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x86: move stac/clac from user copy routines into callers 

This is preparatory work for inlining the 'rep movs' case, but also a
cleanup.  The __copy_user_nocache() function was mis-used by the rdma
code to do uncached kernel copies that don't actually want user copies
at all, and as a result doesn't want the stac/clac either.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Linus Torvalds 2023-04-15 13:39:15 -07:00
parent d2c95f9d68
commit 3639a53558
4 changed files with 15 additions and 12 deletions
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8
arch/x86/include/asm/uaccess_64.h
View File

@ -27,6 +27,7 @@ copy_user_generic(void *to, const void *from, unsigned len)
{
unsigned ret;
stac();
/*
* If CPU has FSRM feature, use 'rep movs'.
* Otherwise, use copy_user_generic_unrolled.
@ -38,6 +39,7 @@ copy_user_generic(void *to, const void *from, unsigned len)
"=d" (len)),
"1" (to), "2" (from), "3" (len)
: "memory", "rcx", "r8", "r9", "r10", "r11");
clac();
return ret;
}
@ -64,8 +66,12 @@ static inline int
__copy_from_user_inatomic_nocache(void *dst, const void __user *src,
unsigned size)
{
long ret;
kasan_check_write(dst, size);
return __copy_user_nocache(dst, src, size, 0);
stac();
ret = __copy_user_nocache(dst, src, size, 0);
clac();
return ret;
}
static inline int

10
arch/x86/lib/copy_user_64.S
View File

@ -51,7 +51,6 @@
* eax uncopied bytes or 0 if successful.
*/
SYM_FUNC_START(copy_user_generic_unrolled)
ASM_STAC
cmpl $8,%edx
jb .Lcopy_user_short_string_bytes
ALIGN_DESTINATION
@ -123,15 +122,12 @@ EXPORT_SYMBOL(copy_user_generic_unrolled)
* eax uncopied bytes or 0 if successful.
*/
SYM_FUNC_START(copy_user_fast_string)
ASM_STAC
movl %edx,%ecx
1: rep movsb
xorl %eax,%eax
ASM_CLAC
RET
12: movl %ecx,%eax /* ecx is zerorest also */
ASM_CLAC
RET
_ASM_EXTABLE_CPY(1b, 12b)
@ -160,12 +156,10 @@ SYM_CODE_START_LOCAL(.Lcopy_user_handle_tail)
movl %edx,%ecx
1: rep movsb
2: mov %ecx,%eax
ASM_CLAC
RET
3:
movl %edx,%eax
ASM_CLAC
RET
_ASM_EXTABLE_CPY(1b, 2b)
@ -209,7 +203,6 @@ SYM_CODE_START_LOCAL(copy_user_short_string)
decl %ecx
jnz 21b
23: xor %eax,%eax
ASM_CLAC
RET
40: leal (%rdx,%rcx,8),%edx
@ -233,8 +226,6 @@ SYM_CODE_END(copy_user_short_string)
* - Require 4-byte alignment when size is 4 bytes.
*/
SYM_FUNC_START(__copy_user_nocache)
ASM_STAC
/* If size is less than 8 bytes, go to 4-byte copy */
cmpl $8,%edx
jb .L_4b_nocache_copy_entry
@ -327,7 +318,6 @@ SYM_FUNC_START(__copy_user_nocache)
/* Finished copying; fence the prior stores */
.L_finish_copy:
xorl %eax,%eax
ASM_CLAC
sfence
RET

6
arch/x86/lib/usercopy_64.c
View File

@ -45,7 +45,11 @@ EXPORT_SYMBOL_GPL(arch_wb_cache_pmem);
long __copy_user_flushcache(void *dst, const void __user *src, unsigned size)
{
unsigned long flushed, dest = (unsigned long) dst;
long rc = __copy_user_nocache(dst, src, size, 0);
long rc;
stac();
rc = __copy_user_nocache(dst, src, size, 0);
clac();
/*
* __copy_user_nocache() uses non-temporal stores for the bulk

3
tools/objtool/check.c
View File

@ -1285,6 +1285,9 @@ static const char *uaccess_safe_builtin[] = {
"copy_mc_enhanced_fast_string",
"ftrace_likely_update", /* CONFIG_TRACE_BRANCH_PROFILING */
"clear_user_original",
"copy_user_generic_unrolled",
"copy_user_fast_string",
"__copy_user_nocache",
NULL
};