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SubjectRe: [PATCH 19/28] ktap: add userspace/symbol.[c|h]
(2014/03/28 22:47), Jovi Zhangwei wrote:
> This file is use for uprobe(include SDT) symbol lookup,
> for example:
>
> trace probe:/lib64/libc.so.6:malloc {
> print("malloc entry:", execname)
> }
>
> trace sdt:/lib64/libc.so.6:* {
> print(execname, argstr)
> }
>
> It need libelf library support.

Hmm, I think I should support this in perf-probe too...

Thank you,

>
> Signed-off-by: Jovi Zhangwei <jovi.zhangwei@gmail.com>
> ---
> tools/ktap/userspace/kp_symbol.c | 360 +++++++++++++++++++++++++++++++++++++++
> tools/ktap/userspace/kp_symbol.h | 50 ++++++
> 2 files changed, 410 insertions(+)
> create mode 100644 tools/ktap/userspace/kp_symbol.c
> create mode 100644 tools/ktap/userspace/kp_symbol.h
>
> diff --git a/tools/ktap/userspace/kp_symbol.c b/tools/ktap/userspace/kp_symbol.c
> new file mode 100644
> index 0000000..59f8b5e
> --- /dev/null
> +++ b/tools/ktap/userspace/kp_symbol.c
> @@ -0,0 +1,360 @@
> +/*
> + * symbol.c
> + *
> + * This file is part of ktap by Jovi Zhangwei.
> + *
> + * Copyright (C) 2013 Azat Khuzhin <a3at.mail@gmail.com>.
> + *
> + * ktap is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * ktap is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
> + */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <unistd.h>
> +#include <fcntl.h>
> +#include <string.h>
> +#include <linux/limits.h>
> +
> +#include <libelf.h>
> +
> +#include "../include/ktap_types.h"
> +#include "kp_symbol.h"
> +
> +const char *dbg_link_name = ".gnu_debuglink";
> +const char *dbg_bin_dir = "/usr/lib/debug";
> +
> +static Elf_Scn *elf_section_by_name(Elf *elf, GElf_Ehdr *ep,
> + GElf_Shdr *shp, const char *name)
> +{
> + Elf_Scn *scn = NULL;
> +
> + /* Elf is corrupted/truncated, avoid calling elf_strptr. */
> + if (!elf_rawdata(elf_getscn(elf, ep->e_shstrndx), NULL))
> + return NULL;
> +
> + while ((scn = elf_nextscn(elf, scn)) != NULL) {
> + char *str;
> +
> + gelf_getshdr(scn, shp);
> + str = elf_strptr(elf, ep->e_shstrndx, shp->sh_name);
> + if (!strcmp(name, str))
> + break;
> + }
> +
> + return scn;
> +}
> +
> +/**
> + * @return v_addr of "LOAD" program header, that have zero offset.
> + */
> +static int find_load_address(Elf *elf, vaddr_t *load_address)
> +{
> + GElf_Phdr phdr;
> + size_t i, phdrnum;
> +
> + if (elf_getphdrnum(elf, &phdrnum))
> + return -1;
> +
> + for (i = 0; i < phdrnum; i++) {
> + if (gelf_getphdr(elf, i, &phdr) == NULL)
> + return -1;
> +
> + if (phdr.p_type != PT_LOAD || phdr.p_offset != 0)
> + continue;
> +
> + *load_address = phdr.p_vaddr;
> + return 0;
> + }
> +
> + /* cannot found load address */
> + return -1;
> +}
> +
> +static size_t elf_symbols(GElf_Shdr shdr)
> +{
> + return shdr.sh_size / shdr.sh_entsize;
> +}
> +
> +static int dso_symbols(Elf *elf, symbol_actor actor, void *arg)
> +{
> + Elf_Data *elf_data = NULL;
> + Elf_Scn *scn = NULL;
> + GElf_Sym sym;
> + GElf_Shdr shdr;
> + int symbols_count = 0;
> + vaddr_t load_address;
> +
> + if (find_load_address(elf, &load_address))
> + return -1;
> +
> + while ((scn = elf_nextscn(elf, scn))) {
> + int i;
> +
> + gelf_getshdr(scn, &shdr);
> +
> + if (shdr.sh_type != SHT_SYMTAB)
> + continue;
> +
> + elf_data = elf_getdata(scn, elf_data);
> +
> + for (i = 0; i < elf_symbols(shdr); i++) {
> + char *name;
> + vaddr_t addr;
> + int ret;
> +
> + gelf_getsym(elf_data, i, &sym);
> +
> + if (GELF_ST_TYPE(sym.st_info) != STT_FUNC)
> + continue;
> +
> + name = elf_strptr(elf, shdr.sh_link, sym.st_name);
> + addr = sym.st_value - load_address;
> +
