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    SubjectRe: [PATCH 02/25] bpf: Add size arg to build_id_parse function
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    > On Nov 26, 2020, at 9:00 AM, Jiri Olsa <jolsa@kernel.org> wrote:
    >
    > It's possible to have other build id types (other than default SHA1).
    > Currently there's also ld support for MD5 build id.
    >
    > Adding size argument to build_id_parse function, that returns (if defined)
    > size of the parsed build id, so we can recognize the build id type.
    >
    > Cc: Alexei Starovoitov <ast@kernel.org>
    > Cc: Song Liu <songliubraving@fb.com>
    > Signed-off-by: Jiri Olsa <jolsa@kernel.org>

    Sorry for the late response. The patch looks good to me.

    Acked-by: Song Liu <songliubraving@fb.com>

    with one nitpick below.

    > ---
    > include/linux/buildid.h | 3 ++-
    > kernel/bpf/stackmap.c | 2 +-
    > lib/buildid.c | 29 +++++++++++++++++++++--------
    > 3 files changed, 24 insertions(+), 10 deletions(-)
    >
    > diff --git a/include/linux/buildid.h b/include/linux/buildid.h
    > index 3be5b49719f1..72639d433873 100644
    > --- a/include/linux/buildid.h
    > +++ b/include/linux/buildid.h
    > @@ -6,6 +6,7 @@
    >
    > #define BUILD_ID_SIZE 20

    Since we are handling build-id with different sizes, how about we
    rename this as BUILD_ID_SIZE_MAX or BUILD_ID_SIZE_DEFAULT?

    >
    > -int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id);
    > +int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
    > + __u32 *size);
    >
    > #endif
    > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
    > index 7df08f8af5a1..a05fac2cbb05 100644
    > --- a/kernel/bpf/stackmap.c
    > +++ b/kernel/bpf/stackmap.c
    > @@ -199,7 +199,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
    >
    > for (i = 0; i < trace_nr; i++) {
    > vma = find_vma(current->mm, ips[i]);
    > - if (!vma || build_id_parse(vma, id_offs[i].build_id)) {
    > + if (!vma || build_id_parse(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];
    > diff --git a/lib/buildid.c b/lib/buildid.c
    > index e8d5feb7ef20..dbe1b7e247f3 100644
    > --- a/lib/buildid.c
    > +++ b/lib/buildid.c
    > @@ -12,6 +12,7 @@
    > */
    > static inline int parse_build_id(void *page_addr,
    > unsigned char *build_id,
    > + __u32 *size,
    > void *note_start,
    > Elf32_Word note_size)
    > {
    > @@ -38,6 +39,8 @@ static inline int parse_build_id(void *page_addr,
    > nhdr->n_descsz);
    > memset(build_id + nhdr->n_descsz, 0,
    > BUILD_ID_SIZE - nhdr->n_descsz);
    > + if (size)
    > + *size = nhdr->n_descsz;
    > return 0;
    > }
    > new_offs = note_offs + sizeof(Elf32_Nhdr) +
    > @@ -50,7 +53,8 @@ static inline int parse_build_id(void *page_addr,
    > }
    >
    > /* Parse build ID from 32-bit ELF */
    > -static int get_build_id_32(void *page_addr, unsigned char *build_id)
    > +static int get_build_id_32(void *page_addr, unsigned char *build_id,
    > + __u32 *size)
    > {
    > Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr;
    > Elf32_Phdr *phdr;
    > @@ -65,7 +69,7 @@ static int get_build_id_32(void *page_addr, unsigned char *build_id)
    >
    > for (i = 0; i < ehdr->e_phnum; ++i) {
    > if (phdr[i].p_type == PT_NOTE &&
    > - !parse_build_id(page_addr, build_id,
    > + !parse_build_id(page_addr, build_id, size,
    > page_addr + phdr[i].p_offset,
    > phdr[i].p_filesz))
    > return 0;
    > @@ -74,7 +78,8 @@ static int get_build_id_32(void *page_addr, unsigned char *build_id)
    > }
    >
    > /* Parse build ID from 64-bit ELF */
    > -static int get_build_id_64(void *page_addr, unsigned char *build_id)
    > +static int get_build_id_64(void *page_addr, unsigned char *build_id,
    > + __u32 *size)
    > {
    > Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr;
    > Elf64_Phdr *phdr;
    > @@ -89,7 +94,7 @@ static int get_build_id_64(void *page_addr, unsigned char *build_id)
    >
    > for (i = 0; i < ehdr->e_phnum; ++i) {
    > if (phdr[i].p_type == PT_NOTE &&
    > - !parse_build_id(page_addr, build_id,
    > + !parse_build_id(page_addr, build_id, size,
    > page_addr + phdr[i].p_offset,
    > phdr[i].p_filesz))
    > return 0;
    > @@ -97,8 +102,16 @@ static int get_build_id_64(void *page_addr, unsigned char *build_id)
    > return -EINVAL;
    > }
    >
    > -/* Parse build ID of ELF file mapped to vma */
    > -int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id)
    > +/*
    > + * 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
    > + *
    > + * Returns 0 on success, otherwise error (< 0).
    > + */
    > +int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
    > + __u32 *size)
    > {
    > Elf32_Ehdr *ehdr;
    > struct page *page;
    > @@ -126,9 +139,9 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id)
    > goto out;
    >
    > if (ehdr->e_ident[EI_CLASS] == ELFCLASS32)
    > - ret = get_build_id_32(page_addr, build_id);
    > + ret = get_build_id_32(page_addr, build_id, size);
    > else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64)
    > - ret = get_build_id_64(page_addr, build_id);
    > + ret = get_build_id_64(page_addr, build_id, size);
    > out:
    > kunmap_atomic(page_addr);
    > put_page(page);
    > --
    > 2.26.2
    >

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