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authorManeesh Soni <manesoni@cisco.com>2011-11-08 15:38:26 +0400
committerRalf Baechle <ralf@linux-mips.org>2011-12-08 02:04:03 +0400
commit6457a396bbc20656009eaf950ca165912a943520 (patch)
tree5a940616d2b1b55f182d4022a39c4d37a9cda1e7 /arch/mips/include/asm/kprobes.h
parentd8d4e3ae0b5c179c0bfd3f0af5b352d13bea9cfa (diff)
downloadlinux-6457a396bbc20656009eaf950ca165912a943520.tar.xz
MIPS Kprobes: Support branch instructions probing
This patch provides support for kprobes on branch instructions. The branch instruction at the probed address is actually emulated and not executed out-of-line like other normal instructions. Instead the delay-slot instruction is copied and single stepped out of line. At the time of probe hit, the original branch instruction is evaluated and the target cp0_epc is computed similar to compute_retrun_epc(). It is also checked if the delay slot instruction can be skipped, which is true if there is a NOP in delay slot or branch is taken in case of branch likely instructions. Once the delay slot instruction is single stepped the normal execution resume with the cp0_epc updated the earlier computed cp0_epc as per the branch instructions. Signed-off-by: Maneesh Soni <manesoni@cisco.com> Signed-off-by: Victor Kamensky <kamensky@cisco.com> Cc: David Daney <david.daney@cavium.com> Cc: ananth@in.ibm.com Cc: linux-kernel@vger.kernel.org Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/2914/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch/mips/include/asm/kprobes.h')
-rw-r--r--arch/mips/include/asm/kprobes.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/mips/include/asm/kprobes.h b/arch/mips/include/asm/kprobes.h
index e6ea4d4d7205..1fbbca01e681 100644
--- a/arch/mips/include/asm/kprobes.h
+++ b/arch/mips/include/asm/kprobes.h
@@ -74,6 +74,8 @@ struct prev_kprobe {
: MAX_JPROBES_STACK_SIZE)
+#define SKIP_DELAYSLOT 0x0001
+
/* per-cpu kprobe control block */
struct kprobe_ctlblk {
unsigned long kprobe_status;
@@ -82,6 +84,9 @@ struct kprobe_ctlblk {
unsigned long kprobe_saved_epc;
unsigned long jprobe_saved_sp;
struct pt_regs jprobe_saved_regs;
+ /* Per-thread fields, used while emulating branches */
+ unsigned long flags;
+ unsigned long target_epc;
u8 jprobes_stack[MAX_JPROBES_STACK_SIZE];
struct prev_kprobe prev_kprobe;
};