libbpf: fix USDT SIB argument handling causing unrecognized register error #5749
+225
−7
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
![kernel-patches-daemon-bpf-rc[bot]](https://avatars.githubusercontent.com/u/70728002?s=60&v=4){kind=small}
|
Upstream branch: 0786654 |
kernel-patches-daemon-bpf-rc
bot
force-pushed
the
bpf-next_base
branch
from
5e1a4c1 to
91606c1
Compare
|
Upstream branch: dc0fe95 |
kernel-patches-daemon-bpf-rc
bot
force-pushed
the
series/991613=>bpf-next
branch
from
6254683 to
ed3beff
Compare
kernel-patches-daemon-bpf-rc
bot
force-pushed
the
bpf-next_base
branch
from
91606c1 to
9e5d665
Compare
|
Upstream branch: c80d797 |
kernel-patches-daemon-bpf-rc
bot
force-pushed
the
series/991613=>bpf-next
branch
from
ed3beff to
88af277
Compare
kernel-patches-daemon-bpf-rc
bot
force-pushed
the
bpf-next_base
branch
from
9e5d665 to
f86fd37
Compare
|
Upstream branch: abdaf49 |
kernel-patches-daemon-bpf-rc
bot
force-pushed
the
series/991613=>bpf-next
branch
from
88af277 to
269d9e2
Compare
kernel-patches-daemon-bpf-rc
bot
force-pushed
the
bpf-next_base
branch
from
f86fd37 to
2842450
Compare
…error On x86-64, USDT arguments can be specified using Scale-Index-Base (SIB) addressing, e.g. "1@-96(%rbp,%rax,8)". The current USDT implementation in libbpf cannot parse this format, causing `bpf_program__attach_usdt()` to fail with -ENOENT (unrecognized register). This patch fixes this by implementing the necessary changes: - add correct handling for SIB-addressed arguments in `bpf_usdt_arg`. - add adaptive support to `__bpf_usdt_arg_type` and `__bpf_usdt_arg_spec` to represent SIB addressing parameters. Signed-off-by: Jiawei Zhao <[email protected]>
…dling logic When using GCC on x86-64 to compile an usdt prog with -O1 or higher optimization, the compiler will generate SIB addressing mode for global array and PC-relative addressing mode for global variable, e.g. "1@-96(%rbp,%rax,8)" and "-1@4+t1(%rip)". In this patch: - add usdt_o2 test case to cover SIB addressing usdt argument spec handling logic Signed-off-by: Jiawei Zhao <[email protected]>
usdt_o2 is intended to exercise the SIB (Scale-Index-Base) argument
handling in libbpf's USDT path. With GCC 13 this reliably produced a
SIB-form argument (e.g. 8@(%rdx,%rax,8)), but with newer GCC (e.g. 15)
the compiler frequently optimizes the probe argument into a plain
register (e.g. 8@%rax) or a stack slot, so the test stops covering the
SIB code path and becomes flaky across toolchains.
Force a SIB memory operand in the probe by:
* placing the base pointer into %rdx and the index into %rax using an
empty inline asm with output constraints ("=d", "=a") and matching
inputs
* immediately passing base[idx] to STAP_PROBE1.
* only enable on x86 platform.
This makes the compiler encode the operand as SIB (base + index8),
which in .note.stapsdt shows up as 8@(%rdx,%rax,8) regardless of GCC
version. A memory clobber and noinline prevent reordering/re-allocation
around the probe site.
This change is x86_64-specific and does not alter program semantics; it
only stabilizes the USDT argument shape so the test consistently
validates SIB handling. Clang historically prefers stack temporaries for
such operands, but the selftests build with GCC, and this keeps behavior
stable across GCC versions without introducing a separate .S file.
Signed-off-by: Jiawei Zhao <[email protected]>
|
Upstream branch: 3ec8560 |
kernel-patches-daemon-bpf-rc
bot
force-pushed
the
series/991613=>bpf-next
branch
from
269d9e2 to
c43f8a7
Compare
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Pull request for series with
subject: libbpf: fix USDT SIB argument handling causing unrecognized register error
version: 10
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=991613