From 492e639f0c222784e2e0f121966375f641c61b15 Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Sat, 9 May 2020 10:59:14 -0700 Subject: bpf: Add bpf_seq_printf and bpf_seq_write helpers Two helpers bpf_seq_printf and bpf_seq_write, are added for writing data to the seq_file buffer. bpf_seq_printf supports common format string flag/width/type fields so at least I can get identical results for netlink and ipv6_route targets. For bpf_seq_printf and bpf_seq_write, return value -EOVERFLOW specifically indicates a write failure due to overflow, which means the object will be repeated in the next bpf invocation if object collection stays the same. Note that if the object collection is changed, depending how collection traversal is done, even if the object still in the collection, it may not be visited. For bpf_seq_printf, format %s, %p{i,I}{4,6} needs to read kernel memory. Reading kernel memory may fail in the following two cases: - invalid kernel address, or - valid kernel address but requiring a major fault If reading kernel memory failed, the %s string will be an empty string and %p{i,I}{4,6} will be all 0. Not returning error to bpf program is consistent with what bpf_trace_printk() does for now. bpf_seq_printf may return -EBUSY meaning that internal percpu buffer for memory copy of strings or other pointees is not available. Bpf program can return 1 to indicate it wants the same object to be repeated. Right now, this should not happen on no-RT kernels since migrate_disable(), which guards bpf prog call, calls preempt_disable(). Signed-off-by: Yonghong Song Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20200509175914.2476661-1-yhs@fb.com --- scripts/bpf_helpers_doc.py | 2 ++ 1 file changed, 2 insertions(+) (limited to 'scripts/bpf_helpers_doc.py') diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py index f43d193aff3a..ded304c96a05 100755 --- a/scripts/bpf_helpers_doc.py +++ b/scripts/bpf_helpers_doc.py @@ -414,6 +414,7 @@ class PrinterHelpers(Printer): 'struct sk_reuseport_md', 'struct sockaddr', 'struct tcphdr', + 'struct seq_file', 'struct __sk_buff', 'struct sk_msg_md', @@ -450,6 +451,7 @@ class PrinterHelpers(Printer): 'struct sk_reuseport_md', 'struct sockaddr', 'struct tcphdr', + 'struct seq_file', } mapped_types = { 'u8': '__u8', -- cgit From ab8d78093dfa2e7820ca0c28dda9142aa771c510 Mon Sep 17 00:00:00 2001 From: Quentin Monnet Date: Mon, 11 May 2020 17:15:35 +0100 Subject: bpf: Minor fixes to BPF helpers documentation Minor improvements to the documentation for BPF helpers: * Fix formatting for the description of "bpf_socket" for bpf_getsockopt() and bpf_setsockopt(), thus suppressing two warnings from rst2man about "Unexpected indentation". * Fix formatting for return values for bpf_sk_assign() and seq_file helpers. * Fix and harmonise formatting, in particular for function/struct names. * Remove blank lines before "Return:" sections. * Replace tabs found in the middle of text lines. * Fix typos. * Add a note to the footer (in Python script) about "bpftool feature probe", including for listing features available to unprivileged users, and add a reference to bpftool man page. Thanks to Florian for reporting two typos (duplicated words). Signed-off-by: Quentin Monnet Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20200511161536.29853-4-quentin@isovalent.com --- scripts/bpf_helpers_doc.py | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'scripts/bpf_helpers_doc.py') diff --git a/scripts/bpf_helpers_doc.py b/scripts/bpf_helpers_doc.py index ded304c96a05..91fa668fa860 100755 --- a/scripts/bpf_helpers_doc.py +++ b/scripts/bpf_helpers_doc.py @@ -318,6 +318,11 @@ may be interested in: of eBPF maps are used with a given helper function. * *kernel/bpf/* directory contains other files in which additional helpers are defined (for cgroups, sockmaps, etc.). +* The bpftool utility can be used to probe the availability of helper functions + on the system (as well as supported program and map types, and a number of + other parameters). To do so, run **bpftool feature probe** (see + **bpftool-feature**\ (8) for details). Add the **unprivileged** keyword to + list features available to unprivileged users. Compatibility between helper functions and program types can generally be found in the files where helper functions are defined. Look for the **struct @@ -338,6 +343,7 @@ SEE ALSO ======== **bpf**\ (2), +**bpftool**\ (8), **cgroups**\ (7), **ip**\ (8), **perf_event_open**\ (2), -- cgit