xref: /freebsd/usr.bin/gprof/elf.c (revision 7f3dea244c40159a41ab22da77a434d7c5b5e85a)
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 
13 static bool wantsym(const Elf_Sym *, const char *);
14 
15 /* Things which get -E excluded by default. */
16 static char	*excludes[] = { ".mcount", "_mcleanup", NULL };
17 
18 int
19 elf_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 
90 static bool
91 wantsym(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