Re: [PATCH v2 1/9] gdb: Generalize handling of the shadow stack pointer.

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

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

> Christina Schimpe <christina.schimpe@intel.com> writes:
>
>> +static bool
>> +amd64_linux_top_addr_empty_shadow_stack
>> +  (gdbarch *gdbarch, const CORE_ADDR addr,
>> +   const std::pair<CORE_ADDR, CORE_ADDR> range)
>>  {
>> -  if (regnum == gdbarch_pc_regnum (gdbarch))
>> -    reg->how = DWARF2_FRAME_REG_RA;
>> -  else if (regnum == gdbarch_sp_regnum (gdbarch))
>> -    reg->how = DWARF2_FRAME_REG_CFA;
>> -  else if (regnum == AMD64_PL3_SSP_REGNUM)
>> -    {
>> -      reg->how = DWARF2_FRAME_REG_FN;
>> -      reg->loc.fn = amd64_linux_dwarf2_prev_ssp;
>> -    }
>> +  return addr == range.second;
>>  }
>
> Next week I'll provide the AArch64 implementation of this hook,
> if you can squash it into your patch.

It turns out I had it in my notes for patch 6:

diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 836af863d3ad..112d42c6a1ac 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -1909,6 +1909,23 @@ aarch64_pop_gcs_entry (regcache *regs)
   regcache_cooked_write_unsigned (regs, tdep->gcs_reg_base, gcs_addr + 8);
 }
 
+static bool
+aarch64_top_addr_empty_shadow_stack (gdbarch *gdbarch, const CORE_ADDR addr,
+				     const std::pair<CORE_ADDR, CORE_ADDR> range)
+{
+  gdb_assert (addr >= range.first);
+
+  /* For AArch64, addr must be strictly less than the upper address in the
+     range, but other architectures allow it to be equal to the upper
+     address when the stack is empty so GDB core works with those addresses
+     and can send them our way.  */
+  gdb_assert (addr <= range.second);
+
+  /* The GCS grows down, and the oldest entry isn't an address.
+     Just the value '0'.  */
+  return addr >= range.second - 8;
+}
+
 /* Implement the "push_dummy_call" gdbarch method.  */
 
 static CORE_ADDR
@@ -4790,7 +4807,12 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 
   /* AArch64's shadow stack pointer is the GCSPR.  */
   if (tdep->has_gcs ())
-    set_gdbarch_ssp_regnum (gdbarch, tdep->gcs_reg_base);
+    {
+      /* AArch64's shadow stack pointer is the GCSPR.  */
+      set_gdbarch_ssp_regnum (gdbarch, tdep->gcs_reg_base);
+      set_gdbarch_top_addr_empty_shadow_stack
+	(gdbarch, aarch64_top_addr_empty_shadow_stack);
+    }
 
   /* ABI */
   set_gdbarch_short_bit (gdbarch, 16);


So with the above, for this patch:

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>

-- 
Thiago