[PATCH] libdwfl: Find and handle compressed vmlinuz image.

[PATCH] libdwfl: Find and handle compressed vmlinuz image.

[Mark Wielaard]

Both the dwfl_linux_kernel_find_elf callback and the
dwfl_linux_kernel_report_offline reporting function only handled
vmlinix images possibly compressed with .gz, .bz2 or .xz extension.
They did not find or handle the much more common vmlinuz compressed
images.

It is not completely clear why we didn't up to now. Support for
compressed ELF files was added in 2009 and the code was updated to
to try to find the .gz, .bz2 or .xz extension variants in 2011.
But not the vmlinuz named variant.

Reported-by: Aaron Merey <amerey@redhat.com>
Tested-by: Frank Ch. Eigler <fche@redhat.com>
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 libdwfl/ChangeLog              |  5 +++++
 libdwfl/linux-kernel-modules.c | 23 +++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/libdwfl/ChangeLog b/libdwfl/ChangeLog
index b8222189..b6b427d4 100644
--- a/libdwfl/ChangeLog
+++ b/libdwfl/ChangeLog
@@ -1,3 +1,8 @@
+2019-12-05  Mark Wielaard  <mark@klomp.org>
+
+	* linux-kernel-modules.c (find_kernel_elf): Also try to find
+	vmlinux image.
+
 2019-10-28  Aaron Merey  <amerey@redhat.com>
 
 	* dwfl_build_id_find_elf.c (dwfl_build_id_find_elf): Call debuginfod
diff --git a/libdwfl/linux-kernel-modules.c b/libdwfl/linux-kernel-modules.c
index d46ab5aa..48fb1ff0 100644
--- a/libdwfl/linux-kernel-modules.c
+++ b/libdwfl/linux-kernel-modules.c
@@ -174,6 +174,8 @@ kernel_release (void)
 static int
 find_kernel_elf (Dwfl *dwfl, const char *release, char **fname)
 {
+  /* First try to find an uncompressed vmlinux image.  Possibly
+     including debuginfo.  */
   if ((release[0] == '/'
        ? asprintf (fname, "%s/vmlinux", release)
        : asprintf (fname, "/boot/vmlinux-%s", release)) < 0)
@@ -188,6 +190,27 @@ find_kernel_elf (Dwfl *dwfl, const char *release, char **fname)
       fd = try_kernel_name (dwfl, fname, true);
     }
 
+  /* There might be a compressed vmlinuz image.  Probably without
+     debuginfo, but try to find it under the debug path also, just in
+     case.  */
+  if (fd < 0)
+    {
+      free (*fname);
+      if ((release[0] == '/'
+           ? asprintf (fname, "%s/vmlinuz", release)
+           : asprintf (fname, "/boot/vmlinuz-%s", release)) < 0)
+        return -1;
+
+      fd = try_kernel_name (dwfl, fname, true);
+      if (fd < 0 && release[0] != '/')
+	{
+	  free (*fname);
+	  if (asprintf (fname, MODULEDIRFMT "/vmlinuz", release) < 0)
+	    return -1;
+	  fd = try_kernel_name (dwfl, fname, true);
+	}
+    }
+
   return fd;
 }
 
-- 
2.18.1

Re: [PATCH] libdwfl: Find and handle compressed vmlinuz image.

[Mark Wielaard]

On Thu, 2019-12-05 at 15:21 +0100, Mark Wielaard wrote:
> Both the dwfl_linux_kernel_find_elf callback and the
> dwfl_linux_kernel_report_offline reporting function only handled
> vmlinix images possibly compressed with .gz, .bz2 or .xz extension.
> They did not find or handle the much more common vmlinuz compressed
> images.
> 
> It is not completely clear why we didn't up to now. Support for
> compressed ELF files was added in 2009 and the code was updated to
> to try to find the .gz, .bz2 or .xz extension variants in 2011.
> But not the vmlinuz named variant.

Testing (against systemtap) looks good. Pushed to master.

Cheers,

Mark