| Message ID | 20200226130345.209469-5-jolsa@kernel.org |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | bpf: Add trampoline and dispatcher to /proc/kallsyms | expand |
On Wed, Feb 26, 2020 at 5:04 AM Jiri Olsa <jolsa@kernel.org> wrote: > > Adding name to 'struct bpf_ksym' object to carry the name > of the symbol for bpf_prog, bpf_trampoline, bpf_dispatcher. > > The current benefit is that name is now generated only when > the symbol is added to the list, so we don't need to generate > it every time it's accessed. > > Signed-off-by: Jiri Olsa <jolsa@kernel.org> The patch looks good. But I wonder whether we want pay the cost of extra 128 bytes per bpf program. Maybe make it a pointer and only generate the string when it is first used? Thanks, Song
On Wed, Feb 26, 2020 at 01:14:43PM -0800, Song Liu wrote: > On Wed, Feb 26, 2020 at 5:04 AM Jiri Olsa <jolsa@kernel.org> wrote: > > > > Adding name to 'struct bpf_ksym' object to carry the name > > of the symbol for bpf_prog, bpf_trampoline, bpf_dispatcher. > > > > The current benefit is that name is now generated only when > > the symbol is added to the list, so we don't need to generate > > it every time it's accessed. > > > > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > > The patch looks good. But I wonder whether we want pay the cost of > extra 128 bytes per bpf program. Maybe make it a pointer and only > generate the string when it is first used? I thought 128 would not be that bad, also the code is quite simple because of that.. if that's really a concern I could make the changes, but that would probably mean changing the design jirka
On Thu, Feb 27, 2020 at 12:50 AM Jiri Olsa <jolsa@redhat.com> wrote: > > On Wed, Feb 26, 2020 at 01:14:43PM -0800, Song Liu wrote: > > On Wed, Feb 26, 2020 at 5:04 AM Jiri Olsa <jolsa@kernel.org> wrote: > > > > > > Adding name to 'struct bpf_ksym' object to carry the name > > > of the symbol for bpf_prog, bpf_trampoline, bpf_dispatcher. > > > > > > The current benefit is that name is now generated only when > > > the symbol is added to the list, so we don't need to generate > > > it every time it's accessed. > > > > > > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > > > > The patch looks good. But I wonder whether we want pay the cost of > > extra 128 bytes per bpf program. Maybe make it a pointer and only > > generate the string when it is first used? > > I thought 128 would not be that bad, also the code is quite > simple because of that.. if that's really a concern I could > make the changes, but that would probably mean changing the > design I guess this is OK. We can further optimize it if needed. Acked-by: Song Liu <songliubraving@fb.com>
On Thu, Feb 27, 2020 at 10:59:57AM -0800, Song Liu wrote: > On Thu, Feb 27, 2020 at 12:50 AM Jiri Olsa <jolsa@redhat.com> wrote: > > > > On Wed, Feb 26, 2020 at 01:14:43PM -0800, Song Liu wrote: > > > On Wed, Feb 26, 2020 at 5:04 AM Jiri Olsa <jolsa@kernel.org> wrote: > > > > > > > > Adding name to 'struct bpf_ksym' object to carry the name > > > > of the symbol for bpf_prog, bpf_trampoline, bpf_dispatcher. > > > > > > > > The current benefit is that name is now generated only when > > > > the symbol is added to the list, so we don't need to generate > > > > it every time it's accessed. > > > > > > > > Signed-off-by: Jiri Olsa <jolsa@kernel.org> > > > > > > The patch looks good. But I wonder whether we want pay the cost of > > > extra 128 bytes per bpf program. Maybe make it a pointer and only > > > generate the string when it is first used? > > > > I thought 128 would not be that bad, also the code is quite > > simple because of that.. if that's really a concern I could > > make the changes, but that would probably mean changing the > > design > > I guess this is OK. We can further optimize it if needed. > > Acked-by: Song Liu <songliubraving@fb.com> > ok, thanks for the review, I still have to make some changes, so I'll keep your acked-by on patches that won't be changed, please scream otherwise ;-) thanks, jirka
