Commit b5cabbcb authored Sep 24, 2015 by Adrian Hunter Committed by Arnaldo Carvalho de Melo Sep 25, 2015

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: 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>

parent 597ee407

tools/perf/util/symbol-elf.c

+13 −22

Original line number	Diff line number	Diff line
		@@ -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;
		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;

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