mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-09-13 06:08:07 +00:00
Code Issues Releases Wiki Activity

x86/fpu: Return proper error codes from user access functions

Browse source 
[ Upstream commit aee8c67a4f ]

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 separate 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>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121457.601480369@linutronix.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Thomas Gleixner 2021-06-23 14:02:30 +02:00 committed by Greg Kroah-Hartman
parent f58ab0b02e
commit 12f8d6e7f2
1 changed files with 12 additions and 7 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

19
arch/x86/include/asm/fpu/internal.h
View file

@ -102,6 +102,7 @@ static inline void fpstate_init_fxstate(struct fxregs_state *fx)
}
extern void fpstate_sanitize_xstate(struct fpu *fpu);
/* Returns 0 or the negated trap number, which results in -EFAULT for #PF */
#define user_insn(insn, output, input...) \
({ \
int err; \
@ -109,14 +110,14 @@ extern void fpstate_sanitize_xstate(struct fpu *fpu);
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; \
})
@ -210,16 +211,20 @@ static inline void copy_fxregs_to_kernel(struct fpu *fpu)
#define XRSTOR ".byte " REX_PREFIX "0x0f,0xae,0x2f"
#define XRSTORS ".byte " REX_PREFIX "0x0f,0xc7,0x1f"
/*
* After this @err contains 0 on success or the negated trap number when
* the operation raises an exception. For faults this results in -EFAULT.
*/
#define XSTATE_OP(op, st, lmask, hmask, err) \
asm volatile("1:" op "\n\t" \
"xor %[err], %[err]\n" \
"2:\n\t" \
".pushsection .fixup,\"ax\"\n\t" \
"3: movl $-2,%[err]\n\t" \
"3: negl %%eax\n\t" \
"jmp 2b\n\t" \
".popsection\n\t" \
_ASM_EXTABLE(1b, 3b) \
: [err] "=r" (err) \
_ASM_EXTABLE_FAULT(1b, 3b) \
: [err] "=a" (err) \
: "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \
: "memory")