Re: [PATCH] recordmcount: Fix spurious mcount entries on powerpc
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2019-06-27 05:55:57
Also in:
lkml
"Naveen N. Rao" [off-list ref] writes:
The recent change enabling HAVE_C_RECORDMCOUNT on powerpc started
showing the following issue:
# modprobe kprobe_example
ftrace-powerpc: Not expected bl: opcode is 3c4c0001
WARNING: CPU: 0 PID: 227 at kernel/trace/ftrace.c:2001 ftrace_bug+0x90/0x318
Modules linked in:
CPU: 0 PID: 227 Comm: modprobe Not tainted 5.2.0-rc6-00678-g1c329100b942 #2
NIP: c000000000264318 LR: c00000000025d694 CTR: c000000000f5cd30
REGS: c000000001f2b7b0 TRAP: 0700 Not tainted (5.2.0-rc6-00678-g1c329100b942)
MSR: 900000010282b033 <SF,HV,VEC,VSX,EE,FP,ME,IR,DR,RI,LE,TM[E]> CR: 28228222 XER: 00000000
CFAR: c0000000002642fc IRQMASK: 0
<snip>
NIP [c000000000264318] ftrace_bug+0x90/0x318
LR [c00000000025d694] ftrace_process_locs+0x4f4/0x5e0
Call Trace:
[c000000001f2ba40] [0000000000000004] 0x4 (unreliable)
[c000000001f2bad0] [c00000000025d694] ftrace_process_locs+0x4f4/0x5e0
[c000000001f2bb90] [c00000000020ff10] load_module+0x25b0/0x30c0
[c000000001f2bd00] [c000000000210cb0] sys_finit_module+0xc0/0x130
[c000000001f2be20] [c00000000000bda4] system_call+0x5c/0x70
Instruction dump:
419e0018 2f83ffff 419e00bc 2f83ffea 409e00cc 4800001c 0fe00000 3c62ff96
39000001 39400000 386386d0 480000c4 <0fe00000> 3ce20003 39000001 3c62ff96
---[ end trace 4c438d5cebf78381 ]---
ftrace failed to modify
[<c0080000012a0008>] 0xc0080000012a0008
actual: 01:00:4c:3c
Initializing ftrace call sites
ftrace record flags: 2000000
(0)
expected tramp: c00000000006af4cAha, thanks. I saw that on one of my text boxes but hadn't pinned it down to this commit.
Fixes: c7d64b560ce80 ("powerpc/ftrace: Enable C Version of recordmcount")That commit is the tip of my next, so I'll drop it for now and merge them in the other order so there's breakage. Steve are you OK if I merge this via the powerpc tree? I'll reword the commit message so that it makes sense coming prior to the commit mentioned above. cheers
quoted hunk ↗ jump to hunk
Signed-off-by: Naveen N. Rao <redacted> --- scripts/recordmcount.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h index 13c5e6c8829c..47fca2c69a73 100644 --- a/scripts/recordmcount.h +++ b/scripts/recordmcount.h@@ -325,7 +325,8 @@ static uint_t *sift_rel_mcount(uint_t *mlocp, if (!mcountsym) mcountsym = get_mcountsym(sym0, relp, str0); - if (mcountsym == Elf_r_sym(relp) && !is_fake_mcount(relp)) { + if (mcountsym && mcountsym == Elf_r_sym(relp) && + !is_fake_mcount(relp)) { uint_t const addend = _w(_w(relp->r_offset) - recval + mcount_adjust); mrelp->r_offset = _w(offbase-- 2.22.0