Adds tls_edit utility which patches irt_core.nexe's TLS usage.

src/untrusted/irt/tls_edit.c

+#include <errno.h>

[Roland McGrath, 2014/01/24 18:50:49]

Needs copyright header at top.

+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#include "native_client/src/include/elf32.h"
+#include "native_client/src/include/elf64.h"
+#include "native_client/src/include/arm_sandbox.h"
+#include "native_client/src/include/portability.h"
+#include "native_client/src/trusted/validator_ragel/validator.h"
+
+#ifndef O_BINARY
+# define O_BINARY 0
+#endif
+
+static void *g_contents;
+static size_t g_contents_size;
+static uint8_t *g_code_start;
+static Elf32_Addr g_code_addr;
+static int g_errors;
+static int g_changes;
+
+static void ReportError(const void *insn, const char *message) {
+  Elf32_Addr insn_addr = (Elf32_Addr) ((uint8_t *) insn - g_code_start) +
+                         g_code_addr;
+
+  fprintf(stderr, "%#x: %s\n", (unsigned int) insn_addr, message);
+  ++g_errors;
+}
+
+static void EditArmCode(void *code, size_t code_length) {
+  Elf32_Word *const words = code;
+  Elf32_Word *const end = (void *) ((uint8_t *) code + code_length);
+  Elf32_Word *insn;
+
+  for (insn = words; insn < end; ++insn) {
+    if (*insn == NACL_INSTR_ARM_LITERAL_POOL_HEAD) {
+      if ((insn - words) % 4 != 0) {
+        ReportError(insn, "Roadblock not at start of bundle");
+      } else {
+        /*
+         * Ignore the rest of this bundle.
+         */
+        insn += 3;
+      }
+    } else if ((*insn & 0x0FFF0FFF) == 0x05990000) {
+      /*
+       * This is 'ldr REG, [r9, #0]'.
+       * Turn it into 'ldr REG, [r9, #4]'.
+       */
+      *insn |= 4;
+      ++g_changes;
+    }
+  }
+}
+
+static Bool ConsiderOneInsn(const uint8_t *insn_begin, const uint8_t *insn_end,
+                            uint32_t validation_info, void *data) {
+  UNREFERENCED_PARAMETER(data);
+  if (insn_begin[0] == 0x65) {  /* GS prefix */
+    if (insn_end - insn_begin < 6) {
+      ReportError(insn_begin, "Unexpected GS prefix");
+    } else if (insn_end[-1] != 0 || insn_end[-2] != 0 ||
+               insn_end[-3] != 0 || insn_end[-4] != 0) {
+      ReportError(insn_begin, "Unexpected %gs address");
+    } else {
+      /*
+       * This is 'something %gs:0'.
+       * Turn it into 'something %gs:4'.
+       */
+      ((uint8_t *) insn_end)[-4] = 4;
+      ++g_changes;
+    }
+  }
+
+  return (validation_info & (VALIDATION_ERRORS_MASK | BAD_JUMP_TARGET)) == 0;
+}
+
+static void EditX86_32Code(void *code, size_t code_length) {
+  const NaClCPUFeaturesX86* cpu_features = &kFullCPUIDFeatures;
+  if (!ValidateChunkIA32(code, code_length,
+                         CALL_USER_CALLBACK_ON_EACH_INSTRUCTION,
+                         cpu_features, &ConsiderOneInsn, NULL))
+    ReportError(code, "Validation failed");
+}
+
+static void ReadInput(const char *filename) {
+  struct stat st;
+  FILE *fp = fopen(filename, "rb");
+  if (fp == NULL) {
+    fprintf(stderr, "open: %s: %s\n",

[Roland McGrath, 2014/01/24 18:50:49]

Say fopen in the message since that's what you called.

+            filename, strerror(errno));
+    exit(1);
+  }
+
+  if (fstat(fileno(fp), &st) < 0) {
+    fprintf(stderr, "fstat: %s: %s\n",
+            filename, strerror(errno));
+    exit(1);
+  }
+
+  g_contents_size = st.st_size;
+  g_contents = malloc(g_contents_size);
+  if (g_contents == NULL) {
+    fprintf(stderr, "Cannot allocate %u bytes: %s\n",
+            (unsigned int) st.st_size, strerror(errno));
+    exit(1);
+  }
+
+  {
+    size_t read_bytes = fread(g_contents, 1, g_contents_size, fp);
+    if (read_bytes != g_contents_size) {
+      int error_num = ferror(fp);

[Roland McGrath, 2014/01/24 18:50:49]

ferror and feof return a Boolean value, not an errno code.
If ferror returns true, then use strerror(errno) in the message.
If feof returns true, just say "premature EOF" and there is no associated errno
value.

