Re: [PATCH 2/3] perf symbol: Implement a very simple ELF symbol parser

From: Arnaldo Carvalho de Melo
Date: Fri Nov 07 2014 - 10:27:58 EST

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In reply to: Namhyung Kim: "[PATCH 2/3] perf symbol: Implement a very simple ELF symbol parser"
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Em Fri, Nov 07, 2014 at 02:20:05PM +0900, Namhyung Kim escreveu:
> It'll be used to show (userspace) symbol names when libelf isn't (or
> cannot be) linked.

Does this deals with prelink, etc?

- Arnaldo

> # Overhead Command Shared Object Symbol
> # ........ .......... ................. .........................
> #
> 37.01% mem-memcpy libc-2.17.so [.] __memcpy_ssse3_back
> 24.25% perf ld-2.17.so [.] _dl_relocate_object
> 22.16% perf [kernel.kallsyms] [k] kmem_cache_alloc
> 14.29% mem-memset libc-2.17.so [.] __memset_sse2
> 2.21% perf [kernel.kallsyms] [k] flush_signal_handlers
> 0.07% perf [kernel.kallsyms] [k] intel_pmu_enable_all
>
> Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> ---
> tools/perf/util/symbol-minimal.c | 143 ++++++++++++++++++++++++++++++++++++---
> tools/perf/util/symbol-minimal.h | 64 ++++++++++++++++++
> tools/perf/util/symbol.h | 10 ++-
> 3 files changed, 208 insertions(+), 9 deletions(-)
> create mode 100644 tools/perf/util/symbol-minimal.h
>
> diff --git a/tools/perf/util/symbol-minimal.c b/tools/perf/util/symbol-minimal.c
> index 226cf41ed7e6..9da571d83a25 100644
> --- a/tools/perf/util/symbol-minimal.c
> +++ b/tools/perf/util/symbol-minimal.c
> @@ -1,11 +1,13 @@
> #include "symbol.h"
> #include "util.h"
> +#include "debug.h"
>
> #include <stdio.h>
> #include <fcntl.h>
> #include <string.h>
> #include <byteswap.h>
> #include <sys/stat.h>
> +#include <sys/mman.h>
>
>
> static bool check_need_swap(int file_endian)
> @@ -242,22 +244,81 @@ int sysfs__read_build_id(const char *filename, void *build_id, size_t size)
> return ret;
> }
>
> +static const char *symsrc__symname(struct symsrc *ss, Elf_Shdr *strsec, int idx)
> +{
> + return ss->ptr + strsec->sh_offset + idx;
> +}
> +
> int symsrc__init(struct symsrc *ss, struct dso *dso __maybe_unused,
> const char *name,
> enum dso_binary_type type)
> {
> - int fd = open(name, O_RDONLY);
> + int fd;
> + unsigned i;
> + Elf_Ehdr ehdr;
> + struct stat stbuf;
> + void *ptr;
> +
> + fd = open(name, O_RDONLY);
> if (fd < 0)
> return -1;
>
> ss->name = strdup(name);
> - if (!ss->name)
> - goto out_close;
> + if (!ss->name) {
> + close(fd);
> + return -1;
> + }
>
> ss->fd = fd;
> ss->type = type;
>
> + /* only consider native case (no swap) */
> + if (read(fd, &ehdr, sizeof(ehdr)) < 0)
> + goto out_close;
> +
> + if (memcmp(ehdr.e_ident, ELFMAG, SELFMAG) ||
> + ehdr.e_ident[EI_VERSION] != EV_CURRENT)
> + goto out_close;
> +
> + if (ehdr.e_ident[EI_CLASS] != ELFCLASS)
> + goto out_close;
> +
> + if (check_need_swap(ehdr.e_ident[EI_DATA]))
> + goto out_close;
> +
> + if (ehdr.e_shentsize != sizeof(Elf_Shdr))
> + goto out_close;
> +
> + if (fstat(fd, &stbuf) < 0)
> + goto out_close;
> +
> + ptr = mmap(NULL, stbuf.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
> + if (ptr == MAP_FAILED)
> + goto out_close;
> +
> + ss->ptr = ptr;
