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| author | Xianting Tian <xianting.tian@linux.alibaba.com> | 2022-08-11 15:41:46 +0800 |
|---|---|---|
| committer | Palmer Dabbelt <palmer@rivosinc.com> | 2022-08-11 08:54:40 -0700 |
| commit | 59c026c359c30f116fef6ee958e24d04983efbb0 (patch) | |
| tree | 423a108c283a87fb94ee54cefbb4f3651278b02f | |
| parent | 357628e68f5c08ad578a718dc62a0031e06dbe91 (diff) | |
| download | linux-59c026c359c30f116fef6ee958e24d04983efbb0.tar.gz | |
RISC-V: Fixup get incorrect user mode PC for kernel mode regs
When use 'echo c > /proc/sysrq-trigger' to trigger kdump, riscv_crash_save_regs()
will be called to save regs for 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")
Co-developed-by: Guo Ren <guoren@kernel.org>
Signed-off-by: Xianting Tian <xianting.tian@linux.alibaba.com>
Link: https://lore.kernel.org/r/20220811074150.3020189-3-xianting.tian@linux.alibaba.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
| -rw-r--r-- | arch/riscv/kernel/crash_save_regs.S | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/riscv/kernel/crash_save_regs.S b/arch/riscv/kernel/crash_save_regs.S index 7832fb763abacf..b2a1908c0463e4 100644 --- a/arch/riscv/kernel/crash_save_regs.S +++ b/arch/riscv/kernel/crash_save_regs.S @@ -44,7 +44,7 @@ SYM_CODE_START(riscv_crash_save_regs) REG_S t6, PT_T6(a0) /* x31 */ csrr t1, CSR_STATUS - csrr t2, CSR_EPC + auipc t2, 0x0 csrr t3, CSR_TVAL csrr t4, CSR_CAUSE |