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Subject[PATCH V2 04/10] perf tools: workaround objdump difficulties with kcore
Date
objdump fails to annotate module symbols when looking
at kcore. Workaround this by extracting object code
from kcore and putting it in a temporary file for
objdump to use instead. The temporary file is created
to look like kcore but contains only the function
being disassembled.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/util/annotate.c | 21 ++++
tools/perf/util/symbol-elf.c | 221 +++++++++++++++++++++++++++++++++++++++
tools/perf/util/symbol-minimal.c | 9 ++
tools/perf/util/symbol.h | 14 +++
4 files changed, 265 insertions(+)

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index f7bdc01..a65e3fc 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -879,6 +879,8 @@ int symbol__annotate(struct symbol *sym, struct map *map, size_t privsize)
FILE *file;
int err = 0;
char symfs_filename[PATH_MAX];
+ struct kcore_extract kce;
+ bool delete_extract = false;

if (filename) {
snprintf(symfs_filename, sizeof(symfs_filename), "%s%s",
@@ -940,6 +942,23 @@ fallback:
pr_debug("annotating [%p] %30s : [%p] %30s\n",
dso, dso->long_name, sym, sym->name);

+ if (dso__is_kcore(dso)) {
+ kce.kcore_filename = symfs_filename;
+ kce.addr = map__rip_2objdump(map, sym->start);
+ kce.offs = sym->start;
+ kce.len = sym->end + 1 - sym->start;
+ if (!create_kcore_extract(&kce)) {
+ delete_extract = true;
+ strncpy(symfs_filename, kce.extract_filename,
+ sizeof(symfs_filename));
+ if (free_filename) {
+ free(filename);
+ free_filename = false;
+ }
+ filename = symfs_filename;
+ }
+ }
+
snprintf(command, sizeof(command),
"%s %s%s --start-address=0x%016" PRIx64
" --stop-address=0x%016" PRIx64
@@ -972,6 +991,8 @@ fallback:

pclose(file);
out_free_filename:
+ if (delete_extract)
+ delete_kcore_extract(&kce);
if (free_filename)
free(filename);
return err;
diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index a7b9ab5..79b27fc7 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1002,6 +1002,227 @@ int file__read_maps(int fd, bool exe, mapfn_t mapfn, void *data,
return err;
}

