3 files changed, 84 insertions, 10 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);
 }
diff --git a/src/usertestelf.c b/src/usertestelf.c
index 19f0096..c3ab289 100644
--- a/src/usertestelf.c
+++ b/src/usertestelf.c
@@ -1,6 +1,68 @@
+#include <shared/printf.h>
+#include <user/lib/elf.h>
 #include <user/lib/syscall.c>
 
+const char *str = "Hello!\n", *str2 = "World.\n";
+
+__attribute__((visibility("hidden")))
+extern struct Elf64_Dyn _DYNAMIC[];
+
+__attribute__((visibility("hidden")))
+extern char _image_base;
+
+static void printf_backend(void *arg, const char *buf, size_t len) {
+	(void)arg;
+	_syscall_write(1, buf, len, -1);
+}
+
+int printf(const char *fmt, ...) {
+	int ret = 0;
+	va_list argp;
+	va_start(argp, fmt);
+	ret = __printf_internal(fmt, argp, printf_backend, 0);
+	va_end(argp);
+	return ret;
+}
+
+
+static struct Elf64_Dyn *dyn_gettag(Elf64_Xword tag) {
+	for (size_t i = 0;; i++) {
+		if (_DYNAMIC[i].d_tag == tag) return &_DYNAMIC[i];
+		if (_DYNAMIC[i].d_tag == DT_NULL) return NULL;
+	}
+}
+
+static void reloc(void) {
+	printf("hi?\n");
+	// TODO DT_REL
+	if (dyn_gettag(DT_PLTGOT) || dyn_gettag(DT_JMPREL)) {
+		printf("elf: unimplemented tag in _DYNAMIC\n");
+	}
+
+	struct Elf64_Dyn *rela_tag = dyn_gettag(DT_RELA);
+	if (rela_tag) {
+		/* not checking pointer validity,
+		 * crashing on an invalid elf is fine */
+		size_t relasz = dyn_gettag(DT_RELASZ)->d_val;
+		size_t relaent = dyn_gettag(DT_RELAENT)->d_val;
+		for (size_t o = 0; o < relasz; o += relaent) {
+			struct Elf64_Rela *r = &_image_base + rela_tag->d_ptr + o;
+			uintptr_t *target = &_image_base + r->r_offset;
+
+			switch (ELF64_R_TYPE(r->r_info)) {
+				case R_X86_64_RELATIVE:
+					*target = &_image_base + r->r_addend;
+					break;
+				default:
+					printf("elf: unsupported relocation type\n");
+			}
+		}
+	}
+}
+
 int main(void) {
-	_syscall_write(1, "Hello!", 6, 0);
+	reloc();
+	printf(str);
+	printf(str2);
 	_syscall_exit(0);
 }
diff --git a/src/usertestelf.ld b/src/usertestelf.ld
index 2567f77..fcb5fc8 100644
--- a/src/usertestelf.ld
+++ b/src/usertestelf.ld
@@ -2,7 +2,7 @@ ENTRY(main)
 
 SECTIONS
 {
-	. = 8M;
+	_image_base = .;
 	.text BLOCK(4K) : ALIGN(4K)
 	{
 		*(.text)