ARM: kprobes: introduces checker
This patch introdces 'checker' to decoding phase, and calls checkers
when instruction decoding. This allows further decoding for specific
instructions. This patch introduces a stub call of checkers in kprobe
arch_prepare_kprobe() as an example and for further expansion.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Reviewed-by: Jon Medhurst <tixy@linaro.org>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jon Medhurst <tixy@linaro.org>
diff --git a/arch/arm/probes/decode.c b/arch/arm/probes/decode.c
index 3b05d57..c7d4420 100644
--- a/arch/arm/probes/decode.c
+++ b/arch/arm/probes/decode.c
@@ -342,6 +342,31 @@
[DECODE_TYPE_REJECT] = sizeof(struct decode_reject)
};
+static int run_checkers(const struct decode_checker *checkers[],
+ int action, probes_opcode_t insn,
+ struct arch_probes_insn *asi,
+ const struct decode_header *h)
+{
+ const struct decode_checker **p;
+
+ if (!checkers)
+ return INSN_GOOD;
+
+ p = checkers;
+ while (*p != NULL) {
+ int retval;
+ probes_check_t *checker_func = (*p)[action].checker;
+
+ retval = INSN_GOOD;
+ if (checker_func)
+ retval = checker_func(insn, asi, h);
+ if (retval == INSN_REJECTED)
+ return retval;
+ p++;
+ }
+ return INSN_GOOD;
+}
+
/*
* probes_decode_insn operates on data tables in order to decode an ARM
* architecture instruction onto which a kprobe has been placed.
@@ -388,11 +413,17 @@
int __kprobes
probes_decode_insn(probes_opcode_t insn, struct arch_probes_insn *asi,
const union decode_item *table, bool thumb,
- bool emulate, const union decode_action *actions)
+ bool emulate, const union decode_action *actions,
+ const struct decode_checker *checkers[])
{
const struct decode_header *h = (struct decode_header *)table;
const struct decode_header *next;
bool matched = false;
+ /*
+ * @insn can be modified by decode_regs. Save its original
+ * value for checkers.
+ */
+ probes_opcode_t origin_insn = insn;
if (emulate)
insn = prepare_emulated_insn(insn, asi, thumb);
@@ -422,24 +453,41 @@
}
case DECODE_TYPE_CUSTOM: {
+ int err;
struct decode_custom *d = (struct decode_custom *)h;
- return actions[d->decoder.action].decoder(insn, asi, h);
+ int action = d->decoder.action;
+
+ err = run_checkers(checkers, action, origin_insn, asi, h);
+ if (err == INSN_REJECTED)
+ return INSN_REJECTED;
+ return actions[action].decoder(insn, asi, h);
}
case DECODE_TYPE_SIMULATE: {
+ int err;
struct decode_simulate *d = (struct decode_simulate *)h;
- asi->insn_handler = actions[d->handler.action].handler;
+ int action = d->handler.action;
+
+ err = run_checkers(checkers, action, origin_insn, asi, h);
+ if (err == INSN_REJECTED)
+ return INSN_REJECTED;
+ asi->insn_handler = actions[action].handler;
return INSN_GOOD_NO_SLOT;
}
case DECODE_TYPE_EMULATE: {
+ int err;
struct decode_emulate *d = (struct decode_emulate *)h;
+ int action = d->handler.action;
+
+ err = run_checkers(checkers, action, origin_insn, asi, h);
+ if (err == INSN_REJECTED)
+ return INSN_REJECTED;
if (!emulate)
- return actions[d->handler.action].decoder(insn,
- asi, h);
+ return actions[action].decoder(insn, asi, h);
- asi->insn_handler = actions[d->handler.action].handler;
+ asi->insn_handler = actions[action].handler;
set_emulated_insn(insn, asi, thumb);
return INSN_GOOD;
}