Re: FAILED unresolved symbol vfs_truncate on arm64 with LLVM

On Thu, Feb 11, 2021 at 5:07 PM Jiri Olsa [off-list ref] wrote:

On Thu, Feb 11, 2021 at 04:43:48PM +0100, Sedat Dilek wrote:

SNIP

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filled with elf functions start/end values, right?

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                        /*
                         * We iterate over sorted array, so we can easily skip
                         * not valid item and move following valid field into


So the idea is to use address segments and check whether there is a
segment that overlaps with a given address by first binary searching
for a segment with the largest starting address that is <= addr. And
then just confirming that segment does overlap with the requested
address.

WDYT?

heya,
with your approach I ended up with change below, it gives me same
results as with the previous change

I think I'll separate the kmod bool address computation later on,
but I did not want to confuse this change for now

I have applied your diff on top of pahole-v1.20 with Yonghong Son's
"btf_encoder: sanitize non-regular int base type" applied.
This is on x86-64 with LLVM-12, so I am not directly affected.
If it is out of interest I can offer vmlinux (or .*btf* files) w/ and
w/o your diff.

if you could run your tests/workloads and check the new change does not
break your stuff, that'd be great

we need soem testsuite ;-) I have some stupid test script which runs over
few vmlinux binaries and check the diff in BTF data.. problem is that these
vmlinux binaries are ~300M each, so it's not great for sharing

also I was checking if we could use BPF_BTF_LOAD syscall and load BTF in
kernel and back at the end of pahole processing to check it's valid ;-)

Just finished a new build.

What I did:

cd /path/to/linux/git
rm -v .*btf* vmlinux*
<re-run my build-script with modified pahole>

I collected some commands in CBL issue #1297.

$ /usr/sbin/bpftool btf dump file vmlinux | rg 'vfs_truncate|bpf_d_path'
[22259] TYPEDEF 'btf_bpf_d_path' type_id=22260
[29970] FUNC 'vfs_truncate' type_id=29969 linkage=static

Tests?

$MAKE $MAKE_OPTS -C tools/testing/selftests/bpf/

^^^ ???

- Sedat -

[1] https://github.com/ClangBuiltLinux/linux/issues/1297

thanks,
jirka