Messages in this thread | | | Date | Fri, 1 Jul 2022 22:57:54 -0700 | Subject | Re: [PATCH v2 bpf-next 1/2] bpf: add a ksym BPF iterator | From | Yonghong Song <> |
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On 7/1/22 2:26 AM, Alan Maguire wrote: > add a "ksym" 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 | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 89 insertions(+) > > diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c > index fbdf8d3..8b662da 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 +800,91 @@ static int s_show(struct seq_file *m, void *p) > .show = s_show > }; > > +#ifdef CONFIG_BPF_SYSCALL > + > +struct bpf_iter__ksym { > + __bpf_md_ptr(struct bpf_iter_meta *, meta); > + __bpf_md_ptr(struct kallsym_iter *, ksym); > +}; > + > +static int ksym_prog_seq_show(struct seq_file *m, bool in_stop) > +{ > + struct bpf_iter__ksym 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.ksym = m ? m->private : NULL; > + return bpf_iter_run_prog(prog, &ctx); > +} > + > +static int bpf_iter_ksym_seq_show(struct seq_file *m, void *p) > +{ > + return ksym_prog_seq_show(m, false); > +} > + > +static void bpf_iter_ksym_seq_stop(struct seq_file *m, void *p) > +{ > + if (!p) > + (void) ksym_prog_seq_show(m, true); > + else > + s_stop(m, p); > +} > + > +static const struct seq_operations bpf_iter_ksym_ops = { > + .start = s_start, > + .next = s_next, > + .stop = bpf_iter_ksym_seq_stop, > + .show = bpf_iter_ksym_seq_show, > +}; > + > +static int bpf_iter_ksym_init(void *priv_data, struct bpf_iter_aux_info *aux) > +{ > + struct kallsym_iter *iter = priv_data; > + > + reset_iter(iter, 0); > + > + iter->show_value = true;
I think instead of always having show_value = true, we should have iter->show_value = kallsyms_show_value(...);
this is consistent with what `cat /proc/kallsyms` is doing, and also consistent with bpf_dump_raw_ok() used when dumping various kernel info in syscall.c.
We don't have a file here, so credential can be from the current process with current_cred().
> + > + return 0; > +} > + > +DEFINE_BPF_ITER_FUNC(ksym, struct bpf_iter_meta *meta, struct kallsym_iter *ksym) > + > +static const struct bpf_iter_seq_info ksym_iter_seq_info = { > + .seq_ops = &bpf_iter_ksym_ops, > + .init_seq_private = bpf_iter_ksym_init, > + .fini_seq_private = NULL, > + .seq_priv_size = sizeof(struct kallsym_iter), > +}; > + > +static struct bpf_iter_reg ksym_iter_reg_info = { > + .target = "ksym", > + .ctx_arg_info_size = 1, > + .ctx_arg_info = { > + { offsetof(struct bpf_iter__ksym, ksym), > + PTR_TO_BTF_ID_OR_NULL }, > + }, > + .seq_info = &ksym_iter_seq_info, > +}; > + > +BTF_ID_LIST(btf_ksym_iter_id) > +BTF_ID(struct, kallsym_iter) > + > +static void __init bpf_ksym_iter_register(void) > +{ > + ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id; > + if (bpf_iter_reg_target(&ksym_iter_reg_info)) > + pr_warn("Warning: could not register bpf ksym iterator\n"); > +} > + > +#endif /* CONFIG_BPF_SYSCALL */ > + > static inline int kallsyms_for_perf(void) > { > #ifdef CONFIG_PERF_EVENTS > @@ -885,6 +971,9 @@ 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) > + bpf_ksym_iter_register();
You can inline this function here and if bpf_iter_reg_target(...) failed, just return the error code.
> +#endif > return 0; > } > device_initcall(kallsyms_init);
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