Reenable F_SETFL which is necessary for enabling O_NONBLOCK

lrowe · lrowe · commit bc68858d2e1a · 2025-06-02T17:18:59.000-07:00
This should be safe as file access mode and file creation flags are ignored according to the man page.
diff --git a/lib/tinykvm/linux/system_calls.cpp b/lib/tinykvm/linux/system_calls.cpp
@@ -1646,8 +1646,11 @@ void Machine::setup_linux_system_calls(bool unsafe_syscalls)
 				else if (cmd == F_SETFL)
 				{
 					const int writable_fd = cpu.machine().fds().translate_writable_vfd(vfd);
-					(void)writable_fd;
-					regs.rax = 0; // Ignore the new flags
+					const int flags = fcntl(writable_fd, cmd, regs.rdx);
+					if (flags < 0)
+						regs.rax = -errno;
+					else
+						regs.rax = 0;
 				}
 				else if (cmd == F_GETLK64)
 				{

Original file line number	Diff line number	Diff line change
`@@ -1646,8 +1646,11 @@ void Machine::setup_linux_system_calls(bool unsafe_syscalls)`
`1646`	`1646`	`else if (cmd == F_SETFL)`
`1647`	`1647`	`{`
`1648`	`1648`	`const int writable_fd = cpu.machine().fds().translate_writable_vfd(vfd);`
`1649`		`- (void)writable_fd;`
`1650`		`- regs.rax = 0; // Ignore the new flags`
	`1649`	`+ const int flags = fcntl(writable_fd, cmd, regs.rdx);`
	`1650`	`+ if (flags < 0)`
	`1651`	`+ regs.rax = -errno;`
	`1652`	`+ else`
	`1653`	`+ regs.rax = 0;`
`1651`	`1654`	`}`
`1652`	`1655`	`else if (cmd == F_GETLK64)`
`1653`	`1656`	`{`