# git rev-parse -q --verify c14cbef0319d21339a76247c3061230ae2950a7c^{commit}
c14cbef0319d21339a76247c3061230ae2950a7c
already have revision, skipping fetch
# git checkout -q -f -B kisskb c14cbef0319d21339a76247c3061230ae2950a7c
# git clean -qxdf
# < git log -1
# commit c14cbef0319d21339a76247c3061230ae2950a7c
# Author: Christophe Leroy <christophe.leroy@c-s.fr>
# Date:   Mon Jun 3 08:20:28 2019 +0000
# 
#     powerpc: fix kexec failure on book3s/32
#     
#     In the old days, _PAGE_EXEC didn't exist on 6xx aka book3s/32.
#     Therefore, allthough __mapin_ram_chunk() was already mapping kernel
#     text with PAGE_KERNEL_TEXT and the rest with PAGE_KERNEL, the entire
#     memory was executable. Part of the memory (first 512kbytes) was
#     mapped with BATs instead of page table, but it was also entirely
#     mapped as executable.
#     
#     In commit 385e89d5b20f ("powerpc/mm: add exec protection on
#     powerpc 603"), we started adding exec protection to some 6xx, namely
#     the 603, for pages mapped via pagetables.
#     
#     Then, in commit 63b2bc619565 ("powerpc/mm/32s: Use BATs for
#     STRICT_KERNEL_RWX"), the exec protection was extended to BAT mapped
#     memory, so that really only the kernel text could be executed.
#     
#     The problem here is that kexec is based on copying some code into
#     upper part of memory then executing it from there in order to install
#     a fresh new kernel at its definitive location.
#     
#     However, the code is position independant and first part of it is
#     just there to deactivate the MMU and jump to the second part. So it
#     is possible to run this first part inplace instead of running the
#     copy. Once the MMU is off, there is no protection anymore and the
#     second part of the code will just run as before.
#     
#     Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
#     Fixes: 63b2bc619565 ("powerpc/mm/32s: Use BATs for STRICT_KERNEL_RWX")
#     Cc: stable@vger.kernel.org
#     Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
#     Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /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 c14cbef0319d21339a76247c3061230ae2950a7c
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_44x_sequoia_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  44x/sequoia_defconfig
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-fixes_44x_sequoia_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
INFO: Uncompressed kernel (size 0x48bb84) overlaps the address of the wrapper(0x400000)
INFO: Fixing the link_address of wrapper to (0x500000)
Image Name:   Linux-5.2.0-rc2-gc14cbef0319d
Created:      Fri Jun  7 02:14:57 2019
Image Type:   PowerPC Linux Kernel Image (gzip compressed)
Data Size:    2330209 Bytes = 2275.59 KiB = 2.22 MiB
Load Address: 00500000
Entry Point:  00501534
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_44x_sequoia_defconfig_powerpc-gcc5
# Build took: 0:00:33.685340