1 files changed, 39 insertions, 26 deletions

diff --git a/toys/posix/file.c b/toys/posix/file.c
index 4827f8f5..bab59e57 100644
--- a/toys/posix/file.c
+++ b/toys/posix/file.c
@@ -50,7 +50,7 @@ static void do_elf_file(int fd, struct stat *sb)
   int stripped = 1;
   char *map;
   off_t phoff, shoff;
-  int phsize, phnum, shsize, shnum;
+  int phentsize, phnum, shsize, shnum;
 
   printf("ELF ");
 
@@ -89,27 +89,33 @@ static void do_elf_file(int fd, struct stat *sb)
 
   bits--;
   // 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)) {
+  if (!((bits&1)==bits && endian)) {
     printf(", corrupt?\n");
     return;
   }
 
   // Stash what we need from the header; it's okay to reuse toybuf after this.
-  phsize = i;
+  phentsize = elf_int(toybuf+42+12*bits, 2);
   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);
 
+  // With binutils, phentsize seems to only be non-zero if phnum is non-zero.
+  // Such ELF files are rare, but do exist. (Android's crtbegin files, say.)
+  if (phnum && (phentsize != 32+24*bits)) {
+    printf(", corrupt phentsize %d?\n", phentsize);
+    return;
+  }
+
   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.
+  // We need to read the phdrs for dynamic vs static.
   // (Note: fields got reordered for 64 bit)
   for (i = 0; i<phnum; i++) {
-    char *phdr = map+phoff+i*phsize;
+    char *phdr = map+phoff+i*phentsize;
     int p_type = elf_int(phdr, 4);
     long long p_offset, p_filesz;
 
@@ -122,46 +128,53 @@ static void do_elf_file(int fd, struct stat *sb)
 
     if (p_type==3 /*PT_INTERP*/)
       printf(", dynamic (%.*s)", (int)p_filesz, map+p_offset);
-    else {
-      char *note = map+p_offset;
+  }
+  if (!dynamic) printf(", static");
+
+  // We need to read the shdrs for stripped/unstripped and any notes.
+  // Notes are in program headers *and* section headers, but some files don't
+  // contain program headers, so we prefer to check here.
+  // (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);
+    long sh_offset = elf_int(shdr+8+8*(bits+1), 4*(bits+1));
+    int sh_size = elf_int(shdr+8+12*(bits+1), 4);
+
+    if (sh_type == 2 /*SHT_SYMTAB*/) {
+      stripped = 0;
+      break;
+    } else if (sh_type == 7 /*SHT_NOTE*/) {
+      char *note = map+sh_offset;
 
-      // A PT_NOTE phdr is a sequence of entries, each consisting of an
+      // An ELF note 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.
+      while (sh_size >= 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*/) {
+          if (n_type==3 /*NT_GNU_BUILD_ID*/) {
             printf(", BuildID=");
             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));
+          if (n_type==1 /*.android.note.ident*/) {
+            printf(", for Android %d", (int)elf_int(note+20, 4));
+            if (n_descsz > 24)
+              printf(", built by NDK %.64s (%.64s)", note+24, note+24+64);
+          }
         }
 
         note += notesz;
-        p_filesz -= notesz;
+        sh_size -= notesz;
       }
     }
   }
-  if (!dynamic) printf(", static");
-
-  // 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');