# git rev-parse -q --verify d02d2129641d6cd22492ddc85e11d112eb0d5a6f^{commit}
d02d2129641d6cd22492ddc85e11d112eb0d5a6f
already have revision, skipping fetch
# git checkout -q -f -B kisskb d02d2129641d6cd22492ddc85e11d112eb0d5a6f
# git clean -qxdf
# < git log -1
# commit d02d2129641d6cd22492ddc85e11d112eb0d5a6f
# Author: Russell Currey <ruscur@russell.cc>
# Date:   Fri Mar 1 01:49:17 2019 +1100
# 
#     powerpc/64s: Implement KUAP for Radix MMU
#     
#     Kernel Userspace Access Prevention utilises a feature of the Radix MMU
#     which disallows read and write access to userspace addresses. By
#     utilising this, the kernel is prevented from accessing user data from
#     outside of trusted paths that perform proper safety checks, such as
#     copy_{to/from}_user() and friends.
#     
#     Userspace access is disabled from early boot and is only enabled when
#     performing an operation like copy_{to/from}_user().  The register that
#     controls this (AMR) does not prevent userspace from accessing itself,
#     so there is no need to save and restore when entering and exiting
#     userspace.
#     
#     This feature has a slight performance impact which I roughly measured
#     to be 3% slower in the worst case (performing 1GB of 1 byte
#     read()/write() syscalls), and is gated behind the CONFIG_PPC_KUAP
#     option for performance-critical builds.
#     
#     This feature can be tested by using the lkdtm driver (CONFIG_LKDTM=y)
#     and performing the following:
#     
#       # (echo ACCESS_USERSPACE) > [debugfs]/provoke-crash/DIRECT
#     
#     If enabled, this should send SIGSEGV to the thread.
#     
#     mpe: Drop the unused paca flags. Zero the UAMOR to be safe. Save the
#     AMR when we enter the kernel from the kernel and then lock it again.
#     Restore on the way back to the kernel. This means we handle nesting of
#     interrupts properly, ie. we are protected inside the page fault
#     handler caused by a user access. Add paranoid checking of AMR in
#     switch and syscall return. Add an isync() to prevent_user_access()
#     
#     Signed-off-by: Russell Currey <ruscur@russell.cc>
#     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 d02d2129641d6cd22492ddc85e11d112eb0d5a6f
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_mpc7448_hpc2_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  mpc7448_hpc2_defconfig
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_mpc7448_hpc2_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
INFO: Uncompressed kernel (size 0x5022d8) overlaps the address of the wrapper(0x400000)
INFO: Fixing the link_address of wrapper to (0x600000)
INFO: Uncompressed kernel (size 0x4f1c60) overlaps the address of the wrapper(0x400000)
INFO: Fixing the link_address of wrapper to (0x500000)
Image Name:   Linux-5.0.0-rc2-gd02d2129641d
Created:      Fri Mar  1 02:52:41 2019
Image Type:   PowerPC Linux Kernel Image (gzip compressed)
Data Size:    2569143 Bytes = 2508.93 KiB = 2.45 MiB
Load Address: 00000000
Entry Point:  00000000
Image Name:   Linux-5.0.0-rc2-gd02d2129641d
Created:      Fri Mar  1 02:52:41 2019
Image Type:   PowerPC Linux Kernel Image (gzip compressed)
Data Size:    2597127 Bytes = 2536.26 KiB = 2.48 MiB
Load Address: 00600000
Entry Point:  006001d4
Completed OK
# rm -rf /kisskb/build/powerpc-next_mpc7448_hpc2_defconfig_powerpc-gcc5
# Build took: 0:00:41.013330