[acme@kernel.org: [PATCH 3/3] perf tools: Fix copying of /proc/kcore]

[acme@kernel.org: [PATCH 3/3] perf tools: Fix copying of /proc/kcore]

[Arnaldo Carvalho de Melo]

Sorry, forgot the "vger.", but I guess it would be nice to have a
forwarder from stable@kernel.org to stable@vger.kernel.org :-)

- Arnaldo

----- Forwarded message from Arnaldo Carvalho de Melo <acme@kernel.org> -----

Date: Fri, 25 Sep 2015 12:28:38 -0300
From: Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: [PATCH 3/3] perf tools: Fix copying of /proc/kcore
To: Ingo Molnar <mingo@kernel.org>
Cc: linux-kernel@vger.kernel.org, Adrian Hunter <adrian.hunter@intel.com>, Jiri Olsa <jolsa@redhat.com>, stable@kernel.org, Arnaldo Carvalho de Melo
	<acme@redhat.com>

From: Adrian Hunter <adrian.hunter@intel.com>

A copy of /proc/kcore containing the kernel text can be made to the
buildid cache. e.g.

	perf buildid-cache -v -k /proc/kcore

To workaround objdump limitations, a copy is also made when annotating
against /proc/kcore.

The copying process stops working from libelf about v1.62 onwards (the
problem was found with v1.63).

The cause is that a call to gelf_getphdr() in kcore__add_phdr() fails
because additional validation has been added to gelf_getphdr().

The use of gelf_getphdr() is a misguided attempt to get default
initialization of the Gelf_Phdr structure.  That should not be
necessary because every member of the Gelf_Phdr structure is
subsequently assigned.  So just remove the call to gelf_getphdr().

Similarly, a call to gelf_getehdr() in gelf_kcore__init() can be
removed also.

Committer notes:

Note to stable@kernel.org, from Adrian in the cover letter for this
patchkit:

The "Fix copying of /proc/kcore" problem goes back to v3.13 if you think
it is important enough for stable.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@kernel.org
Link: http://lkml.kernel.org/r/1443089122-19082-3-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/symbol-elf.c | 35 +++++++++++++----------------------
 1 file changed, 13 insertions(+), 22 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index f78ea3dc4c08..475d88d0a1c9 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1271,8 +1271,6 @@ out_close:
 static int kcore__init(struct kcore *kcore, char *filename, int elfclass,
 		       bool temp)
 {
-	GElf_Ehdr *ehdr;
-
 	kcore->elfclass = elfclass;
 
 	if (temp)
@@ -1289,9 +1287,7 @@ static int kcore__init(struct kcore *kcore, char *filename, int elfclass,
 	if (!gelf_newehdr(kcore->elf, elfclass))
 		goto out_end;
 
-	ehdr = gelf_getehdr(kcore->elf, &kcore->ehdr);
-	if (!ehdr)
-		goto out_end;
+	memset(&kcore->ehdr, 0, sizeof(GElf_Ehdr));
 
 	return 0;
 
@@ -1348,23 +1344,18 @@ static int kcore__copy_hdr(struct kcore *from, struct kcore *to, size_t count)
 static int kcore__add_phdr(struct kcore *kcore, int idx, off_t offset,
 			   u64 addr, u64 len)
 {
-	GElf_Phdr gphdr;
-	GElf_Phdr *phdr;
-
-	phdr = gelf_getphdr(kcore->elf, idx, &gphdr);
-	if (!phdr)
-		return -1;
-
-	phdr->p_type	= PT_LOAD;
-	phdr->p_flags	= PF_R | PF_W | PF_X;
-	phdr->p_offset	= offset;
-	phdr->p_vaddr	= addr;
-	phdr->p_paddr	= 0;
-	phdr->p_filesz	= len;
-	phdr->p_memsz	= len;
-	phdr->p_align	= page_size;
-
-	if (!gelf_update_phdr(kcore->elf, idx, phdr))
+	GElf_Phdr phdr = {
+		.p_type		= PT_LOAD,
+		.p_flags	= PF_R | PF_W | PF_X,
+		.p_offset	= offset,
+		.p_vaddr	= addr,
+		.p_paddr	= 0,
+		.p_filesz	= len,
+		.p_memsz	= len,
+		.p_align	= page_size,
+	};
+
+	if (!gelf_update_phdr(kcore->elf, idx, &phdr))
 		return -1;
 
 	return 0;
-- 
2.1.0

----- End forwarded message -----

Re: [acme@kernel.org: [PATCH 3/3] perf tools: Fix copying of /proc/kcore]

[Greg KH]

On Fri, Sep 25, 2015 at 12:30:43PM -0300, Arnaldo Carvalho de Melo wrote:
> Sorry, forgot the "vger.", but I guess it would be nice to have a
> forwarder from stable@kernel.org to stable@vger.kernel.org :-)

My scripts know to pick up both of these, thanks, I got it now.

greg k-h

Re: [acme@kernel.org: [PATCH 3/3] perf tools: Fix copying of /proc/kcore]

[Arnaldo Carvalho de Melo]

Em Tue, Oct 13, 2015 at 01:13:21PM -0700, Greg KH escreveu:
> On Fri, Sep 25, 2015 at 12:30:43PM -0300, Arnaldo Carvalho de Melo wrote:
> > Sorry, forgot the "vger.", but I guess it would be nice to have a
> > forwarder from stable@kernel.org to stable@vger.kernel.org :-)
> 
> My scripts know to pick up both of these, thanks, I got it now.

Great,

- Arnaldo