implement more syscalls

myfile

@@ -1 +1,5 @@
-hello
+stuff
+stuff
+stuff
+something
+stuff

src/main.c

@@ -1,4 +1,3 @@
-#include "syscall.h"
 #define _GNU_SOURCE
 #include <stdio.h>
 #include <stdint.h>
@@ -18,12 +17,14 @@
 #include "mach.h"
 #include "tos.h"
 #include "sys.h"
+#include "syscall.h"
 
 #define ALIGN(v, a) (((v) + (a) - 1) & ~((a) - 1))
 #define DONE_ERR(M_err, M_ret) do { fprintf(stderr, (M_err)); defer_status = (M_ret); goto done; } while(0)
 
 static char sud_intercept = SYSCALL_DISPATCH_FILTER_ALLOW;
-
+void *data_segment = NULL;
+size_t data_segment_size = 0;
 
 extern void start(uintptr_t entry, Tos* tos, int argc, char **argv);
 void enter(uintptr_t entry, int argc, char **argv)
@@ -45,14 +46,41 @@ void handle_sigsys(int sig, siginfo_t *info, void *ptr)
 	int64_t *sp = (int64_t *)gregs[REG_RSP];
 	int64_t syscall = gregs[REG_RBP];
 
-	printf("syscall %ld\n", syscall);
+	/*
+	printf("0x%"PRIxPTR"\n", (uintptr_t)info->si_call_addr);
+
+	for (int i = -4; i < 3; i++)
+		printf("%d:  0x%"PRIxPTR"\n", i, sp[i]);
+	printf("donezo\n");
+	*/
 
 	switch (syscall) {
 	case OPEN:
 		ret = sys$open((char *)sp[1], (int)sp[2]);
 		break;
+	case EXITS:
+		sys$exits((char *)sp[1]);
+		ret = -1;
+		break;
+	case PREAD:
+		ret = sys$pread((int)sp[1], (void*)sp[2], (int64_t)sp[3], (int64_t)sp[4]);
+		break;
+	case PWRITE:
+		ret = sys$pwrite((int)sp[1], (void*)sp[2], (int64_t)sp[3], (int64_t)sp[4]);
+		break;
+	case CLOSE:
+		ret = sys$close((int)sp[1]);
+		break;
+	case BRK_:
+		ret = sys$brk((void*)sp[1], data_segment, &data_segment_size);
+		break;
+	default:
+		printf("unimplemented syscall %ld\n", syscall);
+		break;
 	}
 
+	//printf("ret = %ld\n", ret);
+
 	gregs[REG_RAX] = ret;
 }
 
@@ -79,7 +107,7 @@ int findlibc(struct dl_phdr_info *info, size_t size, void *ptr)
 }
 
 static char *program_argv[] = {
-	"out",
+	"sam",
 	"../myfile",
 	NULL
 };
@@ -93,7 +121,7 @@ int main()
 	size_t text_addr = 0x200000;
 	size_t data_addr;
 
-	f = fopen("../a.out", "rb");
+	f = fopen("../sam", "rb");
 
 	if (fread(&header, 1, sizeof(header), f) != sizeof(header)) {
 		DONE_ERR("failed to read file header\n", 1);
@@ -109,6 +137,8 @@ int main()
 
 	data_addr = ALIGN(text_addr + header.text, 0x200000);
 
+	fseek(f, 0, SEEK_SET);
+
 	size_t segments_size = sizeof(Exec) + header.text + header.data;
 	file_segments = malloc(segments_size);
 	if (!file_segments) {
@@ -125,14 +155,15 @@ int main()
 	}
 	printf("mapped text segment at 0x%"PRIxPTR"\n", (uintptr_t)text_segment);
 
