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BACKPORT: ARM: 8905/1: Emit __gnu_mcount_nc when using Clang 10.0.0 o…
…r newer commit b0fe66cf095016e0b238374c10ae366e1f087d11 upstream. Currently, multi_v7_defconfig + CONFIG_FUNCTION_TRACER fails to build with clang: arm-linux-gnueabi-ld: kernel/softirq.o: in function `_local_bh_enable': softirq.c:(.text+0x504): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o: in function `__local_bh_enable_ip': softirq.c:(.text+0x58c): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o: in function `do_softirq': softirq.c:(.text+0x6c8): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o: in function `irq_enter': softirq.c:(.text+0x75c): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o: in function `irq_exit': softirq.c:(.text+0x840): undefined reference to `mcount' arm-linux-gnueabi-ld: kernel/softirq.o:softirq.c:(.text+0xa50): more undefined references to `mcount' follow clang can emit a working mcount symbol, __gnu_mcount_nc, when '-meabi gnu' is passed to it. Until r369147 in LLVM, this was broken and caused the kernel not to boot with '-pg' because the calling convention was not correct. Always build with '-meabi gnu' when using clang but ensure that '-pg' (which is added with CONFIG_FUNCTION_TRACER and its prereq CONFIG_HAVE_FUNCTION_TRACER) cannot be added with it unless this is fixed (which means using clang 10.0.0 and newer). Link: ClangBuiltLinux/linux#35 Link: https://bugs.llvm.org/show_bug.cgi?id=33845 Link: llvm/llvm-project@16fa8b0 Reviewed-by: Matthias Kaehlcke <mka@chromium.org> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Stefan Agner <stefan@agner.ch> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> Bug: 145525910 [nd: Kconfig clang version check removed due to significant size of backporting 469cb73/2fd5b09c201e. Android R will not have a version of Clang < clang-10] Change-Id: I186771b7a3553652b84ee66dac6b53f7932b7076 Signed-off-by: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: UtsavBalar1231 <utsavbalar1231@gmail.com>
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