On Wed, Jul 24, 2024 at 03:52:10PM -0700, Andrii Nakryiko wrote:
SNIP
> +extern char build_id_start[];
> +extern char build_id_end[];
> +
> +int __attribute__((weak)) trigger_uprobe(bool build_id_resident)
> +{
> + int page_sz = sysconf(_SC_PAGESIZE);
> + void *addr;
> +
> + /* page-align build ID start */
> + addr = (void *)((uintptr_t)&build_id_start & ~(page_sz - 1));
> +
> + /* to guarantee MADV_PAGEOUT work reliably, we need to ensure that
> + * memory range is mapped into current process, so we unconditionally
> + * do MADV_POPULATE_READ, and then MADV_PAGEOUT, if necessary
> + */
> + madvise(addr, page_sz, MADV_POPULATE_READ);
> + if (!build_id_resident)
> + madvise(addr, page_sz, MADV_PAGEOUT);
could this fail? should we at least print the error,
might be tricky to display that becase it's called through system() ?
jirka
> +
> + (void)uprobe();
> +
> + return 0;
> +}
> +
> int main(int argc, char **argv)
> {
> if (argc != 2)
> @@ -84,6 +121,10 @@ int main(int argc, char **argv)
> return bench();
> if (!strcmp("usdt", argv[1]))
> return usdt();
> + if (!strcmp("uprobe-paged-out", argv[1]))
> + return trigger_uprobe(false /* page-out build ID */);
> + if (!strcmp("uprobe-paged-in", argv[1]))
> + return trigger_uprobe(true /* page-in build ID */);
>
> error:
> fprintf(stderr, "usage: %s <bench|usdt>\n", argv[0]);
> diff --git a/tools/testing/selftests/bpf/uprobe_multi.ld b/tools/testing/selftests/bpf/uprobe_multi.ld
> new file mode 100644
> index 000000000000..a2e94828bc8c
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/uprobe_multi.ld
> @@ -0,0 +1,11 @@
> +SECTIONS
> +{
> + . = ALIGN(4096);
> + .note.gnu.build-id : { *(.note.gnu.build-id) }
> + . = ALIGN(4096);
> +}
> +INSERT AFTER .text;
> +
> +build_id_start = ADDR(.note.gnu.build-id);
> +build_id_end = ADDR(.note.gnu.build-id) + SIZEOF(.note.gnu.build-id);
> +
> --
> 2.43.0
>
>
