Enhance backtracing code to print out userspace registers in case we
are at syscall entry. Other architectures supported by crash are
already doing this.

Signed-off-by: Mika Westerberg <ext-mika.1.westerberg@nokia.com>
---
I tested this with both unwind tables and framepointers enabled on
my test vmcores, and also on live system.

arm.c | 31 ++++++++++++++++++++++++++++++-
1 files changed, 30 insertions(+), 1 deletions(-)

diff --git a/arm.c b/arm.c
index 985f78e..a8a34b9 100644
--- a/arm.c
+++ b/arm.c
@@ -31,6 +31,7 @@ static int arm_verify_symbol(const char *, ulong, char);
static int arm_is_module_addr(ulong);
static int arm_is_kvaddr(ulong);
static int arm_in_exception_text(ulong);
+static int arm_in_ret_from_syscall(ulong);
static void arm_back_trace(struct bt_info *);
static void arm_back_trace_cmd(struct bt_info *);
static ulong arm_processor_speed(void);
@@ -668,6 +669,16 @@ arm_in_exception_text(ulong pc)
}

/*
+ * Returns TRUE if given pc points to a return from syscall entrypoint.
+ */
+static int
+arm_in_ret_from_syscall(ulong pc)
+{
+ return (pc == symbol_value("ret_fast_syscall") ||
+ pc == symbol_value("ret_slow_syscall"));
+}
+
+/*
* Unroll the kernel stack using a minimal amount of gdb services.
*/
static void
@@ -1188,8 +1199,26 @@ arm_dump_backtrace_entry(struct bt_info *bt, int level, ulong from, ulong sp)
fprintf(fp, " %s
", buf);
}

- if (arm_in_exception_text(bt->instptr))
+ if (arm_in_exception_text(bt->instptr)) {
arm_dump_exception_stack(sp, sp + sizeof(struct arm_pt_regs));
+ } else if (arm_in_ret_from_syscall(from)) {
+ /*
+ * When we are returning from the syscall, here is
+ * what the stack frame looks like:
+ *
+ * SP + 0 {r4, r5}
+ * SP + 8 user pt_regs
+ *
+ * The asm syscall handler pushes fifth and sixth
+ * registers onto the stack before calling the
+ * actual syscall handler.
+ *
+ * So in order to print out the user registers when
+ * the syscall was made, we need to adjust sp for 8.
+ */
+ arm_dump_exception_stack(sp + 8,
+ sp + 8 + sizeof(struct arm_pt_regs));
+ }

if (bt->flags & BT_FULL) {
if (kt->flags & DWARF_UNWIND) {
--
1.7.3.2

--
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