1 files changed, 182 insertions, 0 deletions
diff --git a/src/libc/elfload.c b/src/libc/elfload.c
new file mode 100644
index 0000000..c1a08f8
--- /dev/null
+++ b/src/libc/elfload.c
@@ -0,0 +1,182 @@
+#include <camellia/execbuf.h>
+#include <camellia/flags.h>
+#include <camellia/syscalls.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include "elf.h"
+#include <elfload.h>
+
+void elf_execf(FILE *f, char **argv, char **envp) {
+	size_t ret;
+	void *buf;
+	long buflen;
+
+	fseek(f, 0, SEEK_END);
+	buflen = ftell(f);
+	if (buflen < 0) return; /* errno set by fseek */
+	buf = malloc(buflen);
+
+	// TODO don't read the entire file into memory
+	fseek(f, 0, SEEK_SET);
+	if (!buf) return;
+	ret = fread(buf, buflen, 1, f);
+	fclose(f);
+	if (ret == 1) {
+		elf_exec(buf, argv, envp);
+	}
+	free(buf);
+}
+
+static bool valid_ehdr(const struct Elf64_Ehdr *h) {
+	return h->e_ident[0] == 0x7f
+		&& h->e_ident[1] == 'E'
+		&& h->e_ident[2] == 'L'
+		&& h->e_ident[3] == 'F'
+		&& h->e_machine == EM_X86_64
+		&& h->e_version == 1;
+}
+
+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);
+		return false;
+	}
+	// TODO overlap check
+	// TODO don't ignore flags
+	_sys_memflag(exebase + phdr->p_vaddr, phdr->p_memsz, MEMFLAG_PRESENT);
+	// TODO check that filesz <= memsz
+	memcpy(exebase + phdr->p_vaddr, elf + phdr->p_offset, phdr->p_filesz);
+	return true;
+}
+
+static size_t elf_spread(const void *elf) {
+	const struct Elf64_Ehdr *ehdr = elf;
+	uintptr_t high = 0, low = ~0;
+	for (size_t phi = 0; phi < ehdr->e_phnum; phi++) {
+		const struct Elf64_Phdr *phdr = elf + ehdr->e_phoff + phi * ehdr->e_phentsize;
+		if (high < phdr->p_vaddr + phdr->p_memsz)
+			high = phdr->p_vaddr + phdr->p_memsz;
+		if (low > phdr->p_vaddr)
+			low = phdr->p_vaddr;
+	}
+	return high - low;
+}
+
+static void *memdup(const void *orig, size_t len) {
+	void *n = malloc(len);
+	if (n) memcpy(n, orig, len);
+	return n;
+}
+
+static const char *default_argv[] = {NULL};
+
+/* 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, 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) {
+	// TODO error checking
+	// although i guess it's fine for it to crash
+	// also TODO just alloc a new stack
+	void *stack = (void*)~0;
+	struct execdata ed;
+	size_t argv_len;
+	size_t cwd_len = absolutepath(NULL, NULL, 0);
+
+	if (!argv) argv = default_argv;
+
+	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]);
+	}
+	ed.cwd = malloc(cwd_len);
+	getcwd(ed.cwd, cwd_len);
+
+	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;
+	}
+	ed.argv[ed.argc] = NULL;
+
+	/* push cwd */
+	stack -= cwd_len;
+	memcpy(stack, ed.cwd, cwd_len);
+	ed.cwd = stack;
+
+	stack -= sizeof ed;
+	memcpy(stack, &ed, sizeof ed);
+
+	uintptr_t high = (uintptr_t)low + imglen;
+	uint64_t buf[] = {
+		EXECBUF_SYSCALL, _SYS_MEMFLAG, 0, (uintptr_t)low, 0, 0, 0,
+		EXECBUF_SYSCALL, _SYS_MEMFLAG, high, ~0 - 0xF000 - high, 0, 0, 0,
+		EXECBUF_JMP, (uintptr_t)entry,
+	};
+	execbuf_chstack(stack, buf, sizeof buf);
+}
+
+static void *elf_loadmem(struct Elf64_Ehdr *ehdr) {
+	void *exebase;
+	size_t spread = elf_spread(ehdr);
+	switch (ehdr->e_type) {
+		case ET_EXEC:
+			exebase = (void*)0;
+			break;
+		case ET_DYN:
+			exebase = _sys_memflag((void*)0x1000, spread, MEMFLAG_FINDFREE);
+			if (!exebase)
+				return NULL;
+			break;
+		default:
+			return NULL;
+	}
+	for (size_t phi = 0; phi < ehdr->e_phnum; phi++) {
+		if (!load_phdr((void*)ehdr, exebase, phi)) {
+			_sys_memflag(exebase, spread, 0);
+			return NULL;
+		}
+	}
+	return exebase;
+}
+
+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;
+
+	void *newstack = _sys_memflag((void*)0x11000, 0x1000, MEMFLAG_FINDFREE | MEMFLAG_PRESENT) + 0x1000 - 8;
+	if (!newstack) return;
+
+	_freejmp_chstack(exebase + ehdr->e_entry, exebase, elf_spread(ehdr) + 0x1000, (const char**)argv, envp, newstack);
+}
+
+void *elf_partialexec(void *base) {
+	struct Elf64_Ehdr *ehdr = base;
+	if (!valid_ehdr(ehdr)) return NULL;
+
+	void *exebase = elf_loadmem(ehdr);
+	if (!exebase) return NULL;
+
+	return exebase + ehdr->e_entry;
+}