From 4aee2f759ab7bf2ad9534941afef0195040ba5db Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Tue, 26 Jul 2022 22:40:28 +0200
Subject: user/libc: a _start that automatically selfrelocates PIEs

---
 src/user/app/init/main.c    |  5 +----
 src/user/app/testelf/main.c | 15 +++------------
 src/user/bootstrap/main.c   |  4 +++-
 src/user/lib/crt0.c         | 10 ++++++++++
 src/user/linker.ld          |  2 +-
 5 files changed, 18 insertions(+), 18 deletions(-)
 create mode 100644 src/user/lib/crt0.c

(limited to 'src')

diff --git a/src/user/app/init/main.c b/src/user/app/init/main.c
index 426933f..788fd78 100644
--- a/src/user/app/init/main.c
+++ b/src/user/app/init/main.c
@@ -11,10 +11,7 @@
 __attribute__((visibility("hidden")))
 extern char _image_base[];
 
-__attribute__((section(".text.startup")))
 int main(void) {
-	elf_selfreloc();
-
 	freopen("/kdev/com1", "a+", stdout);
 	printf("in init (stage 2), loaded at 0x%x\n", &_image_base);
 
@@ -73,5 +70,5 @@ int main(void) {
 
 	_syscall_await();
 	printf("init: quitting\n");
-	exit(0);
+	return 0;
 }
diff --git a/src/user/app/testelf/main.c b/src/user/app/testelf/main.c
index 93a5e11..a3e54b8 100644
--- a/src/user/app/testelf/main.c
+++ b/src/user/app/testelf/main.c
@@ -1,18 +1,9 @@
-#include <camellia/syscalls.h>
 #include <stdio.h>
-#include <user/lib/elf.h>
-#include <user/lib/elfload.h>
-#include <unistd.h>
 
 const char *str = "Hello!\n", *str2 = "World.\n";
 
-__attribute__((visibility("hidden")))
-extern char _image_base[];
-
 int main(void) {
-	elf_selfreloc();
-	printf("loaded at %x\n", &_image_base);
-	printf(str);
-	printf(str2);
-	exit(0);
+	printf("elftest's &main == 0x%x\n", &main);
+	printf("%s%s", str, str2);
+	return 0;
 }
diff --git a/src/user/bootstrap/main.c b/src/user/bootstrap/main.c
index fecd38f..089fd68 100644
--- a/src/user/bootstrap/main.c
+++ b/src/user/bootstrap/main.c
@@ -11,7 +11,7 @@ extern char _bss_end;
 extern char _initrd;
 
 __attribute__((section(".text.startup")))
-int main(void) {
+void _start(void) {
 	_syscall_memflag(&_bss_start, &_bss_end - &_bss_start, MEMFLAG_PRESENT);
 
 	/* move everything provided by the kernel to /kdev */
@@ -34,3 +34,5 @@ int main(void) {
 	}
 	_syscall_exit(1);
 }
+
+int main(void) {return 0;} // dummy, needed to link
diff --git a/src/user/lib/crt0.c b/src/user/lib/crt0.c
new file mode 100644
index 0000000..91bbb05
--- /dev/null
+++ b/src/user/lib/crt0.c
@@ -0,0 +1,10 @@
+#include "elfload.h"
+#include <unistd.h>
+
+int main();
+
+__attribute__((__weak__))
+void _start(void) {
+	elf_selfreloc();
+	exit(main());
+}
diff --git a/src/user/linker.ld b/src/user/linker.ld
index fcb5fc8..e638289 100644
--- a/src/user/linker.ld
+++ b/src/user/linker.ld
@@ -1,4 +1,4 @@
-ENTRY(main)
+ENTRY(_start)
 
 SECTIONS
 {
-- 
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