Due to the introduction of NULL pointer detection feature, page 0 will be
disabled if the feature is enabled, which will cause legacy code failed to
update legacy data in page 0. This macro is introduced to make sure the
page 0 is enabled before those code and restore the original status of it
afterwards.
Another reason to introduce this macro is to eliminate the dependency on
the PcdNullPointerDetectionPropertyMask. Because this is a new PCD, it
could cause some backward compatibility issue for some old packages.
This macro will simply check if the page 0 is disabled or not. If it's
disabled, it will enable it before code updating page 0 and disable it
afterwards. Otherwise, this macro will do nothing to page 0.
The usage of the macro will be look like (similar to DEBUG_CODE macro):
ACCESS_PAGE0_CODE(
{
<code accessing page 0>
}
);
Cc: Liming Gao <liming....@intel.com>
Cc: Michael D Kinney <michael.d.kin...@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Jian J Wang <jian.j.w...@intel.com>
---
IntelFrameworkPkg/Include/Protocol/LegacyBios.h | 34 +++++++++++++++++++++++++
1 file changed, 34 insertions(+)
diff --git a/IntelFrameworkPkg/Include/Protocol/LegacyBios.h
b/IntelFrameworkPkg/Include/Protocol/LegacyBios.h
index 641f101bce..f77c92ba21 100644
--- a/IntelFrameworkPkg/Include/Protocol/LegacyBios.h
+++ b/IntelFrameworkPkg/Include/Protocol/LegacyBios.h
@@ -1518,6 +1518,40 @@ struct _EFI_LEGACY_BIOS_PROTOCOL {
EFI_LEGACY_BIOS_BOOT_UNCONVENTIONAL_DEVICE BootUnconventionalDevice;
};
+//
+// Legacy BIOS needs to access memory in page 0 (0-4095), which is disabled if
+// NULL pointer detection feature is enabled. Following macro can be used to
+// enable/disable page 0 before/after accessing it.
+//
+#define ACCESS_PAGE0_CODE(statements) \
+ do { \
+ EFI_STATUS Status_; \
+ EFI_GCD_MEMORY_SPACE_DESCRIPTOR Desc_; \
+ \
+ Status_ = gDS->GetMemorySpaceDescriptor (0, &Desc_); \
+ if (!EFI_ERROR (Status_)) { \
+ if ((Desc_.Attributes & EFI_MEMORY_RP) != 0) { \
+ Status_ = gDS->SetMemorySpaceAttributes ( \
+ 0, \
+ EFI_PAGES_TO_SIZE(1), \
+ Desc_.Attributes &= ~EFI_MEMORY_RP \
+ ); \
+ ASSERT_EFI_ERROR (Status_); \
+ } \
+ \
+ statements; \
+ \
+ if ((Desc_.Attributes & EFI_MEMORY_RP) != 0) { \
+ Status_ = gDS->SetMemorySpaceAttributes ( \
+ 0, \
+ EFI_PAGES_TO_SIZE(1), \
+ Desc_.Attributes \
+ ); \
+ ASSERT_EFI_ERROR (Status_); \
+ } \
+ } \
+ } while (FALSE)
+
extern EFI_GUID gEfiLegacyBiosProtocolGuid;
#endif
--
2.15.1.windows.2
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