Re: [PATCH 13/13] samples/kprobes: Add batch probe example

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] samples/kprobes: missing ANNOTATE_NOCFI_SYM() on
  kprobe_many_call_function()
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commit 0bb6f0bd88ba358a50c5bd0da72b9a9137c6b243
Author: Jiri Olsa <jolsa@kernel.org>

samples/kprobes: Add batch probe example

This commit adds 50,000 generated x86 functions and a sample module that
registers kprobes on them in a batch and calls each function to verify
the probes.

> diff --git a/samples/kprobes/kprobe_many_example.c b/samples/kprobes/kprobe_many_example.c
> new file mode 100644
> index 0000000000000..5a58908c840c7
> --- /dev/null
> +++ b/samples/kprobes/kprobe_many_example.c

[ ... ]

> +/* The generated assembly functions have no CFI type metadata. */
> +static noinline __nocfi void
> +kprobe_many_call_function(char *functions, unsigned int index)
> +{
> +	void (*function)(void);
> +
> +	function = (void (*)(void))(functions + index * KPROBE_MANY_FUNC_SIZE);
> +	function();
> +}

[Severity: Low]
Does kprobe_many_call_function() need
ANNOTATE_NOCFI_SYM(kprobe_many_call_function)?

Because __nocfi omits the kCFI ud2 sequence before the indirect call,
building with CONFIG_MITIGATION_RETPOLINE=y, CONFIG_CALL_PADDING=y and
CONFIG_CFI=y causes objtool's validate_retpoline() to emit a "no-cfi
indirect call!" warning (breaking the build when CONFIG_OBJTOOL_WERROR=y
is enabled) unless the function symbol is annotated with
ANNOTATE_NOCFI_SYM().

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261109194916.1089703-1-jolsa@kernel.org?part=13