> + ret = actor(name, addr, arg);
> + if (ret)
> + return ret;
> +
> + ++symbols_count;
> + }
> + }
> +
> + return symbols_count;
> +}
> +
> +#define SDT_NOTE_TYPE 3
> +#define SDT_NOTE_COUNT 3
> +#define SDT_NOTE_SCN ".note.stapsdt"
> +#define SDT_NOTE_NAME "stapsdt"
> +
> +static vaddr_t sdt_note_addr(Elf *elf, const char *data, size_t len, int type)
> +{
> + vaddr_t vaddr;
> +
> + /*
> + * Three addresses need to be obtained :
> + * Marker location, address of base section and semaphore location
> + */
> + union {
> + Elf64_Addr a64[3];
> + Elf32_Addr a32[3];
> + } buf;
> +
> + /*
> + * dst and src are required for translation from file to memory
> + * representation
> + */
> + Elf_Data dst = {
> + .d_buf = &buf, .d_type = ELF_T_ADDR, .d_version = EV_CURRENT,
> + .d_size = gelf_fsize(elf, ELF_T_ADDR, SDT_NOTE_COUNT, EV_CURRENT),
> + .d_off = 0, .d_align = 0
> + };
> +
> + Elf_Data src = {
> + .d_buf = (void *) data, .d_type = ELF_T_ADDR,
> + .d_version = EV_CURRENT, .d_size = dst.d_size, .d_off = 0,
> + .d_align = 0
> + };
> +
> + /* Check the type of each of the notes */
> + if (type != SDT_NOTE_TYPE)
> + return 0;
> +
> + if (len < dst.d_size + SDT_NOTE_COUNT)
> + return 0;
> +
> + /* Translation from file representation to memory representation */
> + if (gelf_xlatetom(elf, &dst, &src,
> + elf_getident(elf, NULL)[EI_DATA]) == NULL)
> + return 0; /* TODO */
> +
> + memcpy(&vaddr, &buf, sizeof(vaddr));
> +
> + return vaddr;
> +}
> +
> +static const char *sdt_note_name(Elf *elf, GElf_Nhdr *nhdr, const char *data)
> +{
> + const char *provider = data + gelf_fsize(elf,
> + ELF_T_ADDR, SDT_NOTE_COUNT, EV_CURRENT);
> + const char *name = (const char *)memchr(provider, '\0',
> + data + nhdr->n_descsz - provider);
> +
> + if (name++ == NULL)
> + return NULL;
> +
> + return name;
> +}
> +
> +static const char *sdt_note_data(const Elf_Data *data, size_t off)
> +{
> + return ((data->d_buf) + off);
> +}
> +
> +static int dso_sdt_notes(Elf *elf, symbol_actor actor, void *arg)
> +{
> + GElf_Ehdr ehdr;
> + Elf_Scn *scn = NULL;
> + Elf_Data *data;
> + GElf_Shdr shdr;
> + size_t shstrndx;
> + size_t next;
> + GElf_Nhdr nhdr;
> + size_t name_off, desc_off, offset;
> + vaddr_t vaddr = 0;
> + int symbols_count = 0;
> +
> + if (gelf_getehdr(elf, &ehdr) == NULL)
> + return 0;
> + if (elf_getshdrstrndx(elf, &shstrndx) != 0)
> + return 0;
> +
> + /*
> + * Look for section type = SHT_NOTE, flags = no SHF_ALLOC
> + * and name = .note.stapsdt
> + */
> + scn = elf_section_by_name(elf, &ehdr, &shdr, SDT_NOTE_SCN);
> + if (!scn)
> + return 0;
> + if (!(shdr.sh_type == SHT_NOTE) || (shdr.sh_flags & SHF_ALLOC))
> + return 0;
> +
> + data = elf_getdata(scn, NULL);
> +
> + for (offset = 0;
> + (next = gelf_getnote(data, offset, &nhdr, &name_off, &desc_off)) > 0;
> + offset = next) {
> + const char *name;
> + int ret;
> +
> + if (nhdr.n_namesz != sizeof(SDT_NOTE_NAME) ||
> + memcmp(data->d_buf + name_off, SDT_NOTE_NAME,
> + sizeof(SDT_NOTE_NAME)))
> + continue;
> +
> + name = sdt_note_name(elf, &nhdr, sdt_note_data(data, desc_off));
> + if (!name)
> + continue;
> +
> + vaddr = sdt_note_addr(elf, sdt_note_data(data, desc_off),
> + nhdr.n_descsz, nhdr.n_type);
> + if (!vaddr)
> + continue;
> +
> + ret = actor(name, vaddr, arg);
> + if (ret)
> + return ret;
> +
> + ++symbols_count;
> + }
> +
> + return symbols_count;
> +}
> +
> +int dso_follow_debuglink(Elf *elf,
> + const char *orig_exec,
> + int type,
> + symbol_actor actor,
> + void *arg)
> +{
> + GElf_Ehdr ehdr;
> + size_t shstrndx, orig_exec_dir_len;
> + GElf_Shdr shdr;
> + Elf_Scn *dbg_link_scn;
