| Message ID | 1656089118-577-2-git-send-email-alan.maguire@oracle.com (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf: add a kallsyms BPF iterator | expand |
On Fri, Jun 24, 2022 at 9:45 AM Alan Maguire <alan.maguire@oracle.com> wrote: > > add a "kallsyms" iterator which provides access to a "struct kallsym_iter" > for each symbol. Intent is to support more flexible symbol parsing > as discussed in [1]. > > [1] https://lore.kernel.org/all/YjRPZj6Z8vuLeEZo@krava/ > > Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> > Signed-off-by: Alan Maguire <alan.maguire@oracle.com> > --- > kernel/kallsyms.c | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 93 insertions(+) > > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c > index fbdf8d3..ffaf464 100644 > --- a/kernel/kallsyms.c > +++ b/kernel/kallsyms.c > @@ -30,6 +30,7 @@ > #include <linux/module.h> > #include <linux/kernel.h> > #include <linux/bsearch.h> > +#include <linux/btf_ids.h> > > /* > * These will be re-linked against their real values > @@ -799,6 +800,95 @@ static int s_show(struct seq_file *m, void *p) > .show = s_show > }; > > +#ifdef CONFIG_BPF_SYSCALL > + > +struct bpf_iter__kallsyms { So I know this is derived from /proc/kallsyms, but for BPF iterators we have a singular name convention (e.g., iter/task and iter/task_vma), which makes sense because we call BPF program for each individual item. So here it seems like "iter/ksym" would make good sense? > + __bpf_md_ptr(struct bpf_iter_meta *, meta); > + __bpf_md_ptr(struct kallsym_iter *, kallsym_iter); nit: can we call this field just "ksym"? > +}; > + > +static int s_prog_seq_show(struct seq_file *m, bool in_stop) > +{ > + struct bpf_iter__kallsyms ctx; > + struct bpf_iter_meta meta; > + struct bpf_prog *prog; > + > + meta.seq = m; > + prog = bpf_iter_get_info(&meta, in_stop); > + if (!prog) > + return 0; > + > + ctx.meta = &meta; > + ctx.kallsym_iter = m ? m->private : NULL; > + return bpf_iter_run_prog(prog, &ctx); > +} > + > +static int bpf_iter_s_seq_show(struct seq_file *m, void *p) stupid question, but what does "_s_" part stand for? Is it for "sym"? If yes, maybe then "bpf_iter_ksym_seq_show"? > +{ > + return s_prog_seq_show(m, false); > +} > + [...] > +static struct bpf_iter_reg kallsyms_iter_reg_info = { > + .target = "kallsyms", > + .ctx_arg_info_size = 1, > + .ctx_arg_info = { > + { offsetof(struct bpf_iter__kallsyms, kallsym_iter), > + PTR_TO_BTF_ID_OR_NULL }, > + }, > + .seq_info = &kallsyms_iter_seq_info, > +}; > + > +BTF_ID_LIST(btf_kallsym_iter_id) > +BTF_ID(struct, kallsym_iter) > + > +static void __init bpf_kallsyms_iter_register(void) > +{ > + kallsyms_iter_reg_info.ctx_arg_info[0].btf_id = *btf_kallsym_iter_id; > + if (bpf_iter_reg_target(&kallsyms_iter_reg_info)) > + pr_warn("Warning: could not register bpf kallsyms iterator\n"); > +} > + > +#endif /* CONFIG_PROC_FS */ Is there any reason to depend on CONFIG_PROC_FS for BPF iterator? Seems like kernel/kallsyms.c itself is only depending on CONFIG_KALLSYMS? So why adding unnecessary dependency? > + > +#endif /* CONFIG_BPF_SYSCALL */ > + > static inline int kallsyms_for_perf(void) > { > #ifdef CONFIG_PERF_EVENTS > @@ -885,6 +975,9 @@ const char *kdb_walk_kallsyms(loff_t *pos) > static int __init kallsyms_init(void) > { > proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); > +#if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS) > + bpf_kallsyms_iter_register(); > +#endif > return 0; > } > device_initcall(kallsyms_init); > -- > 1.8.3.1 >
