Messages in this thread Patch in this message | | | Subject | Re: [PATCH] powerpc/kprobes: Fix kprobe Oops happens in booke | From | Pu Lehui <> | Date | Fri, 6 Aug 2021 16:59:44 +0800 |
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On 2021/8/5 17:51, Christophe Leroy wrote: > > > Le 04/08/2021 à 16:37, Pu Lehui a écrit : >> When using kprobe on powerpc booke series processor, Oops happens >> as show bellow: >> >> [ 35.861352] Oops: Exception in kernel mode, sig: 5 [#1] >> [ 35.861676] BE PAGE_SIZE=4K SMP NR_CPUS=24 QEMU e500 >> [ 35.861905] Modules linked in: >> [ 35.862144] CPU: 0 PID: 76 Comm: sh Not tainted >> 5.14.0-rc3-00060-g7e96bf476270 #18 >> [ 35.862610] NIP: c0b96470 LR: c00107b4 CTR: c0161c80 >> [ 35.862805] REGS: c387fe70 TRAP: 0700 Not tainted >> (5.14.0-rc3-00060-g7e96bf476270) >> [ 35.863198] MSR: 00029002 <CE,EE,ME> CR: 24022824 XER: 20000000 >> [ 35.863577] >> [ 35.863577] GPR00: c0015218 c387ff20 c313e300 c387ff50 00000004 >> 40000002 40000000 0a1a2cce >> [ 35.863577] GPR08: 00000000 00000004 00000000 59764000 24022422 >> 102490c2 00000000 00000000 >> [ 35.863577] GPR16: 00000000 00000000 00000040 10240000 10240000 >> 10240000 10240000 10220000 >> [ 35.863577] GPR24: ffffffff 10240000 00000000 00000000 bfc655e8 >> 00000800 c387ff50 00000000 >> [ 35.865367] NIP [c0b96470] schedule+0x0/0x130 >> [ 35.865606] LR [c00107b4] interrupt_exit_user_prepare_main+0xf4/0x100 >> [ 35.865974] Call Trace: >> [ 35.866142] [c387ff20] [c0053224] irq_exit+0x114/0x120 (unreliable) >> [ 35.866472] [c387ff40] [c0015218] interrupt_return+0x14/0x13c >> [ 35.866728] --- interrupt: 900 at 0x100af3dc >> [ 35.866963] NIP: 100af3dc LR: 100de020 CTR: 00000000 >> [ 35.867177] REGS: c387ff50 TRAP: 0900 Not tainted >> (5.14.0-rc3-00060-g7e96bf476270) >> [ 35.867488] MSR: 0002f902 <CE,EE,PR,FP,ME> CR: 20022422 XER: >> 20000000 >> [ 35.867808] >> [ 35.867808] GPR00: c001509c bfc65570 1024b4d0 00000000 100de020 >> 20022422 bfc655a8 100af3dc >> [ 35.867808] GPR08: 0002f902 00000000 00000000 00000000 72656773 >> 102490c2 00000000 00000000 >> [ 35.867808] GPR16: 00000000 00000000 00000040 10240000 10240000 >> 10240000 10240000 10220000 >> [ 35.867808] GPR24: ffffffff 10240000 00000000 00000000 bfc655e8 >> 10245910 ffffffff 00000001 >> [ 35.869406] NIP [100af3dc] 0x100af3dc >> [ 35.869578] LR [100de020] 0x100de020 >> [ 35.869751] --- interrupt: 900 >> [ 35.870001] Instruction dump: >> [ 35.870283] 40c20010 815e0518 714a0100 41e2fd04 39200000 913e00c0 >> 3b1e0450 4bfffd80 >> [ 35.870666] 0fe00000 92a10024 4bfff1a9 60000000 <7fe00008> 7c0802a6 >> 93e1001c 7c5f1378 >> [ 35.871339] ---[ end trace 23ff848139efa9b9 ]--- >> >> There is no real mode for booke arch and the MMU translation is >> always on. The corresponding MSR_IS/MSR_DS bit in booke is used >> to switch the address space, but not for real mode judgment. > > Can you explain more the link between that explanation and the Oops > itself ? > In fact, the same Oops appears when any probed function is hit, like do_nanosleep
/ # echo "p:myprobe do_nanosleep" > /sys/kernel/debug/tracing/kprobe_events / # echo 1 > /sys/kernel/debug/tracing/events/kprobes/myprobe/enable / # sleep 1 [ 50.076730] Oops: Exception in kernel mode, sig: 5 [#1] [ 50.077017] BE PAGE_SIZE=4K SMP NR_CPUS=24 QEMU e500 [ 50.077221] Modules linked in: [ 50.077462] CPU: 0 PID: 77 Comm: sleep Not tainted 5.14.0-rc4-00022-g251a1524293d #21 [ 50.077887] NIP: c0b9c4e0 LR: c00ebecc CTR: 00000000 [ 50.078067] REGS: c3883de0 TRAP: 0700 Not tainted (5.14.0-rc4-00022-g251a1524293d) [ 50.078349] MSR: 00029000 <CE,EE,ME> CR: 24000228 XER: 20000000 [ 50.078675] [ 50.078675] GPR00: c00ebdf0 c3883e90 c313e300 c3883ea0 00000001 00000000 c3883ecc 00000001 [ 50.078675] GPR08: c100598c c00ea250 00000004 00000000 24000222 102490c2 bff4180c 101e60d4 [ 50.078675] GPR16: 00000000 102454ac 00000040 10240000 10241100 102410f8 10240000 