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bpf: add a ksym BPF iterator

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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>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/r/1657629105-7812-2-git-send-email-alan.maguire@oracle.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Alan Maguire 2022-07-12 13:31:44 +01:00 committed by Alexei Starovoitov
parent f16214c102
commit 647cafa223
1 changed files with 91 additions and 0 deletions
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91
kernel/kallsyms.c
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@ -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