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>

diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 59ea54a..3398837 100644 (file)
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -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

diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S
index d0283bc..818f2f7 100644 (file)
--- a/arch/x86/lib/copy_user_64.S
+++ b/arch/x86/lib/copy_user_64.S
@@ -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
 

diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index 6c1f8ac..15704c6 100644 (file)
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -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

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 4907545..ea62a4e 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -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
 };