execve(): support for ETXTBSY via a new ioctl() call to test in kernel space with open_exec()

executer/include/uprotocol.h

@@ -42,6 +42,8 @@
 #define MCEXEC_UP_PREPARE_DMA    0x30a02910
 #define MCEXEC_UP_FREE_DMA       0x30a02911
 
+#define MCEXEC_UP_TEST_OPEN_EXEC 0x30a02912
+
 #define MCEXEC_UP_TRANSFER_TO_REMOTE	0
 #define MCEXEC_UP_TRANSFER_FROM_REMOTE	1
 

executer/kernel/control.c

@@ -29,6 +29,8 @@
 #include <linux/wait.h>
 #include <linux/mm.h>
 #include <linux/gfp.h>
+#include <linux/fs.h>
+#include <linux/file.h>
 #include <asm/uaccess.h>
 #include <asm/delay.h>
 #include <asm/msr.h>
@@ -690,6 +692,24 @@ long mcexec_ret_syscall(ihk_os_t os, struct syscall_ret_desc *__user arg)
 	return 0;
 }
 
+int mcexec_test_open_exec(ihk_os_t os, char * __user filename)
+{
+	struct file *file;
+	int retval;
+
+	file = open_exec(filename);
+	retval = PTR_ERR(file);
+	if (IS_ERR(file)) {
+		goto out_return;
+	}
+
+	retval = 0;
+	fput(file);
+
+out_return:
+	return -retval;
+}
+
 long mcexec_strncpy_from_user(ihk_os_t os, struct strncpy_from_user_desc * __user arg)
 {
 	struct strncpy_from_user_desc desc;
@@ -770,7 +790,11 @@ long __mcctrl_control(ihk_os_t os, unsigned int req, unsigned long arg)
 		return mcexec_get_cpu(os);
 
 	case MCEXEC_UP_STRNCPY_FROM_USER:
-		return mcexec_strncpy_from_user(os, (struct strncpy_from_user_desc *)arg);
+		return mcexec_strncpy_from_user(os, 
+				(struct strncpy_from_user_desc *)arg);
+
+	case MCEXEC_UP_TEST_OPEN_EXEC:
+		return mcexec_test_open_exec(os, (char *)arg);
 
 	case MCEXEC_UP_PREPARE_DMA:
 		return mcexec_pin_region(os, (unsigned long *)arg);

executer/kernel/driver.c

@@ -57,6 +57,7 @@ static struct ihk_os_user_call_handler mcctrl_uchs[] = {
 	{ .request = MCEXEC_UP_STRNCPY_FROM_USER, .func = mcctrl_ioctl },
 	{ .request = MCEXEC_UP_PREPARE_DMA, .func = mcctrl_ioctl },
 	{ .request = MCEXEC_UP_FREE_DMA, .func = mcctrl_ioctl },
+	{ .request = MCEXEC_UP_TEST_OPEN_EXEC, .func = mcctrl_ioctl },
 };
 
 static struct ihk_os_user_call mcctrl_uc_proto = {

executer/user/mcexec.c

@@ -520,6 +520,12 @@ int load_elf_desc(char *filename, struct program_load_desc **desc_p,
 
 	rewind(fp);
 	
+	if ((ret = ioctl(fd, MCEXEC_UP_TEST_OPEN_EXEC, filename)) != 0) {
+		fprintf(stderr, "Error: open_exec() fails for %s: %d (fd: %d)\n", 
+			filename, ret, fd);
+		return ret;
+	}
+	
 	desc = load_elf(fp, &interp_path);
 	if (!desc) {
 		fclose(fp);
@@ -989,6 +995,13 @@ int main(int argc, char **argv)
 	}
 	__dprintf("%s", "\n");
 
+	/* Open OS chardev for ioctl() */
+	fd = open(dev, O_RDWR);
+	if (fd < 0) {
+		fprintf(stderr, "Error: Failed to open %s.\n", dev);
+		return 1;
+	}
+
 	if (lookup_exec_path(argv[optind], path, sizeof(path)) != 0) {
 		fprintf(stderr, "error: finding file: %s\n", argv[optind]);
 		return 1;
@@ -1053,12 +1066,6 @@ int main(int argc, char **argv)
 	desc->rlimit_stack_cur = rlim_stack.rlim_cur;
 	desc->rlimit_stack_max = rlim_stack.rlim_max;
 
-	fd = open(dev, O_RDWR);
-	if (fd < 0) {
-		fprintf(stderr, "Error: Failed to open %s.\n", dev);
-		return 1;
-	}
-
 	ncpu = ioctl(fd, MCEXEC_UP_GET_CPU, 0);
 	if(ncpu == -1){
 		fprintf(stderr, "No CPU found.\n");