diff options
| author | Josh Poimboeuf <jpoimboe@kernel.org> | 2026-04-23 15:53:17 -0700 |
|---|---|---|
| committer | Josh Poimboeuf <jpoimboe@kernel.org> | 2026-05-04 21:16:07 -0700 |
| commit | fc0bb9915bce0c333f918ca76958d804ccd79f89 (patch) | |
| tree | 4623f5e23f16b8d185f7a59b1f61c625947594c7 /lib | |
| parent | cca84cb12908f1cfcecaef80a7692017e2d6a945 (diff) | |
| download | lwn-fc0bb9915bce0c333f918ca76958d804ccd79f89.tar.gz lwn-fc0bb9915bce0c333f918ca76958d804ccd79f89.zip | |
objtool: Grow __cfi_* prefix symbols for all CFI+CALL_PADDING
For all CONFIG_CFI+CONFIG_CALL_PADDING configs, for C functions, the
__cfi_ symbols only cover the 5-byte kCFI type hash. After that there
also N bytes of NOP padding between the hash and the function entry
which aren't associated with any symbol.
The NOPs can be replaced with actual code at runtime. Without a symbol,
unwinders and tooling have no way of knowing where those bytes belong.
Grow the existing __cfi_* symbols to fill that gap.
Note that assembly functions with SYM_TYPED_FUNC_START() aren't affected
by this issue, their __cfi_ symbols also cover the padding.
Also, CONFIG_PREFIX_SYMBOLS has no reason to exist: CONFIG_CALL_PADDING
is what causes the compiler to emit NOP padding before function entry
(via -fpatchable-function-entry), so it's the right condition for
creating prefix symbols.
Remove CONFIG_PREFIX_SYMBOLS, as it's no longer needed. Simplify the
LONGEST_SYM_KUNIT_TEST dependency accordingly. Rework objtool's
arguments a bit to handle the variety of prefix/cfi-related cases.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/Kconfig.debug | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 8ff5adcfe1e0..4f7496b3268d 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -3070,7 +3070,7 @@ config FORTIFY_KUNIT_TEST config LONGEST_SYM_KUNIT_TEST tristate "Test the longest symbol possible" if !KUNIT_ALL_TESTS depends on KUNIT && KPROBES - depends on !PREFIX_SYMBOLS && !CFI && !GCOV_KERNEL + depends on !CALL_PADDING && !CFI && !GCOV_KERNEL default KUNIT_ALL_TESTS help Tests the longest symbol possible |