# git rev-parse -q --verify bb86adc4825afb5a01be747f451317c4a29a3607^{commit}
bb86adc4825afb5a01be747f451317c4a29a3607
already have revision, skipping fetch
# git checkout -q -f -B kisskb bb86adc4825afb5a01be747f451317c4a29a3607
# git clean -qxdf
# < git log -1
# commit bb86adc4825afb5a01be747f451317c4a29a3607
# Author: Naveen N Rao <naveen@kernel.org>
# Date:   Fri Oct 18 23:06:32 2024 +0530
# 
#     powerpc64/bpf: Add support for bpf trampolines
#     
#     Add support for bpf_arch_text_poke() and arch_prepare_bpf_trampoline()
#     for 64-bit powerpc. While the code is generic, BPF trampolines are only
#     enabled on 64-bit powerpc. 32-bit powerpc will need testing and some
#     updates.
#     
#     BPF Trampolines adhere to the existing ftrace ABI utilizing a
#     two-instruction profiling sequence, as well as the newer ABI utilizing a
#     three-instruction profiling sequence enabling return with a 'blr'. The
#     trampoline code itself closely follows x86 implementation.
#     
#     BPF prog JIT is extended to mimic 64-bit powerpc approach for ftrace
#     having a single nop at function entry, followed by the function
#     profiling sequence out-of-line and a separate long branch stub for calls
#     to trampolines that are out of range. A dummy_tramp is provided to
#     simplify synchronization similar to arm64.
#     
#     When attaching a bpf trampoline to a bpf prog, we can patch up to three
#     things:
#     - the nop at bpf prog entry to go to the out-of-line stub
#     - the instruction in the out-of-line stub to either call the bpf trampoline
#     directly, or to branch to the long_branch stub.
#     - the trampoline address before the long_branch stub.
#     
#     We do not need any synchronization here since we always have a valid
#     branch target regardless of the order in which the above stores are
#     seen. dummy_tramp ensures that the long_branch stub goes to a valid
#     destination on other cpus, even when the branch to the long_branch stub
#     is seen before the updated trampoline address.
#     
#     However, when detaching a bpf trampoline from a bpf prog, or if changing
#     the bpf trampoline address, we need synchronization to ensure that other
#     cpus can no longer branch into the older trampoline so that it can be
#     safely freed. bpf_tramp_image_put() uses rcu_tasks to ensure all cpus
#     make forward progress, but we still need to ensure that other cpus
#     execute isync (or some CSI) so that they don't go back into the
#     trampoline again. While here, update the stale comment that describes
#     the redzone usage in ppc64 BPF JIT.
#     
#     Signed-off-by: Naveen N Rao <naveen@kernel.org>
#     Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Link: https://patch.msgid.link/20241018173632.277333-18-hbathini@linux.ibm.com
# < /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 bb86adc4825afb5a01be747f451317c4a29a3607
# make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig+KEXEC_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  ppc64e_defconfig
# Added to kconfig CONFIG_KEXEC=y
# < make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig+KEXEC_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig+KEXEC_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
.config:3238:warning: override: reassigning to symbol KEXEC
# make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig+KEXEC_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-next_ppc64e_defconfig+KEXEC_powerpc-gcc5
# Build took: 0:03:27.850577