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authorElliott Hughes <enh@google.com>2016-07-02 12:53:40 -0700
committerRob Landley <rob@landley.net>2016-07-03 22:12:30 -0500
commitc5e7ee27f606ed0bdb20d54e9de1a4adb56fc5d3 (patch)
treebc6334757d07e40a8beb4537cfcb7e1871adb92a /toys/pending/file.c
parent746e565c097ed311ebb65842ac8a6527535993a7 (diff)
downloadtoybox-c5e7ee27f606ed0bdb20d54e9de1a4adb56fc5d3.tar.gz
Improve file(1)'s ELF support.
Read any PT_NOTE sections to look for NT_GNU_BUILD_ID or Android API level notes. I deliberately didn't NT_GNU_ABI_TAG because it's noisy -- every Linux executable has one -- but not something most command-line users will have any use for. (And you can ask readelf(1) anyway.) Also read the section headers to implement "stripped"/"not stripped". This patch removes "uses %d libs" because it was actually just counting dynamic sections in the ELF file, and there are only 0 or 1 of those in a valid ELF flie. (If you really want this functionality, you have to *parse* the dynamic section looking for the DT_NEEDED entries. But that's more of a job for readelf(1) than file(1).)
Diffstat (limited to 'toys/pending/file.c')
-rw-r--r--toys/pending/file.c125
1 files changed, 82 insertions, 43 deletions
diff --git a/toys/pending/file.c b/toys/pending/file.c
index 18941227..b53bec0a 100644
--- a/toys/pending/file.c
+++ b/toys/pending/file.c
@@ -26,7 +26,7 @@ GLOBALS(
// We don't trust elf.h to be there, and two codepaths for 32/64 is awkward
// anyway, so calculate struct offsets manually. (It's a fixed ABI.)
-static void do_elf_file(int fd)
+static void do_elf_file(int fd, struct stat *sb)
{
int endian = toybuf[5], bits = toybuf[4], i, j;
int64_t (*elf_int)(void *ptr, unsigned size) = peek_le;
@@ -45,6 +45,11 @@ static void do_elf_file(int fd)
{191, "tilegx"}, {3, "386"}, {6, "486"}, {62, "x86-64"}, {94, "xtensa"},
{0xabc7, "xtensa-old"}
};
+ int dynamic = 0;
+ int stripped = 1;
+ char *map;
+ off_t phoff, shoff;
+ int phsize, phnum, shsize, shnum;
printf("ELF ");
@@ -82,53 +87,87 @@ static void do_elf_file(int fd)
else printf("(unknown arch %d)", j);
bits--;
- // If we know our bits and endianness and phentsize agrees show dynamic linker
- if ((bits&1)==bits && endian &&
- (i = elf_int(toybuf+42+12*bits, 2)) == 32+24*bits)
- {
- char *map, *phdr;
- int phsize = i, phnum = elf_int(toybuf+44+12*bits, 2),
- psz = sysconf(_SC_PAGE_SIZE), lib = 0;
- off_t phoff = elf_int(toybuf+28+4*bits, 4+4*bits),
- mapoff = phoff^(phoff&(psz-1));
-
- // map e_phentsize*e_phnum bytes at e_phoff
- map = mmap(0, phsize*phnum, PROT_READ, MAP_SHARED, fd, mapoff);
- if (map) {
- // Find PT_INTERP entry. (Note: fields got reordered for 64 bit)
- for (i = 0; i<phnum; i++) {
- long long dlpos, dllen;
-
- // skip non-PT_INTERP entries
- j = elf_int(phdr = map+(phoff-mapoff)+i*phsize, 4);
- if (j==2) lib++;
- if (j!=3) continue;
-
- // Read p_offset and p_filesz
- j = bits+1;
- dlpos = elf_int(phdr+4*j, 4*j);
- dllen = elf_int(phdr+16*j, 4*j);
- if (dllen<0 || dllen>sizeof(toybuf)-128
- || dlpos!=lseek(fd, dlpos, SEEK_SET)
- || dllen!=readall(fd, toybuf+128, dllen)) break;
- printf(", dynamic (%.*s", (int)dllen, toybuf+128);
+ // If what we've seen so far doesn't seem consistent, bail.
+ if (!((bits&1)==bits && endian &&
+ (i = elf_int(toybuf+42+12*bits, 2)) == 32+24*bits)) {
+ printf(", corrupt?\n");
+ return;
+ }
+
+ // Stash what we need from the header; it's okay to reuse toybuf after this.
