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Thu, 05 Mar 2026 19:57:12 -0800 (PST) Received: from localhost ([2804:14d:7e39:8083:f04c:42e3:5943:38f6]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-56b09a40cbdsm193605e0c.9.2026.03.05.19.57.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Mar 2026 19:57:12 -0800 (PST) From: Thiago Jung Bauermann To: Christina Schimpe Cc: gdb-patches@sourceware.org Subject: Re: [PATCH v2 1/9] gdb: Generalize handling of the shadow stack pointer. In-Reply-To: <871phxzlzr.fsf@linaro.org> (Thiago Jung Bauermann's message of "Fri, 06 Mar 2026 00:15:52 -0300") References: <20260123080532.878738-1-christina.schimpe@intel.com> <20260123080532.878738-2-christina.schimpe@intel.com> <871phxzlzr.fsf@linaro.org> User-Agent: mu4e 1.12.15; emacs 30.2 Date: Fri, 06 Mar 2026 00:57:10 -0300 Message-ID: <87tsuty5ih.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain 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 Thiago Jung Bauermann writes: > Christina Schimpe writes: > >> +static bool >> +amd64_linux_top_addr_empty_shadow_stack >> + (gdbarch *gdbarch, const CORE_ADDR addr, >> + const std::pair 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 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