elf.c revision 48519 
1#include <sys/types.h>
2#include <sys/mman.h>
3#include <sys/stat.h>
4
5#include <elf.h>
6#include <err.h>
7#include <fcntl.h>
8#include <string.h>
9#include <unistd.h>
10
11#include "gprof.h"
12
13static bool wantsym(const Elf_Sym *, const char *);
14
15/* Things which get -E excluded by default. */
16static char	*excludes[] = { ".mcount", "_mcleanup", NULL };
17
18int
19elf_getnfile(const char *filename, char ***defaultEs)
20{
21    int fd;
22    Elf_Ehdr h;
23    struct stat s;
24    void *mapbase;
25    const char *base;
26    const Elf_Shdr *shdrs;
27    const Elf_Shdr *sh_symtab;
28    const Elf_Shdr *sh_strtab;
29    const char *strtab;
30    const Elf_Sym *symtab;
31    int symtabct;
32    int i;
33
34    if ((fd = open(filename, O_RDONLY)) == -1)
35	err(1, "%s", filename);
36    if (read(fd, &h, sizeof h) != sizeof h || !IS_ELF(h)) {
37	close(fd);
38	return -1;
39    }
40    if (fstat(fd, &s) == -1)
41	err(1, "Cannot fstat %s", filename);
42    if ((mapbase = mmap(0, s.st_size, PROT_READ, MAP_SHARED, fd, 0)) ==
43      MAP_FAILED)
44	err(1, "Cannot mmap %s", filename);
45    close(fd);
46
47    base = (const char *)mapbase;
48    shdrs = (const Elf_Shdr *)(base + h.e_shoff);
49
50    /* Find the symbol table and associated string table section. */
51    for (i = 1;  i < h.e_shnum;  i++)
52	if (shdrs[i].sh_type == SHT_SYMTAB)
53	    break;
54    if (i == h.e_shnum)
55	errx(1, "%s has no symbol table", filename);
56    sh_symtab = &shdrs[i];
57    sh_strtab = &shdrs[sh_symtab->sh_link];
58
59    symtab = (const Elf_Sym *)(base + sh_symtab->sh_offset);
60    symtabct = sh_symtab->sh_size / sh_symtab->sh_entsize;
61    strtab = (const char *)(base + sh_strtab->sh_offset);
62
63    /* Count the symbols that we're interested in. */
64    nname = 0;
65    for (i = 1;  i < symtabct;  i++)
66	if (wantsym(&symtab[i], strtab))
67	    nname++;
68
69    /* Allocate memory for them, plus a terminating entry. */
70    if ((nl = (nltype *)calloc(nname + 1, sizeof(nltype))) == NULL)
71	errx(1, "Insufficient memory for symbol table");
72
73    /* Read them in. */
74    npe = nl;
75    for (i = 1;  i < symtabct;  i++) {
76	const Elf_Sym *sym = &symtab[i];
77
78	if (wantsym(sym, strtab)) {
79	    npe->value = sym->st_value;
80	    npe->name = strtab + sym->st_name;
81	    npe++;
82	}
83    }
84    npe->value = -1;
85
86    *defaultEs = excludes;
87    return 0;
88}
89
90static bool
91wantsym(const Elf_Sym *sym, const char *strtab)
92{
93    int type;
94    int bind;
95
96    type = ELF_ST_TYPE(sym->st_info);
97    bind = ELF_ST_BIND(sym->st_info);
98
99    if (type != STT_FUNC ||
100      (aflag && bind == STB_LOCAL) ||
101      (uflag && strchr(strtab + sym->st_name, '.') != NULL))
102	return 0;
103
104    return 1;
105}
106