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x86/uaccess: Move copy_user_handle_tail() into asm
By writing the function in asm we avoid cross object code flow and objtool no longer gets confused about a 'stray' CLAC. Also; the asm version is actually _simpler_. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
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4 changed files with 48 additions and 47 deletions
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@ -148,30 +148,6 @@
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_ASM_PTR (entry); \
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.popsection
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.macro ALIGN_DESTINATION
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/* check for bad alignment of destination */
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movl %edi,%ecx
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andl $7,%ecx
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jz 102f /* already aligned */
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subl $8,%ecx
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negl %ecx
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subl %ecx,%edx
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100: movb (%rsi),%al
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101: movb %al,(%rdi)
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incq %rsi
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incq %rdi
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decl %ecx
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jnz 100b
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102:
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.section .fixup,"ax"
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103: addl %ecx,%edx /* ecx is zerorest also */
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jmp copy_user_handle_tail
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.previous
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_ASM_EXTABLE_UA(100b, 103b)
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_ASM_EXTABLE_UA(101b, 103b)
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.endm
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#else
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# define _EXPAND_EXTABLE_HANDLE(x) #x
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# define _ASM_EXTABLE_HANDLE(from, to, handler) \
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@ -207,9 +207,6 @@ __copy_from_user_flushcache(void *dst, const void __user *src, unsigned size)
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return __copy_user_flushcache(dst, src, size);
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}
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unsigned long
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copy_user_handle_tail(char *to, char *from, unsigned len);
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unsigned long
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mcsafe_handle_tail(char *to, char *from, unsigned len);
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@ -16,6 +16,30 @@
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#include <asm/smap.h>
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#include <asm/export.h>
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.macro ALIGN_DESTINATION
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/* check for bad alignment of destination */
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movl %edi,%ecx
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andl $7,%ecx
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jz 102f /* already aligned */
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subl $8,%ecx
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negl %ecx
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subl %ecx,%edx
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100: movb (%rsi),%al
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101: movb %al,(%rdi)
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incq %rsi
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incq %rdi
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decl %ecx
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jnz 100b
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102:
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.section .fixup,"ax"
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103: addl %ecx,%edx /* ecx is zerorest also */
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jmp copy_user_handle_tail
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.previous
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_ASM_EXTABLE_UA(100b, 103b)
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_ASM_EXTABLE_UA(101b, 103b)
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.endm
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/*
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* copy_user_generic_unrolled - memory copy with exception handling.
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* This version is for CPUs like P4 that don't have efficient micro
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@ -193,6 +217,30 @@ ENTRY(copy_user_enhanced_fast_string)
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ENDPROC(copy_user_enhanced_fast_string)
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EXPORT_SYMBOL(copy_user_enhanced_fast_string)
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/*
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* Try to copy last bytes and clear the rest if needed.
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* Since protection fault in copy_from/to_user is not a normal situation,
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* it is not necessary to optimize tail handling.
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*
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* Input:
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* rdi destination
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* rsi source
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* rdx count
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*
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* Output:
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* eax uncopied bytes or 0 if successful.
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*/
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ALIGN;
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copy_user_handle_tail:
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movl %edx,%ecx
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1: rep movsb
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2: mov %ecx,%eax
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ASM_CLAC
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ret
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_ASM_EXTABLE_UA(1b, 2b)
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ENDPROC(copy_user_handle_tail)
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/*
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* copy_user_nocache - Uncached memory copy with exception handling
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* This will force destination out of cache for more performance.
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@ -54,26 +54,6 @@ unsigned long clear_user(void __user *to, unsigned long n)
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}
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EXPORT_SYMBOL(clear_user);
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/*
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* Try to copy last bytes and clear the rest if needed.
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* Since protection fault in copy_from/to_user is not a normal situation,
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* it is not necessary to optimize tail handling.
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*/
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__visible unsigned long
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copy_user_handle_tail(char *to, char *from, unsigned len)
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{
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for (; len; --len, to++) {
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char c;
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if (__get_user_nocheck(c, from++, sizeof(char)))
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break;
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if (__put_user_nocheck(c, to, sizeof(char)))
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break;
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}
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clac();
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return len;
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}
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/*
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* Similar to copy_user_handle_tail, probe for the write fault point,
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* but reuse __memcpy_mcsafe in case a new read error is encountered.
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