVE("", __stringify(__ASM_CLAC), X86_FEATURE_SMAP) @@ -69,6 +86,9 @@ static __always_inline void stac(void) static inline void clac(void) { } static inline void stac(void) { } +static inline unsigned long smap_save(void) { return 0; } +static inline void smap_restore(unsigned long flags) { } + #define ASM_CLAC #define ASM_STAC --- a/arch/x86/include/asm/uaccess.h +++ b/arch/x86/include/asm/uaccess.h @@ -716,6 +716,9 @@ static __must_check __always_inline bool #define user_access_begin(a,b) user_access_begin(a,b) #define user_access_end() __uaccess_end() +#define user_access_save() smap_save() +#define user_access_restore(x) smap_restore(x) + #define unsafe_put_user(x, ptr, label) \ __put_user_size((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr)), label) --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -268,6 +268,8 @@ extern long strncpy_from_unsafe(char *ds #define user_access_end() do { } while (0) #define unsafe_get_user(x, ptr, err) do { if (unlikely(__get_user(x, ptr))) goto err; } while (0) #define unsafe_put_user(x, ptr, err) do { if (unlikely(__put_user(x, ptr))) goto err; } while (0) +static inline unsigned long user_access_save(void) { return 0UL; } +static void user_access_restore(unsigned long flags) { } #endif #ifdef CONFIG_HARDENED_USERCOPY
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