[powerpc/merge] ftrace warning while running stress_code_patching

[Sachin Sant]

While running stress_code_patching.sh (powerpc/mm selftest) against
latest powerpc/merge branch (5.16.0-rc2-g2dbc3a3e8fc1) following
warning is seen:

Reverting following patch allows the test to run successfully.
commit 8b8a8f0ab3f5 :
powerpc/code-patching: Improve verification of patchability

I did try the 3 patch series [1] (powerpc/code-patching) posted by Nick, but that does not
seem to fix the problem.

ftrace-powerpc: Unexpected call sequence at 000000001d3f5e8d: 4801c5ad 2c230000
------------[ ftrace bug ]------------
ftrace failed to modify 
[<c008000007110004>] fuse_len_args+0x4/0x80 [fuse]
 actual:   ad:c5:01:48
Setting ftrace call site to call ftrace function
ftrace record flags: 80000001
(1)  
expected tramp: c000000000082494
------------[ cut here ]------------
WARNING: CPU: 18 PID: 1991307 at kernel/trace/ftrace.c:2068 ftrace_bug+0x274/0x2e8
Modules linked in: dm_mod bonding nft_ct nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables rfkill libcrc32c nfnetlink sunrpc pseries_rng xts vmx_crypto sch_fq_codel ip_tables ext4 mbcache jbd2 sd_mod t10_pi sg ibmvscsi ibmveth scsi_transport_srp fuse
CPU: 18 PID: 1991307 Comm: stress_code_pat Not tainted 5.16.0-rc2-g2dbc3a3e8fc1 #1
NIP:  c0000000002d710c LR: c0000000002d7108 CTR: c0000000001f5e40
REGS: c000000039d9b760 TRAP: 0700   Not tainted  (5.16.0-rc2-g2dbc3a3e8fc1)
MSR:  800000000282b033 <SF,VEC,VSX,EE,FP,ME,IR,DR,RI,LE>  CR: 48228224  XER: 20040009
CFAR: c0000000001f99e0 IRQMASK: 0 
GPR00: c0000000002d7108 c000000039d9ba00 c000000002a00500 0000000000000022 
GPR04: 00000000ffff7fff c000000039d9b720 0000000000000027 c000000efd747e18 
GPR08: 0000000000000023 0000000000000001 0000000000000027 0000000000000001 
GPR12: 0000000000008000 c000000effbf8280 0000000040000000 000000012d9f9798 
GPR16: 000000012d9f9724 000000012d996be8 000000012d92f4f0 000000012d9fd568 
GPR20: 000000015bed3ed0 0000000000000001 000000012d9a99d8 00007fffc36f7f54 
GPR24: 0000000000000001 0000000000000000 c000000039d9bc70 c000000000faf228 
GPR28: c000000000ff3730 c000000000fac298 c008000007110004 c000000016690000 
NIP [c0000000002d710c] ftrace_bug+0x274/0x2e8
LR [c0000000002d7108] ftrace_bug+0x270/0x2e8
Call Trace:
[c000000039d9ba00] [c0000000002d7108] ftrace_bug+0x270/0x2e8 (unreliable)
[c000000039d9ba90] [c0000000002d05c8] ftrace_modify_all_code+0x108/0x1c0
[c000000039d9bac0] [c0000000000822b8] arch_ftrace_update_code+0x18/0x30
[c000000039d9bae0] [c0000000002d07b8] ftrace_run_update_code+0x58/0xe0
[c000000039d9bb10] [c0000000002d5a78] ftrace_startup+0xf8/0x1a0
[c000000039d9bb50] [c0000000002d5b6c] register_ftrace_function+0x4c/0xc0
[c000000039d9bb80] [c0000000002f9b38] function_trace_init+0x88/0x100
[c000000039d9bbb0] [c0000000002efaf8] tracing_set_tracer+0x368/0x550
[c000000039d9bc50] [c0000000002efdf8] tracing_set_trace_write+0x118/0x180
[c000000039d9bd10] [c000000000491e50] vfs_write+0xf0/0x340
[c000000039d9bd60] [c00000000049227c] ksys_write+0x7c/0x140
[c000000039d9bdb0] [c000000000033284] system_call_exception+0x174/0x370
[c000000039d9be10] [c00000000000c74c] system_call_common+0xec/0x250
--- interrupt: c00 at 0x7fffb4f0bd74
NIP:  00007fffb4f0bd74 LR: 00007fffb4e834c4 CTR: 0000000000000000
REGS: c000000039d9be80 TRAP: 0c00   Not tainted  (5.16.0-rc2-g2dbc3a3e8fc1)
MSR:  800000000280f033 <SF,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE>  CR: 28222222  XER: 00000000
IRQMASK: 0 
GPR00: 0000000000000004 00007fffc36f7d30 00007fffb5007100 0000000000000001 
GPR04: 000000015bed1750 0000000000000009 0000000000000010 000000006e6f6974 
GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000 
GPR12: 0000000000000000 00007fffb513aeb0 0000000040000000 000000012d9f9798 
GPR16: 000000012d9f9724 000000012d996be8 000000012d92f4f0 000000012d9fd568 
GPR20: 000000015bed3ed0 0000000000000001 000000012d9a99d8 00007fffc36f7f54 
GPR24: 00007fffc36f7f50 000000012d9faf94 0000000000000009 000000015bed1750 
GPR28: 0000000000000009 00007fffb5001848 000000015bed1750 0000000000000009 
NIP [00007fffb4f0bd74] 0x7fffb4f0bd74
LR [00007fffb4e834c4] 0x7fffb4e834c4
--- interrupt: c00
Instruction dump:
48000014 3c62fe5f 386333e0 4bf228b1 60000000 7fe3fb78 4bff88c5 7c641b78 
3c62fe5f 386333f8 4bf22895 60000000 <0fe00000> 38210090 39000001 3d22fd68 
---[ end trace c4abf5aea4841297 ]---

Thanks
-Sachin

[1] https://lore.kernel.org/linuxppc-dev/f9e53405-b5b9-15d1-eaf9-0616a5b87424@csgroup.eu/T/