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index fbdf8d3..ffaf464 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -30,6 +30,7 @@ #include <linux/module.h> #include <linux/kernel.h> #include <linux/bsearch.h> +#include <linux/btf_ids.h> /* * These will be re-linked against their real values @@ -799,6 +800,95 @@ static int s_show(struct seq_file *m, void *p) .show = s_show }; +#ifdef CONFIG_BPF_SYSCALL + +struct bpf_iter__kallsyms { + __bpf_md_ptr(struct bpf_iter_meta *, meta); + __bpf_md_ptr(struct kallsym_iter *, kallsym_iter); +}; + +static int s_prog_seq_show(struct seq_file *m, bool in_stop) +{ + struct bpf_iter__kallsyms ctx; + struct bpf_iter_meta meta; + struct bpf_prog *prog; + + meta.seq = m; + prog = bpf_iter_get_info(&meta, in_stop); + if (!prog) + return 0; + + ctx.meta = &meta; + ctx.kallsym_iter = m ? m->private : NULL; + return bpf_iter_run_prog(prog, &ctx); +} + +static int bpf_iter_s_seq_show(struct seq_file *m, void *p) +{ + return s_prog_seq_show(m, false); +} + +static void bpf_iter_s_seq_stop(struct seq_file *m, void *p) +{ + if (!p) + (void) s_prog_seq_show(m, true); + else + s_stop(m, p); +} + +static const struct seq_operations bpf_iter_kallsyms_ops = { + .start = s_start, + .next = s_next, + .stop = bpf_iter_s_seq_stop, + .show = bpf_iter_s_seq_show, +}; + +#if defined(CONFIG_PROC_FS) + +static int bpf_iter_s_init(void *priv_data, struct bpf_iter_aux_info *aux) +{ + struct kallsym_iter *iter = priv_data; + + reset_iter(iter, 0); + + iter->show_value = true; + + return 0; +} + +DEFINE_BPF_ITER_FUNC(kallsyms, struct bpf_iter_meta *meta, struct kallsym_iter *kallsym_iter) + +static const struct bpf_iter_seq_info kallsyms_iter_seq_info = { + .seq_ops = &bpf_iter_kallsyms_ops, + .init_seq_private = bpf_iter_s_init, + .fini_seq_private = NULL, + .seq_priv_size = sizeof(struct kallsym_iter), +}; + +static struct bpf_iter_reg kallsyms_iter_reg_info = { + .target = "kallsyms", + .ctx_arg_info_size = 1, + .ctx_arg_info = { + { offsetof(struct bpf_iter__kallsyms, kallsym_iter), + PTR_TO_BTF_ID_OR_NULL }, + }, + .seq_info = &kallsyms_iter_seq_info, +}; + +BTF_ID_LIST(btf_kallsym_iter_id) +BTF_ID(struct, kallsym_iter) + +static void __init bpf_kallsyms_iter_register(void) +{ + kallsyms_iter_reg_info.ctx_arg_info[0].btf_id = *btf_kallsym_iter_id; + if (bpf_iter_reg_target(&kallsyms_iter_reg_info)) + pr_warn("Warning: could not register bpf kallsyms iterator\n"); +} + +#endif /* CONFIG_PROC_FS */ + +#endif /* CONFIG_BPF_SYSCALL */ + static inline int kallsyms_for_perf(void) { #ifdef CONFIG_PERF_EVENTS @@ -885,6 +975,9 @@ const char *kdb_walk_kallsyms(loff_t *pos) static int __init kallsyms_init(void) { proc_create("kallsyms", 0444, NULL, &kallsyms_proc_ops); +#if defined(CONFIG_BPF_SYSCALL) && defined(CONFIG_PROC_FS) + bpf_kallsyms_iter_register(); +#endif return 0; } device_initcall(kallsyms_init);
add a "kallsyms" iterator which provides access to a "struct kallsym_iter" for each symbol. Intent is to support more flexible symbol parsing as discussed in [1]. [1] https://lore.kernel.org/all/YjRPZj6Z8vuLeEZo@krava/ Suggested-by: Alexei Starovoitov <alexei.starovoitov@gmail.com> Signed-off-by: Alan Maguire <alan.maguire@oracle.com> --- kernel/kallsyms.c | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 93 insertions(+)