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Commit b5cabbcb authored by Adrian Hunter's avatar Adrian Hunter Committed by Arnaldo Carvalho de Melo
Browse files

perf tools: Fix copying of /proc/kcore 



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: default avatarAdrian 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: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 597ee407

tools/perf/util/symbol-elf.c

+13 −22
Original line number Diff line number Diff line
@@ -1271,8 +1271,6 @@ static int kcore__open(struct kcore *kcore, const char *filename) 
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;

	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;