From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AB892FF8861 for ; Sat, 25 Apr 2026 15:52:26 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1wGfIi-00083p-8K; Sat, 25 Apr 2026 11:52:12 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wGfIU-00080V-2Q for qemu-devel@nongnu.org; Sat, 25 Apr 2026 11:51:58 -0400 Received: from tor.source.kernel.org ([172.105.4.254]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1wGfIS-000127-E9 for qemu-devel@nongnu.org; Sat, 25 Apr 2026 11:51:57 -0400 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 2F731600CB; Sat, 25 Apr 2026 15:51:48 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 773DEC2BCB6; Sat, 25 Apr 2026 15:51:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777132307; bh=N0SltF6kWrhKYQvGQd+k67AMBYWPlgGMkWYMzuPa5JM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ivy2zczBHzMWbM+4FCuEJC/Ca78ks/MI9FIjvCRZPCXuPo3leVywMOb1mj1FYRDGF /Ak3b07ncGbpFC0BYAr+K78MFFwcHMVEU2v/byy6pdRvmpuZT7N0WpeMMsqi4M3pOa MiMPoPgVooMC2aSADUrfOUOgXg4w5fc1VB2Eby5XXW99Yw8bmYEVZdpEvFyj+uRKXM 4/HrGjZHZFvJ9pgvY5ZsBe1UmpxARTPOro8gJTk0h+DNZHMAV0urLXTag/5iLo1fMz ZoS3twJUL3JC/jP5SY79/hzOMllEM/tgsj8Xv/rIUyEJysLftw7EUVwMXDSNuENoHJ QFcMEq0sonNbQ== From: Helge Deller To: qemu-devel@nongnu.org Cc: Helge Deller , Jiaxun Yang , Laurent Vivier , Pierrick Bouvier , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= Subject: [PULL 02/14] linux-user/ppc: Fix ppc64 rt_sigframe stack offset Date: Sat, 25 Apr 2026 17:51:28 +0200 Message-ID: <20260425155140.50186-3-deller@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260425155140.50186-1-deller@kernel.org> References: <20260425155140.50186-1-deller@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=172.105.4.254; envelope-from=deller@kernel.org; helo=tor.source.kernel.org X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org From: Matt Turner The kernel's 64-bit signal delivery (signal_64.c) uses: newsp = frame - __SIGNAL_FRAMESIZE while the 32-bit path (signal_32.c) uses: newsp = frame - (__SIGNAL_FRAMESIZE + 16) The extra 16 bytes in the 32-bit case is to place siginfo and ucontext at the same offsets as older kernels (see the comment in signal_32.c). The 64-bit rt_sigframe starts with ucontext directly and does not need this adjustment. QEMU's setup_rt_frame() unconditionally used (SIGNAL_FRAMESIZE + 16) for both 32-bit and 64-bit, placing the handler's SP 16 bytes too low on ppc64. Signal delivery and return still worked because do_rt_sigreturn had the matching wrong offset, but the vDSO DWARF unwind info encodes the correct kernel offset. This caused any DWARF unwinder (libunwind, libgcc, etc.) to compute a CFA that is 16 bytes off, reading garbage register values from the signal frame. Define RT_SIGFRAME_ADJUST (0 on ppc64, 16 on ppc32) and use it in both setup_rt_frame and do_rt_sigreturn to match the kernel. This was verified by A/B testing with libunwind's test suite: ppc64le: Gtest-bt, Ltest-bt, Gtest-concurrent, Ltest-concurrent, and Ltest-sig-context all change from FAIL to PASS. ppc64be: Gtest-bt, Ltest-bt, and Ltest-sig-context all change from FAIL to PASS. Signed-off-by: Matt Turner Reviewed-by: Peter Maydell Signed-off-by: Helge Deller Cc: qemu-stable@nongnu.org --- linux-user/ppc/signal.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c index 24e5a02a78..a9c10e0987 100644 --- a/linux-user/ppc/signal.c +++ b/linux-user/ppc/signal.c @@ -210,6 +210,18 @@ QEMU_BUILD_BUG_ON(offsetof(struct target_rt_sigframe, uc.tuc_mcontext) #endif +#ifdef TARGET_PPC64 +#define RT_SIGFRAME_ADJUST 0 +#else +/* + * For 32-bit rt sigframes we have an extra 16 bytes of gap + * on top of __SIGNAL_FRAMESIZE; this is to get the siginfo + * and ucontext in the same positions as in older kernels. + * See Linux's arch/powerpc/kernel/signal_32.c. + */ +#define RT_SIGFRAME_ADJUST 16 +#endif + #if defined(TARGET_PPC64) struct target_func_ptr { @@ -525,7 +537,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka, env->fpscr = 0; /* Create a stack frame for the caller of the handler. */ - newsp = rt_sf_addr - (SIGNAL_FRAMESIZE + 16); + newsp = rt_sf_addr - (SIGNAL_FRAMESIZE + RT_SIGFRAME_ADJUST); err |= put_user(env->gpr[1], newsp, target_ulong); if (err) @@ -641,7 +653,7 @@ long do_rt_sigreturn(CPUPPCState *env) struct target_rt_sigframe *rt_sf = NULL; target_ulong rt_sf_addr; - rt_sf_addr = env->gpr[1] + SIGNAL_FRAMESIZE + 16; + rt_sf_addr = env->gpr[1] + SIGNAL_FRAMESIZE + RT_SIGFRAME_ADJUST; if (!lock_user_struct(VERIFY_READ, rt_sf, rt_sf_addr, 1)) goto sigsegv; -- 2.53.0