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3f9969f2c0
Currently, the pos pointer in bpf iterator map/task/task_file seq_ops->start() is always incremented. This is incorrect. It should be increased only if *pos is 0 (for SEQ_START_TOKEN) since these start() function actually returns the first real object. If *pos is not 0, it merely found the object based on the state in seq->private, and not really advancing the *pos. This patch fixed this issue by only incrementing *pos if it is 0. Note that the old *pos calculation, although not correct, does not affect correctness of bpf_iter as bpf_iter seq_file->read() does not support llseek. This patch also renamed "mid" in bpf_map iterator seq_file private data to "map_id" for better clarity. Fixes:6086d29def("bpf: Add bpf_map iterator") Fixes:eaaacd2391("bpf: Add task and task/file iterator targets") Signed-off-by: Yonghong Song <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Link: https://lore.kernel.org/bpf/20200722195156.4029817-1-yhs@fb.com
103 lines
2.2 KiB
C
103 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/* Copyright (c) 2020 Facebook */
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#include <linux/bpf.h>
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#include <linux/fs.h>
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#include <linux/filter.h>
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#include <linux/kernel.h>
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#include <linux/btf_ids.h>
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struct bpf_iter_seq_map_info {
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u32 map_id;
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};
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static void *bpf_map_seq_start(struct seq_file *seq, loff_t *pos)
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{
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struct bpf_iter_seq_map_info *info = seq->private;
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struct bpf_map *map;
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map = bpf_map_get_curr_or_next(&info->map_id);
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if (!map)
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return NULL;
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if (*pos == 0)
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++*pos;
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return map;
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}
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static void *bpf_map_seq_next(struct seq_file *seq, void *v, loff_t *pos)
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{
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struct bpf_iter_seq_map_info *info = seq->private;
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++*pos;
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++info->map_id;
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bpf_map_put((struct bpf_map *)v);
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return bpf_map_get_curr_or_next(&info->map_id);
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}
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struct bpf_iter__bpf_map {
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__bpf_md_ptr(struct bpf_iter_meta *, meta);
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__bpf_md_ptr(struct bpf_map *, map);
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};
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DEFINE_BPF_ITER_FUNC(bpf_map, struct bpf_iter_meta *meta, struct bpf_map *map)
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static int __bpf_map_seq_show(struct seq_file *seq, void *v, bool in_stop)
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{
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struct bpf_iter__bpf_map ctx;
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struct bpf_iter_meta meta;
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struct bpf_prog *prog;
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int ret = 0;
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ctx.meta = &meta;
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ctx.map = v;
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meta.seq = seq;
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prog = bpf_iter_get_info(&meta, in_stop);
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if (prog)
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ret = bpf_iter_run_prog(prog, &ctx);
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return ret;
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}
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static int bpf_map_seq_show(struct seq_file *seq, void *v)
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{
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return __bpf_map_seq_show(seq, v, false);
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}
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static void bpf_map_seq_stop(struct seq_file *seq, void *v)
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{
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if (!v)
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(void)__bpf_map_seq_show(seq, v, true);
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else
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bpf_map_put((struct bpf_map *)v);
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}
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static const struct seq_operations bpf_map_seq_ops = {
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.start = bpf_map_seq_start,
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.next = bpf_map_seq_next,
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.stop = bpf_map_seq_stop,
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.show = bpf_map_seq_show,
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};
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BTF_ID_LIST(btf_bpf_map_id)
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BTF_ID(struct, bpf_map)
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static struct bpf_iter_reg bpf_map_reg_info = {
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.target = "bpf_map",
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.seq_ops = &bpf_map_seq_ops,
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.init_seq_private = NULL,
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.fini_seq_private = NULL,
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.seq_priv_size = sizeof(struct bpf_iter_seq_map_info),
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.ctx_arg_info_size = 1,
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.ctx_arg_info = {
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{ offsetof(struct bpf_iter__bpf_map, map),
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PTR_TO_BTF_ID_OR_NULL },
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},
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};
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static int __init bpf_map_iter_init(void)
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{
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bpf_map_reg_info.ctx_arg_info[0].btf_id = *btf_bpf_map_id;
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return bpf_iter_reg_target(&bpf_map_reg_info);
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}
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late_initcall(bpf_map_iter_init);
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