perf symbols: Workaround objdump difficulties with kcore

The objdump tool 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>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1381320078-16497-3-git-send-email-adrian.hunter@intel.com
[ Renamed 'index' to 'idx' to avoid shadowing string.h's 'index' in Fedora 12,
  Replace local with variable length with malloc/free to fix build in Fedora 12 ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 273 insertions, 0 deletions

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index d73e8008aada..882bb864cee0 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 (!kcore_extract__create(&kce)) {
+                        delete_extract = true;
+                        strlcpy(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)
+                kcore_extract__delete(&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 c37693052800..499c71d30225 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1018,6 +1018,235 @@ 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)
+{
+        ssize_t r;
+        size_t n;
+        int err = -1;
+        char *buf = malloc(page_size);
+
+        if (buf == NULL)
+                return -1;
+
+        if (lseek(to, to_offs, SEEK_SET) != to_offs)
+                goto out;
+
+        if (lseek(from, from_offs, SEEK_SET) != from_offs)
+                goto out;
+
+        while (len) {
+                n = page_size;
+                if (len < n)
+                        n = len;
+                /* Use read because mmap won't work on proc files */
+                r = read(from, buf, n);
+                if (r < 0)
+                        goto out;
+                if (!r)
+                        break;
+                n = r;
+                r = write(to, buf, n);
+                if (r < 0)
+                        goto out;
+                if ((size_t)r != n)
+                        goto out;
+                len -= n;
+        }
+
+        err = 0;
+out:
+        free(buf);
+        return err;
+}
+
+struct kcore {
+        int fd;
+        int elfclass;
+        Elf *elf;
+        GElf_Ehdr ehdr;
+};
+
+static int kcore__open(struct kcore *kcore, const char *filename)
+{
+        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__init(struct kcore *kcore, char *filename, 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 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))
+                return -1;
+
+        return 0;
+}
+
+static off_t kcore__write(struct kcore *kcore)
+{
+        return elf_update(kcore->elf, ELF_C_WRITE);
+}
+
+int kcore_extract__create(struct kcore_extract *kce)
+{
+        struct kcore kcore;
+        struct kcore extract;
+        size_t count = 1;
+        int idx = 0, err = -1;
+        off_t offset = page_size, sz;
+
+        if (kcore__open(&kcore, kce->kcore_filename))
+                return -1;
+
+        strcpy(kce->extract_filename, PERF_KCORE_EXTRACT);
+        if (kcore__init(&extract, kce->extract_filename, kcore.elfclass, true))
+                goto out_kcore_close;
+
+        if (kcore__copy_hdr(&kcore, &extract, count))
+                goto out_extract_close;
+
+        if (kcore__add_phdr(&extract, idx, 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 kcore_extract__delete(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 3a802c300fc5..928556d2508f 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 kcore_extract__create(struct kcore_extract *kce __maybe_unused)
+{
+        return -1;
+}
+
+void kcore_extract__delete(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 2d3eb43ab9f9..fb107e13e925 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 kcore_extract__create(struct kcore_extract *kce);
+void kcore_extract__delete(struct kcore_extract *kce);
+
 #endif /* __PERF_SYMBOL */