> + ss->len = stbuf.st_size;
> + ss->sec = ptr + ehdr.e_shoff;
> +
> + ss->symtab = NULL;
> + for (i = 0; i < ehdr.e_shnum; i++) {
> + Elf_Shdr *shdrp = &ss->sec[i];
> + const char *shname;
> +
> + shname = symsrc__symname(ss, &ss->sec[ehdr.e_shstrndx],
> + shdrp->sh_name);
> +
> + if (!strcmp(shname, ".text"))
> + ss->adjust_offset = shdrp->sh_addr - shdrp->sh_offset;
> +
> + if (shdrp->sh_type == SHT_SYMTAB) {
> + ss->symtab = shdrp;
> + ss->strtab = &ss->sec[shdrp->sh_link];
> + }
> + }
> +
> return 0;
> +
> out_close:
> close(fd);
> return -1;
> @@ -276,6 +337,7 @@ bool symsrc__has_symtab(struct symsrc *ss __maybe_unused)
>
> void symsrc__destroy(struct symsrc *ss)
> {
> + munmap(ss->ptr, ss->len);
> zfree(&ss->name);
> close(ss->fd);
> }
> @@ -332,7 +394,9 @@ int dso__load_sym(struct dso *dso, struct map *map __maybe_unused,
> symbol_filter_t filter __maybe_unused,
> int kmodule __maybe_unused)
> {
> - unsigned char *build_id[BUILD_ID_SIZE];
> + Elf_Ehdr *ehdr = ss->ptr;
> + Elf_Sym *symtab;
> + size_t i, nr_sym;
> int ret;
>
> if (dso->kernel)
> @@ -342,11 +406,74 @@ int dso__load_sym(struct dso *dso, struct map *map __maybe_unused,
> if (ret >= 0)
> dso->is_64_bit = ret;
>
> - if (filename__read_build_id(ss->name, build_id, BUILD_ID_SIZE) > 0) {
> - dso__set_build_id(dso, build_id);
> - return 1;
> + if (dso->has_build_id) {
> + u8 build_id[BUILD_ID_SIZE];
> +
> + if (filename__read_build_id(ss->name, build_id, BUILD_ID_SIZE) < 0)
> + return -1;
> +
> + if (!dso__build_id_equal(dso, build_id))
> + return -1;
> }
> - return 0;
> +
> + if (map->type != MAP__FUNCTION)
> + return 0;
> +
> + if (!ss->symtab)
> + return 0;
> +
> + symtab = ss->ptr + ss->symtab->sh_offset;
> + nr_sym = ss->symtab->sh_size / ss->symtab->sh_entsize;
> +
> + pr_debug4("loading symbols from %s\n", ss->name);
> + ret = 0;
> + for (i = 0; i < nr_sym; i++) {
> + struct symbol *s;
> + Elf_Sym *sym = &symtab[i];
> + const char *symname = symsrc__symname(ss, ss->strtab, sym->st_name);
> + unsigned long sym_addr = sym->st_value;
> +
> + if (ELF_ST_TYPE(sym->st_info) != STT_FUNC)
> + continue;
> +
> + if (sym->st_shndx == SHN_UNDEF)
> + continue;
> +
> + if (ehdr->e_machine == EM_ARM) {
> + /* Reject ARM ELF "mapping symbols": these aren't unique
> + * and don't identify functions, so will confuse the
> + * profile output: */
> + if (!strcmp(symname, "$a") ||
> + !strcmp(symname, "$d") ||
> + !strcmp(symname, "$t"))
> + continue;
> +
> + /* On ARM, symbols for thumb functions have 1 added to
> + * the symbol address as a flag - remove it */
> + if (sym->st_value & 1)
> + sym_addr--;
> + }
> + sym_addr -= ss->adjust_offset;
> +
> + pr_debug4("sym: %s (%lx+%lu)\n", symname, sym_addr, sym->st_size);
> + s = symbol__new(sym_addr, sym->st_size,
> + ELF_ST_BIND(sym->st_info), symname);
> + if (!s)
> + break;
> +
> + if (filter && filter(map, s))
> + symbol__delete(s);
> + else {
> + symbols__insert(&dso->symbols[map->type], s);
> + ret++;
> + }
> + }
> +
> + if (ret > 0) {
> + symbols__fixup_duplicate(&dso->symbols[map->type]);
> + symbols__fixup_end(&dso->symbols[map->type]);
> + }
> + return ret;
> }
>
> int file__read_maps(int fd __maybe_unused, bool exe __maybe_unused,
