# git rev-parse -q --verify 6865920b3f27b31bb9280088f3a837fd2090a327^{commit}
6865920b3f27b31bb9280088f3a837fd2090a327
already have revision, skipping fetch
# git checkout -q -f -B kisskb 6865920b3f27b31bb9280088f3a837fd2090a327
# git clean -qxdf
# < git log -1
# commit 6865920b3f27b31bb9280088f3a837fd2090a327
# Author: Michael Ellerman <mpe@ellerman.id.au>
# Date:   Tue Oct 10 22:47:50 2023 +1100
# 
#     powerpc/47x: Fix 47x syscall return crash
#     
#     Eddie reported that newer kernels were crashing during boot on his 476
#     FSP2 system:
#     
#       kernel tried to execute user page (b7ee2000) - exploit attempt? (uid: 0)
#       BUG: Unable to handle kernel instruction fetch
#       Faulting instruction address: 0xb7ee2000
#       Oops: Kernel access of bad area, sig: 11 [#1]
#       BE PAGE_SIZE=4K FSP-2
#       Modules linked in:
#       CPU: 0 PID: 61 Comm: mount Not tainted 6.1.55-d23900f.ppcnf-fsp2 #1
#       Hardware name: ibm,fsp2 476fpe 0x7ff520c0 FSP-2
#       NIP:  b7ee2000 LR: 8c008000 CTR: 00000000
#       REGS: bffebd83 TRAP: 0400   Not tainted (6.1.55-d23900f.ppcnf-fs p2)
#       MSR:  00000030 <IR,DR>  CR: 00001000  XER: 20000000
#       GPR00: c00110ac bffebe63 bffebe7e bffebe88 8c008000 00001000 00000d12 b7ee2000
#       GPR08: 00000033 00000000 00000000 c139df10 48224824 1016c314 10160000 00000000
#       GPR16: 10160000 10160000 00000008 00000000 10160000 00000000 10160000 1017f5b0
#       GPR24: 1017fa50 1017f4f0 1017fa50 1017f740 1017f630 00000000 00000000 1017f4f0
#       NIP [b7ee2000] 0xb7ee2000
#       LR [8c008000] 0x8c008000
#       Call Trace:
#       Instruction dump:
#       XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
#       XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
#       ---[ end trace 0000000000000000 ]---
#     
#     The problem is in ret_from_syscall where the check for
#     icache_44x_need_flush is done. When the flush is needed the code jumps
#     out-of-line to do the flush, and then intends to jump back to continue
#     the syscall return.
#     
#     However the branch back to label 1b doesn't return to the correct
#     location, instead branching back just prior to the return to userspace,
#     causing bogus register values to be used by the rfi.
#     
#     The breakage was introduced by commit 6f76a01173cc
#     ("powerpc/syscall: implement system call entry/exit logic in C for PPC32") which
#     inadvertently removed the "1" label and reused it elsewhere.
#     
#     Fix it by adding named local labels in the correct locations. Note that
#     the return label needs to be outside the ifdef so that CONFIG_PPC_47x=n
#     compiles.
#     
#     Fixes: 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32")
#     Cc: stable@vger.kernel.org # v5.12+
#     Reported-by: Eddie James <eajames@linux.ibm.com>
#     Tested-by: Eddie James <eajames@linux.ibm.com>
#     Link: https://lore.kernel.org/linuxppc-dev/fdaadc46-7476-9237-e104-1d2168526e72@linux.ibm.com/
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
#     Link: https://msgid.link/20231010114750.847794-1-mpe@ellerman.id.au
# < /opt/cross/kisskb/korg/gcc-12.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-12.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-ld --version
# < git log --format=%s --max-count=1 6865920b3f27b31bb9280088f3a837fd2090a327
# make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64le_defconfig+NO_KPROBES_powerpc-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  ppc64le_defconfig
Using /kisskb/src/arch/powerpc/configs/ppc64_defconfig as base
Merging /kisskb/src/arch/powerpc/configs/le.config
#
# merged configuration written to .config (needs make)
#
# Added to kconfig CONFIG_KPROBES=n
# < make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64le_defconfig+NO_KPROBES_powerpc-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  help
# make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64le_defconfig+NO_KPROBES_powerpc-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  olddefconfig
# make -s -j 24 ARCH=powerpc O=/kisskb/build/powerpc-fixes_ppc64le_defconfig+NO_KPROBES_powerpc-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_ppc64le_defconfig+NO_KPROBES_powerpc-gcc12
# Build took: 0:07:29.466248