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authorLinus Torvalds <torvalds@linux-foundation.org>2016-05-21 21:44:51 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2019-01-04 18:00:49 -0800
commit4a789213c9a54c8b618924d3421e56e98df8a447 (patch)
tree1e6775ba2fc12cb9893f09b203c85e2014de256b
parent594cc251fdd0d231d342d88b2fdff4bc42fb0690 (diff)
downloadlinux-4a789213c9a54c8b618924d3421e56e98df8a447.tar.gz
x86 uaccess: Introduce __put_user_goto
This is finally the actual reason for the odd error handling in the "unsafe_get/put_user()" functions, introduced over three years ago. Using a "jump to error label" interface is somewhat odd, but very convenient as a programming interface, and more importantly, it fits very well with simply making the target be the exception handler address directly from the inline asm. The reason it took over three years to actually do this? We need "asm goto" support for it, which only became the default on x86 last year. It's now been a year that we've forced asm goto support (see commit e501ce957a78 "x86: Force asm-goto"), and so let's just do it here too. [ Side note: this commit was originally done back in 2016. The above commentary about timing is obviously about it only now getting merged into my real upstream tree - Linus ] Sadly, gcc still only supports "asm goto" with asms that do not have any outputs, so we are limited to only the put_user case for this. Maybe in several more years we can do the get_user case too. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--arch/x86/include/asm/uaccess.h28
1 files changed, 17 insertions, 11 deletions
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index a87ab5290ab4..7328343e7204 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -463,17 +463,23 @@ struct __large_struct { unsigned long buf[100]; };
* we do not write to any memory gcc knows about, so there are no
* aliasing issues.
*/
-#define __put_user_asm(x, addr, err, itype, rtype, ltype, errret) \
- asm volatile("\n" \
- "1: mov"itype" %"rtype"1,%2\n" \
- "2:\n" \
- ".section .fixup,\"ax\"\n" \
- "3: mov %3,%0\n" \
- " jmp 2b\n" \
- ".previous\n" \
- _ASM_EXTABLE_UA(1b, 3b) \
- : "=r"(err) \
- : ltype(x), "m" (__m(addr)), "i" (errret), "0" (err))
+#define __put_user_goto(x, addr, itype, rtype, ltype, label) \
+ asm_volatile_goto("\n" \
+ "1: mov"itype" %"rtype"0,%1\n" \
+ _ASM_EXTABLE_UA(1b, %l2) \
+ : : ltype(x), "m" (__m(addr)) \
+ : : label)
+
+#define __put_user_failed(x, addr, itype, rtype, ltype, errret) \
+ ({ __label__ __puflab; \
+ int __pufret = errret; \
+ __put_user_goto(x,addr,itype,rtype,ltype,__puflab); \
+ __pufret = 0; \
+ __puflab: __pufret; })
+
+#define __put_user_asm(x, addr, retval, itype, rtype, ltype, errret) do { \
+ retval = __put_user_failed(x, addr, itype, rtype, ltype, errret); \
+} while (0)
#define __put_user_asm_ex(x, addr, itype, rtype, ltype) \
asm volatile("1: mov"itype" %"rtype"0,%1\n" \