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s390/stackleak: provide fast __stackleak_poison() implementation 

Provide an s390 specific __stackleak_poison() implementation which is
faster than the generic variant.

For the original implementation with an enforced 4kb stackframe for the
getpid() system call the system call overhead increases by a factor of 3 if
the stackleak feature is enabled. Using the s390 mvc based variant this is
reduced to an increase of 25% instead.

This is within the expected area, since the mvc based implementation is
more or less a memset64() variant which comes with similar results. See
commit 0b77d6701c ("s390: implement memset16, memset32 & memset64").

Reviewed-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/r/20230405130841.1350565-3-hca@linux.ibm.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2023-04-05 15:08:41 +02:00 committed by Vasily Gorbik
parent 491a78663e
commit 2a405f6bb3
1 changed files with 35 additions and 0 deletions
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35
arch/s390/include/asm/processor.h
View File

@ -118,6 +118,41 @@ unsigned long vdso_size(void);
#define HAVE_ARCH_PICK_MMAP_LAYOUT
#define __stackleak_poison __stackleak_poison
static __always_inline void __stackleak_poison(unsigned long erase_low,
unsigned long erase_high,
unsigned long poison)
{
unsigned long tmp, count;
count = erase_high - erase_low;
if (!count)
return;
asm volatile(
" cghi %[count],8\n"
" je 2f\n"
" aghi %[count],-(8+1)\n"
" srlg %[tmp],%[count],8\n"
" ltgr %[tmp],%[tmp]\n"
" jz 1f\n"
"0: stg %[poison],0(%[addr])\n"
" mvc 8(256-8,%[addr]),0(%[addr])\n"
" la %[addr],256(%[addr])\n"
" brctg %[tmp],0b\n"
"1: stg %[poison],0(%[addr])\n"
" larl %[tmp],3f\n"
" ex %[count],0(%[tmp])\n"
" j 4f\n"
"2: stg %[poison],0(%[addr])\n"
" j 4f\n"
"3: mvc 8(1,%[addr]),0(%[addr])\n"
"4:\n"
: [addr] "+&a" (erase_low), [count] "+&d" (count), [tmp] "=&a" (tmp)
: [poison] "d" (poison)
: "memory", "cc"
);
}
/*
* Thread structure
*/