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-rw-r--r--util/statetrace/arch/tracechild_arm.cc36
1 files changed, 21 insertions, 15 deletions
diff --git a/util/statetrace/arch/tracechild_arm.cc b/util/statetrace/arch/tracechild_arm.cc
index 4687b46f0..b52c0694a 100644
--- a/util/statetrace/arch/tracechild_arm.cc
+++ b/util/statetrace/arch/tracechild_arm.cc
@@ -203,22 +203,28 @@ ostream & ARMTraceChild::outputStartState(ostream & os)
bool ARMTraceChild::step()
{
+ const uint32_t bkpt_inst = 0xe7f001f0;
- const uint32_t bkpt_inst = 0xE1200070;
- const uint32_t bkpt_mask = 0xFFF000F0;
-
- const uint32_t swi_inst = 0x0F0000000;
- const uint32_t swi_mask = 0x0F0000000;
-
- uint32_t next_op = ptrace(PTRACE_PEEKDATA, pid, getPC(), 0);
- if ((next_op & swi_mask) == swi_inst) {
- ptrace(PTRACE_POKEDATA, pid, next_op + sizeof(uint32_t), bkpt_inst);
- ptraceSingleStep();
- ptrace(PTRACE_POKEDATA, pid, next_op + sizeof(uint32_t), next_op);
- }
- else
- {
- ptraceSingleStep();
+ uint32_t lr = getRegVal(14);
+ uint32_t pc = getPC();
+ uint32_t lrOp;
+
+ // Since ARM uses software breakpoints behind the scenes, they don't work
+ // in read only areas like the page of routines provided by the kernel. The
+ // link register generally holds the address the process wants to the
+ // kernel to return to after it's done, so we'll install a software
+ // breakpoint there. If the lr happens to point to the next instruction
+ // we'll leave out our breakpoint to avoid an infinite loop. This isn't a
+ // fool proof strategy, but it should work well in all the reasonable
+ // scenarios I can think of right now.
+
+ if (pc != lr) {
+ lrOp = ptrace(PTRACE_PEEKDATA, pid, lr, 0);
+ ptrace(PTRACE_POKEDATA, pid, lr, bkpt_inst);
+ }
+ ptraceSingleStep();
+ if (pc != lr) {
+ ptrace(PTRACE_POKEDATA, pid, lr, lrOp);
}
}