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 5ad8eea1cd37..e7b2e9fc256c 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -18,6 +18,7 @@ #include <linux/refcount.h> #include <linux/mutex.h> #include <linux/module.h> +#include <linux/kallsyms.h> struct bpf_verifier_env; struct bpf_verifier_log; @@ -465,6 +466,7 @@ void notrace __bpf_prog_exit(struct bpf_prog *prog, u64 start); struct bpf_ksym { unsigned long start; unsigned long end; + char name[KSYM_NAME_LEN]; }; enum bpf_tramp_prog_type { diff --git a/include/linux/filter.h b/include/linux/filter.h index eafe72644282..a945c250ad53 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -1062,7 +1062,6 @@ bpf_address_lookup(unsigned long addr, unsigned long *size, void bpf_prog_kallsyms_add(struct bpf_prog *fp); void bpf_prog_kallsyms_del(struct bpf_prog *fp); -void bpf_get_prog_name(const struct bpf_prog *prog, char *sym); #else /* CONFIG_BPF_JIT */ @@ -1131,11 +1130,6 @@ static inline void bpf_prog_kallsyms_del(struct bpf_prog *fp) { } -static inline void bpf_get_prog_name(const struct bpf_prog *prog, char *sym) -{ - sym[0] = '\0'; -} - #endif /* CONFIG_BPF_JIT */ void bpf_prog_kallsyms_del_all(struct bpf_prog *fp); diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 39a9e4184900..a7aaa81035b1 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -535,8 +535,9 @@ bpf_get_prog_addr_region(const struct bpf_prog *prog) prog->aux->ksym.end = addr + hdr->pages * PAGE_SIZE; } -void bpf_get_prog_name(const struct bpf_prog *prog, char *sym) +static void bpf_get_prog_name(const struct bpf_prog *prog) { + char *sym = prog->aux->ksym.name; const char *end = sym + KSYM_NAME_LEN; const struct btf_type *type; const char *func_name; @@ -643,6 +644,7 @@ void bpf_prog_kallsyms_add(struct bpf_prog *fp) return; bpf_get_prog_addr_region(fp); + bpf_get_prog_name(fp); spin_lock_bh(&bpf_lock); bpf_prog_ksym_node_add(fp->aux); @@ -681,7 +683,7 @@ const char *__bpf_address_lookup(unsigned long addr, unsigned long *size, unsigned long symbol_start = prog->aux->ksym.start; unsigned long symbol_end = prog->aux->ksym.end; - bpf_get_prog_name(prog, sym); + strncpy(sym, prog->aux->ksym.name, KSYM_NAME_LEN); ret = sym; if (size) @@ -738,7 +740,7 @@ int bpf_get_kallsym(unsigned int symnum, unsigned long *value, char *type, if (it++ != symnum) continue; - bpf_get_prog_name(aux->prog, sym); + strncpy(sym, aux->ksym.name, KSYM_NAME_LEN); *value = (unsigned long)aux->prog->bpf_func; *type = BPF_SYM_ELF_TYPE; diff --git a/kernel/events/core.c b/kernel/events/core.c index e453589da97c..a2cfb9e5f262 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8255,23 +8255,22 @@ static void perf_event_bpf_emit_ksymbols(struct bpf_prog *prog, enum perf_bpf_event_type type) { bool unregister = type == PERF_BPF_EVENT_PROG_UNLOAD; - char sym[KSYM_NAME_LEN]; int i; if (prog->aux->func_cnt == 0) { - bpf_get_prog_name(prog, sym); perf_event_ksymbol(PERF_RECORD_KSYMBOL_TYPE_BPF, (u64)(unsigned long)prog->bpf_func, - prog->jited_len, unregister, sym); + prog->jited_len, unregister, + prog->aux->ksym.name); } else { for (i = 0; i < prog->aux->func_cnt; i++) { struct bpf_prog *subprog = prog->aux->func[i]; - bpf_get_prog_name(subprog, sym); perf_event_ksymbol( PERF_RECORD_KSYMBOL_TYPE_BPF, (u64)(unsigned long)subprog->bpf_func, - subprog->jited_len, unregister, sym); + subprog->jited_len, unregister, + prog->aux->ksym.name); } } }
Adding name to 'struct bpf_ksym' object to carry the name of the symbol for bpf_prog, bpf_trampoline, bpf_dispatcher. The current benefit is that name is now generated only when the symbol is added to the list, so we don't need to generate it every time it's accessed. Signed-off-by: Jiri Olsa <jolsa@kernel.org> --- include/linux/bpf.h | 2 ++ include/linux/filter.h | 6 ------ kernel/bpf/core.c | 8 +++++--- kernel/events/core.c | 9 ++++----- 4 files changed, 11 insertions(+), 14 deletions(-)