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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=G95KKuekTz1iA7Zr8ZdyT9EdDFTvRs8dYtvTVOv4Dfc=; b=BrqQ49CALi2sqNMfy/wdfjUjsa9UywROg5WZVXGtRrDxYXNtiZOvdupYU0/7RzUcQr D4ecjxyFgj8NiiKQ3e2CdZvyQ5DgAzRIumIMYV3mJCx8hOAgVja+K7440T3jGSaN4AsZ a+m8Jvg9uTT7TTsNtnkDNr9gRqfiDbMuA8Wu/hn2+s9kEdiWy5I3MRYCZGBB7WFwqfub qRzalLkNOSDSDsPZ72YIhsKfouj3ydbds+JBsVovdQzcDyc6O12fpmzxwZLhfkEl7gnW SENde8H4lmsknmk+rP3ZGrr3m92HZ4EaKHbMmm4jWgOOTC6+p8P9Eud3U0W+2o60LG2j dhTQ== X-Gm-Message-State: AOAM530ITpbBviUHCIsvTDGT6S3/M3zIFoDxdaKgyOUQCabyFmq7E4E5 bnLocSNdnVILaLiXWVOtxfMauyq4QPqV9qMkhig= X-Google-Smtp-Source: ABdhPJx9IM+NZ+Dy+UO1H89OWuA1mQwu+ABN06cb8h6aN7Xpr4/KTHo0SHpRsO8t4uShHvxZa2ijHx26yaXliUNcOww= X-Received: by 2002:a25:40cb:: with SMTP id n194mr1171359yba.380.1596142286622; Thu, 30 Jul 2020 13:51:26 -0700 (PDT) Date: Thu, 30 Jul 2020 13:51:09 -0700 In-Reply-To: <20200730205112.2099429-1-ndesaulniers@google.com> Message-Id: <20200730205112.2099429-2-ndesaulniers@google.com> Mime-Version: 1.0 References: <20200730205112.2099429-1-ndesaulniers@google.com> X-Mailer: git-send-email 2.28.0.163.g6104cc2f0b6-goog Subject: [PATCH 1/4] ARM: backtrace-clang: check for NULL lr From: Nick Desaulniers To: Nathan Huckleberry , Russell King X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200730_165130_256411_311B2974 X-CRM114-Status: GOOD ( 14.01 ) 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 , Chunyan Zhang , Dmitry Safonov <0x7f454c46@gmail.com>, linux-kernel@vger.kernel.org, stable@vger.kernel.org, clang-built-linux@googlegroups.com, Miles Chen , linux-mediatek@lists.infradead.org, Matthias Brugger , Andrew Morton , Lvqiang Huang , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org If the link register was zeroed out, do not attempt to use it for address calculations for which there are currently no fixup handlers, which can lead to a panic during unwind. Since panicking triggers another unwind, this can lead to an infinite loop. If this occurs during start_kernel(), this can prevent a kernel from booting. commit 59b6359dd92d ("ARM: 8702/1: head-common.S: Clear lr before jumping to start_kernel()") intentionally zeros out the link register in __mmap_switched which tail calls into start kernel. Test for this condition so that we can stop unwinding when initiated within start_kernel() correctly. Cc: stable@vger.kernel.org Fixes: commit 6dc5fd93b2f1 ("ARM: 8900/1: UNWINDER_FRAME_POINTER implementation for Clang") Reported-by: Miles Chen Signed-off-by: Nick Desaulniers --- arch/arm/lib/backtrace-clang.S | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/arm/lib/backtrace-clang.S b/arch/arm/lib/backtrace-clang.S index 6174c45f53a5..5388ac664c12 100644 --- a/arch/arm/lib/backtrace-clang.S +++ b/arch/arm/lib/backtrace-clang.S @@ -144,6 +144,8 @@ for_each_frame: tst frame, mask @ Check for address exceptions */ 1003: ldr sv_lr, [sv_fp, #4] @ get saved lr from next frame + tst sv_lr, #0 @ If there's no previous lr, + beq finished_setup @ we're done. ldr r0, [sv_lr, #-4] @ get call instruction ldr r3, .Lopcode+4 and r2, r3, r0 @ is this a bl call -- 2.28.0.163.g6104cc2f0b6-goog _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel