From 339ff8995a8fdd33c5ef1ac492e627c22fee941c Mon Sep 17 00:00:00 2001
From: Travis Geiselbrecht <geist@foobox.com>
Date: Thu, 9 May 2024 19:51:32 -0700
Subject: [PATCH] [arch][barriers] add default memory barriers for all of the
 architectures

Most are pretty straightforward, but a few of the more esoteric
architectures just defaults are implemented.
---
 arch/arm/include/arch/arch_ops.h        |  1 +
 arch/m68k/include/arch/arch_ops.h       |  2 +-
 arch/microblaze/include/arch/arch_ops.h |  9 +++++++++
 arch/mips/include/arch/arch_ops.h       | 10 +++++++++
 arch/or1k/include/arch/arch_ops.h       | 10 +++++++++
 arch/x86/include/arch/arch_ops.h        | 27 +++++++++++++++++++++++++
 6 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/arch/arm/include/arch/arch_ops.h b/arch/arm/include/arch/arch_ops.h
index 73a21d23de..4a2c7f8b1e 100644
--- a/arch/arm/include/arch/arch_ops.h
+++ b/arch/arm/include/arch/arch_ops.h
@@ -210,6 +210,7 @@ static inline void arch_set_current_thread(struct thread *t) {
 
 #endif
 
+// TODO: use less strong versions of these (dsb sy/ld/st)
 #define mb()        DSB
 #define wmb()       DSB
 #define rmb()       DSB
diff --git a/arch/m68k/include/arch/arch_ops.h b/arch/m68k/include/arch/arch_ops.h
index 552f70d702..1e651d6cfe 100644
--- a/arch/m68k/include/arch/arch_ops.h
+++ b/arch/m68k/include/arch/arch_ops.h
@@ -47,7 +47,7 @@ static inline uint arch_curr_cpu_num(void) {
     return 0;
 }
 
-// TODO: see if there's a proper (or required) memory barrier on 68k
+// Default barriers for architectures that generally don't need them
 #define mb()        CF
 #define wmb()       CF
 #define rmb()       CF
diff --git a/arch/microblaze/include/arch/arch_ops.h b/arch/microblaze/include/arch/arch_ops.h
index 8e2d85f8d5..ab22f5dee7 100644
--- a/arch/microblaze/include/arch/arch_ops.h
+++ b/arch/microblaze/include/arch/arch_ops.h
@@ -66,3 +66,12 @@ static inline uint arch_curr_cpu_num(void) {
     return 0;
 }
 
+// Default barriers for architectures that generally don't need them
+// TODO: do we need these for microblaze?
+#define mb()        CF
+#define wmb()       CF
+#define rmb()       CF
+#define smp_mb()    CF
+#define smp_wmb()   CF
+#define smp_rmb()   CF
+
diff --git a/arch/mips/include/arch/arch_ops.h b/arch/mips/include/arch/arch_ops.h
index a20838a5a0..2e3fcb4e9b 100644
--- a/arch/mips/include/arch/arch_ops.h
+++ b/arch/mips/include/arch/arch_ops.h
@@ -57,3 +57,13 @@ static inline uint arch_curr_cpu_num(void) {
     return 0;
 }
 
+// Default barriers for architectures that generally don't need them
+// TODO: do we need these for mips?
+#define mb()        CF
+#define wmb()       CF
+#define rmb()       CF
+#define smp_mb()    CF
+#define smp_wmb()   CF
+#define smp_rmb()   CF
+
+
diff --git a/arch/or1k/include/arch/arch_ops.h b/arch/or1k/include/arch/arch_ops.h
index 32356c7b94..ff8f785fc1 100644
--- a/arch/or1k/include/arch/arch_ops.h
+++ b/arch/or1k/include/arch/arch_ops.h
@@ -82,4 +82,14 @@ static inline ulong arch_cycle_count(void) { return 0; }
 static inline uint arch_curr_cpu_num(void) {
     return 0;
 }
+
+// Default barriers for architectures that generally don't need them
+// TODO: do we need these for or1k?
+#define mb()        CF
+#define wmb()       CF
+#define rmb()       CF
+#define smp_mb()    CF
+#define smp_wmb()   CF
+#define smp_rmb()   CF
+
 #endif // !ASSEMBLY
diff --git a/arch/x86/include/arch/arch_ops.h b/arch/x86/include/arch/arch_ops.h
index 65f25b465f..b3092d6020 100644
--- a/arch/x86/include/arch/arch_ops.h
+++ b/arch/x86/include/arch/arch_ops.h
@@ -65,4 +65,31 @@ static inline uint arch_curr_cpu_num(void) {
     return 0;
 }
 
+#if ARCH_X86_64
+// relies on SSE2
+#define mb()        __asm__ volatile("mfence" : : : "memory")
+#define rmb()       __asm__ volatile("lfence" : : : "memory")
+#define wmb()       __asm__ volatile("sfence" : : : "memory")
+#else
+// Store to the top of the stack as a load/store barrier. Cannot
+// rely on SS2 being intrinsically available for older i386 class hardware.
+#define __storeload_barrier \
+    __asm__ volatile("lock; addl $0, (%%esp)" : : : "memory", "cc")
+#define mb()        __storeload_barrier
+#define rmb()       __storeload_barrier
+#define wmb()       __storeload_barrier
+#endif
+
+#ifdef WITH_SMP
+// XXX probably too strict
+#define smp_mb()    mb
+#define smp_rmb()   rmb
+#define smp_wmb()   wmb
+#else
+#define smp_mb()    CF
+#define smp_wmb()   CF
+#define smp_rmb()   CF
+#endif
+
+
 #endif // !ASSEMBLY