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Sun, 19 Jul 2026 01:57:47 -0700 (PDT) Received: from [192.168.0.38] ([86.12.216.189]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47f63ed2313sm18259369f8f.23.2026.07.19.01.57.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 19 Jul 2026 01:57:47 -0700 (PDT) Message-ID: Date: Sun, 19 Jul 2026 09:57:46 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] GDB: aarch64: Fix inferior function call if GCS is present but disabled Content-Language: en-US To: Thiago Jung Bauermann , gdb-patches@sourceware.org References: <20260708060331.347616-1-thiago.bauermann@linaro.org> From: Luis In-Reply-To: <20260708060331.347616-1-thiago.bauermann@linaro.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gdb-patches-bounces~public-inbox=simark.ca@sourceware.org Hi Thiago. Thanks for the patch. On 08/07/2026 07:03, Thiago Jung Bauermann wrote: > On AArch64, even if the Guarded Control Stack feature is present on the > system the inferior may not have enabled it. > > There's a bug in GDB's GCS support in that if the system supports GCS, > GDB will always push a GCS entry when doing an inferior function call > even if the inferior doesn't have it enabled. This causes inferior > function calls to fail. E.g.: > > (gdb) p foo () > Can't write to Guarded Control Stack. > > The error message is because the GCSPR doesn't point to a valid memory > address. > > Fix by checking whether GCS is enabled in the inferior before trying to > push a GCS entry. > > Regression tested on an aarch64-linux-gnu QEMU VM with GCS present. > --- > > GCS support first appeared in GDB 17, so if this patch is approved for > trunk is it ok to also commit it to the branch? Sounds good to me. > > gdb/aarch64-tdep.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c > index 886e7ce1e7b6..b4437dcccc8a 100644 > --- a/gdb/aarch64-tdep.c > +++ b/gdb/aarch64-tdep.c > @@ -1934,7 +1934,11 @@ static void > aarch64_shadow_stack_push (gdbarch *gdbarch, CORE_ADDR new_addr, > regcache *regcache) > { > - aarch64_push_gcs_entry (regcache, new_addr); > + bool gcs_is_enabled; > + > + gdbarch_get_shadow_stack_pointer (gdbarch, regcache, gcs_is_enabled); > + if (gcs_is_enabled) > + aarch64_push_gcs_entry (regcache, new_addr); > } > > /* Implement the "push_dummy_call" gdbarch method. */ LGTM, with Baris' suggestion. Approved-By: Luis Machado