Intial experiment for building dynamic images without glibc under pnacl

tests/pnacl_ld_experiments/hello1.c

+#include <unistd.h>

[jvoung - send to chromium..., 2012/05/01 23:30:49]

Copyright notice.

[robertm, 2012/05/02 17:33:12]

Done.

+#include <stdlib.h>
+
+#define NACL_INSTR_BLOCK_SHIFT         5

[jvoung - send to chromium..., 2012/05/01 23:30:49]

Note about this experiment being tailored to x86?

[Robert Muth (chromium), 2012/05/02 16:18:32]

IIRC this works for all archs

+#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))
+
+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);
+
+#include <bits/nacl_syscalls.h>

[jvoung - send to chromium..., 2012/05/01 23:30:49]

Does this have to be included down here, or can it be included with the rest of
the includes?

[Robert Muth (chromium), 2012/05/02 16:18:32]

Done.

+
+/* ====================================================================== */

[jvoung - send to chromium..., 2012/05/01 23:30:49]

Comment about the purpose of this particular sub-experiment?

[Robert Muth (chromium), 2012/05/02 16:18:32]

Done.

+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)  {

[jvoung - send to chromium..., 2012/05/01 23:30:49]

Is that parameter a "l" or a "1"? Could you name it something else, like "fd"?

[jvoung - send to chromium..., 2012/05/02 17:20:42]

Well, I do think it will be clearer, since you do (write)(1, s, mystrlen(s))
above, which is a 1 instead of l.

+  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);

[jvoung - send to chromium..., 2012/05/01 23:30:49]

perhaps print "tdata1 (expecting 1): " first, same with "tdata2 (expecting 3): "

[robertm, 2012/05/02 17:33:12]

Done.

+  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));
+}