Re: [Crash-utility] [PATCH V5 4/6] RISC-V: Fixup getting correct current pc

On 02/08/2022 13:18, Xianting Tian wrote: > When use 'echo c > /proc/sysrq-trigger' to trigger kdump, riscv_crash_save_regs() > will be called to save regs to vmcore, we found "epc" value 00ffffffa5537400 > is not a valid kernel virtual address, but is a user virtual address. Other > regs(eg, ra, sp, gp...) are correct kernel virtual address. > Actually 0x00ffffffb0dd9400 is the user mode PC of 'PID: 113 Comm: sh', which > is saved in the task's stack. > > [ 21.201701] CPU: 0 PID: 113 Comm: sh Kdump: loaded Not tainted 5.18.9 #45 > [ 21.201979] Hardware name: riscv-virtio,qemu (DT) > [ 21.202160] epc : 00ffffffa5537400 ra : ffffffff80088640 sp : ff20000010333b90 > [ 21.202435] gp : ffffffff810dde38 tp : ff6000000226c200 t0 : ffffffff8032be7c > [ 21.202707] t1 : 0720072007200720 t2 : 30203a7375746174 s0 : ff20000010333cf0 > [ 21.202973] s1 : 0000000000000000 a0 : ff20000010333b98 a1 : 0000000000000001 > [ 21.203243] a2 : 0000000000000010 a3 : 0000000000000000 a4 : 28c8f0aeffea4e00 > [ 21.203519] a5 : 28c8f0aeffea4e00 a6 : 0000000000000009 a7 : ffffffff8035c9b8 > [ 21.203794] s2 : ffffffff810df0a8 s3 : ffffffff810df718 s4 : ff20000010333b98 > [ 21.204062] s5 : 0000000000000000 s6 : 0000000000000007 s7 : ffffffff80c4a468 > [ 21.204331] s8 : 00ffffffef451410 s9 : 0000000000000007 s10: 00aaaaaac0510700 > [ 21.204606] s11: 0000000000000001 t3 : ff60000001218f00 t4 : ff60000001218f00 > [ 21.204876] t5 : ff60000001218000 t6 : ff200000103338b8 > [ 21.205079] status: 0000000200000020 badaddr: 0000000000000000 cause: 0000000000000008 > > With the incorrect PC, the backtrace showed by crash tool as below, the first > stack frame is abnormal, > > crash> bt > PID: 113 TASK: ff60000002269600 CPU: 0 COMMAND: "sh" > #0 [ff2000001039bb90] __efistub_.Ldebug_info0 at 00ffffffa5537400 <-- Abnormal > #1 [ff2000001039bcf0] panic at ffffffff806578ba > #2 [ff2000001039bd50] sysrq_reset_seq_param_set at ffffffff8038c030 > #3 [ff2000001039bda0] __handle_sysrq at ffffffff8038c5f8 > #4 [ff2000001039be00] write_sysrq_trigger at ffffffff8038cad8 > #5 [ff2000001039be20] proc_reg_write at ffffffff801b7edc > #6 [ff2000001039be40] vfs_write at ffffffff80152ba6 > #7 [ff2000001039be80] ksys_write at ffffffff80152ece > #8 [ff2000001039bed0] sys_write at ffffffff80152f46 > > With the patch, we can get current kernel mode PC, the output as below, > > [ 17.607658] CPU: 0 PID: 113 Comm: sh Kdump: loaded Not tainted 5.18.9 #42 > [ 17.607937] Hardware name: riscv-virtio,qemu (DT) > [ 17.608150] epc : ffffffff800078f8 ra : ffffffff8008862c sp : ff20000010333b90 > [ 17.608441] gp : ffffffff810dde38 tp : ff6000000226c200 t0 : ffffffff8032be68 > [ 17.608741] t1 : 0720072007200720 t2 : 666666666666663c s0 : ff20000010333cf0 > [ 17.609025] s1 : 0000000000000000 a0 : ff20000010333b98 a1 : 0000000000000001 > [ 17.609320] a2 : 0000000000000010 a3 : 0000000000000000 a4 : 0000000000000000 > [ 17.609601] a5 : ff60000001c78000 a6 : 000000000000003c a7 : ffffffff8035c9a4 > [ 17.609894] s2 : ffffffff810df0a8 s3 : ffffffff810df718 s4 : ff20000010333b98 > [ 17.610186] s5 : 0000000000000000 s6 : 0000000000000007 s7 : ffffffff80c4a468 > [ 17.610469] s8 : 00ffffffca281410 s9 : 0000000000000007 s10: 00aaaaaab5bb6700 > [ 17.610755] s11: 0000000000000001 t3 : ff60000001218f00 t4 : ff60000001218f00 > [ 17.611041] t5 : ff60000001218000 t6 : ff20000010333988 > [ 17.611255] status: 0000000200000020 badaddr: 0000000000000000 cause: 0000000000000008 > > With the correct PC, the backtrace showed by crash tool as below, > > crash> bt > PID: 113 TASK: ff6000000226c200 CPU: 0 COMMAND: "sh" > #0 [ff20000010333b90] riscv_crash_save_regs at ffffffff800078f8 <--- Normal > #1 [ff20000010333cf0] panic at ffffffff806578c6 > #2 [ff20000010333d50] sysrq_reset_seq_param_set at ffffffff8038c03c > #3 [ff20000010333da0] __handle_sysrq at ffffffff8038c604 > #4 [ff20000010333e00] write_sysrq_trigger at ffffffff8038cae4 > #5 [ff20000010333e20] proc_reg_write at ffffffff801b7ee8 > #6 [ff20000010333e40] vfs_write at ffffffff80152bb2 > #7 [ff20000010333e80] ksys_write at ffffffff80152eda > #8 [ff20000010333ed0] sys_write at ffffffff80152f52 > > Fixes: e53d28180d4d ("RISC-V: Add kdump support") This patch is also a fix, but not at the start of the series which (I think) makes it less likely to be picked up for an auto-backport. As it doesn't seem to depend on the prior patches, can you move this up to 2/6 in the series?