+      int eof_error = feof(fp);
+      if (error_num) {
+        fprintf(stderr, "read: %s: %s\n",

[Roland McGrath, 2014/01/24 18:50:49]

Say fread in the messages since that's what you called.

+                filename, strerror(error_num));
+      } else if (eof_error) {
+        fprintf(stderr, "read: %s: premature EOF: %s\n",
+                filename, strerror(eof_error));
+      } else {
+        fprintf(stderr, "read: %s: unknown error\n",
+                filename);
+      }
+      exit(1);
+    }
+  }
+
+  fclose(fp);
+}
+
+static void WriteOutput(const char *filename) {
+  FILE *fp = fopen(filename, "wb+");
+  if (fp == NULL) {
+    fprintf(stderr, "open: %s: %s\n", filename, strerror(errno));
+    exit(1);
+  }
+
+  {
+    size_t nwrote = fwrite(g_contents, 1, g_contents_size, fp);
+    if (nwrote != g_contents_size) {
+      fprintf(stderr, "write: %s: %s\n", filename, strerror(errno));
+      exit(1);
+    }
+  }
+
+  fclose(fp);
+}
+
+static Bool Process32BitFile(const char* infile)

[Roland McGrath, 2014/01/24 18:50:49]

brace on end of decl line

[Roland McGrath, 2014/01/24 18:50:49]

'const char *infile'.  This is C, not C++.

+{
+  const Elf32_Ehdr *ehdr;
+  const Elf32_Phdr *phdr;
+  size_t code_length;
+  int i;
+
+  ehdr = g_contents;
+  if (ehdr->e_phoff > g_contents_size) {
+    fprintf(stderr, "%s: bogus e_phoff\n",
+            infile);
+    return FALSE;
+  }
+  if (ehdr->e_ident[EI_CLASS] != ELFCLASS32) {
+    fprintf(stderr, "%s: not an ELFCLASS32 file\n",
+            infile);
+    return FALSE;
+  }
+  if (ehdr->e_phentsize != sizeof(Elf32_Phdr)) {
+    fprintf(stderr, "%s: wrong e_phentsize: %u\n",
+            infile, ehdr->e_phentsize);
+    return FALSE;
+  }
+  if (g_contents_size - ehdr->e_phoff < ehdr->e_phnum * sizeof(Elf32_Phdr)) {
+    fprintf(stderr, "%s: bogus elf32 e_phnum\n",
+            infile);
+    return FALSE;
+  }
+
+  if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB) {
+    fprintf(stderr, "%s: not an ELFDATA2LSB file\n",
+            infile);
+    return FALSE;
+  }
+
+  phdr = (const void *) ((uint8_t *) g_contents + ehdr->e_phoff);
+  for (i = 0; i < ehdr->e_phnum; ++i) {
+    if (phdr[i].p_type == PT_LOAD && (phdr[i].p_flags & PF_X) != 0)
+      break;
+    }
+  if (i == ehdr->e_phnum) {
+    fprintf(stderr, "%s: Could not find executable load segment!\n",
+            infile);
+    return FALSE;
+  }
+
+  if (phdr[i].p_offset > g_contents_size ||

[Roland McGrath, 2014/01/24 18:50:49]

Don't repeat all this logic in the 32/64 variants.
Just call a common function with the values of p_offset, p_filesz, p_vaddr,
e_machine.

+      g_contents_size - phdr[i].p_offset < phdr[i].p_filesz) {
+    fprintf(stderr, "%s: Program header %d has invalid offset or size!\n",
+            infile, i);
+    return FALSE;
+  }
+
+  g_code_addr = phdr[i].p_vaddr;
+  g_code_start = (uint8_t *) g_contents + phdr[i].p_offset;
+  code_length = phdr[i].p_filesz;
+
+  switch (ehdr->e_machine) {
+    case EM_ARM:
+      EditArmCode(g_code_start, code_length);
+      break;
+    case EM_386:
+      EditX86_32Code(g_code_start, code_length);
+      break;
+    default:
+      fprintf(stderr, "%s: Unsupported e_machine %d\n",
+              infile, ehdr->e_machine);
+      return FALSE;
+  }
+
+  if (g_changes == 0) {
+    fprintf(stderr, "%s: Found no changes to make!\n",
+            infile);
+    return FALSE;
+  } else {
+    printf("%s: %d instructions changed\n",
+           infile, g_changes);
+  }
+
+  return TRUE;
+}
+
+static Bool Process64BitFile(const char* infile)

