[PATCH] arm64/kprobes: Tidy up sign-extension usage
Robin Murphy
robin.murphy at arm.com
Tue Oct 18 05:46:27 PDT 2016
Kprobes does not need its own homebrewed (and frankly inscrutable) sign
extension macro; just use the standard kernel functions instead. Since
the compiler actually recognises the sign-extension idiom of the latter,
we also get the small bonus of some nicer codegen, as each displacement
calculation helper then compiles to a single optimal SBFX instruction.
Signed-off-by: Robin Murphy <robin.murphy at arm.com>
---
arch/arm64/kernel/probes/simulate-insn.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/arch/arm64/kernel/probes/simulate-insn.c b/arch/arm64/kernel/probes/simulate-insn.c
index 8977ce9d009d..357d3efe1366 100644
--- a/arch/arm64/kernel/probes/simulate-insn.c
+++ b/arch/arm64/kernel/probes/simulate-insn.c
@@ -13,28 +13,26 @@
* General Public License for more details.
*/
+#include <linux/bitops.h>
#include <linux/kernel.h>
#include <linux/kprobes.h>
#include "simulate-insn.h"
-#define sign_extend(x, signbit) \
- ((x) | (0 - ((x) & (1 << (signbit)))))
-
#define bbl_displacement(insn) \
- sign_extend(((insn) & 0x3ffffff) << 2, 27)
+ sign_extend32(((insn) & 0x3ffffff) << 2, 27)
#define bcond_displacement(insn) \
- sign_extend(((insn >> 5) & 0x7ffff) << 2, 20)
+ sign_extend32(((insn >> 5) & 0x7ffff) << 2, 20)
#define cbz_displacement(insn) \
- sign_extend(((insn >> 5) & 0x7ffff) << 2, 20)
+ sign_extend32(((insn >> 5) & 0x7ffff) << 2, 20)
#define tbz_displacement(insn) \
- sign_extend(((insn >> 5) & 0x3fff) << 2, 15)
+ sign_extend32(((insn >> 5) & 0x3fff) << 2, 15)
#define ldr_displacement(insn) \
- sign_extend(((insn >> 5) & 0x7ffff) << 2, 20)
+ sign_extend32(((insn >> 5) & 0x7ffff) << 2, 20)
static inline void set_x_reg(struct pt_regs *regs, int reg, u64 val)
{
@@ -106,7 +104,7 @@ static bool __kprobes check_tbnz(u32 opcode, struct pt_regs *regs)
xn = opcode & 0x1f;
imm = ((opcode >> 3) & 0x1ffffc) | ((opcode >> 29) & 0x3);
- imm = sign_extend(imm, 20);
+ imm = sign_extend64(imm, 20);
if (opcode & 0x80000000)
val = (imm<<12) + (addr & 0xfffffffffffff000);
else
--
1.9.1
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