| Date | Fri, 18 Jun 2021 16:19:27 +0200 | From | Thomas Gleixner <> | Subject | [patch V3 64/66] x86/fpu: Return proper error codes from user access functions |
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When *RSTOR from user memory raises an exception there is no way to differentiate them. That's bad because it forces the slow path even when the failure was not a fault. If the operation raised eg. #GP then going through the slow path is pointless.
Use _ASM_EXTABLE_FAULT() which stores the trap number and let the exception fixup return the negated trap number as error.
This allows to seperate the fast path and let it handle faults directly and avoid the slow path for all other exceptions.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- arch/x86/include/asm/fpu/internal.h | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
--- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -87,6 +87,7 @@ extern void fpstate_init_soft(struct swr static inline void fpstate_init_soft(struct swregs_state *soft) {} #endif +/* Returns 0 or the negated trap number, which results in -EFAULT for #PF */ #define user_insn(insn, output, input...) \ ({ \ int err; \ @@ -94,14 +95,14 @@ static inline void fpstate_init_soft(str might_fault(); \ \ asm volatile(ASM_STAC "\n" \ - "1:" #insn "\n\t" \ + "1: " #insn "\n" \ "2: " ASM_CLAC "\n" \ ".section .fixup,\"ax\"\n" \ - "3: movl $-1,%[err]\n" \ + "3: negl %%eax\n" \ " jmp 2b\n" \ ".previous\n" \ - _ASM_EXTABLE(1b, 3b) \ - : [err] "=r" (err), output \ + _ASM_EXTABLE_FAULT(1b, 3b) \ + : [err] "=a" (err), output \ : "0"(0), input); \ err; \ })
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