From ae2f69d3b8c8cd93c8f79aef17ad8092c5140355 Mon Sep 17 00:00:00 2001
From: Qwinci <32550582+Qwinci@users.noreply.github.com>
Date: Mon, 13 Jan 2025 16:15:08 +0200
Subject: [PATCH] elf: add AT_EXECFN

---
 kernel-src/include/kernel/elf.h  |  4 +++-
 kernel-src/sys/elf.c             | 13 ++++++++++---
 kernel-src/sys/proc.c            |  2 +-
 kernel-src/sys/syscalls/execve.c |  2 +-
 4 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/kernel-src/include/kernel/elf.h b/kernel-src/include/kernel/elf.h
index beec12ca..28aff67a 100644
--- a/kernel-src/include/kernel/elf.h
+++ b/kernel-src/include/kernel/elf.h
@@ -28,6 +28,7 @@
 #define AT_PHENT 4
 #define AT_PHNUM 5
 #define AT_ENTRY 9
+#define AT_EXECFN 31
 
 typedef struct {
 	uint64_t type;
@@ -39,6 +40,7 @@ typedef struct {
 	auxv64_t phnum;
 	auxv64_t phent;
 	auxv64_t entry;
+	auxv64_t execfn;
 	auxv64_t null;
 } auxv64list_t;
 
@@ -83,6 +85,6 @@ typedef struct{
 } __attribute__((packed)) elfph64_t;
 
 int elf_load(vnode_t *vnode, void *base, void **entry, char **interpreter, auxv64list_t *auxv64);
-void *elf_preparestack(void *top, auxv64list_t *auxv64, char **argv, char **envp);
+void *elf_preparestack(void *top, auxv64list_t *auxv64, char **argv, char **envp, char *path);
 
 #endif
diff --git a/kernel-src/sys/elf.c b/kernel-src/sys/elf.c
index 74b7a6a5..91cf57a4 100644
--- a/kernel-src/sys/elf.c
+++ b/kernel-src/sys/elf.c
@@ -215,11 +215,12 @@ int elf_load(vnode_t *vnode, void *base, void **entry, char **interpreter, auxv6
 #define STACK_SIZE (1024 * 1024 * 4)
 #define STACK_TOP_BUFFER 8
 
-void *elf_preparestack(void *top, auxv64list_t *auxv64, char **argv, char **envp) {
+void *elf_preparestack(void *top, auxv64list_t *auxv64, char **argv, char **envp, char *path) {
 	size_t argc;
 	size_t envc;
 	size_t argdatasize = 0;
 	size_t envdatasize = 0;
+	size_t pathsize = strlen(path) + 1;
 
 	for (argc = 0; argv[argc]; ++argc)
 		argdatasize += strlen(argv[argc]) + 1;
@@ -231,7 +232,7 @@ void *elf_preparestack(void *top, auxv64list_t *auxv64, char **argv, char **envp
 	int alignment = ((argc + 1) + (envc + 1) + 1) & 1 ? 8 : 0;
 
 	// env data + arg data + pointers to arg and env data + argc + buffer at the top
-	size_t initialsize = argdatasize + envdatasize + (argc + envc) * sizeof(char *) + sizeof(size_t) + sizeof(auxv64list_t) + alignment + STACK_TOP_BUFFER;
+	size_t initialsize = argdatasize + envdatasize + pathsize + (argc + envc) * sizeof(char *) + sizeof(size_t) + sizeof(auxv64list_t) + alignment + STACK_TOP_BUFFER;
 
 	size_t initialsizeround = ROUND_UP(initialsize, PAGE_SIZE);
 	void *initialpagebase = (void *)((uintptr_t)top - initialsizeround);
@@ -247,7 +248,8 @@ void *elf_preparestack(void *top, auxv64list_t *auxv64, char **argv, char **envp
 
 	char *argdatastart = (char *)((uintptr_t)top - argdatasize);
 	char *envdatastart = (char *)((uintptr_t)argdatastart - envdatasize);
-	auxv64list_t *auxvstart = (auxv64list_t *)envdatastart - 1;
+	char *pathdatastart = (char *)((uintptr_t)envdatastart - pathsize);
+	auxv64list_t *auxvstart = (auxv64list_t *)pathdatastart - 1;
 
 	auxvstart = (auxv64list_t *)(((uintptr_t)auxvstart & ~(uintptr_t)0xf) - alignment);
 
@@ -256,6 +258,11 @@ void *elf_preparestack(void *top, auxv64list_t *auxv64, char **argv, char **envp
 	char **argstart = (char **)envstart - argc - 1;
 	size_t *argcptr = (size_t *)argstart - 1;
 
+	auxv64->execfn.type = AT_EXECFN;
+	auxv64->execfn.val = (uint64_t)pathdatastart;
+
+	memcpy(pathdatastart, path, pathsize);
+
 	memcpy(auxvstart, auxv64, sizeof(auxv64list_t));
 
 	for (int i = 0; i < argc; ++i) {
diff --git a/kernel-src/sys/proc.c b/kernel-src/sys/proc.c
index 89383060..f56ebb81 100644
--- a/kernel-src/sys/proc.c
+++ b/kernel-src/sys/proc.c
@@ -361,7 +361,7 @@ void proc_run_init() {
 	char *argv[] = {"/init", cmdline_get("initarg"), NULL};
 	char *envp[] = {NULL};
 
-	void *stack = elf_preparestack(STACK_TOP, &auxv64, argv, envp);
+	void *stack = elf_preparestack(STACK_TOP, &auxv64, argv, envp, "/init");
 	__assert(stack);
 
 	// reenter kernel context
diff --git a/kernel-src/sys/syscalls/execve.c b/kernel-src/sys/syscalls/execve.c
index 51d87740..d067de4e 100644
--- a/kernel-src/sys/syscalls/execve.c
+++ b/kernel-src/sys/syscalls/execve.c
@@ -258,7 +258,7 @@ static syscallret_t execve(context_t *context, char *upath, char *uargv[], char
 		VOP_RELEASE(interpnode);
 	}
 
-	stack = elf_preparestack(STACK_TOP, &auxv64, argv, envp);
+	stack = elf_preparestack(STACK_TOP, &auxv64, argv, envp, path);
 	if (stack == NULL) {
 		ret.errno = ENOMEM;
 		goto error;