Patch "perf tools: Fix copying of /proc/kcore" has been added to the 3.14-stable tree

This is a note to let you know that I've just added the patch titled

perf tools: Fix copying of /proc/kcore

to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
perf-tools-fix-copying-of-proc-kcore.patch
and it can be found in the queue-3.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Adrian Hunter <[email protected]>
Date: Thu, 24 Sep 2015 13:05:22 +0300
Subject: perf tools: Fix copying of /proc/kcore

From: Adrian Hunter <[email protected]>

commit b5cabbcbd157a4bf5a92dfc85134999a3b55342d upstream.

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 [email protected], 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.

---
 tools/perf/util/symbol-elf.c |   33 ++++++++++++---------------------
 1 file changed, 12 insertions(+), 21 deletions(-)

@@ -1100,8 +1100,6 @@ out_close:
 static int kcore__init(struct kcore *kcore, char *filename, int elfclass,
 		       bool temp)
 {
-	GElf_Ehdr *ehdr;
-
 	kcore->elfclass = elfclass;
 
 	if (temp)

@@ -1118,9 +1116,7 @@ static int kcore__init(struct kcore *kco
 	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;
 

@@ -1177,23 +1173,18 @@ static int kcore__copy_hdr(struct kcore
 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;
+	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))
+	if (!gelf_update_phdr(kcore->elf, idx, &phdr))
 		return -1;
 
 	return 0;

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/perf-stat-get-correct-cpu-id-for-print_aggr.patch queue-3.14/perf-tools-fix-copying-of-proc-kcore.patch queue-3.14/perf-header-fixup-reading-of-header_nrcpus-feature.patch