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authorYonghong Song <yhs@fb.com>2020-05-09 10:59:14 -0700
committerAlexei Starovoitov <ast@kernel.org>2020-05-09 17:05:26 -0700
commit492e639f0c222784e2e0f121966375f641c61b15 (patch)
tree316f1e3a1ddee5a9bd5bebb586b7aa405b8295ac /scripts
parentb121b341e5983bdccf7a5d6cf9236a45c965a31f (diff)
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 <yhs@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/20200509175914.2476661-1-yhs@fb.com
Diffstat (limited to 'scripts')
-rwxr-xr-xscripts/bpf_helpers_doc.py2
1 files changed, 2 insertions, 0 deletions
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',