On Mon, Jun 27, 2011 at 6:01 PM, Ananth N Mavinakayanahalli <ana...@in.ibm.com> wrote: > On Sun, Jun 26, 2011 at 11:47:13PM +0900, Masami Hiramatsu wrote: >> (2011/06/24 19:29), Steven Rostedt wrote: >> > On Fri, 2011-06-24 at 17:21 +0800, Yong Zhang wrote: >> >> Hi, >> >> >> >> When I use kprobe to do something, I found some wired thing. >> >> >> >> When CONFIG_FUNCTION_TRACER is disabled: >> >> (gdb) disassemble do_fork >> >> Dump of assembler code for function do_fork: >> >> 0xc0037390 <+0>: mflr r0 >> >> 0xc0037394 <+4>: stwu r1,-64(r1) >> >> 0xc0037398 <+8>: mfcr r12 >> >> 0xc003739c <+12>: stmw r27,44(r1) >> >> >> >> Then I: >> >> modprobe kprobe_example func=do_fork offset=4 >> >> ls >> >> Things works well. >> >> >> >> But when CONFIG_FUNCTION_TRACER is enabled: >> >> (gdb) disassemble do_fork >> >> Dump of assembler code for function do_fork: >> >> 0xc0040334 <+0>: mflr r0 >> >> 0xc0040338 <+4>: stw r0,4(r1) >> >> 0xc004033c <+8>: bl 0xc00109d4 <mcount> >> >> 0xc0040340 <+12>: stwu r1,-80(r1) >> >> 0xc0040344 <+16>: mflr r0 >> >> 0xc0040348 <+20>: stw r0,84(r1) >> >> 0xc004034c <+24>: mfcr r12 >> >> Then I: >> >> modprobe kprobe_example func=do_fork offset=12 >> >> ls >> >> 'ls' will never retrun. system freeze. >> > >> > I'm not sure if x86 had a similar issue. >> > >> > Masami, have any ideas to why this happened? >> >> No, I don't familiar with ppc implementation. I guess >> that single-step resume code failed to emulate the >> instruction, but it strongly depends on ppc arch. >> Maybe IBM people may know what happened. >> >> Ananth, Jim, would you have any ideas? > > On powerpc, we emulate sstep whenever possible. Only recently support to > emulate loads and stores got added. I don't have access to a powerpc box > today... but will try to recreate the problem ASAP and see what could be > happening in the presence of mcount.
After taking more testing on it, it looks like the issue doesn't depend on mcount (AKA. CONFIG_FUNCTION_TRACER) As I said in the first email, with eldk-5.0 CONFIG_FUNCTION_TRACER=n will work well. But when I'm using eldk-4.2[1], both will fail. But the funny thing is when I set kprobe at several functions some works fine but some will fail. For example, at this time do_fork() works well, but show_interrupt() will crash. root@unknown:/root> insmod kprobe_example.ko func=show_interrupts Planted kprobe at c009be18 root@unknown:/root> cat /proc/interrupts pre_handler: p->addr = 0xc009be18, nip = 0xc009be18, msr = 0x29000 post_handler: p->addr = 0xc009be18, msr = 0x29000,boostable = 1 Oops: Exception in kernel mode, sig: 11 [#1] PREEMPT MPC8536 DS Modules linked in: kprobe_example NIP: df159e74 LR: c0106f40 CTR: c009be18 REGS: df159d90 TRAP: 0700 Not tainted (3.0.0-rc4-00001-ge8ffcca-dirty) MSR: 00029000 <EE,ME,CE> CR: 20202688 XER: 00000000 TASK = dfaa5340[613] 'cat' THREAD: df158000 GPR00: fffff000 df159e40 dfaa5340 df024a00 df159e78 00000000 df159f20 00000001 GPR08: c10060d0 c009be18 00029000 df159e70 00000000 1001ca74 1ffb5f00 100a01cc GPR16: 00000000 00000000 00000000 00000000 df024a28 df159f20 00000000 dfbff080 GPR24: 10016000 00001000 df159f20 df159e78 dfbff080 df159e78 df024a00 df159e70 NIP [df159e74] 0xdf159e74 LR [c0106f40] seq_read+0x2a4/0x568 Call Trace: [df159e40] [00029000] 0x29000 (unreliable) [df159e74] [00000000] (null) Instruction dump: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX ---[ end trace 60026bfc1fe79aed ]--- Segmentation fault Thanks, Yong [1]: http://ftp.denx.de/pub/eldk/4.2/ -- Only stand for myself _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev