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bpf: Add support for bpf iterator programs to use sleepable helpers

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This patch allows bpf iterator programs to use sleepable helpers by
changing `bpf_iter_run_prog` to use the appropriate synchronization.
With sleepable bpf iterator programs, we can no longer use
`rcu_read_lock()` and must use `rcu_read_lock_trace()` instead
to protect the bpf program.

Signed-off-by: Kenny Yu <kennyyu@fb.com>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220124185403.468466-2-kennyyu@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Kenny Yu 2022-01-24 10:54:00 -08:00 committed by Alexei Starovoitov
parent caaba96131
commit b77fb25dcb
1 changed files with 15 additions and 5 deletions
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20
kernel/bpf/bpf_iter.c
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@ -5,6 +5,7 @@
#include <linux/anon_inodes.h>
#include <linux/filter.h>
#include <linux/bpf.h>
#include <linux/rcupdate_trace.h>
struct bpf_iter_target_info {
struct list_head list;
@ -684,11 +685,20 @@ int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx)
{
int ret;
rcu_read_lock();
migrate_disable();
ret = bpf_prog_run(prog, ctx);
migrate_enable();
rcu_read_unlock();
if (prog->aux->sleepable) {
rcu_read_lock_trace();
migrate_disable();
might_fault();
ret = bpf_prog_run(prog, ctx);
migrate_enable();
rcu_read_unlock_trace();
} else {
rcu_read_lock();
migrate_disable();
ret = bpf_prog_run(prog, ctx);
migrate_enable();
rcu_read_unlock();
}
/* bpf program can only return 0 or 1:
* 0 : okay