+static int copy_bytes(int from, off_t from_offs, int to, off_t to_offs, u64 len)
+{
+ char buf[page_size];
+ ssize_t r;
+ size_t n;
+
+ if (lseek(to, to_offs, SEEK_SET) != to_offs)
+ return -1;
+
+ if (lseek(from, from_offs, SEEK_SET) != from_offs)
+ return -1;
+
+ while (len) {
+ n = sizeof(buf);
+ if (len < n)
+ n = len;
+ /* Use read because mmap won't work on proc files */
+ r = read(from, buf, n);
+ if (r < 0)
+ return -1;
+ if (!r)
+ break;
+ n = r;
+ r = write(to, buf, n);
+ if (r < 0)
+ return -1;
+ if ((size_t)r != n)
+ return -1;
+ len -= n;
+ }
+ return 0;
+}
+
+struct kcore {
+ int fd;
+ int elfclass;
+ Elf *elf;
+ GElf_Ehdr ehdr;
+};
+
+static int kcore_open(const char *filename, struct kcore *kcore)
+{
+ GElf_Ehdr *ehdr;
+
+ kcore->fd = open(filename, O_RDONLY);
+ if (kcore->fd == -1)
+ return -1;
+
+ kcore->elf = elf_begin(kcore->fd, ELF_C_READ, NULL);
+ if (!kcore->elf)
+ goto out_close;
+
+ kcore->elfclass = gelf_getclass(kcore->elf);
+ if (kcore->elfclass == ELFCLASSNONE)
+ goto out_end;
+
+ ehdr = gelf_getehdr(kcore->elf, &kcore->ehdr);
+ if (!ehdr)
+ goto out_end;
+
+ return 0;
+
+out_end:
+ elf_end(kcore->elf);
+out_close:
+ close(kcore->fd);
+ return -1;
+}
+
+static int kcore_new(char *filename, struct kcore *kcore, int elfclass,
+ bool temp)
+{
+ GElf_Ehdr *ehdr;
+
+ kcore->elfclass = elfclass;
+
+ if (temp)
+ kcore->fd = mkstemp(filename);
+ else
+ kcore->fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0400);
+ if (kcore->fd == -1)
+ return -1;
+
+ kcore->elf = elf_begin(kcore->fd, ELF_C_WRITE, NULL);
+ if (!kcore->elf)
+ goto out_close;
+
+ if (!gelf_newehdr(kcore->elf, elfclass))
+ goto out_end;
+
+ ehdr = gelf_getehdr(kcore->elf, &kcore->ehdr);
+ if (!ehdr)
+ goto out_end;
+
+ return 0;
+
+out_end:
+ elf_end(kcore->elf);
+out_close:
+ close(kcore->fd);
+ unlink(filename);
+ return -1;
+}
+
+static void kcore_close(struct kcore *kcore)
+{
+ elf_end(kcore->elf);
+ close(kcore->fd);
+}
+
+static int kcore_copy_hdr(struct kcore *from, struct kcore *to, size_t count)
+{
+ GElf_Ehdr *ehdr = &to->ehdr;
+ GElf_Ehdr *kehdr = &from->ehdr;
+
+ memcpy(ehdr->e_ident, kehdr->e_ident, EI_NIDENT);
+ ehdr->e_type = kehdr->e_type;
+ ehdr->e_machine = kehdr->e_machine;
+ ehdr->e_version = kehdr->e_version;
+ ehdr->e_entry = 0;
+ ehdr->e_shoff = 0;
+ ehdr->e_flags = kehdr->e_flags;
+ ehdr->e_phnum = count;
+ ehdr->e_shentsize = 0;
+ ehdr->e_shnum = 0;
+ ehdr->e_shstrndx = 0;
+
+ if (from->elfclass == ELFCLASS32) {
+ ehdr->e_phoff = sizeof(Elf32_Ehdr);
+ ehdr->e_ehsize = sizeof(Elf32_Ehdr);
+ ehdr->e_phentsize = sizeof(Elf32_Phdr);
+ } else {
+ ehdr->e_phoff = sizeof(Elf64_Ehdr);
+ ehdr->e_ehsize = sizeof(Elf64_Ehdr);
+ ehdr->e_phentsize = sizeof(Elf64_Phdr);
+ }
+
+ if (!gelf_update_ehdr(to->elf, ehdr))
+ return -1;
+
+ if (!gelf_newphdr(to->elf, count))
+ return -1;
+
+ return 0;
+}
+
+static int kcore_add_phdr(struct kcore *kcore, int index, off_t offset,
+ u64 addr, u64 len)
+{
+ GElf_Phdr gphdr;
+ GElf_Phdr *phdr;
+
+ phdr = gelf_getphdr(kcore->elf, index, &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, index, phdr))
+ return -1;
+
+ return 0;
+}
+
+static off_t kcore_write(struct kcore *kcore)
+{
+ return elf_update(kcore->elf, ELF_C_WRITE);
+}
+
+int create_kcore_extract(struct kcore_extract *kce)
+{
+ struct kcore kcore;
+ struct kcore extract;
+ size_t count = 1;
+ int index = 0, err = -1;
+ off_t offset = page_size, sz;
+
+ if (kcore_open(kce->kcore_filename, &kcore))
+ return -1;
+
+ strcpy(kce->extract_filename, PERF_KCORE_EXTRACT);
+ if (kcore_new(kce->extract_filename, &extract, kcore.elfclass, true))
+ goto out_kcore_close;
+
+ if (kcore_copy_hdr(&kcore, &extract, count))
+ goto out_extract_close;
+
+ if (kcore_add_phdr(&extract, index, offset, kce->addr, kce->len))
+ goto out_extract_close;
+
+ sz = kcore_write(&extract);
+ if (sz < 0 || sz > offset)
+ goto out_extract_close;
+
+ if (copy_bytes(kcore.fd, kce->offs, extract.fd, offset, kce->len))
+ goto out_extract_close;
+
+ err = 0;
+
+out_extract_close:
+ kcore_close(&extract);
+ if (err)
+ unlink(kce->extract_filename);
+out_kcore_close:
+ kcore_close(&kcore);
+
+ return err;
+}
+
+void delete_kcore_extract(struct kcore_extract *kce)
+{
+ unlink(kce->extract_filename);
+}
+
void symbol__elf_init(void)
{
elf_version(EV_CURRENT);
diff --git a/tools/perf/util/symbol-minimal.c b/tools/perf/util/symbol-minimal.c
index 3a802c3..0330163 100644
--- a/tools/perf/util/symbol-minimal.c
+++ b/tools/perf/util/symbol-minimal.c
@@ -308,6 +308,15 @@ int file__read_maps(int fd __maybe_unused, bool exe __maybe_unused,
return -1;
}

+int create_kcore_extract(struct kcore_extract *kce __maybe_unused)
+{
+ return -1;
+}
+
+void delete_kcore_extract(struct kcore_extract *kce __maybe_unused)
+{
+}
+
void symbol__elf_init(void)
{
}
diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
index a2543f0..54f3ed0 100644
--- a/tools/perf/util/symbol.h
+++ b/tools/perf/util/symbol.h
@@ -256,4 +256,18 @@ typedef int (*mapfn_t)(u64 start, u64 len, u64 pgoff, void *data);
int file__read_maps(int fd, bool exe, mapfn_t mapfn, void *data,
bool *is_64_bit);

+#define PERF_KCORE_EXTRACT "/tmp/perf-kcore-XXXXXX"
+
+struct kcore_extract {
+ char *kcore_filename;
+ u64 addr;
+ u64 offs;
+ u64 len;
+ char extract_filename[sizeof(PERF_KCORE_EXTRACT)];
+ int fd;
+};
+
+int create_kcore_extract(struct kcore_extract *kce);
+void delete_kcore_extract(struct kcore_extract *kce);
+
#endif /* __PERF_SYMBOL */
--
1.7.11.7


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