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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
<icmp_rcv@/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:0>
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 <fche@redhat.com>
Cc: Aaron Merey <amerey@redhat.com>
Cc: Francesco Nigro <fnigro@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/ZyACsIFUETsr7-09@x1
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.