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

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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: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240829174232.3133883-6-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2024-08-29 10:42:27 -07:00 committed by Alexei Starovoitov
parent 4e9d360c4c
commit 45b8fc3096
4 changed files with 26 additions and 7 deletions
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4
include/linux/buildid.h
View File

@ -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)

2
kernel/bpf/stackmap.c
View File

@ -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];

2
kernel/events/core.c
View File

@ -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,

25
lib/buildid.c
View File

@ -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