-	void *data_segment = mmap((void*)data_addr, header.data + header.bss, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+	data_segment_size = header.data + header.bss;
+	data_segment = mmap((void*)data_addr, data_segment_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
 	if (!text_segment) {
 		DONE_ERR("failed to map data segment into memory\n", 1);
 	}
 	printf("mapped data segment at 0x%"PRIxPTR"\n", (uintptr_t)data_segment);
 
-	memcpy(text_segment, file_segments, header.text);
-	memcpy(data_segment, file_segments + sizeof(Exec) + header.text, header.data);
+	memcpy(text_segment, file_segments, header.text + sizeof(Exec));
+	memcpy(data_segment, file_segments + header.text + sizeof(Exec), header.data);
 
 	if (dl_iterate_phdr(findlibc, NULL) != 1) {
 		DONE_ERR("failed to find libc and enable SUD\n", 1);
@@ -144,7 +175,7 @@ int main()
 	};
 	sigaction(SIGSYS, &sa, NULL);
 
-	enter(header.entry32, 2, program_argv);
+	enter(header.entry32, 3, program_argv);
 done:
 	free(file_segments);
 	fclose(f);

src/syscall.c

@@ -2,10 +2,30 @@
 #include <fcntl.h>
 #include <stdio.h>
 #include <inttypes.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/mman.h>
 #include "syscall.h"
 
+char *errstr = NULL;
+
+static int check_error(int ret)
+{
+	if (ret < 0) {
+		errstr = strerror(errno);
+		fprintf(stderr, "errstr says: %s\n", errstr);
+		return -1;
+	}
+
+	return ret;
+}
+
 static int mode_open(char *name, int mode, int perm, int flag)
 {
+	printf("open %s\n", name);
+
 	switch (mode & 3) {
 	case 0: flag |= O_RDONLY; break;
 	case 1: flag |= O_WRONLY; break;
@@ -22,7 +42,54 @@ static int mode_open(char *name, int mode, int perm, int flag)
 
 int sys$open(char *path, int mode)
 {
-	printf("sys$open(0x%"PRIxPTR", %d)\n", (uintptr_t)path, mode);
-
-    return mode_open(path, mode, 0, 0);
+    return check_error(mode_open(path, mode, 0, 0));
+}
+
+int sys$exits(char *msg)
+{
+	if (!msg) {
+		printf("program exited successfully\n");
+		exit(0);
+	}
+
+	printf("program exited with error message: %s\n", msg);
+	exit(1);
+}
+
+int sys$pread(int fd, void *buf, int64_t nbytes, int64_t offset)
+{
+	if (offset < 0) {
+		return check_error(read(fd, buf, nbytes));
+	}
+
+	return check_error(pread(fd, buf, nbytes, offset));
+}
+
+int sys$pwrite(int fd, void *buf, int64_t nbytes, int64_t offset)
+{
+	if (fd != 1 && fd != 2) {
+		fprintf(stderr, "Oh no.\n");
+		exit(1);
+	}
+
+	if (offset < 0) {
+		return check_error(write(fd, buf, nbytes));
+	}
+
+	return check_error(pwrite(fd, buf, nbytes, offset));
+}
+
+int sys$close(int fd)
+{
+	return check_error(close(fd));
+}
+
+int sys$brk(void *addr, void *_data_segment, size_t *_data_segment_size)
+{
+	size_t new_size = addr - _data_segment;
+	if (mremap(_data_segment, *_data_segment_size, new_size, 0) == MAP_FAILED) {
+		return -1;
+	}
+	*_data_segment_size = new_size;
+	return 0;
 }

src/syscall.h

@@ -1,3 +1,11 @@
 #pragma once
 
+#include <stdint.h>
+#include <stdlib.h>
+
 int sys$open(char *path, int mode);
+int sys$exits(char *msg);
+int sys$pread(int fd, void *buf, int64_t nbytes, int64_t offset);
+int sys$pwrite(int fd, void *buf, int64_t nbytes, int64_t offset);
+int sys$close(int fd);
+int sys$brk(void *addr, void *_data_segment, size_t *_data_segment_size);