Re: [PATCH 0/9] Add new command to print the shadow stack backtrace

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

Thiago Jung Bauermann <thiago.bauermann@linaro.org> writes:

> I tested your patches and there's a bug unfortunately:
>
> FAIL: gdb.arch/aarch64-gcs-disp-step.exp: continue to breakpoint at blr
> FAIL: gdb.arch/aarch64-gcs-disp-step.exp: continue until exit
> FAIL: gdb.arch/aarch64-gcs.exp: call inferior function
> FAIL: gdb.arch/aarch64-gcs-return.exp: test inferior call and continue: call (int) call2()
> FAIL: gdb.arch/aarch64-gcs-return.exp: test inferior call and continue: continue until
> exit
> FAIL: gdb.arch/aarch64-gcs-return.exp: test frame level update: check gcspr of frame 1
> FAIL: gdb.arch/aarch64-gcs-return.exp: test frame level update: check gcspr of frame 2
> FAIL: gdb.arch/aarch64-gcs-return.exp: test return from current frame: continue until exit
>
> In each FAIL above a GCS error happens unexpectedly in the inferior. It
> appears that GDB isn't updating the shadow stack correctly. I still have
> to see what exactly is the problem.

The problem turned out to be simple. I just had to set the regnum for
the GCSPR in the gdbarch:

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 95af82c26327..9e866fc319d4 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -4780,6 +4780,10 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   /* Register a hook for converting a memory tag to a string.  */
   set_gdbarch_memtag_to_string (gdbarch, aarch64_memtag_to_string);
 
+  if (tdep->has_gcs ())
+    /* AArch64's shadow stack pointer is the GCSPR.  */
+    set_gdbarch_ssp_regnum (gdbarch, tdep->gcs_reg_base);
+
   /* ABI */
   set_gdbarch_short_bit (gdbarch, 16);
   set_gdbarch_int_bit (gdbarch, 32);

-- 
Thiago