[PATCH] target/arm: Report pauth information to gdb as 'pauth_v2'

[PATCH] target/arm: Report pauth information to gdb as 'pauth_v2'

[Peter Maydell]

So that we can avoid the "older gdb crashes" problem described in
commit 5787d17a42f7af4 and which caused us to disable reporting pauth
information via the gdbstub, newer gdb is going to implement support
for recognizing the pauth information via a new feature name:
 org.gnu.gdb.aarch64.pauth_v2

Older gdb won't recognize this feature name, so we can re-enable the
pauth support under the new name without risking them crashing.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
I think the gdb change isn't quite upstream yet, but this is
for 8.1 so I would expect it to be there by the time we
get around to committing this patch to QEMU.
---
 target/arm/gdbstub.c      | 9 ++++-----
 gdb-xml/aarch64-pauth.xml | 2 +-
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/target/arm/gdbstub.c b/target/arm/gdbstub.c
index 13fbe9b0d7e..03b17c814f6 100644
--- a/target/arm/gdbstub.c
+++ b/target/arm/gdbstub.c
@@ -521,18 +521,17 @@ void arm_cpu_register_gdb_regs_for_features(ARMCPU *cpu)
                                      aarch64_gdb_set_fpu_reg,
                                      34, "aarch64-fpu.xml", 0);
         }
-#if 0
         /*
-         * GDB versions 9 through 12 have a bug which means they will
-         * crash if they see this XML from QEMU; disable it for the 8.0
-         * release, pending a better solution.
+         * Note that we report pauth information via the feature name
+         * org.gnu.gdb.aarch64.pauth_v2, not org.gnu.gdb.aarch64.pauth.
+         * GDB versions 9 through 12 have a bug where they will crash
+         * if they see the latter XML from QEMU.
          */
         if (isar_feature_aa64_pauth(&cpu->isar)) {
             gdb_register_coprocessor(cs, aarch64_gdb_get_pauth_reg,
                                      aarch64_gdb_set_pauth_reg,
                                      4, "aarch64-pauth.xml", 0);
         }
-#endif
 #endif
     } else {
         if (arm_feature(env, ARM_FEATURE_NEON)) {
diff --git a/gdb-xml/aarch64-pauth.xml b/gdb-xml/aarch64-pauth.xml
index 24af5f903c1..0a5c566d668 100644
--- a/gdb-xml/aarch64-pauth.xml
+++ b/gdb-xml/aarch64-pauth.xml
@@ -6,7 +6,7 @@
      notice and this notice are preserved.  -->
 
 <!DOCTYPE feature SYSTEM "gdb-target.dtd">
-<feature name="org.gnu.gdb.aarch64.pauth">
+<feature name="org.gnu.gdb.aarch64.pauth_v2">
   <reg name="pauth_dmask" bitsize="64"/>
   <reg name="pauth_cmask" bitsize="64"/>
   <reg name="pauth_dmask_high" bitsize="64"/>
-- 
2.34.1

Re: [PATCH] target/arm: Report pauth information to gdb as 'pauth_v2'

[Richard Henderson]

On 4/6/23 08:08, Peter Maydell wrote:
> So that we can avoid the "older gdb crashes" problem described in
> commit 5787d17a42f7af4 and which caused us to disable reporting pauth
> information via the gdbstub, newer gdb is going to implement support
> for recognizing the pauth information via a new feature name:
>   org.gnu.gdb.aarch64.pauth_v2
> 
> Older gdb won't recognize this feature name, so we can re-enable the
> pauth support under the new name without risking them crashing.
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
> I think the gdb change isn't quite upstream yet, but this is
> for 8.1 so I would expect it to be there by the time we
> get around to committing this patch to QEMU.
> ---
>   target/arm/gdbstub.c      | 9 ++++-----
>   gdb-xml/aarch64-pauth.xml | 2 +-
>   2 files changed, 5 insertions(+), 6 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~