This atomically test and clear a bit.
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Anthony PERARD <anthony.per...@citrix.com>
---
Change in V2:
- Adding .asm version
- Comment the function
---
OvmfPkg/XenBusDxe/X64/TestAndClearBit.S | 13 +++++++++++++
OvmfPkg/XenBusDxe/X64/TestAndClearBit.asm | 16 ++++++++++++++++
OvmfPkg/XenBusDxe/XenBusDxe.h | 19 +++++++++++++++++++
OvmfPkg/XenBusDxe/XenBusDxe.inf | 2 ++
4 files changed, 50 insertions(+)
create mode 100644 OvmfPkg/XenBusDxe/X64/TestAndClearBit.S
create mode 100644 OvmfPkg/XenBusDxe/X64/TestAndClearBit.asm
diff --git a/OvmfPkg/XenBusDxe/X64/TestAndClearBit.S
b/OvmfPkg/XenBusDxe/X64/TestAndClearBit.S
new file mode 100644
index 0000000..cd9c5ed
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/X64/TestAndClearBit.S
@@ -0,0 +1,13 @@
+
+# INT32
+# EFIAPI
+# TestAndClearBit (
+# IN INT32 Bit, // rcx
+# IN volatile VOID* Address // rdx
+# );
+ASM_GLOBAL ASM_PFX(TestAndClearBit)
+ASM_PFX(TestAndClearBit):
+ lock
+ btrl %ecx, (%rdx)
+ sbbl %eax, %eax
+ ret
diff --git a/OvmfPkg/XenBusDxe/X64/TestAndClearBit.asm
b/OvmfPkg/XenBusDxe/X64/TestAndClearBit.asm
new file mode 100644
index 0000000..c7fc83d
--- /dev/null
+++ b/OvmfPkg/XenBusDxe/X64/TestAndClearBit.asm
@@ -0,0 +1,16 @@
+.code
+
+; INT32
+; EFIAPI
+; TestAndClearBit (
+; IN INT32 Bit, // rcx
+; IN volatile VOID* Address // rdx
+; );
+TestAndClearBit PROC
+ lock
+ btr [rdx], ecx
+ sbb eax, eax
+ ret
+TestAndClearBit ENDP
+
+END
diff --git a/OvmfPkg/XenBusDxe/XenBusDxe.h b/OvmfPkg/XenBusDxe/XenBusDxe.h
index 878e7c5..d690914 100644
--- a/OvmfPkg/XenBusDxe/XenBusDxe.h
+++ b/OvmfPkg/XenBusDxe/XenBusDxe.h
@@ -113,4 +113,23 @@ struct _XENBUS_DEVICE {
shared_info_t *SharedInfo;
};
+/*
+ * Helpers
+ */
+
+/**
+ Atomically test and clear a bit.
+
+ @param Bit Bit index to test in *Address
+ @param Address The Address to the buffer that contain the bit to test.
+
+ @return Value of the Bit before it was cleared.
+**/
+INT32
+EFIAPI
+TestAndClearBit (
+ IN INT32 Bit,
+ IN volatile VOID *Address
+ );
+
#endif
diff --git a/OvmfPkg/XenBusDxe/XenBusDxe.inf b/OvmfPkg/XenBusDxe/XenBusDxe.inf
index 13623bd..e8f362a 100644
--- a/OvmfPkg/XenBusDxe/XenBusDxe.inf
+++ b/OvmfPkg/XenBusDxe/XenBusDxe.inf
@@ -45,6 +45,8 @@
X64/InterlockedCompareExchange16.c | GCC
X64/InterlockedCompareExchange16.asm | INTEL
InterlockedCompareExchange16Intel.c | INTEL
+ X64/TestAndClearBit.S
+ X64/TestAndClearBit.asm
[LibraryClasses]
UefiDriverEntryPoint
--
Anthony PERARD
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