# 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 # 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 # Acked-by: Michael Neuling # Signed-off-by: Michael Ellerman # < /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 e620d45065c7b5b8d6ae11217c09c09380103b83 # < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig+UP_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- ppc64e_defconfig # Added to kconfig CONFIG_SMP=n # yes \n | make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig+UP_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- oldconfig yes: standard output: Broken pipe # make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_ppc64e_defconfig+UP_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- :1478:2: warning: #warning syscall pidfd_send_signal not implemented [-Wcpp] :1481:2: warning: #warning syscall io_uring_setup not implemented [-Wcpp] :1484:2: warning: #warning syscall io_uring_enter not implemented [-Wcpp] :1487:2: warning: #warning syscall io_uring_register not implemented [-Wcpp] /kisskb/src/net/netfilter/nf_nat_masquerade.c:15:21: warning: 'masq_refcnt6' defined but not used [-Wunused-variable] static unsigned int masq_refcnt6 __read_mostly; ^ WARNING: vmlinux.o(.text+0x39e): 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. INFO: Uncompressed kernel (size 0xbcaa00) overlaps the address of the wrapper(0x400000) INFO: Fixing the link_address of wrapper to (0xc00000) Image Name: Linux-5.1.0-rc3-ge620d45065c7 Created: Thu May 2 00:43:00 2019 Image Type: PowerPC Linux Kernel Image (gzip compressed) Data Size: 5056530 Bytes = 4938.02 KiB = 4.82 MiB Load Address: 00000000 Entry Point: 00000000 Completed OK # rm -rf /kisskb/build/powerpc-next_ppc64e_defconfig+UP_powerpc-gcc5 # Build took: 0:01:45.274040