From d0a431c8603955773054529dff5c643105212046 Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Sat, 4 Feb 2023 17:46:05 +0000
Subject: [PATCH] kernel: add basic spinlocks

---
 arch/x86_64/hwlock.S                       | 103 +++++++++++++++++++++
 arch/x86_64/include/socks/machine/hwlock.h |  14 +++
 include/socks/compiler.h                   |   1 +
 include/socks/locks.h                      |  11 ++-
 kernel/spinlock.c                          |  14 ---
 5 files changed, 125 insertions(+), 18 deletions(-)
 create mode 100644 arch/x86_64/hwlock.S
 create mode 100644 arch/x86_64/include/socks/machine/hwlock.h
 delete mode 100644 kernel/spinlock.c

diff --git a/arch/x86_64/hwlock.S b/arch/x86_64/hwlock.S
new file mode 100644
index 0000000..b659333
--- /dev/null
+++ b/arch/x86_64/hwlock.S
@@ -0,0 +1,103 @@
+/* x86_64 hardware locks
+   these are raw spinlocks with support for irq saving and restoring */
+
+	.global ml_hwlock_lock
+	.type ml_hwlock_lock, @function
+
+	/* %rdi = pointer to ml_hwlock_t (int) */
+ml_hwlock_lock:
+	push %rbp
+	mov %rsp, %rbp
+
+	mov $1, %ecx
+
+	cli
+	mfence
+
+1:	mov $0, %eax
+	lock cmpxchg %ecx, (%rdi)
+	jne 1b
+
+	pop %rbp
+	ret
+
+	.global ml_hwlock_unlock
+	.type ml_hwlock_unlock, @function
+
+	/* %rdi = pointer to ml_hwlock_t (int) */
+ml_hwlock_unlock:
+	push %rbp
+	mov %rsp, %rbp
+
+	movl $0, (%rdi)
+	mfence
+	sti
+
+	pop %rbp
+	ret
+
+
+	.global ml_hwlock_lock_irqsave
+	.type ml_hwlock_lock_irqsave, @function
+
+	/* %rdi = pointer to ml_hwlock_t (int)
+	   %rsi = pointer to quadword to store rflags in */
+ml_hwlock_lock_irqsave:	
+	push %rbp
+	mov %rsp, %rbp
+
+	pushfq
+	popq (%rsi)
+
+	cli
+
+	mov $1, %ecx
+
+	mfence
+
+1:	mov $0, %eax
+	lock cmpxchg %ecx, (%rdi)
+	jne 1b
+
+	pop %rbp
+	ret
+
+	.global ml_hwlock_unlock_irqrestore
+	.type ml_hwlock_unlock_irqrestore, @function
+
+	/* %rdi = pointer to ml_hwlock_t (int)
+	   %rsi = quadword with saved rflags */
+ml_hwlock_unlock_irqrestore:
+	push %rbp
+	mov %rsp, %rbp
+
+	movl $0, (%rdi)
+	mfence
+
+	pushfq
+	popq %rax                       /* rax = the current rflags register */
+	                                /* rsi = the saved rflags register */
+
+	andq $0x200, %rsi               /* we only want to copy IF (bit 9, 0x200) */
+	andq $0xFFFFFFFFFFFFFDFF, %rax
+	orq %rsi, %rax
+
+	pushq %rsi
+	popfq
+
+	pop %rbp
+	ret
+
+
+	.global get_rflags
+	.type get_rflags, @function
+
+get_rflags:
+	push %rbp
+	mov %rsp, %rbp
+
+	pushfq
+	popq %rax
+
+	pop %rbp
+	ret
diff --git a/arch/x86_64/include/socks/machine/hwlock.h b/arch/x86_64/include/socks/machine/hwlock.h
new file mode 100644
index 0000000..fa86265
--- /dev/null
+++ b/arch/x86_64/include/socks/machine/hwlock.h
@@ -0,0 +1,14 @@
+#ifndef SOCKS_X86_64_HWLOCK_H_
+#define SOCKS_X86_64_HWLOCK_H_
+
+#define ML_HWLOCK_INIT (0)
+
+typedef int ml_hwlock_t;
+
+extern void ml_hwlock_lock(ml_hwlock_t *lck);
+extern void ml_hwlock_unlock(ml_hwlock_t *lck);
+
+extern void ml_hwlock_lock_irqsave(ml_hwlock_t *lck, unsigned long *flags);
+extern void ml_hwlock_unlock_irqrestore(ml_hwlock_t *lck, unsigned long flags);
+
+#endif
diff --git a/include/socks/compiler.h b/include/socks/compiler.h
index a79d015..61044bb 100644
--- a/include/socks/compiler.h
+++ b/include/socks/compiler.h
@@ -4,5 +4,6 @@
 #define __used __attribute__((used))
 #define __packed __attribute__((packed))
 #define __section(name) __attribute__((section(name)))
+#define __aligned(x) __attribute__((aligned(x)))
 
 #endif
diff --git a/include/socks/locks.h b/include/socks/locks.h
index 9b07aae..1a8f419 100644
--- a/include/socks/locks.h
+++ b/include/socks/locks.h
@@ -1,11 +1,14 @@
 #ifndef SOCKS_LOCKS_H_
 #define SOCKS_LOCKS_H_
 
-typedef int __attribute__((aligned(8))) spin_lock_t;
+#include <socks/compiler.h>
+#include <socks/machine/hwlock.h>
 
-#define SPIN_LOCK_INIT ((spin_lock_t)0)
+typedef __aligned(8) ml_hwlock_t spin_lock_t;
 
-extern void spin_lock_irqsave(spin_lock_t *lck, unsigned long *flags);
-extern void spin_unlock_irqrestore(spin_lock_t *lck, unsigned long flags);
+#define SPIN_LOCK_INIT ML_HWLOCK_INIT
+
+#define spin_lock_irqsave(lck, flags) ml_hwlock_lock_irqsave(lck, flags);
+#define spin_unlock_irqrestore(lck, flags) ml_hwlock_unlock_irqrestore(lck, flags);
 
 #endif
diff --git a/kernel/spinlock.c b/kernel/spinlock.c
deleted file mode 100644
index 0e247d9..0000000
--- a/kernel/spinlock.c
+++ /dev/null
@@ -1,14 +0,0 @@
-#include <socks/locks.h>
-
-void spin_lock_irqsave(spin_lock_t *lck, unsigned long *flags)
-{
-	while (!__sync_bool_compare_and_swap(lck, 0, 1)) {
-		/* pause */
-	}
-}
-
-void spin_unlock_irqrestore(spin_lock_t *lck, unsigned long flags)
-{
-    __sync_lock_release(lck);
-}
-