Message ID | 20200302143154.258569-7-jolsa@kernel.org |
---|---|
State | Changes Requested |
Delegated to: | BPF Maintainers |
Headers | show |
Series | bpf: Add trampoline and dispatcher to /proc/kallsyms | expand |
On Mon, Mar 02, 2020 at 03:31:45PM +0100, Jiri Olsa wrote: > The bpf_tree is used both for kallsyms iterations and searching > for exception tables of bpf programs, which is needed only for > bpf programs. > > Adding bpf_ksym_tree that will hold symbols for all bpf_prog > bpf_trampoline and bpf_dispatcher objects and keeping bpf_tree > only for bpf_prog objects to keep it fast. ... > static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux) > @@ -616,6 +650,7 @@ static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux) > WARN_ON_ONCE(!list_empty(&aux->ksym.lnode)); > list_add_tail_rcu(&aux->ksym.lnode, &bpf_kallsyms); > latch_tree_insert(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops); > + latch_tree_insert(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops); > } > > static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux) > @@ -624,6 +659,7 @@ static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux) > return; > > latch_tree_erase(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops); > + latch_tree_erase(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops); I have to agree with Daniel here. Having bpf prog in two latch trees is unnecessary. Especially looking at the patch 7 that moves update to the other tree. The whole thing becomes assymetrical and harder to follow. Consider that walking extable is slow anyway. It's a page fault. Having trampoline and dispatch in the same tree will not be measurable on the speed of search_bpf_extables->bpf_prog_kallsyms_find. So please consolidate. Also I don't see a hunk that deletes tnode from 'struct bpf_image'. These patches suppose to generalize it too, no? And at the end kernel_text_address() suppose to call is_bpf_text_address() only, right? Instead of is_bpf_text_address() || is_bpf_image_address() ? That _will_ actually speed up backtrace collection.
On Tue, Mar 03, 2020 at 10:03:19AM -0800, Alexei Starovoitov wrote: > On Mon, Mar 02, 2020 at 03:31:45PM +0100, Jiri Olsa wrote: > > The bpf_tree is used both for kallsyms iterations and searching > > for exception tables of bpf programs, which is needed only for > > bpf programs. > > > > Adding bpf_ksym_tree that will hold symbols for all bpf_prog > > bpf_trampoline and bpf_dispatcher objects and keeping bpf_tree > > only for bpf_prog objects to keep it fast. > > ... > > > static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux) > > @@ -616,6 +650,7 @@ static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux) > > WARN_ON_ONCE(!list_empty(&aux->ksym.lnode)); > > list_add_tail_rcu(&aux->ksym.lnode, &bpf_kallsyms); > > latch_tree_insert(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops); > > + latch_tree_insert(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops); > > } > > > > static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux) > > @@ -624,6 +659,7 @@ static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux) > > return; > > > > latch_tree_erase(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops); > > + latch_tree_erase(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops); > > I have to agree with Daniel here. > Having bpf prog in two latch trees is unnecessary. > Especially looking at the patch 7 that moves update to the other tree. > The whole thing becomes assymetrical and harder to follow. > Consider that walking extable is slow anyway. It's a page fault. > Having trampoline and dispatch in the same tree will not be measurable > on the speed of search_bpf_extables->bpf_prog_kallsyms_find. > So please consolidate. ok > > Also I don't see a hunk that deletes tnode from 'struct bpf_image'. > These patches suppose to generalize it too, no? __bpf_ksym_del function added in patch: bpf: Separate kallsyms add/del functions > And at the end kernel_text_address() suppose to call > is_bpf_text_address() only, right? > Instead of is_bpf_text_address() || is_bpf_image_address() ? > That _will_ actually speed up backtrace collection. right, this one could have already used just the ksym tree will send new version.. meanwhile I was checking struct_ops, so will include kallsyms support them as well thanks, jirka
diff --git a/include/linux/bpf.h b/include/linux/bpf.h index f1174d24c185..5d6649cdc3df 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -468,6 +468,7 @@ struct bpf_ksym { unsigned long end; char name[KSYM_NAME_LEN]; struct list_head lnode; + struct latch_tree_node tnode; }; enum bpf_tramp_prog_type { diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 084abfbc3362..c36558c44637 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -607,8 +607,42 @@ static const struct latch_tree_ops bpf_tree_ops = { .comp = bpf_tree_comp, }; +static unsigned long bpf_get_ksym_start(struct latch_tree_node *n) +{ + return container_of(n, struct bpf_ksym, tnode)->start; +} + +static bool +bpf_ksym_tree_less(struct latch_tree_node *a, + struct latch_tree_node *b) +{ + return bpf_get_ksym_start(a) < bpf_get_ksym_start(b); +} + +static int +bpf_ksym_tree_comp(void *key, struct latch_tree_node *n) +{ + unsigned long val = (unsigned long)key; + const struct bpf_ksym *ksym; + + ksym = container_of(n, struct bpf_ksym, tnode); + + if (val < ksym->start) + return -1; + if (val >= ksym->end) + return 1; + + return 0; +} + +static const struct latch_tree_ops bpf_ksym_tree_ops = { + .less = bpf_ksym_tree_less, + .comp = bpf_ksym_tree_comp, +}; + static DEFINE_SPINLOCK(bpf_lock); static LIST_HEAD(bpf_kallsyms); +static struct latch_tree_root bpf_ksym_tree __cacheline_aligned; static struct latch_tree_root bpf_tree __cacheline_aligned; static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux) @@ -616,6 +650,7 @@ static void bpf_prog_ksym_node_add(struct bpf_prog_aux *aux) WARN_ON_ONCE(!list_empty(&aux->ksym.lnode)); list_add_tail_rcu(&aux->ksym.lnode, &bpf_kallsyms); latch_tree_insert(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops); + latch_tree_insert(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops); } static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux) @@ -624,6 +659,7 @@ static void bpf_prog_ksym_node_del(struct bpf_prog_aux *aux) return; latch_tree_erase(&aux->ksym_tnode, &bpf_tree, &bpf_tree_ops); + latch_tree_erase(&aux->ksym.tnode, &bpf_ksym_tree, &bpf_ksym_tree_ops); list_del_rcu(&aux->ksym.lnode); } @@ -672,19 +708,27 @@ static struct bpf_prog *bpf_prog_kallsyms_find(unsigned long addr) NULL; } +static struct bpf_ksym *bpf_ksym_find(unsigned long addr) +{ + struct latch_tree_node *n; + + n = latch_tree_find((void *)addr, &bpf_ksym_tree, &bpf_ksym_tree_ops); + return n ? container_of(n, struct bpf_ksym, tnode) : NULL; +} + const char *__bpf_address_lookup(unsigned long addr, unsigned long *size, unsigned long *off, char *sym) { - struct bpf_prog *prog; + struct bpf_ksym *ksym; char *ret = NULL; rcu_read_lock(); - prog = bpf_prog_kallsyms_find(addr); - if (prog) { - unsigned long symbol_start = prog->aux->ksym.start; - unsigned long symbol_end = prog->aux->ksym.end; + ksym = bpf_ksym_find(addr); + if (ksym) { + unsigned long symbol_start = ksym->start; + unsigned long symbol_end = ksym->end; - strncpy(sym, prog->aux->ksym.name, KSYM_NAME_LEN); + strncpy(sym, ksym->name, KSYM_NAME_LEN); ret = sym; if (size)