Commit 647cafa2 authored by Alan Maguire's avatar Alan Maguire Committed by Alexei Starovoitov
Browse files

bpf: add a ksym BPF iterator 

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: default avatarAlexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: default avatarAlan Maguire <alan.maguire@oracle.com>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/1657629105-7812-2-git-send-email-alan.maguire@oracle.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent f16214c1

kernel/kallsyms.c

+91 −0
Original line number Diff line number Diff line
@@ -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 +800,96 @@ static const struct seq_operations kallsyms_op = { 
	.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);



	/* cache here as in kallsyms_open() case; use current process

	 * credentials to tell BPF iterators if values should be shown.

	 */

	iter->show_value = kallsyms_show_value(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",

	.feature		= BPF_ITER_RESCHED,

	.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 int __init bpf_ksym_iter_register(void)

{

	ksym_iter_reg_info.ctx_arg_info[0].btf_id = *btf_ksym_iter_id;

	return bpf_iter_reg_target(&ksym_iter_reg_info);

}



late_initcall(bpf_ksym_iter_register);



#endif /* CONFIG_BPF_SYSCALL */



static inline int kallsyms_for_perf(void)

{

#ifdef CONFIG_PERF_EVENTS