user/libc: execve() supports passing argv now

6 files changed, 74 insertions, 21 deletions

diff --git a/src/user/lib/crt0.c b/src/user/lib/crt0.c
deleted file mode 100644
index 91bbb05..0000000
--- a/src/user/lib/crt0.c
+++ /dev/null
@@ -1,10 +0,0 @@
-#include "elfload.h"
-#include <unistd.h>
-
-int main();
-
-__attribute__((__weak__))
-void _start(void) {
-	elf_selfreloc();
-	exit(main());
-}
diff --git a/src/user/lib/crt0.s b/src/user/lib/crt0.s
new file mode 100644
index 0000000..dd9ab1b
--- /dev/null
+++ b/src/user/lib/crt0.s
@@ -0,0 +1,18 @@
+.section .text
+.global _start
+.type _start, @function
+.weak _start
+_start:
+	mov %rsp, %rbp
+	and $~0xF, %rsp
+	call elf_selfreloc
+
+	mov %rbp, %rsp
+	/* pushed by _freejmp */
+	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 5ba596f..6cf09c7 100644
--- a/src/user/lib/elfload.c
+++ b/src/user/lib/elfload.c
@@ -8,13 +8,14 @@
 #include <user/lib/elf.h>
 #include <user/lib/elfload.h>
 
-void elf_execf(FILE *f) {
+void elf_execf(FILE *f, char **argv, char **envp) {
 	const size_t cap = 0x60000;
 	size_t pos = 0;
 	void *buf = malloc(cap); // TODO a way to get file size
 	fseek(f, 0, SEEK_SET);
+
 	if (buf && fread(buf, 1, cap - pos, f))
-		elf_exec(buf);
+		elf_exec(buf, argv, envp);
 	free(buf);
 }
 
@@ -58,16 +59,40 @@ static size_t elf_spread(const void *elf) {
 	return high - low;
 }
 
-/* frees memory outside of [low; low + len] and jumps to *entry */
-static void freejmp(void *entry, void *low, size_t len) {
+/* frees memory outside of [low; low + len] and jumps to *entry
+ * also sets up main's stack */
+void _freejmp_chstack(void *entry, void *low, size_t len, 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 len, char **argv, char **envp) {
+	void *stack = (void*)~0;
+	size_t *stack_w;
+	int argc = 0;
+	if (argv) {
+		size_t len;
+		for (int i = 0; argv[i]; i++) {
+			len = strlen(argv[i]) + 1; // including the null byte
+			stack -= len;
+			memcpy(stack, argv[i], len);
+			argv[i] = stack;
+			argc++;
+		}
+		len = sizeof(char*) * argc;
+		stack -= len;
+		memcpy(stack, argv, len);
+		argv = stack;
+	}
+	stack_w = stack;
+	*--stack_w = (uintptr_t)envp;
+	*--stack_w = (uintptr_t)argv;
+	*--stack_w = argc;
+
 	uintptr_t high = (uintptr_t)low + len;
 	uint64_t buf[] = {
 		EXECBUF_SYSCALL, _SYSCALL_MEMFLAG, 0, (uintptr_t)low, 0, 0,
 		EXECBUF_SYSCALL, _SYSCALL_MEMFLAG, high, ~0 - 0xF000 - high, 0, 0,
 		EXECBUF_JMP, (uintptr_t)entry,
 	};
-	_syscall_execbuf(buf, sizeof buf);
-	// should never return
+	execbuf_chstack(stack_w, buf, sizeof buf);
 }
 
 static void *elf_loadmem(struct Elf64_Ehdr *ehdr) {
@@ -94,14 +119,17 @@ static void *elf_loadmem(struct Elf64_Ehdr *ehdr) {
 	return exebase;
 }
 
-void elf_exec(void *base) {
+void elf_exec(void *base, char **argv, char **envp) {
 	struct Elf64_Ehdr *ehdr = base;
 	if (!valid_ehdr(ehdr)) return;
 
 	void *exebase = elf_loadmem(ehdr);
 	if (!exebase) return;
 
-	freejmp(exebase + ehdr->e_entry, exebase, elf_spread(ehdr) + 0x1000);
+	void *newstack = _syscall_memflag((void*)0x1000, 0x1000, MEMFLAG_FINDFREE | MEMFLAG_PRESENT);
+	if (!newstack) return;
+
+	_freejmp_chstack(exebase + ehdr->e_entry, exebase, elf_spread(ehdr) + 0x1000, argv, envp, newstack);
 }
 
 void *elf_partialexec(void *base) {
diff --git a/src/user/lib/elfload.h b/src/user/lib/elfload.h
index d0fb29d..283efd8 100644
--- a/src/user/lib/elfload.h
+++ b/src/user/lib/elfload.h
@@ -1,8 +1,8 @@
 #pragma once
 #include <bits/file.h>
 
-void elf_execf(FILE *f);
-void elf_exec(void *elf);
+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 */
 
 void elf_selfreloc(void); // elfreloc.c
diff --git a/src/user/lib/elfload.s b/src/user/lib/elfload.s
new file mode 100644
index 0000000..faab85f
--- /dev/null
+++ b/src/user/lib/elfload.s
@@ -0,0 +1,17 @@
+.section .text
+.global _freejmp_chstack
+.type _freejmp_chstack, @function
+// void _freejmp_chstack(void *entry, void *low, size_t len, char **argv, char **envp, void *stack);
+_freejmp_chstack:
+	mov %r9, %rsp
+	jmp _freejmp
+
+.section .text
+.global execbuf_chstack
+.type execbuf_chstack, @function
+// _Noreturn void execbuf_chstack(void *stack, void __user *buf, size_t len);
+execbuf_chstack:
+	mov %rdi, %rsp
+	mov $100, %rdi
+	syscall
+	jmp 0 // if execbuf failed we might as well crash
diff --git a/src/user/lib/stdlib.c b/src/user/lib/stdlib.c
index 179bd8f..0795d3d 100644
--- a/src/user/lib/stdlib.c
+++ b/src/user/lib/stdlib.c
@@ -25,7 +25,7 @@ int execv(const char *path, char *const argv[]) {
 	if (!file)
 		return -1;
 
-	elf_execf(file);
+	elf_execf(file, (void*)argv, NULL);
 	fclose(file);
 	errno = EINVAL;
 	return -1;