mirror of
https://github.com/cirosantilli/linux-kernel-module-cheat.git
synced 2026-01-25 11:11:35 +01:00
25 lines
559 B
ArmAsm
25 lines
559 B
ArmAsm
/* https://cirosantilli.com/linux-kernel-module-cheat#x86-shift-and-rotate-instructions */
|
|
|
|
#include <lkmc.h>
|
|
|
|
LKMC_PROLOGUE
|
|
/* 0xFF == -1 in 2's complement with 8-bits. */
|
|
mov $0xFF, %r12
|
|
sal %r12b
|
|
LKMC_ASSERT(jc)
|
|
/* 0xFE == -2 in 2's complement with 8-bits. */
|
|
LKMC_ASSERT_EQ(%r12, $0xFE)
|
|
|
|
/* SAR*/
|
|
sar %r12b
|
|
LKMC_ASSERT(jnc)
|
|
/* -1 */
|
|
LKMC_ASSERT_EQ(%r12, $0xFF)
|
|
|
|
/* SAR rounds to -infinity: -1 goes to -1 again. */
|
|
sar %r12b
|
|
LKMC_ASSERT(jc)
|
|
/* -1 */
|
|
LKMC_ASSERT_EQ(%r12, $0xFF)
|
|
LKMC_EPILOGUE
|