Re: [PATCH v3 bpf-next 2/4] bpf: introduce helper bpf_get_task_stack()
From: Andrii Nakryiko <hidden>
Date: 2020-06-27 20:36:09
Also in:
bpf, lkml
On Fri, Jun 26, 2020 at 5:29 PM Song Liu [off-list ref] wrote:
Introduce helper bpf_get_task_stack(), which dumps stack trace of given task. This is different to bpf_get_stack(), which gets stack track of current task. One potential use case of bpf_get_task_stack() is to call it from bpf_iter__task and dump all /proc/<pid>/stack to a seq_file. bpf_get_task_stack() uses stack_trace_save_tsk() instead of get_perf_callchain() for kernel stack. The benefit of this choice is that stack_trace_save_tsk() doesn't require changes in arch/. The downside of using stack_trace_save_tsk() is that stack_trace_save_tsk() dumps the stack trace to unsigned long array. For 32-bit systems, we need to translate it to u64 array. Acked-by: Andrii Nakryiko <redacted> Signed-off-by: Song Liu <redacted> --- include/linux/bpf.h | 1 + include/uapi/linux/bpf.h | 36 +++++++++++++++- kernel/bpf/stackmap.c | 75 ++++++++++++++++++++++++++++++++-- kernel/bpf/verifier.c | 4 +- kernel/trace/bpf_trace.c | 2 + scripts/bpf_helpers_doc.py | 2 + tools/include/uapi/linux/bpf.h | 36 +++++++++++++++- 7 files changed, 150 insertions(+), 6 deletions(-)
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quoted hunk
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 7de98906ddf4a..b608185e1ffd5 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c@@ -4864,7 +4864,9 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn if (err) return err; - if (func_id == BPF_FUNC_get_stack && !env->prog->has_callchain_buf) { + if ((func_id == BPF_FUNC_get_stack || + func_id == BPF_FUNC_get_task_stack) && + !env->prog->has_callchain_buf) { const char *err_str;
I'm glad it was so simple :) Thanks for checking! [...]