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a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=cHSpMAjXfyGfwJeb9KkrKwdJRoh7Aq/xdZj4zd+a3E4=; b=eOmA6fjXdOQ4VbF7GUSopkBzUh2rUsZlL9c6MT20HIQG0l/4It9p/x1XEnKmwu7p70 5mFmkqd/eFUzP8WVNclVJ5+GbBju9JsxdobaKoD9aPR6Wc2oer0RkPHjPhVhXP3gwwlM WI90HfVGKtXVuWYpubSB2QCAsgqdO1XWCXN1dB3MEgcyO2FcwN4ZbWo3Dm7V8k/QuUiO DsRCo1ef5zK3Ll02KszCdPZfCOc+UPkpRqbLN5nC3ThchKGIe6iYUET1pV5OsxM4SDAa CEHk7EArh5drN6qQ3ZZeUEr2+UTwuFaLVMdRCbHiNeLnHmvEStXjTdShBtatu9aYcfAx hNnA== X-Gm-Message-State: AOAM532X8JFEm3uEJ7+6ozwlgRjrYqYWU1AmaafU6h8ILQc8ZY2tcNVB 9IJ5JbfCwuX0by0o1XxIr9tG0dabgA== X-Google-Smtp-Source: ABdhPJz97JiuiNeTxt8V2AAsnvn1Ge3fjw/Spk4/6TFwHd5hb2O+4+a0e1D7100P4MNwrcg15aJ7cqhRsA== X-Received: by 2002:a25:d8cd:: with SMTP id p196mr8176207ybg.55.1592347012784; Tue, 16 Jun 2020 15:36:52 -0700 (PDT) Date: Tue, 16 Jun 2020 22:36:33 +0000 Message-Id: <20200616223633.73971-1-nhuck@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.27.0.290.gba653c62da-goog Subject: [PATCH] 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-20200616_153654_452167_51AF105B X-CRM114-Status: GOOD ( 10.47 ) X-Spam-Score: -7.7 (-------) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.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:b4a listed in] [list.dnswl.org] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -7.5 USER_IN_DEF_DKIM_WL From: address is in the default DKIM white-list -0.1 DKIM_VALID_EF Message has a valid DKIM or DK signature from envelope-from domain -0.1 DKIM_VALID_AU Message has a valid DKIM or DK signature from author's domain 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature -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: clang-built-linux@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Nathan Huckleberry 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 Signed-off-by: Nathan Huckleberry Reported-by: Miles Chen Reviewed-by: Nick Desaulniers Tested-by: Miles Chen --- 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; }