On 5/5/20 1:25 PM, Andrii Nakryiko wrote:
On Sun, May 3, 2020 at 11:28 PM Yonghong Song <yhs@xxxxxx> wrote:Macro DEFINE_BPF_ITER_FUNC is implemented so target can define an init function to capture the BTF type which represents the target. The bpf_iter_meta is a structure holding meta data, common to all targets in the bpf program. Additional marker functions are called before/after bpf_seq_read() show() and stop() callback functions to help calculate precise seq_num and whether call bpf_prog inside stop(). Two functions, bpf_iter_get_info() and bpf_iter_run_prog(), are implemented so target can get needed information from bpf_iter infrastructure and can run the program. Signed-off-by: Yonghong Song <yhs@xxxxxx> --- include/linux/bpf.h | 11 +++++ kernel/bpf/bpf_iter.c | 94 ++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 100 insertions(+), 5 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 26daf85cba10..70c71c3cd9e8 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -1129,6 +1129,9 @@ int bpf_obj_pin_user(u32 ufd, const char __user *pathname); int bpf_obj_get_user(const char __user *pathname, int flags); #define BPF_ITER_FUNC_PREFIX "__bpf_iter__" +#define DEFINE_BPF_ITER_FUNC(target, args...) \ + extern int __bpf_iter__ ## target(args); \ + int __init __bpf_iter__ ## target(args) { return 0; }Why is extern declaration needed here? Doesn't the same macro define
Silence sparse warning. Apparently in kernel, any global function, they want a declaration?
global function itself? I'm probably missing some C semantics thingy, sorry...typedef int (*bpf_iter_init_seq_priv_t)(void *private_data); typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data); @@ -1141,11 +1144,19 @@ struct bpf_iter_reg { u32 seq_priv_size; }; +struct bpf_iter_meta { + __bpf_md_ptr(struct seq_file *, seq); + u64 session_id; + u64 seq_num; +}; +[...]/* bpf_seq_read, a customized and simpler version for bpf iterator. * no_llseek is assumed for this file. * The following are differences from seq_read(): @@ -83,12 +119,15 @@ static ssize_t bpf_seq_read(struct file *file, char __user *buf, size_t size, if (!p || IS_ERR(p)) goto Stop; + bpf_iter_inc_seq_num(seq);so seq_num is one-based, not zero-based? So on first show() call it will be set to 1, not 0, right?
It is 1 based, we need to document this clearly. I forgot to adjust my bpf program for this. Will adjust them properly in the next revision.
err = seq->op->show(seq, p); if (seq_has_overflowed(seq)) { + bpf_iter_dec_seq_num(seq); err = -E2BIG; goto Error_show; } else if (err) { /* < 0: go out, > 0: skip */ + bpf_iter_dec_seq_num(seq); if (likely(err < 0)) goto Error_show; seq->count = 0;[...]
