user: basic elf relocations, PIE support

1 files changed, 20 insertions, 8 deletions

diff --git a/src/user/lib/elfload.c b/src/user/lib/elfload.c
index 67cef68..deb7b44 100644
--- a/src/user/lib/elfload.c
+++ b/src/user/lib/elfload.c
@@ -26,14 +26,15 @@ static bool valid_ehdr(const struct Elf64_Ehdr *h) {
 		&& h->e_ident[1] == 'E'
 		&& h->e_ident[2] == 'L'
 		&& h->e_ident[3] == 'F'
-		&& h->e_type == ET_EXEC
 		&& h->e_machine == EM_X86_64
 		&& h->e_version == 1;
 }
 
-static bool load_phdr(const void *base, size_t idx) {
-	const struct Elf64_Ehdr *ehdr = base;
-	const struct Elf64_Phdr *phdr = base + ehdr->e_phoff + idx * ehdr->e_phentsize;
+static bool load_phdr(const void *elf, void *exebase, size_t idx) {
+	const struct Elf64_Ehdr *ehdr = elf;
+	const struct Elf64_Phdr *phdr = elf + ehdr->e_phoff + idx * ehdr->e_phentsize;
+
+	if (phdr->p_type == PT_DYNAMIC) return true;
 
 	if (phdr->p_type != PT_LOAD) {
 		printf("unknown type %x\n", phdr->p_type);
@@ -41,19 +42,30 @@ static bool load_phdr(const void *base, size_t idx) {
 	}
 	// TODO overlap check
 	// TODO don't ignore flags
-	_syscall_memflag((void*)phdr->p_vaddr, phdr->p_memsz, MEMFLAG_PRESENT);
+	_syscall_memflag(exebase + phdr->p_vaddr, phdr->p_memsz, MEMFLAG_PRESENT);
 	// TODO check that filesz <= memsz
-	memcpy((void*)phdr->p_vaddr, base + phdr->p_offset, phdr->p_filesz);
+	memcpy(exebase + phdr->p_vaddr, elf + phdr->p_offset, phdr->p_filesz);
 	return true;
 }
 
 void elf_exec(void *base) {
 	struct Elf64_Ehdr *ehdr = base;
+	void *exebase;
 	if (!valid_ehdr(ehdr)) return;
+	switch (ehdr->e_type) {
+		case ET_EXEC:
+			exebase = (void*)0;
+			break;
+		case ET_DYN:
+			exebase = (void*)0x800000; // TODO search for free memory
+			break;
+		default:
+			return;
+	}
 	for (size_t phi = 0; phi < ehdr->e_phnum; phi++) {
-		if (!load_phdr(base, phi))
+		if (!load_phdr(base, exebase, phi))
 			return;
 	}
-	((void(*)())ehdr->e_entry)();
+	((void(*)())exebase + ehdr->e_entry)();
 	_syscall_exit(1);
 }