# git gc
# git rev-parse -q --verify dc8b1290efbbe974d9968106a03077823d0863d6^{commit}
# git fetch -q -n -f git://gitlab.ozlabs.ibm.com/linuxppc/linux.git next-test
# git rev-parse -q --verify dc8b1290efbbe974d9968106a03077823d0863d6^{commit}
dc8b1290efbbe974d9968106a03077823d0863d6
# git checkout -q -f -B kisskb dc8b1290efbbe974d9968106a03077823d0863d6
# git clean -qxdf
# < git log -1
# commit dc8b1290efbbe974d9968106a03077823d0863d6
# 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
#        block user access again if it's not already blocked.
#      - 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 isync()'s around AMR writes as per the ISA.
#      - Support selectively disabling read or write, with no support for
#        nesting.
#     
#     Co-authored-by: Michael Ellerman <mpe@ellerman.id.au>
#     Signed-off-by: Russell Currey <ruscur@russell.cc>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     ---
#     
#     v5:
#      - On kernel entry check if the AMR is already blocking user access
#        and if so don't do the mtspr again (pointed out by Nick).
#      - Rework the constants to make the asm a bit cleaner and avoid any
#        hard coded shifts.
#      - Selectively disable read or write, we don't support nesting and
#        shouldn't need to (famous last words).
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-ld --version
# < git log --format=%s --max-count=1 dc8b1290efbbe974d9968106a03077823d0863d6
# < make -s -j 120 ARCH=ia64 O=/kisskb/build/powerpc-next_ia64-defconfig_ia64 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-  defconfig
# make -s -j 120 ARCH=ia64 O=/kisskb/build/powerpc-next_ia64-defconfig_ia64 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/ia64-linux/bin/ia64-linux-  
<stdin>:1186:2: warning: #warning syscall perf_event_open not implemented [-Wcpp]
<stdin>:1240:2: warning: #warning syscall seccomp not implemented [-Wcpp]
<stdin>:1318:2: warning: #warning syscall pkey_mprotect not implemented [-Wcpp]
<stdin>:1321:2: warning: #warning syscall pkey_alloc not implemented [-Wcpp]
<stdin>:1324:2: warning: #warning syscall pkey_free not implemented [-Wcpp]
<stdin>:1327:2: warning: #warning syscall statx not implemented [-Wcpp]
<stdin>:1333:2: warning: #warning syscall io_pgetevents not implemented [-Wcpp]
<stdin>:1336:2: warning: #warning syscall rseq not implemented [-Wcpp]
/kisskb/src/kernel/fork.c:766:13: warning: 'task_struct_whitelist' defined but not used [-Wunused-function]
/kisskb/src/kernel/cgroup/cgroup-v1.c: In function 'cgroup1_mount':
/kisskb/src/kernel/cgroup/cgroup-v1.c:1263:20: warning: 'root' may be used uninitialized in this function [-Wuninitialized]
/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/mm/vmstat.c: In function 'sysctl_vm_numa_stat_handler':
/kisskb/src/mm/vmstat.c:89:5: warning: 'oldval' 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/drivers/i2c/i2c-core-base.c: In function 'i2c_generic_scl_recovery':
/kisskb/src/drivers/i2c/i2c-core-base.c:235:5: warning: 'ret' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/mm/hugetlb.c: In function 'alloc_pool_huge_page':
/kisskb/src/mm/hugetlb.c:1434:5: warning: 'page' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/fs/udf/unicode.c: In function 'udf_name_conv_char':
/kisskb/src/fs/udf/unicode.c:132:8: warning: 'c' may be used uninitialized in this function [-Wuninitialized]
/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
/kisskb/src/fs/nfsd/nfs4xdr.c: In function 'nfsd4_encode_components_esc':
/kisskb/src/fs/nfsd/nfs4xdr.c:2076:9: warning: 'str' may be used uninitialized in this function [-Wuninitialized]
No errors detected in 21239 functions.
  Kernel: vmlinux.gz is ready
Completed OK
# rm -rf /kisskb/build/powerpc-next_ia64-defconfig_ia64
# Build took: 0:03:46.562172