xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

x86, smap: Reduce the SMAP overhead for signal handling

Browse Source 
Signal handling contains a bunch of accesses to individual user space
items, which causes an excessive number of STAC and CLAC
instructions.  Instead, let get/put_user_try ... get/put_user_catch()
contain the STAC and CLAC instructions.

This means that get/put_user_try no longer nests, and furthermore that
it is no longer legal to use user space access functions other than
__get/put_user_ex() inside those blocks.  However, these macros are
x86-specific anyway and are only used in the signal-handling paths; a
simple reordering of moving the larger subroutine calls out of the
try...catch blocks resolves that problem.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/1348256595-29119-12-git-send-email-hpa@linux.intel.com
This commit is contained in:
H. Peter Anvin
2012-09-21 12:43:15 -07:00
parent 40d3cd6695
commit 5e88353d8b
3 changed files with 27 additions and 23 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
arch/x86/include/asm/uaccess.h
View File

@@ -416,9 +416,8 @@ do { \
} while (0)
#define __get_user_asm_ex(x, addr, itype, rtype, ltype) \
asm volatile(ASM_STAC "\n" \
"1: mov"itype" %1,%"rtype"0\n" \
"2: " ASM_CLAC "\n" \
asm volatile("1: mov"itype" %1,%"rtype"0\n" \
"2:\n" \
_ASM_EXTABLE_EX(1b, 2b) \
: ltype(x) : "m" (__m(addr)))
@@ -460,9 +459,8 @@ struct __large_struct { unsigned long buf[100]; };
: ltype(x), "m" (__m(addr)), "i" (errret), "0" (err))
#define __put_user_asm_ex(x, addr, itype, rtype, ltype) \
asm volatile(ASM_STAC "\n" \
"1: mov"itype" %"rtype"0,%1\n" \
"2: " ASM_CLAC "\n" \
asm volatile("1: mov"itype" %"rtype"0,%1\n" \
"2:\n" \
_ASM_EXTABLE_EX(1b, 2b) \
: : ltype(x), "m" (__m(addr)))
@@ -470,13 +468,13 @@ struct __large_struct { unsigned long buf[100]; };
* uaccess_try and catch
*/
#define uaccess_try do { \
int prev_err = current_thread_info()->uaccess_err; \
current_thread_info()->uaccess_err = 0; \
stac(); \
barrier();
#define uaccess_catch(err) \
clac(); \
(err) |= (current_thread_info()->uaccess_err ? -EFAULT : 0); \
current_thread_info()->uaccess_err = prev_err; \
} while (0)
/**