# git rev-parse -q --verify 8a96efd384e6d0797a06a34503ebf21f133c74cb^{commit} 8a96efd384e6d0797a06a34503ebf21f133c74cb already have revision, skipping fetch # git checkout -q -f -B kisskb 8a96efd384e6d0797a06a34503ebf21f133c74cb # git clean -qxdf # < git log -1 # commit 8a96efd384e6d0797a06a34503ebf21f133c74cb # Author: Madhavan Srinivasan # Date: Tue Aug 27 15:46:35 2019 +0530 # # powerpc/imc: Dont create debugfs files for cpu-less nodes # # Commit <684d984038aa> ('powerpc/powernv: Add debugfs interface for # imc-mode and imc') added debugfs interface for the nest imc pmu # devices to support changing of different ucode modes. Primarily adding # this capability for debug. But when doing so, the code did not # consider the case of cpu-less nodes. So when reading the _cmd_ or # _mode_ file of a cpu-less node will create this crash. # # Faulting instruction address: 0xc0000000000d0d58 # Oops: Kernel access of bad area, sig: 11 [#1] # ... # CPU: 67 PID: 5301 Comm: cat Not tainted 5.2.0-rc6-next-20190627+ #19 # NIP: c0000000000d0d58 LR: c00000000049aa18 CTR:c0000000000d0d50 # REGS: c00020194548f9e0 TRAP: 0300 Not tainted (5.2.0-rc6-next-20190627+) # MSR: 9000000000009033 CR:28022822 XER: 00000000 # CFAR: c00000000049aa14 DAR: 000000000003fc08 DSISR:40000000 IRQMASK: 0 # ... # NIP imc_mem_get+0x8/0x20 # LR simple_attr_read+0x118/0x170 # Call Trace: # simple_attr_read+0x70/0x170 (unreliable) # debugfs_attr_read+0x6c/0xb0 # __vfs_read+0x3c/0x70 # vfs_read+0xbc/0x1a0 # ksys_read+0x7c/0x140 # system_call+0x5c/0x70 # # Patch fixes the issue with a more robust check for vbase to NULL. # # Before patch, ls output for the debugfs imc directory # # # ls /sys/kernel/debug/powerpc/imc/ # imc_cmd_0 imc_cmd_251 imc_cmd_253 imc_cmd_255 imc_mode_0 imc_mode_251 imc_mode_253 imc_mode_255 # imc_cmd_250 imc_cmd_252 imc_cmd_254 imc_cmd_8 imc_mode_250 imc_mode_252 imc_mode_254 imc_mode_8 # # After patch, ls output for the debugfs imc directory # # # ls /sys/kernel/debug/powerpc/imc/ # imc_cmd_0 imc_cmd_8 imc_mode_0 imc_mode_8 # # Actual bug here is that, we have two loops with potentially different # loop counts. That is, in imc_get_mem_addr_nest(), loop count is # obtained from the dt entries. But in case of export_imc_mode_and_cmd(), # loop was based on for_each_nid() count. Patch fixes the loop count in # latter based on the struct mem_info. Ideally it would be better to # have array size in struct imc_pmu. # # Fixes: 684d984038aa ('powerpc/powernv: Add debugfs interface for imc-mode and imc') # Reported-by: Qian Cai # Suggested-by: Michael Ellerman # Signed-off-by: Madhavan Srinivasan # Signed-off-by: Michael Ellerman # Link: https://lore.kernel.org/r/20190827101635.6942-1-maddy@linux.vnet.ibm.com # < /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 8a96efd384e6d0797a06a34503ebf21f133c74cb # < make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_44x_warp_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- 44x/warp_defconfig # make -s -j 48 ARCH=powerpc O=/kisskb/build/powerpc-next_44x_warp_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux- INFO: Uncompressed kernel (size 0x6357bc) overlaps the address of the wrapper(0x400000) INFO: Fixing the link_address of wrapper to (0x700000) Image Name: Linux-5.3.0-rc2-pika+ Created: Wed Sep 4 20:47:05 2019 Image Type: PowerPC Linux Kernel Image (gzip compressed) Data Size: 3218400 Bytes = 3142.97 KiB = 3.07 MiB Load Address: 00700000 Entry Point: 00701524 Completed OK # rm -rf /kisskb/build/powerpc-next_44x_warp_defconfig_powerpc-gcc5 # Build took: 0:01:02.416424