[PATCH] split __libc_start_main.c into two files (Wasm)

[Nicholas Wilson <nicholas.wilson@realvnc.com>]

Hi,

I've got some more patches to try and get in for Wasm support.

Here's one that should be fairly straightforward? In Musl, most (non-static) functions are in a file of their own, which is good from a linkage point of view.

I'd like to have __libc_start_main.c split into two files, because for Wasm I'd like to be able to call __libc_start_init (from within the CRT directory) but without having to link in exit(), since many Wasm applications will never call exit() and won't necessarily use main.

There's no pollution of the codebase, it's purely splitting a file.

Patch below.

Nick


========================
commit 3096e0e5e17ff5ee14288574503ad22d8e3d119c
Author: Nicholas Wilson <nicholas.wilson@realvnc.com>
Date:   Thu Dec 7 11:52:32 2017 +0000

    [Wasm] split __libc_start_main.c into two files, for archs that want __libc_start_init but might potentially not link in exit()

diff --git a/src/env/__libc_start_init.c b/src/env/__libc_start_init.c
new file mode 100644
index 00000000..ec05e1df
--- /dev/null
+++ b/src/env/__libc_start_init.c
@@ -0,0 +1,64 @@
+#include <elf.h>
+#include <poll.h>
+#include <fcntl.h>
+#include <signal.h>
+#include "syscall.h"
+#include "atomic.h"
+#include "libc.h"
+
+void __init_tls(size_t *);
+
+static void dummy(void) {}
+weak_alias(dummy, _init);
+
+__attribute__((__weak__, __visibility__("hidden")))
+extern void (*const __init_array_start)(void), (*const __init_array_end)(void);
+
+static void dummy1(void *p) {}
+weak_alias(dummy1, __init_ssp);
+
+#define AUX_CNT 38
+
+void __init_libc(char **envp, char *pn)
+{
+	size_t i, *auxv, aux[AUX_CNT] = { 0 };
+	__environ = envp;
+	for (i=0; envp[i]; i++);
+	libc.auxv = auxv = (void *)(envp+i+1);
+	for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
+	__hwcap = aux[AT_HWCAP];
+	__sysinfo = aux[AT_SYSINFO];
+	libc.page_size = aux[AT_PAGESZ];
+
+	if (!pn) pn = (void*)aux[AT_EXECFN];
+	if (!pn) pn = "";
+	__progname = __progname_full = pn;
+	for (i=0; pn[i]; i++) if (pn[i]=='/') __progname = pn+i+1;
+
+	__init_tls(aux);
+	__init_ssp((void *)aux[AT_RANDOM]);
+
+	if (aux[AT_UID]==aux[AT_EUID] && aux[AT_GID]==aux[AT_EGID]
+		&& !aux[AT_SECURE]) return;
+
+	struct pollfd pfd[3] = { {.fd=0}, {.fd=1}, {.fd=2} };
+#ifdef SYS_poll
+	__syscall(SYS_poll, pfd, 3, 0);
+#else
+	__syscall(SYS_ppoll, pfd, 3, &(struct timespec){0}, 0, _NSIG/8);
+#endif
+	for (i=0; i<3; i++) if (pfd[i].revents&POLLNVAL)
+		if (__sys_open("/dev/null", O_RDWR)<0)
+			a_crash();
+	libc.secure = 1;
+}
+
+static void libc_start_init(void)
+{
+	_init();
+	uintptr_t a = (uintptr_t)&__init_array_start;
+	for (; a<(uintptr_t)&__init_array_end; a+=sizeof(void(*)()))
+		(*(void (**)(void))a)();
+}
+
+weak_alias(libc_start_init, __libc_start_init);
diff --git a/src/env/__libc_start_main.c b/src/env/__libc_start_main.c
index 2d758af7..8236749e 100644
--- a/src/env/__libc_start_main.c
+++ b/src/env/__libc_start_main.c
@@ -1,67 +1,7 @@
-#include <elf.h>
-#include <poll.h>
-#include <fcntl.h>
-#include <signal.h>
-#include "syscall.h"
-#include "atomic.h"
-#include "libc.h"
+#include <stdlib.h>
 
-void __init_tls(size_t *);
-
-static void dummy(void) {}
-weak_alias(dummy, _init);
-
-__attribute__((__weak__, __visibility__("hidden")))
-extern void (*const __init_array_start)(void), (*const __init_array_end)(void);
-
-static void dummy1(void *p) {}
-weak_alias(dummy1, __init_ssp);
-
-#define AUX_CNT 38
-
-void __init_libc(char **envp, char *pn)
-{
-	size_t i, *auxv, aux[AUX_CNT] = { 0 };
-	__environ = envp;
-	for (i=0; envp[i]; i++);
-	libc.auxv = auxv = (void *)(envp+i+1);
-	for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
-	__hwcap = aux[AT_HWCAP];
-	__sysinfo = aux[AT_SYSINFO];
-	libc.page_size = aux[AT_PAGESZ];
-
-	if (!pn) pn = (void*)aux[AT_EXECFN];
-	if (!pn) pn = "";
-	__progname = __progname_full = pn;
-	for (i=0; pn[i]; i++) if (pn[i]=='/') __progname = pn+i+1;
-
-	__init_tls(aux);
-	__init_ssp((void *)aux[AT_RANDOM]);
-
-	if (aux[AT_UID]==aux[AT_EUID] && aux[AT_GID]==aux[AT_EGID]
-		&& !aux[AT_SECURE]) return;
-
-	struct pollfd pfd[3] = { {.fd=0}, {.fd=1}, {.fd=2} };
-#ifdef SYS_poll
-	__syscall(SYS_poll, pfd, 3, 0);
-#else
-	__syscall(SYS_ppoll, pfd, 3, &(struct timespec){0}, 0, _NSIG/8);
-#endif
-	for (i=0; i<3; i++) if (pfd[i].revents&POLLNVAL)
-		if (__sys_open("/dev/null", O_RDWR)<0)
-			a_crash();
-	libc.secure = 1;
-}
-
-static void libc_start_init(void)
-{
-	_init();
-	uintptr_t a = (uintptr_t)&__init_array_start;
-	for (; a<(uintptr_t)&__init_array_end; a+=sizeof(void(*)()))
-		(*(void (**)(void))a)();
-}
-
-weak_alias(libc_start_init, __libc_start_init);
+extern void __libc_start_init(void);
+extern void __init_libc(char **envp, char *pn);
 
 int __libc_start_main(int (*main)(int,char **,char **), int argc, char **argv)
 {