# 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/gcc-4.6.3-nolibc/alpha-linux/bin/alpha-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/alpha-linux/bin/alpha-linux-ld --version
# < git log --format=%s --max-count=1 d02d2129641d6cd22492ddc85e11d112eb0d5a6f
# < make -s -j 120 ARCH=alpha O=/kisskb/build/powerpc-next_alpha-defconfig_alpha CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/alpha-linux/bin/alpha-linux-  defconfig
# make -s -j 120 ARCH=alpha O=/kisskb/build/powerpc-next_alpha-defconfig_alpha CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/alpha-linux/bin/alpha-linux-  
<stdin>:1333:2: warning: #warning syscall io_pgetevents not implemented [-Wcpp]
<stdin>:1336:2: warning: #warning syscall rseq not implemented [-Wcpp]
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:186:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c: In function 'proc_reg_open':
/kisskb/src/include/linux/list.h:65:12: warning: 'pdeo' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/proc/inode.c:339:21: note: 'pdeo' was declared here
/kisskb/src/net/ipv4/ip_output.c: In function '__ip_append_data':
/kisskb/src/include/linux/skbuff.h:1338:6: warning: 'extra_uref' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/ipv4/ip_output.c:885:14: note: 'extra_uref' was declared here
WARNING: "saved_config" [vmlinux] is COMMON symbol
  Kernel arch/alpha/boot/vmlinux.gz is ready
Completed OK
# rm -rf /kisskb/build/powerpc-next_alpha-defconfig_alpha
# Build took: 0:00:29.401428