# git rev-parse -q --verify 24321ac668e452a4942598533d267805f291fdc9^{commit}
24321ac668e452a4942598533d267805f291fdc9
already have revision, skipping fetch
# git checkout -q -f -B kisskb 24321ac668e452a4942598533d267805f291fdc9
# git clean -qxdf
# < git log -1
# commit 24321ac668e452a4942598533d267805f291fdc9
# Author: Raoni Fassina Firmino <raoni@linux.ibm.com>
# Date:   Mon Feb 1 17:05:05 2021 -0300
# 
#     powerpc/64/signal: Fix regression in __kernel_sigtramp_rt64() semantics
#     
#     Commit 0138ba5783ae ("powerpc/64/signal: Balance return predictor
#     stack in signal trampoline") changed __kernel_sigtramp_rt64() VDSO and
#     trampoline code, and introduced a regression in the way glibc's
#     backtrace()[1] detects the signal-handler stack frame. Apart from the
#     practical implications, __kernel_sigtramp_rt64() was a VDSO function
#     with the semantics that it is a function you can call from userspace
#     to end a signal handling. Now this semantics are no longer valid.
#     
#     I believe the aforementioned change affects all releases since 5.9.
#     
#     This patch tries to fix both the semantics and practical aspect of
#     __kernel_sigtramp_rt64() returning it to the previous code, whilst
#     keeping the intended behaviour of 0138ba5783ae by adding a new symbol
#     to serve as the jump target from the kernel to the trampoline. Now the
#     trampoline has two parts, a new entry point and the old return point.
#     
#     [1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2021-January/223194.html
#     
#     Fixes: 0138ba5783ae ("powerpc/64/signal: Balance return predictor stack in signal trampoline")
#     Cc: stable@vger.kernel.org # v5.9+
#     Signed-off-by: Raoni Fassina Firmino <raoni@linux.ibm.com>
#     Acked-by: Nicholas Piggin <npiggin@gmail.com>
#     [mpe: Minor tweaks to change log formatting, add stable tag]
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Link: https://lore.kernel.org/r/20210201200505.iz46ubcizipnkcxe@work-tp
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version
# < git log --format=%s --max-count=1 24321ac668e452a4942598533d267805f291fdc9
# < make -s -j 32 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64le_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  ppc64le_defconfig
# < make -s -j 32 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64le_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 32 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64le_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 32 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64le_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_ppc64le_defconfig_powerpc-gcc5
# Build took: 0:03:44.321905