> + Elf_Data *dbg_link_scn_data;
> + char *dbg_link, *dbg_bin, *last_slash;
> + int symbols_count;
> +
> + /* First try to find the .gnu_debuglink section in the binary. */
> + if (gelf_getehdr(elf, &ehdr) == NULL)
> + return 0;
> + if (elf_getshdrstrndx(elf, &shstrndx) != 0)
> + return 0;
> +
> + dbg_link_scn = elf_section_by_name(elf, &ehdr, &shdr, dbg_link_name);
> + if (dbg_link_scn == NULL)
> + return 0;
> +
> + /* Debug link section found, read of the content (only get the first
> + string, no checksum checking atm). This is debug binary file name. */
> + dbg_link_scn_data = elf_getdata(dbg_link_scn, NULL);
> + if (dbg_link_scn_data == NULL ||
> + dbg_link_scn_data->d_size <= 0 ||
> + dbg_link_scn_data->d_buf == NULL)
> + return 0;
> +
> + /* Now compose debug executable name */
> + dbg_link = (char *)(dbg_link_scn_data->d_buf);
> + dbg_bin = malloc(strlen(dbg_bin_dir) + 1 +
> + strlen(orig_exec) + 1 +
> + strlen(dbg_link) + 1);
> + if (!dbg_bin)
> + return 0;
> +
> + orig_exec_dir_len = PATH_MAX;
> + last_slash = strrchr(orig_exec, '/');
> + if (last_slash != NULL)
> + orig_exec_dir_len = last_slash - orig_exec;
> +
> + sprintf(dbg_bin, "%s/%.*s/%s",
> + dbg_bin_dir, (int)orig_exec_dir_len, orig_exec, dbg_link);
> +
> + /* Retry symbol seach with the debug binary */
> + symbols_count = parse_dso_symbols(dbg_bin, type, actor, arg);
> +
> + free(dbg_bin);
> +
> + return symbols_count;
> +}
> +
> +int parse_dso_symbols(const char *exec, int type, symbol_actor actor, void *arg)
> +{
> + int symbols_count = 0;
> + Elf *elf;
> + int fd;
> +
> + if (elf_version(EV_CURRENT) == EV_NONE)
> + return -1;
> +
> + fd = open(exec, O_RDONLY);
> + if (fd < 0)
> + return -1;
> +
> + elf = elf_begin(fd, ELF_C_READ, NULL);
> + if (elf) {
> + switch (type) {
> + case FIND_SYMBOL:
> + symbols_count = dso_symbols(elf, actor, arg);
> + if (symbols_count != 0)
> + break;
> + /* If no symbols found, try in the debuglink binary. */
> + symbols_count = dso_follow_debuglink(elf,
> + exec,
> + type,
> + actor,
> + arg);
> + break;
> + case FIND_STAPSDT_NOTE:
> + symbols_count = dso_sdt_notes(elf, actor, arg);
> + break;
> + }
> +
> + elf_end(elf);
> + }
> +
> + close(fd);
> + return symbols_count;
> +}
> diff --git a/tools/ktap/userspace/kp_symbol.h b/tools/ktap/userspace/kp_symbol.h
> new file mode 100644
> index 0000000..650e785
> --- /dev/null
> +++ b/tools/ktap/userspace/kp_symbol.h
> @@ -0,0 +1,50 @@
> +/*
> + * symbol.h - extract symbols from DSO.
> + *
> + * This file is part of ktap by Jovi Zhangwei.
> + *
> + * Copyright (C) 2013 Azat Khuzhin <a3at.mail@gmail.com>.
> + *
> + * ktap is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * ktap is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
> + */
> +
> +
> +#define FIND_SYMBOL 1
> +#define FIND_STAPSDT_NOTE 2
> +
> +#ifndef NO_LIBELF
> +
> +#include <gelf.h>
> +#include <sys/queue.h>
> +
> +typedef GElf_Addr vaddr_t;
> +typedef int (*symbol_actor)(const char *name, vaddr_t addr, void *arg);
> +
> +/**
> + * Parse all DSO symbols/sdt notes and all for every of them
> + * an actor.
> + *
> + * @exec - path to DSO
> + * @type - see FIND_*
> + * @symbol_actor - actor to call (callback)
> + * @arg - argument for @actor
> + *
> + * @return
> + * If there have errors, return negative value;
> + * No symbols found, return 0;
> + * Otherwise return number of dso symbols found
> + */
> +int
> +parse_dso_symbols(const char *exec, int type, symbol_actor actor, void *arg);
> +#endif
>


--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com




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