Add a minimal "hello world" program which uses IRT interfaces directly

Author: Mark Seaborn

hellow_minimal_irt.c

@@ -0,0 +1,43 @@
+
+/*
+ * This is a minimal NaCl "hello world" program.  It uses NaCl's
+ * stable IRT ABI.
+ */
+
+#include <stdint.h>
+
+#include "nacl_irt_interfaces.h"
+
+struct nacl_irt_basic __libnacl_irt_basic;
+struct nacl_irt_fdio __libnacl_irt_fdio;
+TYPE_nacl_irt_query __nacl_irt_query;
+
+static void grok_auxv(const Elf32_auxv_t *auxv) {
+  const Elf32_auxv_t *av;
+  for (av = auxv; av->a_type != AT_NULL; ++av) {
+    if (av->a_type == AT_SYSINFO) {
+      __nacl_irt_query = (TYPE_nacl_irt_query) av->a_un.a_val;
+    }
+  }
+}
+
+static void __libnacl_mandatory_irt_query(const char *interface,
+                                          void *table, size_t table_size) {
+  __nacl_irt_query(interface, table, table_size);
+}
+
+#define DO_QUERY(ident, name)                                   \
+  __libnacl_mandatory_irt_query(ident, &__libnacl_irt_##name,   \
+                                sizeof(__libnacl_irt_##name))
+
+void _start(uint32_t *info) {
+  Elf32_auxv_t *auxv = nacl_startup_auxv(info);
+  grok_auxv(auxv);
+  DO_QUERY(NACL_IRT_BASIC_v0_1, basic);
+  DO_QUERY(NACL_IRT_FDIO_v0_1, fdio);
+
+  const char string[] = "Hello world!\n";
+  size_t written;
+  __libnacl_irt_fdio.write(2, string, sizeof(string) - 1, &written);
+  __libnacl_irt_basic.exit(0);
+}

nacl_irt_interfaces.h

@@ -4,6 +4,14 @@
 
 /* This is a subset of NaCl's IRT interfaces. */
 
+#include <sys/types.h>
+
+struct stat;
+struct dirent;
+struct timeval;
+struct timespec;
+
+
 /* From native_client/src/untrusted/irt/irt.h: */
 
 #define NACL_IRT_BASIC_v0_1     "nacl-irt-basic-0.1"
@@ -28,17 +36,54 @@ struct nacl_irt_fdio {
   int (*getdents)(int fd, struct dirent *, size_t count, size_t *nread);
 };
 
+typedef size_t (*TYPE_nacl_irt_query)(const char *interface_ident,
+                                      void *table, size_t tablesize);
+
+
 /* From native_client/src/include/elf32.h: */
 
-struct Elf32_auxv {
+typedef struct {
   int a_type;
   union {
     int a_val;
   } a_un;
-};
+} Elf32_auxv_t;
+
 
 /* From native_client/src/include/elf_auxv.h: */
 
+#define AT_NULL 0
 #define AT_SYSINFO 32
 
+
+/* From native_client/src/untrusted/nacl/nacl_startup.h: */
+
+enum NaClStartupInfoIndex {
+  NACL_STARTUP_FINI,  /* Cleanup function pointer for dynamic linking.  */
+  NACL_STARTUP_ENVC,  /* Count of envp[] pointers.  */
+  NACL_STARTUP_ARGC,  /* Count of argv[] pointers.  */
+  NACL_STARTUP_ARGV   /* argv[0] pointer.  */
+};
+
+static inline int nacl_startup_argc(const uint32_t info[]) {
+  return info[NACL_STARTUP_ARGC];
+}
+
+static inline char **nacl_startup_argv(const uint32_t *info) {
+  return (char **) &info[NACL_STARTUP_ARGV];
+}
+
+static inline int nacl_startup_envc(const uint32_t info[]) {
+  return info[NACL_STARTUP_ENVC];
+}
+
+static inline char **nacl_startup_envp(const uint32_t *info) {
+  return &nacl_startup_argv(info)[nacl_startup_argc(info) + 1];
+}
+
+static inline Elf32_auxv_t *nacl_startup_auxv(const uint32_t *info) {
+  char **envend = &nacl_startup_envp(info)[nacl_startup_envc(info) + 1];
+  return (Elf32_auxv_t *) envend;
+}
+
 #endif

run.sh

@@ -38,4 +38,8 @@ g++ -m32 \
   $($llvm_config --ldflags --libs) -ldl \
   -o run_program
 
+clang -m32 -O2 -c -emit-llvm hellow_minimal_irt.c -o hellow_minimal_irt.pexe
+
 ./codegen_test
+
+./run_program hellow_minimal_irt.pexe

run_program.cc

@@ -59,7 +59,7 @@ struct startup_info {
   int argc;
   char *argv0;
   char *envp0;
-  struct Elf32_auxv auxv[2];
+  Elf32_auxv_t auxv[2];
 };
 
 int main(int argc, char **argv) {