linux/arch/arm/kernel/jump_label.c
Wang Nan 0dc016dbd8 ARM: kprobes: enable OPTPROBES for ARM 32
This patch introduce kprobeopt for ARM 32.

Limitations:
 - Currently only kernel compiled with ARM ISA is supported.

 - Offset between probe point and optinsn slot must not larger than
   32MiB. Masami Hiramatsu suggests replacing 2 words, it will make
   things complex. Futher patch can make such optimization.

Kprobe opt on ARM is relatively simpler than kprobe opt on x86 because
ARM instruction is always 4 bytes aligned and 4 bytes long. This patch
replace probed instruction by a 'b', branch to trampoline code and then
calls optimized_callback(). optimized_callback() calls opt_pre_handler()
to execute kprobe handler. It also emulate/simulate replaced instruction.

When unregistering kprobe, the deferred manner of unoptimizer may leave
branch instruction before optimizer is called. Different from x86_64,
which only copy the probed insn after optprobe_template_end and
reexecute them, this patch call singlestep to emulate/simulate the insn
directly. Futher patch can optimize this behavior.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Will Deacon <will.deacon@arm.com>
Reviewed-by: Jon Medhurst (Tixy) <tixy@linaro.org>
Signed-off-by: Jon Medhurst <tixy@linaro.org>
2015-01-13 16:10:17 +00:00

39 lines
815 B
C

#include <linux/kernel.h>
#include <linux/jump_label.h>
#include <asm/patch.h>
#include <asm/insn.h>
#ifdef HAVE_JUMP_LABEL
static void __arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type,
bool is_static)
{
void *addr = (void *)entry->code;
unsigned int insn;
if (type == JUMP_LABEL_ENABLE)
insn = arm_gen_branch(entry->code, entry->target);
else
insn = arm_gen_nop();
if (is_static)
__patch_text_early(addr, insn);
else
patch_text(addr, insn);
}
void arch_jump_label_transform(struct jump_entry *entry,
enum jump_label_type type)
{
__arch_jump_label_transform(entry, type, false);
}
void arch_jump_label_transform_static(struct jump_entry *entry,
enum jump_label_type type)
{
__arch_jump_label_transform(entry, type, true);
}
#endif