Messages in this thread | | | Subject | Re: [PATCH bpf-next 2/3] bpf: Add size arg to build_id_parse function | From | Yonghong Song <> | Date | Thu, 14 Jan 2021 10:56:33 -0800 |
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On 1/14/21 5:40 AM, Jiri Olsa wrote: > It's possible to have other build id types (other than default SHA1). > Currently there's also ld support for MD5 build id.
Currently, bpf build_id based stackmap does not returns the size of the build_id. Did you see an issue here? I guess user space can check the length of non-zero bits of the build id to decide what kind of type it is, right?
> > 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> > --- > 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 08028a212589..40232f90db6e 100644 > --- a/include/linux/buildid.h > +++ b/include/linux/buildid.h > @@ -6,6 +6,7 @@ > > #define BUILD_ID_SIZE_MAX 20 > > -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 55d254a59f07..cabaf7db8efc 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -189,7 +189,7 @@ 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 4a4f520c0e29..6156997c3895 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_MAX - 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, > } > [...]
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