user/libc: rework exec(), use a C _start2

5 files changed, 62 insertions, 62 deletions

diff --git a/src/user/lib/_start.s b/src/user/lib/_start.s
new file mode 100644
index 0000000..0d5b5de
--- /dev/null
+++ b/src/user/lib/_start.s
@@ -0,0 +1,11 @@
+.section .text
+.global _start
+.type _start, @function
+.weak _start
+_start:
+	mov %rsp, %rdi
+	and $~0xF, %rsp
+	call _start2
+	hlt
+	/* the call shouldn't return, thus the hlt.
+	 * using a call instead of jmp for stack alignment */
diff --git a/src/user/lib/_start2.c b/src/user/lib/_start2.c
new file mode 100644
index 0000000..6d1431f
--- /dev/null
+++ b/src/user/lib/_start2.c
@@ -0,0 +1,13 @@
+#include <camellia/syscalls.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <user/lib/elfload.h>
+
+int main(int argc, char **argv, char **envp);
+
+_Noreturn void _start2(struct execdata *ed) {
+	elf_selfreloc();
+	__setinitialcwd(ed->cwd);
+	exit(main(ed->argc, ed->argv, ed->envp));
+}
diff --git a/src/user/lib/crt0.s b/src/user/lib/crt0.s
deleted file mode 100644
index 3548264..0000000
--- a/src/user/lib/crt0.s
+++ /dev/null
@@ -1,21 +0,0 @@
-.section .text
-.global _start
-.type _start, @function
-.weak _start
-_start:
-	mov %rsp, %rbp
-	and $~0xF, %rsp
-	call elf_selfreloc
-
-	mov %rbp, %rsp
-
-	pop %rdi
-	call __setinitialcwd
-
-	pop %rdi
-	pop %rsi
-	pop %rdx
-	and $~0xF, %rsp
-	call main
-	mov %rax, %rdi
-	jmp exit
diff --git a/src/user/lib/elfload.c b/src/user/lib/elfload.c
index 777c8b8..9776a13 100644
--- a/src/user/lib/elfload.c
+++ b/src/user/lib/elfload.c
@@ -65,9 +65,9 @@ static size_t elf_spread(const void *elf) {
 	return high - low;
 }
 
-static void *malloccpy(const void *orig, size_t len) {
+static void *memdup(const void *orig, size_t len) {
 	void *n = malloc(len);
-	memcpy(n, orig, len);
+	if (n) memcpy(n, orig, len);
 	return n;
 }
 
@@ -76,50 +76,41 @@ static void *malloccpy(const void *orig, size_t len) {
 void _freejmp_chstack(void *entry, void *low, size_t len, const char **argv, char **envp, void *stack); // elfload.s
 _Noreturn void execbuf_chstack(void *stack, void __user *buf, size_t len);
 void _freejmp(void *entry, void *low, size_t imglen, const char **argv, char **envp) {
-	size_t len;
-	union {void *b; void **ptr; uintptr_t *n;} stack;
-	stack.b = (void*)~0; /* default stack location */
-	void *stack_start = stack.b - 0x1000;
-	void *cwd;
-
-	/* copy argv off the stack */
-	int argc = 0;
-	size_t argv_len;
-	if (argv) {
-		while (argv[argc]) argc++;
-		argv_len = argc * sizeof(char *);
-		if ((void*)argv > stack_start)
-			argv = malloccpy(argv, argv_len);
-		for (int i = 0; argv[i]; i++)
-			if ((void*)argv[i] > stack_start)
-				argv[i] = malloccpy(argv[i], strlen(argv[i]) + 1);
-	}
+	void *stack = (void*)~0;
+	struct execdata ed;
 
-	/* push cwd */
-	len = absolutepath(NULL, NULL, 0);
-	stack.b -= len;
-	cwd = stack.b;
-	getcwd(cwd, len);
-
-	/* push argv */
 	if (argv) {
-		for (int i = 0; i < argc; i++) {
-			len = strlen(argv[i]) + 1;
-			stack.b -= len;
-			memcpy(stack.b, argv[i], len);
-			argv[i] = stack.b;
+		size_t argv_len;
+		ed.argc = 0;
+		while (argv[ed.argc]) ed.argc++;
+		argv_len = (ed.argc+1) * sizeof(char *);
+
+		/* make a copy of argv, so it doesn't get overridden
+		 * if it overlaps with the new stack. */
+		argv = memdup(argv, argv_len);
+		for (int i = 0; i < ed.argc; i++)
+			argv[i] = strdup(argv[i]);
+
+		stack -= argv_len;
+		ed.argv = stack;
+
+		for (int i = 0; i < ed.argc; i++) {
+			size_t len = strlen(argv[i]) + 1;
+			stack -= len;
+			memcpy(stack, argv[i], len);
+			ed.argv[i] = stack;
 		}
-		*--(stack.ptr) = NULL; /* NULL terminate argv */
-		stack.b -= argv_len;
-		memcpy(stack.b, argv, argv_len);
-		argv = stack.b;
+		ed.argv[ed.argc] = NULL;
 	}
 
-	*--(stack.ptr) = envp;
-	*--(stack.ptr) = argv;
-	*--(stack.n)   = argc;
+	/* push cwd */
+	size_t len = absolutepath(NULL, NULL, 0);
+	stack -= len;
+	getcwd(stack, len);
+	ed.cwd = stack;
 
-	*--(stack.ptr) = cwd;
+	stack -= sizeof ed;
+	memcpy(stack, &ed, sizeof ed);
 
 	uintptr_t high = (uintptr_t)low + imglen;
 	uint64_t buf[] = {
@@ -127,7 +118,7 @@ void _freejmp(void *entry, void *low, size_t imglen, const char **argv, char **e
 		EXECBUF_SYSCALL, _SYSCALL_MEMFLAG, high, ~0 - 0xF000 - high, 0, 0, 0,
 		EXECBUF_JMP, (uintptr_t)entry,
 	};
-	execbuf_chstack(stack.b, buf, sizeof buf);
+	execbuf_chstack(stack, buf, sizeof buf);
 }
 
 static void *elf_loadmem(struct Elf64_Ehdr *ehdr) {
diff --git a/src/user/lib/elfload.h b/src/user/lib/elfload.h
index 283efd8..825f765 100644
--- a/src/user/lib/elfload.h
+++ b/src/user/lib/elfload.h
@@ -1,6 +1,12 @@
 #pragma once
 #include <bits/file.h>
 
+struct execdata {
+	int argc;
+	char **argv, **envp;
+	char *cwd;
+};
+
 void elf_execf(FILE *f, char **argv, char **envp);
 void elf_exec(void *base, char **argv, char **envp);
 void *elf_partialexec(void *elf); /* returns pointer to entry point */