00500000 [ 50.078675] GPR24: 00000002 00000000 c3883ea0 00000001 00000000 0000c350 3b9b8d50 00000000 [ 50.080151] NIP [c0b9c4e0] do_nanosleep+0x0/0x190 [ 50.080352] LR [c00ebecc] hrtimer_nanosleep+0x14c/0x1e0 [ 50.080638] Call Trace: [ 50.080801] [c3883e90] [c00ebdf0] hrtimer_nanosleep+0x70/0x1e0 (unreliable) [ 50.081110] [c3883f00] [c00ec004] sys_nanosleep_time32+0xa4/0x110 [ 50.081336] [c3883f40] [c001509c] ret_from_syscall+0x0/0x28 [ 50.081541] --- interrupt: c00 at 0x100a4d08 [ 50.081749] NIP: 100a4d08 LR: 101b5234 CTR: 00000003 [ 50.081931] REGS: c3883f50 TRAP: 0c00 Not tainted (5.14.0-rc4-00022-g251a1524293d) [ 50.082183] MSR: 0002f902 <CE,EE,PR,FP,ME> CR: 24000222 XER: 00000000 [ 50.082457] [ 50.082457] GPR00: 000000a2 bf980040 1024b4d0 bf980084 bf980084 64000000 00555345 fefefeff [ 50.082457] GPR08: 7f7f7f7f 101e0000 00000069 00000003 28000422 102490c2 bff4180c 101e60d4 [ 50.082457] GPR16: 00000000 102454ac 00000040 10240000 10241100 102410f8 10240000 00500000 [ 50.082457] GPR24: 00000002 bf9803f4 10240000 00000000 00000000 100039e0 00000000 102444e8 [ 50.083789] NIP [100a4d08] 0x100a4d08 [ 50.083917] LR [101b5234] 0x101b5234 [ 50.084042] --- interrupt: c00 [ 50.084238] Instruction dump: [ 50.084483] 4bfffc40 60000000 60000000 60000000 9421fff0 39400402 914200c0 38210010 [ 50.084841] 4bfffc20 00000000 00000000 00000000 <7fe00008> 7c0802a6 7c892378 93c10048 [ 50.085487] ---[ end trace f6fffe98e2fa8f3e ]--- [ 50.085678] Trace/breakpoint trap
In current code, kprobe_handler() will be called by 'program check exception' when a probe is hit, and kprobe_handler() will check whether it is in real-mode according to MSR_IR/MSR_DR bit. When in real-mode(MSR_IR/MSR_DR are 0), the following process will be executed to trigger Oops: __exception() -> exception_common() -> die("Exception in kernel mode")
But for booke arch, the corresponding bits, which is called MSR_IS/MSR_DS, are used for switching the non-privileged and privileged virtual address spaces, and users can change both spaces by setting MSR_IS/MSR_DS bit. So, when kernel in privileged space(MSR_IS/MSR_DS are 0), kprobe trap will meet a Oops.
And also, the MMU of booke is always enabled, so when other trap appears, the problem mentioned in 21f8b2fa3ca5 will never met. >> >> Fixes: 21f8b2fa3ca5 ("powerpc/kprobes: Ignore traps that happened in >> real mode") >> Signed-off-by: Pu Lehui <pulehui@huawei.com> >> --- >> arch/powerpc/include/asm/ptrace.h | 6 ++++++ >> arch/powerpc/kernel/kprobes.c | 5 +---- >> 2 files changed, 7 insertions(+), 4 deletions(-) >> >> diff --git a/arch/powerpc/include/asm/ptrace.h >> b/arch/powerpc/include/asm/ptrace.h >> index 3e5d470a6155..4aec1a97024b 100644 >> --- a/arch/powerpc/include/asm/ptrace.h >> +++ b/arch/powerpc/include/asm/ptrace.h >> @@ -187,6 +187,12 @@ static inline unsigned long frame_pointer(struct >> pt_regs *regs) >> #define user_mode(regs) (((regs)->msr & MSR_PR) != 0) >> #endif >> +#ifdef CONFIG_BOOKE >> +#define real_mode(regs) 0 >> +#else >> +#define real_mode(regs) (!((regs)->msr & MSR_IR) || !((regs)->msr >> & MSR_DR)) >> +#endif >> + > > You don't need an #ifdef stuff here, you can base your testing on > IS_ENABLED(CONFIG_BOOKE) > I'll fix in v2. >> #define force_successful_syscall_return() \ >> do { \ >> set_thread_flag(TIF_NOERROR); \ >> diff --git a/arch/powerpc/kernel/kprobes.c >> b/arch/powerpc/kernel/kprobes.c >> index cbc28d1a2e1b..fac9a5974718 100644 >> --- a/arch/powerpc/kernel/kprobes.c >> +++ b/arch/powerpc/kernel/kprobes.c >> @@ -289,10 +289,7 @@ int kprobe_handler(struct pt_regs *regs) >> unsigned int *addr = (unsigned int *)regs->nip; >> struct kprobe_ctlblk *kcb; >> - if (user_mode(regs)) >> - return 0; >> - >> - if (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)) >> + if (user_mode(regs) || real_mode(regs)) >> return 0; >> /* >> > .
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