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SubjectRe: Crash in msm serial on dragonboard with ftrace bootargs
On Thu, 18 Oct 2018 10:51:18 +0530
Sai Prakash Ranjan <> wrote:

> > So something else is causing an issue besides just msm_read.
> >
> > Can you do an objdump -dr of the entire vmlinux binary and gzip it and
> > post it somewhere. Not sure if it would be too big to email. You could
> > try sending it to me privately. I'd like to see the binary that you are
> > using.
> >
> I have sent the objdump and dot config to you privately.

Thanks. I don't see anything that pops out, but then again, my arm asm
foo is very rusty (it has been literally decades since I did any arm
asm). I wonder if it could simply be a timing issue?

ffff0000086eb538 <msm_read.isra.1>:
ffff0000086eb538: a9be7bfd stp x29, x30, [sp,#-32]!
ffff0000086eb53c: 910003fd mov x29, sp
ffff0000086eb540: a90153f3 stp x19, x20, [sp,#16]
ffff0000086eb544: aa0003f4 mov x20, x0
ffff0000086eb548: 2a0103f3 mov w19, w1
ffff0000086eb54c: aa1e03e0 mov x0, x30
ffff0000086eb550: 97e6bae4 bl ffff00000809a0e0 <_mcount>

The above is changed to nop on boot, but then to:

bl ftrace_caller

When ftrace is enabled.

ffff0000086eb554: 8b334280 add x0, x20, w19, uxtw
ffff0000086eb558: b9400000 ldr w0, [x0]
ffff0000086eb55c: a94153f3 ldp x19, x20, [sp,#16]
ffff0000086eb560: a8c27bfd ldp x29, x30, [sp],#32
ffff0000086eb564: d65f03c0 ret

ffff00000809a0e4 <ftrace_caller>:
ffff00000809a0e4: a9bf7bfd stp x29, x30, [sp,#-16]!
ffff00000809a0e8: 910003fd mov x29, sp
ffff00000809a0ec: d10013c0 sub x0, x30, #0x4
ffff00000809a0f0: f94003a1 ldr x1, [x29]
ffff00000809a0f4: f9400421 ldr x1, [x1,#8]
ffff00000809a0f8: d1001021 sub x1, x1, #0x4

ffff00000809a0fc <ftrace_call>:
ffff00000809a0fc: d503201f nop

The above nop gets patched to:

bl ftrace_ops_no_ops

Which will iterate through all the registered functions.

ffff00000809a100 <ftrace_graph_call>:
ffff00000809a100: d503201f nop

The above only gets set when function graph tracer is enabled, which it
is not in this case.

ffff00000809a104: a8c17bfd ldp x29, x30, [sp],#16
ffff00000809a108: d65f03c0 ret

Anyone see any problems here?

-- Steve

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