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authorWang Nan <wangnan0@huawei.com>2015-01-09 14:37:36 +0800
committerJon Medhurst <tixy@linaro.org>2015-01-13 16:10:17 +0000
commit0dc016dbd820260b8ea74337980735b8c88d4ef2 (patch)
tree0a6408b4181016d41858afec026cc4e93455f852 /arch/arm/include/asm/kprobes.h
parentcbf6ab52add20b845f903decc973afbd5463c527 (diff)
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>
Diffstat (limited to 'arch/arm/include/asm/kprobes.h')
-rw-r--r--arch/arm/include/asm/kprobes.h29
1 files changed, 29 insertions, 0 deletions
diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h
index 56f9ac68fbd1..50ff3bc7928e 100644
--- a/arch/arm/include/asm/kprobes.h
+++ b/arch/arm/include/asm/kprobes.h
@@ -50,5 +50,34 @@ int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
int kprobe_exceptions_notify(struct notifier_block *self,
unsigned long val, void *data);
+/* optinsn template addresses */
+extern __visible kprobe_opcode_t optprobe_template_entry;
+extern __visible kprobe_opcode_t optprobe_template_val;
+extern __visible kprobe_opcode_t optprobe_template_call;
+extern __visible kprobe_opcode_t optprobe_template_end;
+extern __visible kprobe_opcode_t optprobe_template_sub_sp;
+extern __visible kprobe_opcode_t optprobe_template_add_sp;
+
+#define MAX_OPTIMIZED_LENGTH 4
+#define MAX_OPTINSN_SIZE \
+ ((unsigned long)&optprobe_template_end - \
+ (unsigned long)&optprobe_template_entry)
+#define RELATIVEJUMP_SIZE 4
+
+struct arch_optimized_insn {
+ /*
+ * copy of the original instructions.
+ * Different from x86, ARM kprobe_opcode_t is u32.
+ */
+#define MAX_COPIED_INSN DIV_ROUND_UP(RELATIVEJUMP_SIZE, sizeof(kprobe_opcode_t))
+ kprobe_opcode_t copied_insn[MAX_COPIED_INSN];
+ /* detour code buffer */
+ kprobe_opcode_t *insn;
+ /*
+ * We always copy one instruction on ARM,
+ * so size will always be 4, and unlike x86, there is no
+ * need for a size field.
+ */
+};
#endif /* _ARM_KPROBES_H */