Commit 45b8fc30 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov
Browse files

lib/buildid: rename build_id_parse() into build_id_parse_nofault() 



Make it clear that build_id_parse() assumes that it can take no page
fault by renaming it and current few users to build_id_parse_nofault().

Also add build_id_parse() stub which for now falls back to non-sleepable
implementation, but will be changed in subsequent patches to take
advantage of sleepable context. PROCMAP_QUERY ioctl() on
/proc/<pid>/maps file is using build_id_parse() and will automatically
take advantage of more reliable sleepable context implementation.

Reviewed-by: default avatarEduard Zingerman <eddyz87@gmail.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240829174232.3133883-6-andrii@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 4e9d360c

include/linux/buildid.h

+2 −2
Original line number Diff line number Diff line
@@ -7,8 +7,8 @@ 
#define BUILD_ID_SIZE_MAX 20



struct vm_area_struct;

int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,

		   __u32 *size);

int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size);

int build_id_parse_nofault(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size);

int build_id_parse_buf(const void *buf, unsigned char *build_id, u32 buf_size);



#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID) || IS_ENABLED(CONFIG_VMCORE_INFO)

kernel/bpf/stackmap.c

+1 −1
Original line number Diff line number Diff line
@@ -156,7 +156,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, 
			goto build_id_valid;

		}

		vma = find_vma(current->mm, ips[i]);

		if (!vma || build_id_parse(vma, id_offs[i].build_id, NULL)) {

		if (!vma || build_id_parse_nofault(vma, id_offs[i].build_id, NULL)) {

			/* per entry fall back to ips */

			id_offs[i].status = BPF_STACK_BUILD_ID_IP;

			id_offs[i].ip = ips[i];

kernel/events/core.c

+1 −1
Original line number Diff line number Diff line
@@ -8851,7 +8851,7 @@ static void perf_event_mmap_event(struct perf_mmap_event *mmap_event) 
	mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;



	if (atomic_read(&nr_build_id_events))

		build_id_parse(vma, mmap_event->build_id, &mmap_event->build_id_size);

		build_id_parse_nofault(vma, mmap_event->build_id, &mmap_event->build_id_size);



	perf_iterate_sb(perf_event_mmap_output,

		       mmap_event,

lib/buildid.c

+22 −3
Original line number Diff line number Diff line
@@ -293,10 +293,12 @@ static int get_build_id_64(struct freader *r, unsigned char *build_id, __u32 *si 
 * @build_id: buffer to store build id, at least BUILD_ID_SIZE long

 * @size:     returns actual build id size in case of success

 *

 * Return: 0 on success, -EINVAL otherwise

 * Assumes no page fault can be taken, so if relevant portions of ELF file are

 * not already paged in, fetching of build ID fails.

 *

 * Return: 0 on success; negative error, otherwise

 */

int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,

		   __u32 *size)

int build_id_parse_nofault(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size)

{

	const Elf32_Ehdr *ehdr;

	struct freader r;
@@ -335,6 +337,23 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, 
	return ret;

}



/*

 * Parse build ID of ELF file mapped to VMA

 * @vma:      vma object

 * @build_id: buffer to store build id, at least BUILD_ID_SIZE long

 * @size:     returns actual build id size in case of success

 *

 * Assumes faultable context and can cause page faults to bring in file data

 * into page cache.

 *

 * Return: 0 on success; negative error, otherwise

 */

int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size)

{

	/* fallback to non-faultable version for now */

	return build_id_parse_nofault(vma, build_id, size);

}



/**

 * build_id_parse_buf - Get build ID from a buffer

 * @buf:      ELF note section(s) to parse