> diff --git a/tools/perf/util/symbol-minimal.h b/tools/perf/util/symbol-minimal.h
> new file mode 100644
> index 000000000000..7b8b38426359
> --- /dev/null
> +++ b/tools/perf/util/symbol-minimal.h
> @@ -0,0 +1,64 @@
> +#ifndef __PERF_SYMBOL_MINIMAL_H
> +#define __PERF_SYMBOL_MINIMAL_H
> +
> +#include <elf.h>
> +#include <linux/bitops.h>
> +
> +#if BITS_PER_LONG == 32
> +
> +# define ELFCLASS ELFCLASS32
> +
> +# define Elf_Half Elf32_Half
> +# define Elf_Word Elf32_Word
> +# define Elf_Sword Elf32_Sword
> +# define Elf_Xword Elf32_Xword
> +# define Elf_Sxword Elf32_Sxword
> +# define Elf_Addr Elf32_Addr
> +# define Elf_Off Elf32_Off
> +# define Elf_Section Elf32_Section
> +# define Elf_Versym Elf32_Versym
> +
> +# define Elf_Ehdr Elf32_Ehdr
> +# define Elf_Phdr Elf32_Phdr
> +# define Elf_Shdr Elf32_Shdr
> +# define Elf_Nhdr Elf32_Nhdr
> +# define Elf_Sym Elf32_Sym
> +# define Elf_Syminfo Elf32_Syminfo
> +# define Elf_Rel Elf32_Rel
> +# define Elf_Rela Elf32_Rela
> +# define Elf_Dyn Elf32_Dyn
> +
> +# define ELF_ST_BIND(val) ELF32_ST_BIND(val)
> +# define ELF_ST_TYPE(val) ELF32_ST_TYPE(val)
> +# define ELF_ST_INFO(bind, type) ELF32_ST_INFO(bind, type)
> +
> +#else /* BITS_PER_LONG == 64 */
> +
> +# define ELFCLASS ELFCLASS64
> +
> +# define Elf_Half Elf64_Half
> +# define Elf_Word Elf64_Word
> +# define Elf_Sword Elf64_Sword
> +# define Elf_Xword Elf64_Xword
> +# define Elf_Sxword Elf64_Sxword
> +# define Elf_Addr Elf64_Addr
> +# define Elf_Off Elf64_Off
> +# define Elf_Section Elf64_Section
> +# define Elf_Versym Elf64_Versym
> +
> +# define Elf_Ehdr Elf64_Ehdr
> +# define Elf_Phdr Elf64_Phdr
> +# define Elf_Shdr Elf64_Shdr
> +# define Elf_Nhdr Elf64_Nhdr
> +# define Elf_Sym Elf64_Sym
> +# define Elf_Syminfo Elf64_Syminfo
> +# define Elf_Rel Elf64_Rel
> +# define Elf_Rela Elf64_Rela
> +# define Elf_Dyn Elf64_Dyn
> +
> +# define ELF_ST_BIND(val) ELF64_ST_BIND(val)
> +# define ELF_ST_TYPE(val) ELF64_ST_TYPE(val)
> +# define ELF_ST_INFO(bind, type) ELF64_ST_INFO(bind, type)
> +
> +#endif /* BITS_PER_LONG == 64 */
> +#endif /* __PERF_SYMBOL_MINIMAL_H */
> diff --git a/tools/perf/util/symbol.h b/tools/perf/util/symbol.h
> index ded3ca7266de..1c1dc5b9b3f8 100644
> --- a/tools/perf/util/symbol.h
> +++ b/tools/perf/util/symbol.h
> @@ -18,8 +18,9 @@
> #ifdef HAVE_LIBELF_SUPPORT
> #include <libelf.h>
> #include <gelf.h>
> +#else
> +#include "symbol-minimal.h"
> #endif
> -#include <elf.h>
>
> #include "dso.h"
>
> @@ -229,6 +230,13 @@ struct symsrc {
>
> bool adjust_symbols;
> bool is_64_bit;
> +#else
> + void *ptr;
> + size_t len;
> + Elf_Shdr *sec;
> + Elf_Shdr *symtab;
> + Elf_Shdr *strtab;
> + long adjust_offset;
> #endif
> };
>
> --
> 2.1.2
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Next message: Arnaldo Carvalho de Melo: "Re: [PATCH 1/3] perf tools: Allow vmlinux to fallback to kallsyms on NO_LIBELF=1"
Previous message: Dale R. Worley: "Re: absurdly high "optimal_io_size" on Seagate SAS disk"
In reply to: Namhyung Kim: "[PATCH 2/3] perf symbol: Implement a very simple ELF symbol parser"
Next in thread: Namhyung Kim: "[PATCH 3/3] perf tools: Clean up libelf feature support code"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]