1. 根目录:
2. tools
3. perf
4. util
5. symbol-minimal.c

#include "symbol.h"

#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <byteswap.h>
#include <sys/stat.h>


static bool check_need_swap(int file_endian)
{
	const int data = 1;
	u8 *check = (u8 *)&data;
	int host_endian;

	if (check[0] == 1)
		host_endian = ELFDATA2LSB;
	else
		host_endian = ELFDATA2MSB;

	return host_endian != file_endian;
}

#define NOTE_ALIGN(sz) (((sz) + 3) & ~3)

#define NT_GNU_BUILD_ID	3

static int read_build_id(void *note_data, size_t note_len, void *bf,
			 size_t size, bool need_swap)
{
	struct {
		u32 n_namesz;
		u32 n_descsz;
		u32 n_type;
	} *nhdr;
	void *ptr;

	ptr = note_data;
	while (ptr < (note_data + note_len)) {
		const char *name;
		size_t namesz, descsz;

		nhdr = ptr;
		if (need_swap) {
			nhdr->n_namesz = bswap_32(nhdr->n_namesz);
			nhdr->n_descsz = bswap_32(nhdr->n_descsz);
			nhdr->n_type = bswap_32(nhdr->n_type);
		}

		namesz = NOTE_ALIGN(nhdr->n_namesz);
		descsz = NOTE_ALIGN(nhdr->n_descsz);

		ptr += sizeof(*nhdr);
		name = ptr;
		ptr += namesz;
		if (nhdr->n_type == NT_GNU_BUILD_ID &&
		    nhdr->n_namesz == sizeof("GNU")) {
			if (memcmp(name, "GNU", sizeof("GNU")) == 0) {
				size_t sz = min(size, descsz);
				memcpy(bf, ptr, sz);
				memset(bf + sz, 0, size - sz);
				return 0;
			}
		}
		ptr += descsz;
	}

	return -1;
}

int filename__read_debuglink(const char *filename __maybe_unused,
			     char *debuglink __maybe_unused,
			     size_t size __maybe_unused)
{
	return -1;
}

/*
 * Just try PT_NOTE header otherwise fails
 */
int filename__read_build_id(const char *filename, void *bf, size_t size)
{
	FILE *fp;
	int ret = -1;
	bool need_swap = false;
	u8 e_ident[EI_NIDENT];
	size_t buf_size;
	void *buf;
	int i;

	fp = fopen(filename, "r");
	if (fp == NULL)
		return -1;

	if (fread(e_ident, sizeof(e_ident), 1, fp) != 1)
		goto out;

	if (memcmp(e_ident, ELFMAG, SELFMAG) ||
	    e_ident[EI_VERSION] != EV_CURRENT)
		goto out;

	need_swap = check_need_swap(e_ident[EI_DATA]);

	/* for simplicity */
	fseek(fp, 0, SEEK_SET);

	if (e_ident[EI_CLASS] == ELFCLASS32) {
		Elf32_Ehdr ehdr;
		Elf32_Phdr *phdr;

		if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1)
			goto out;

		if (need_swap) {
			ehdr.e_phoff = bswap_32(ehdr.e_phoff);
			ehdr.e_phentsize = bswap_16(ehdr.e_phentsize);
			ehdr.e_phnum = bswap_16(ehdr.e_phnum);
		}

		buf_size = ehdr.e_phentsize * ehdr.e_phnum;
		buf = malloc(buf_size);
		if (buf == NULL)
			goto out;

		fseek(fp, ehdr.e_phoff, SEEK_SET);
		if (fread(buf, buf_size, 1, fp) != 1)
			goto out_free;

		for (i = 0, phdr = buf; i < ehdr.e_phnum; i++, phdr++) {
			void *tmp;

			if (need_swap) {
				phdr->p_type = bswap_32(phdr->p_type);
				phdr->p_offset = bswap_32(phdr->p_offset);
				phdr->p_filesz = bswap_32(phdr->p_filesz);
			}

			if (phdr->p_type != PT_NOTE)
				continue;

			buf_size = phdr->p_filesz;
			tmp = realloc(buf, buf_size);
			if (tmp == NULL)
				goto out_free;