+ phsize = i;
+ phnum = elf_int(toybuf+44+12*bits, 2);
+ phoff = elf_int(toybuf+28+4*bits, 4+4*bits);
+ shsize = elf_int(toybuf+46+12*bits, 2);
+ shnum = elf_int(toybuf+48+12*bits, 2);
+ shoff = elf_int(toybuf+32+8*bits, 4+4*bits);
+
+ map = mmap(0, sb->st_size, PROT_READ, MAP_SHARED, fd, 0);
+ if (!map) perror_exit("mmap");
+
+ // We need to read the phdrs for dynamic vs static and any notes.
+ // (Note: fields got reordered for 64 bit)
+ for (i = 0; i<phnum; i++) {
+ char *phdr = map+phoff+i*phsize;
+ int p_type = elf_int(phdr, 4);
+ long long p_offset, p_filesz;
+
+ if (p_type==2 /*PT_DYNAMIC*/) dynamic = 1;
+ if (p_type!=3 /*PT_INTERP*/ && p_type!=4 /*PT_NOTE*/) continue;
+
+ j = bits+1;
+ p_offset = elf_int(phdr+4*j, 4*j);
+ p_filesz = elf_int(phdr+16*j, 4*j);
+
+ if (p_type==3 /*PT_INTERP*/)
+ printf(", dynamic (%.*s)", (int)p_filesz, map+p_offset);
+ else {
+ char *note = map+p_offset;
+
+ // A PT_NOTE phdr is a sequence of entries, each consisting of an
+ // ndhr followed by n_namesz+n_descsz bytes of data (each of those
+ // rounded up to the next 4 bytes, without this being reflected in
+ // the header byte counts themselves).
+ while (p_filesz >= 3*4) { // Don't try to read a truncated entry.
+ int n_namesz = elf_int(note, 4);
+ int n_descsz = elf_int(note+4, 4);
+ int n_type = elf_int(note+8, 4);
+ int notesz = 3*4 + ((n_namesz+3)&~3) + ((n_descsz+3)&~3);
+
+ if (n_namesz==4 && !memcmp(note+12, "GNU", 4)) {
+ if (n_type == 3 /*NT_GNU_BUILD_ID*/) {
+ printf(", BuildID[%s]=", (n_descsz==20)?"sha1":"md5");
+ for (j = 0; j < n_descsz; ++j) printf("%02x", note[16 + j]);
+ }
+ } else if (n_namesz==8 && !memcmp(note+12, "Android", 8)) {
+ if (n_type==1) printf(", for Android %d", (int)elf_int(note+20, 4));
+ }
+
+ note += notesz;
+ p_filesz -= notesz;
}
- if (!lib) printf(", static");
- else printf(" loads %d lib%s)", lib, lib>1 ? "s" : "");
- munmap(map, phsize*phnum);
}
}
+ if (!dynamic) printf(", static");
- // TODO: we'd need to actually parse the ELF file to report the rest...
- // ", dynamically linked"
- // " (uses shared libs)"
- // ", for Linux 2.6.24"
- // ", BuildID[sha1]=SHA"
- // ", stripped"
+ // We need to read the shdrs for stripped/unstripped.
+ // (Note: fields got reordered for 64 bit)
+ for (i = 0; i<shnum; i++) {
+ char *shdr = map+shoff+i*shsize;
+ int sh_type = elf_int(shdr+4, 4);
+
+ if (sh_type == 2 /*SHT_SYMTAB*/) {
+ stripped = 0;
+ break;
+ }
+ }
+ printf(", %sstripped", stripped ? "" : "not ");
xputc('\n');
+
+ munmap(map, sb->st_size);
}
-static void do_regular_file(int fd, char *name)
+static void do_regular_file(int fd, char *name, struct stat *sb)
{
char *s;
int len = read(fd, s = toybuf, sizeof(toybuf)-256);
@@ -136,7 +175,7 @@ static void do_regular_file(int fd, char *name)
if (len<0) perror_msg("%s", name);
- if (len>40 && strstart(&s, "\177ELF")) do_elf_file(fd);
+ if (len>40 && strstart(&s, "\177ELF")) do_elf_file(fd, sb);
else if (len>28 && strstart(&s, "\x89PNG\x0d\x0a\x1a\x0a")) {
// PNG is big-endian: https://www.w3.org/TR/PNG/#7Integers-and-byte-order
int chunk_length = peek_be(s, 4);
@@ -252,7 +291,7 @@ void file_main(void)
if (fd!=-1) {
if (!sb.st_size) what = "empty";
- else do_regular_file(fd, name);
+ else do_regular_file(fd, name, &sb);
if (fd) close(fd);
if (sb.st_size) continue;
}