# git rev-parse -q --verify e620d45065c7b5b8d6ae11217c09c09380103b83^{commit}
e620d45065c7b5b8d6ae11217c09c09380103b83
already have revision, skipping fetch
# git checkout -q -f -B kisskb e620d45065c7b5b8d6ae11217c09c09380103b83
# git clean -qxdf
# < git log -1
# commit e620d45065c7b5b8d6ae11217c09c09380103b83
# Author: Breno Leitao <leitao@debian.org>
# Date:   Wed Jan 16 14:47:44 2019 -0200
# 
#     powerpc/tm: Avoid machine crash on rt_sigreturn()
#     
#     There is a kernel crash that happens if rt_sigreturn() is called inside
#     a transactional block.
#     
#     This crash happens if the kernel hits an in-kernel page fault when
#     accessing userspace memory, usually through copy_ckvsx_to_user(). A
#     major page fault calls might_sleep() function, which can cause a task
#     reschedule. A task reschedule (switch_to()) reclaim and recheckpoint
#     the TM states, but, in the signal return path, the checkpointed memory
#     was already reclaimed, thus the exception stack has MSR that points to
#     MSR[TS]=0.
#     
#     When the code returns from might_sleep() and a task reschedule
#     happened, then this task is returned with the memory recheckpointed,
#     and CPU MSR[TS] = suspended.
#     
#     This means that there is a side effect at might_sleep() if it is
#     called with CPU MSR[TS] = 0 and the task has regs->msr[TS] != 0.
#     
#     This side effect can cause a TM bad thing, since at the exception
#     entrance, the stack saves MSR[TS]=0, and this is what will be used at
#     RFID, but, the processor has MSR[TS] = Suspended, and this transition
#     will be invalid and a TM Bad thing will be raised, causing the
#     following crash:
#     
#       Unexpected TM Bad Thing exception at c00000000000e9ec (msr 0x8000000302a03031) tm_scratch=800000010280b033
#       cpu 0xc: Vector: 700 (Program Check) at [c00000003ff1fd70]
#           pc: c00000000000e9ec: fast_exception_return+0x100/0x1bc
#           lr: c000000000032948: handle_rt_signal64+0xb8/0xaf0
#           sp: c0000004263ebc40
#          msr: 8000000302a03031
#         current = 0xc000000415050300
#         paca    = 0xc00000003ffc4080         irqmask: 0x03   irq_happened: 0x01
#           pid   = 25006, comm = sigfuz
#       Linux version 5.0.0-rc1-00001-g3bd6e94bec12 (breno@debian) (gcc version 8.2.0 (Debian 8.2.0-3)) #899 SMP Mon Jan 7 11:30:07 EST 2019
#       WARNING: exception is not recoverable, can't continue
#       enter ? for help
#       [c0000004263ebc40] c000000000032948 handle_rt_signal64+0xb8/0xaf0 (unreliable)
#       [c0000004263ebd30] c000000000022780 do_notify_resume+0x2f0/0x430
#       [c0000004263ebe20] c00000000000e844 ret_from_except_lite+0x70/0x74
#       --- Exception: c00 (System Call) at 00007fffbaac400c
#       SP (7fffeca90f40) is in userspace
#     
#     The solution for this problem is running the sigreturn code with
#     regs->msr[TS] disabled, thus, avoiding hitting the side effect above.
#     This does not seem to be a problem since regs->msr will be replaced by
#     the ucontext value, so, it is being flushed already. In this case, it
#     is flushed earlier.
#     
#     Signed-off-by: Breno Leitao <leitao@debian.org>
#     Acked-by: Michael Neuling <mikey@neuling.org>
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-gcc --version
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-ld --version
# < git log --format=%s --max-count=1 e620d45065c7b5b8d6ae11217c09c09380103b83
# < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_ps3_defconfig_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-  ps3_defconfig
# make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_ps3_defconfig_powerpc-gcc4.6 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/powerpc-linux/bin/powerpc-linux-  
<stdin>:1478:2: warning: #warning syscall pidfd_send_signal not implemented [-Wcpp]
<stdin>:1481:2: warning: #warning syscall io_uring_setup not implemented [-Wcpp]
<stdin>:1484:2: warning: #warning syscall io_uring_enter not implemented [-Wcpp]
<stdin>:1487:2: warning: #warning syscall io_uring_register not implemented [-Wcpp]
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:187:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c: In function 'init_srcu_struct_fields':
/kisskb/src/kernel/rcu/srcutree.c:140:32: warning: 'levelspread[<U2dc0>]' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/rcu/srcutree.c:88:6: note: 'levelspread[<U2dc0>]' was declared here
/kisskb/src/ipc/shm.c: In function 'ksys_shmdt':
/kisskb/src/ipc/shm.c:1712:59: warning: 'file' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/bluetooth/hidp/core.c: In function 'hidp_connection_add':
/kisskb/src/net/bluetooth/hidp/core.c:1381:18: warning: 'session' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/core/gen_stats.c: In function '__gnet_stats_copy_basic':
/kisskb/src/net/core/gen_stats.c:161:19: warning: 'seq' 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:337:21: note: 'pdeo' was declared here
/kisskb/src/kernel/futex.c: In function 'do_futex':
/kisskb/src/kernel/futex.c:1668:3: warning: 'oldval' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/futex.c:1633:6: note: 'oldval' was declared here
/kisskb/src/net/core/dev.c: In function 'validate_xmit_skb_list':
/kisskb/src/net/core/dev.c:3405:15: warning: 'tail' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/lib/mpi/mpicoder.c: In function 'mpi_read_raw_from_sgl':
/kisskb/src/lib/mpi/mpicoder.c:352:8: warning: 'buff' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/ipv4/ip_output.c: In function '__ip_append_data.isra.41':
/kisskb/src/include/linux/skbuff.h:1397:6: 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/net/ipv6/ip6_output.c: In function '__ip6_append_data.isra.36':
/kisskb/src/include/linux/skbuff.h:1397:6: warning: 'extra_uref' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/ipv6/ip6_output.c:1276:14: note: 'extra_uref' was declared here
/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/lib/rhashtable.c: In function 'rht_deferred_worker':
/kisskb/src/lib/rhashtable.c:264:2: warning: 'next' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/lib/rhashtable.c:229:28: note: 'next' was declared here
/kisskb/src/net/mac80211/tx.c: In function 'ieee80211_build_hdr':
/kisskb/src/net/mac80211/tx.c:2515:27: warning: 'chanctx_conf' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/mac80211/mlme.c: In function 'ieee80211_rx_mgmt_beacon':
/kisskb/src/net/mac80211/mlme.c:1581:3: warning: 'pwr_level_cisco' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/net/mac80211/mlme.c:1538:6: note: 'pwr_level_cisco' was declared here
WARNING: vmlinux.o(.text+0x322a): Section mismatch in reference from the variable start_here_multiplatform to the function .init.text:.early_setup()
The function start_here_multiplatform() references
the function __init .early_setup().
This is often because start_here_multiplatform lacks a __init 
annotation or the annotation of .early_setup is wrong.

Completed OK
# rm -rf /kisskb/build/powerpc-next_ps3_defconfig_powerpc-gcc4.6
# Build took: 0:01:23.779155