			buf = tmp;
			fseek(fp, phdr->p_offset, SEEK_SET);
			if (fread(buf, buf_size, 1, fp) != 1)
				goto out_free;

			ret = read_build_id(buf, buf_size, bf, size, need_swap);
			if (ret == 0)
				ret = size;
			break;
		}
	} else {
		Elf64_Ehdr ehdr;
		Elf64_Phdr *phdr;

		if (fread(&ehdr, sizeof(ehdr), 1, fp) != 1)
			goto out;

		if (need_swap) {
			ehdr.e_phoff = bswap_64(ehdr.e_phoff);
			ehdr.e_phentsize = bswap_16(ehdr.e_phentsize);
			ehdr.e_phnum = bswap_16(ehdr.e_phnum);
		}

		buf_size = ehdr.e_phentsize * ehdr.e_phnum;
		buf = malloc(buf_size);
		if (buf == NULL)
			goto out;

		fseek(fp, ehdr.e_phoff, SEEK_SET);
		if (fread(buf, buf_size, 1, fp) != 1)
			goto out_free;

		for (i = 0, phdr = buf; i < ehdr.e_phnum; i++, phdr++) {
			void *tmp;

			if (need_swap) {
				phdr->p_type = bswap_32(phdr->p_type);
				phdr->p_offset = bswap_64(phdr->p_offset);
				phdr->p_filesz = bswap_64(phdr->p_filesz);
			}

			if (phdr->p_type != PT_NOTE)
				continue;

			buf_size = phdr->p_filesz;
			tmp = realloc(buf, buf_size);
			if (tmp == NULL)
				goto out_free;

			buf = tmp;
			fseek(fp, phdr->p_offset, SEEK_SET);
			if (fread(buf, buf_size, 1, fp) != 1)
				goto out_free;

			ret = read_build_id(buf, buf_size, bf, size, need_swap);
			if (ret == 0)
				ret = size;
			break;
		}
	}
out_free:
	free(buf);
out:
	fclose(fp);
	return ret;
}

int sysfs__read_build_id(const char *filename, void *build_id, size_t size)
{
	int fd;
	int ret = -1;
	struct stat stbuf;
	size_t buf_size;
	void *buf;

	fd = open(filename, O_RDONLY);
	if (fd < 0)
		return -1;

	if (fstat(fd, &stbuf) < 0)
		goto out;

	buf_size = stbuf.st_size;
	buf = malloc(buf_size);
	if (buf == NULL)
		goto out;

	if (read(fd, buf, buf_size) != (ssize_t) buf_size)
		goto out_free;

	ret = read_build_id(buf, buf_size, build_id, size, false);
out_free:
	free(buf);
out:
	close(fd);
	return ret;
}

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);
	if (fd < 0)
		return -1;

	ss->name = strdup(name);
	if (!ss->name)
		goto out_close;

	ss->type = type;

	return 0;
out_close:
	close(fd);
	return -1;
}

bool symsrc__possibly_runtime(struct symsrc *ss __maybe_unused)
{
	/* Assume all sym sources could be a runtime image. */
	return true;
}

bool symsrc__has_symtab(struct symsrc *ss __maybe_unused)
{
	return false;
}

void symsrc__destroy(struct symsrc *ss)
{
	free(ss->name);
	close(ss->fd);
}

int dso__synthesize_plt_symbols(struct dso *dso __maybe_unused,
				struct symsrc *ss __maybe_unused,
				struct map *map __maybe_unused,
				symbol_filter_t filter __maybe_unused)
{
	return 0;
}

int dso__load_sym(struct dso *dso, struct map *map __maybe_unused,
		  struct symsrc *ss,
		  struct symsrc *runtime_ss __maybe_unused,
		  symbol_filter_t filter __maybe_unused,
		  int kmodule __maybe_unused)
{
	unsigned char *build_id[BUILD_ID_SIZE];

	if (filename__read_build_id(ss->name, build_id, BUILD_ID_SIZE) > 0) {
		dso__set_build_id(dso, build_id);
		return 1;
	}
	return 0;
}

void symbol__elf_init(void)
{
}