kernel: add yield syscall

kernel-src/arch/x86-64/syscall.asm

@@ -98,6 +98,7 @@ extern syscall_getcpu
 extern syscall_sysinfo
 extern syscall_writev
 extern syscall_readv
+extern syscall_yield
 syscalltab:
 dq syscall_print
 dq syscall_mmap
@@ -198,7 +199,8 @@ dq syscall_getcpu
 dq syscall_sysinfo
 dq syscall_writev
 dq syscall_readv
-syscallcount equ 99
+dq syscall_yield
+syscallcount equ 100
 section .text
 global arch_syscall_entry
 ; on entry:

kernel-src/sys/syscalls/yield.c

@@ -0,0 +1,10 @@
+#include <kernel/syscalls.h>
+#include <kernel/scheduler.h>
+
+syscallret_t syscall_yield(context_t *) {
+	syscallret_t ret = {0};
+
+	sched_yield();
+
+	return ret;
+}

patches/mlibc/jinx-working-patch.patch

@@ -89,10 +89,10 @@ index 1ed110d..ded9114 100644
 +void backtrace_symbols_fd(void *const *, int, int) {
  }
 diff --git mlibc-clean/sysdeps/astral/generic/generic.cpp mlibc-workdir/sysdeps/astral/generic/generic.cpp
-index 939925e..5ee7fad 100644
+index 939925e..eb6a6aa 100644
 --- mlibc-clean/sysdeps/astral/generic/generic.cpp
 +++ mlibc-workdir/sysdeps/astral/generic/generic.cpp
-@@ -47,6 +47,12 @@ namespace mlibc {
+@@ -47,6 +47,17 @@ namespace mlibc {
  		return 0;
  	}
  
@@ -101,6 +101,11 @@ index 939925e..5ee7fad 100644
 +		// unlockpt is a no-op kernel side, so use this to check for an invalid pty
 +		return sys_ioctl(fd, 0x13376167, NULL, &r);
 +	}
++
++	void sys_yield() {
++		long r;
++		syscall(SYSCALL_YIELD, &r);
++	}
 +
  	int sys_readv(int fd, const struct iovec *iovs, int iovc, ssize_t *bytes_read) {
  		long r;
@@ -121,3 +126,15 @@ index 7e4f2a1..a5f382d 100644
  
  #ifdef __cplusplus
  extern "C" {
+diff --git mlibc-clean/sysdeps/astral/include/astral/syscall.h mlibc-workdir/sysdeps/astral/include/astral/syscall.h
+index a6c4067..d1656ca 100644
+--- mlibc-clean/sysdeps/astral/include/astral/syscall.h
++++ mlibc-workdir/sysdeps/astral/include/astral/syscall.h
+@@ -103,6 +103,7 @@
+ #define SYSCALL_SYSINFO 96
+ #define SYSCALL_WRITEV 97
+ #define SYSCALL_READV 98
++#define SYSCALL_YIELD 99
+ 
+ #ifndef __MLIBC_ABI_ONLY
+