From 54afc56db221c831479dd1b59eb0657c078355d1 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Mon, 28 Oct 2024 18:31:28 -0300 Subject: [PATCH] perf probe: Fix retrieval of source files from a debuginfod server When perf is linked with libdebuginfod: root@number:~# ldd ~/bin/perf | grep debuginfod libdebuginfod.so.1 => /lib64/libdebuginfod.so.1 (0x00007ff5c3930000) root@number:~# perf check feature debuginfod debuginfod: [ on ] # HAVE_DEBUGINFOD_SUPPORT root@number:~# And we don't have a debuginfo package installed for the binary we're trying to use, vmlinux in this case as we didn't specify any using 'perf probe -x', it will use the build for the running kernel: root@number:~# perf buildid-list -k 38e927fd7799d50dbc4d99ec5e3f781b6105a6a9 root@number:~# And communicate with a debuginfo server, be it configured in a ~/.perfconfig file, excerpt from the 'perf config' man page: buildid-cache.* buildid-cache.debuginfod=URLs Specify debuginfod URLs to be used when retrieving perf.data binaries, it follows the same syntax as the DEBUGINFOD_URLS variable, like: buildid-cache.debuginfod=http://192.168.122.174:8002 Or via the DEBUGINFOD_URLS env var, as distros like fedora do by default: root@number:~# echo $DEBUGINFOD_URLS https://debuginfod.fedoraproject.org/ root@number:~# To pick and cache just what is needed, instead of requiring the manual installation of the entire kernel-debuginfo package, which is really large. It will, in this example, use the following cache files, deleted before/after this patch just to test the whole process: root@number:~# rm -f /root/.cache/debuginfod_client/38e927fd7799d50dbc4d99ec5e3f781b6105a6a9/source-a1414a5d-#usr#src#debug#kernel-6.11.4#linux-6.11.4-201.fc40.x86_64#net#ipv4#icmp.c root@number:~# rm -f /root/.cache/debuginfod_client/38e927fd7799d50dbc4d99ec5e3f781b6105a6a9/debuginfo Before this patch: root@number:~# perf probe -L icmp_rcv Failed to find source file path. Error: Failed to show lines. root@number:~# This is because 'perf probe' was using just the relative file name, in this case "net/ipv4/icmp.c", that is where the 'icmp_rcv' function is located, if we add it and comply with the debuginfo_find_source() function man page, it contacts the server, finds the necessary files, cache them locally and all works: root@number:~# perf probe -L icmp_rcv | head 0 int icmp_rcv(struct sk_buff *skb) { 2 enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED; struct rtable *rt = skb_rtable(skb); struct net *net = dev_net(rt->dst.dev); struct icmphdr *icmph; if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) { 8 struct sec_path *sp = skb_sec_path(skb); root@number:~# Acked-by: Frank Ch. Eigler Cc: Aaron Merey Cc: Francesco Nigro Cc: Masami Hiramatsu Signed-off-by: Arnaldo Carvalho de Melo Link: https://lore.kernel.org/r/ZyACsIFUETsr7-09@x1 Signed-off-by: Namhyung Kim --- tools/perf/util/probe-finder.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c index 18181017f5fd..c2ca94e29aca 100644 --- a/tools/perf/util/probe-finder.c +++ b/tools/perf/util/probe-finder.c @@ -1874,7 +1874,11 @@ int find_source_path(const char *raw_path, const char *sbuild_id, const char *prefix = symbol_conf.source_prefix; if (sbuild_id && !prefix) { - if (!get_source_from_debuginfod(raw_path, sbuild_id, new_path)) + char prefixed_raw_path[PATH_MAX]; + + path__join(prefixed_raw_path, sizeof(prefixed_raw_path), comp_dir, raw_path); + + if (!get_source_from_debuginfod(prefixed_raw_path, sbuild_id, new_path)) return 0; } -- 2.50.1