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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=qqoupK5Oq6XKew6i6oyqJ6+pHqm95p/dfVqnR40LUaA=; b=rpxKXrblKlNo37uBp4tLaqpGrayo45N6hCFZW5p9UFUgN4gO7QShTMztGyEnqa9jF7 4yWDzLmDNGvGUAStr/G7cL0KaMbCVDLSMIlphEUcZ1yIaJapjGR7wqyhSz1YUUpHBER9 LBWAOHI3uBp2FZ7YjrjLnXxUMuOzODEKl9QkAsxqQ+g0M7E5YSWGXVTwVkjnbi++vw5R p4+dPjDWENz38k+Atrbw+ZrswWqFsaxiRJs7Q3h+djNsIQ9pvtSmiIUru7i/u/pdvwQm dAHr4WFEXhyguF63OxeW4BWTDO4Qa1Vrwd8hOhK3OZlhLA5DGOYAEYNtyYBh4T+Gb4gD FJOA== X-Gm-Message-State: AOAM532Jc2ZD2QC0/w9hrU31Tqqg7NIkj9jIMQ3uzy0feOtPCuNXt05r hYh40P5MUSJCXJxaFsIu5W8oqeWw2A== X-Google-Smtp-Source: ABdhPJyWVGryZT5XObBbMQLsdgzLLnVckhY0wPAFG2dfmer9W5MvZSPtNAV1kDIPh+YBKZzAr3C5UarrWg== X-Received: by 2002:aca:c683:: with SMTP id w125mr443202oif.37.1594060043510; Mon, 06 Jul 2020 11:27:23 -0700 (PDT) Date: Mon, 6 Jul 2020 18:27:13 +0000 In-Reply-To: <1592531704.23014.1.camel@mtkswgap22> Message-Id: <20200706182713.3693762-1-nhuck@google.com> Mime-Version: 1.0 References: <1592531704.23014.1.camel@mtkswgap22> X-Mailer: git-send-email 2.27.0.212.ge8ba1cc988-goog Subject: [PATCH v2] ARM: stacktrace: Fix unwind_frame for clang-built kernels From: Nathan Huckleberry To: linux@armlinux.org.uk, vincent.whitchurch@axis.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200706_142728_095462_73590DFB X-CRM114-Status: GOOD ( 12.68 ) X-Spam-Score: -7.7 (-------) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-7.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [2607:f8b0:4864:20:0:0:0:24a listed in] [list.dnswl.org] -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.0 DKIMWL_WL_MED DKIMwl.org - Medium sender X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Nick Desaulniers , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Nathan Huckleberry , clang-built-linux@googlegroups.com, Miles Chen , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Since clang does not push pc and sp in function prologues, the current implementation of unwind_frame does not work. By using the previous frame's lr/fp instead of saved pc/sp we get valid unwinds on clang-built kernels. The bounds check on next frame pointer must be changed as well since there are 8 less bytes between frames. This fixes /proc//stack. Link: https://github.com/ClangBuiltLinux/linux/issues/912 Reported-by: Miles Chen Tested-by: Miles Chen Cc: stable@vger.kernel.org Reviewed-by: Nick Desaulniers Signed-off-by: Nathan Huckleberry --- arch/arm/kernel/stacktrace.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c index cc726afea023..76ea4178a55c 100644 --- a/arch/arm/kernel/stacktrace.c +++ b/arch/arm/kernel/stacktrace.c @@ -22,6 +22,19 @@ * A simple function epilogue looks like this: * ldm sp, {fp, sp, pc} * + * When compiled with clang, pc and sp are not pushed. A simple function + * prologue looks like this when built with clang: + * + * stmdb {..., fp, lr} + * add fp, sp, #x + * sub sp, sp, #y + * + * A simple function epilogue looks like this when built with clang: + * + * sub sp, fp, #x + * ldm {..., fp, pc} + * + * * Note that with framepointer enabled, even the leaf functions have the same * prologue and epilogue, therefore we can ignore the LR value in this case. */ @@ -34,6 +47,16 @@ int notrace unwind_frame(struct stackframe *frame) low = frame->sp; high = ALIGN(low, THREAD_SIZE); +#ifdef CONFIG_CC_IS_CLANG + /* check current frame pointer is within bounds */ + if (fp < low + 4 || fp > high - 4) + return -EINVAL; + + frame->sp = frame->fp; + frame->fp = *(unsigned long *)(fp); + frame->pc = frame->lr; + frame->lr = *(unsigned long *)(fp + 4); +#else /* check current frame pointer is within bounds */ if (fp < low + 12 || fp > high - 4) return -EINVAL; @@ -42,6 +65,7 @@ int notrace unwind_frame(struct stackframe *frame) frame->fp = *(unsigned long *)(fp - 12); frame->sp = *(unsigned long *)(fp - 8); frame->pc = *(unsigned long *)(fp - 4); +#endif return 0; }