mips: add native backtrace implementation

Should make debugging crashes on native MIPS targets far easier.
This is by no means a 100% complete or robust implementation but
it seems to handle the vast majority of functions.

Change-Id: Id5f430270e02b5092b79026b6876675c784aa649

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/mipsunwinder/init_context_32.S b/lib/mipsunwinder/init_context_32.S
new file mode 100644
index 0000000000..a943d13dc3
--- /dev/null
+++ b/lib/mipsunwinder/init_context_32.S
@@ -0,0 +1,12 @@
+#include "mips.h"
+
+    .text
+    .global mips_bt_start
+
+mips_bt_start:
+    addiu   v0, ra, -8
+    sw      v0, 0(a0)       /* ctx->pc = ra - 8 */
+    sw      sp, 4(a0)       /* ctx->sp = sp */
+    sw      zero, 8(a0)     /* ctx->depth = 0 */
+    sw      zero, 12(a0)    /* ctx->valid = 0 */
+    jr      ra