Intial experiment for building dynamic images without glibc under pnacl

tests/pnacl_ld_experiments/hello1.c

+/* Copyright 2012 The Native Client Authors.  All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can
+ * be found in the LICENSE file.
+ */
+
+/* This is highly experimental code to test shared/dynamic images
+ * with pnacl.
+ * Currently, only x86-32 is tested.
+ */
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <bits/nacl_syscalls.h>
+
+/* ====================================================================== */
+#define NACL_INSTR_BLOCK_SHIFT         5
+#define NACL_PAGESHIFT                12
+#define NACL_SYSCALL_START_ADDR       (16 << NACL_PAGESHIFT)
+#define NACL_SYSCALL_ADDR(syscall_number)                               \
+  (NACL_SYSCALL_START_ADDR + (syscall_number << NACL_INSTR_BLOCK_SHIFT))
+
+#define NACL_SYSCALL(s) ((TYPE_nacl_ ## s) NACL_SYSCALL_ADDR(NACL_sys_ ## s))
+
+/* ====================================================================== */
+/* proto-types for nacl syscalls */
+
+typedef int (*TYPE_nacl_write) (int desc, void const *buf, int count);
+typedef void (*TYPE_nacl_null) (void);
+typedef void (*TYPE_nacl_exit) (int status);
+
+/* ====================================================================== */
+/* proto-types for functions  inside ld.so */
+extern void _dl_get_tls_static_info(int *static_tls_size,
+                                    int *static_tls_align);
+extern int __tls_get_addr();
+/* ====================================================================== */
+int mystrlen(const char* s) {
+   int count = 0;
+   while (*s++) ++count;
+   return count;
+}
+
+
+void myhextochar(int n, char buffer[9]) {
+  int i;
+  buffer[8] = 0;
+
+  for (i = 0; i < 8; ++i) {
+    int nibble = 0xf & (n >> (4 * (7 - i)));
+    if (nibble <= 9) {
+      buffer[i] = nibble + '0';
+    } else {
+      buffer[i] = nibble - 10 + 'A';
+     }
+  }
+}
+
+#define myprint(s) NACL_SYSCALL(write)(1, s, mystrlen(s))
+
+__thread int tdata1 = 1;
+__thread int tdata2 = 3;
+
+
+ssize_t  write(int l, const void* buf, size_t n)  {
+  return NACL_SYSCALL(write)(l, buf, n);
+}
+
+void exit(int ret) {
+  NACL_SYSCALL(exit)(ret);
+}
+
+void __deregister_frame_info(const void *begin) {
+  myprint("__deregister_frame_info\n");
+}
+
+void __register_frame_info(void *begin, void *ob) {
+  myprint("__register_frame_info\n");
+}
+
+
+int main(int argc, char** argv, char** envp) {
+  myprint("hello world\n");
+  char buffer[9];
+
+  myhextochar(tdata1, buffer);
+  myprint(buffer);
+  myprint("\n");
+
+  myhextochar(tdata2, buffer);
+  myprint(buffer);
+  myprint("\n");
+
+  int static_tls_size;
+  int static_tls_align;
+
+#if 0
+  /* will be enabled soon */
+  int x = (int) & __tls_get_addr;
+  myhextochar(x, buffer);
+  myprint(buffer);
+  myprint("\n");
+  _dl_get_tls_static_info (&static_tls_size, &static_tls_align);
+#endif
+
+  return 0;
+}
+
+char message_init[] = "init\n";
+
+int __libc_csu_init (int argc, char **argv, char **envp) {
+  write(1, message_init, sizeof(message_init));
+  return 0;
+}
+
+char message_fini[] = "fini\n";
+void __libc_csu_fini (void) {
+  write(1, message_fini, sizeof(message_fini));
+}
+
+void __libc_start_main (int (*main) (int argc, char **argv, char **envp),
+                        int argc, char **argv,
+                         int (*init) (int argc, char **argv, char **envp),
+                        void (*fini) (void),
+                        void (*rtld_fini) (void),
+                        void *stack_end) {
+
+  exit(main(0, 0, 0));
+}