[Roland McGrath, 2014/01/24 18:50:49]

brace at end of decl line

+{
+  const Elf64_Ehdr *ehdr;
+
+  ehdr = g_contents;
+  if (ehdr->e_phoff > g_contents_size) {
+    fprintf(stderr, "%s: bogus e_phoff\n",
+            infile);
+    return FALSE;
+  }
+  if (ehdr->e_ident[EI_CLASS] != ELFCLASS64) {
+    fprintf(stderr, "%s: not an ELFCLASS64 file\n",
+            infile);
+    return FALSE;
+  }
+  if (ehdr->e_phentsize != sizeof(Elf64_Phdr)) {
+    fprintf(stderr, "%s: wrong e_phentsize: %u\n",
+            infile, ehdr->e_phentsize);
+    return FALSE;
+  }
+  if (g_contents_size - ehdr->e_phoff < ehdr->e_phnum * sizeof(Elf64_Phdr)) {
+    fprintf(stderr, "%s: bogus elf64 e_phnum\n",
+            infile);
+    return FALSE;
+  }
+
+  if (ehdr->e_ident[EI_DATA] != ELFDATA2LSB) {
+    fprintf(stderr, "%s: not an ELFDATA2LSB file\n",
+            infile);
+    return FALSE;
+  }
+
+  switch (ehdr->e_machine) {
+    case EM_X86_64:
+      printf("%s: x86-64 ELF detected, no instructions changed\n",
+             infile);
+      return TRUE;
+    default:
+      fprintf(stderr, "%s: Unsupported e_machine %d\n",
+              infile, ehdr->e_machine);
+      return FALSE;
+  }
+
+  if (g_changes == 0) {
+    fprintf(stderr, "%s: Found no changes to make!\n",
+            infile);
+    return FALSE;
+  } else {
+    printf("%s: %d instructions changed\n",
+           infile, g_changes);
+  }
+
+  return TRUE;
+}
+
+int main(int argc, char **argv) {
+  const char *infile;
+  const char *outfile;
+
+  if (argc != 3) {
+    fprintf(stderr, "Usage: %s INFILE OUTFILE\n", argv[0]);
+    return 1;
+  }
+
+  infile = argv[1];
+  outfile = argv[2];
+
+  ReadInput(infile);
+
+  if (g_contents_size < SELFMAG) {
+    fprintf(stderr, "%s: too short to be an ELF file\n",
+            infile);
+    return 1;
+  }
+  if (memcmp(g_contents, ELFMAG, SELFMAG) != 0) {
+    fprintf(stderr, "%s: not an ELF file\n",
+            infile);
+    return 1;
+  }
+
+  /*
+  * We will examine the header to figure out whether or not we are dealing
+  * with a 32 bit or 64 bit executable file.
+  */
+  if (g_contents_size >= sizeof(Elf32_Ehdr) &&
+      ((Elf32_Ehdr*)g_contents)->e_ident[EI_CLASS] == ELFCLASS32) {

[Roland McGrath, 2014/01/24 18:50:49]

space before * and after ): '(Elf32_Ehdr *) g_contents'

+    if (!Process32BitFile(infile)) {
+      fprintf(stderr, "%s: Could not process 32 bit ELF file\n",
+              infile);
+      return 1;
+    }
+  } else if (g_contents_size >= sizeof(Elf64_Ehdr) &&
+             ((Elf64_Ehdr*)g_contents)->e_ident[EI_CLASS] == ELFCLASS64) {
+    if (!Process64BitFile(infile)) {
+      fprintf(stderr, "%s: Could not process 64 bit ELF file\n",
+              infile);
+      return 1;
+    }
+  } else {
+    fprintf(stderr, "%s: Invalid ELF file!\n",
+            infile);
+    return 1;
+  }
+
+  if (g_errors != 0)
+    return 1;
+
+  WriteOutput(outfile);
+  return 0;
+}