[SeaBIOS] [PATCH v4] Update EFI_COMPATIBILITY16_TABLE to match 0.98 spec update

[David Woodhouse]

Unless CONFIG_MALLOC_UPPERMEMORY is turned off, we expect to use the
space between the top of option ROMs and the bottom of our own BIOS code
as a stack. OVMF was previously marking the whole region from 0xC0000 to
0xFFFFF read-only before invoking our Legacy16Boot method. Read-only
stack considered harmful.

Version 0.98 of the CSM spec adds the UmaAddress and UmaSize fields which
allow the CSM to specify a memory region that needs to be writeable, so
provide that information.

Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 src/fw/csm.c         |  6 ++++++
 src/std/LegacyBios.h | 20 ++++++++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/src/fw/csm.c b/src/fw/csm.c
index a44ed26..7cdb398 100644
--- a/src/fw/csm.c
+++ b/src/fw/csm.c
@@ -46,8 +46,14 @@ extern void __csm_return(struct bregs *regs) __noreturn;
 static void
 csm_return(struct bregs *regs)
 {
+    u32 rommax = rom_get_max();
+    extern u8 final_readonly_start[];
+
     dprintf(3, "handle_csm returning AX=%04x\n", regs->ax);
 
+    csm_compat_table.UmaAddress = rommax;
+    csm_compat_table.UmaSize = (u32)final_readonly_start - rommax;
+
     PICMask = pic_irqmask_read();
     __csm_return(regs);
 }
diff --git a/src/std/LegacyBios.h b/src/std/LegacyBios.h
index cf0c3c5..5170c37 100644
--- a/src/std/LegacyBios.h
+++ b/src/std/LegacyBios.h
@@ -228,6 +228,26 @@ typedef struct {
   /// Maximum PCI bus number assigned.
   ///
   UINT8                             LastPciBus;
+
+  ///
+  /// Start address of UMB RAM
+  ///
+  UINT32                            UmaAddress;
+
+  ///
+  /// Size of UMB RAM
+  ///
+  UINT32                            UmaSize;
+
+  ///
+  /// Start address of persistent allocation in high (>1MiB) memory
+  ///
+  UINT32                            HiPermanentMemoryAddress;
+
+  ///
+  /// Size of persistent allocation in high (>1MiB) memory
+  ///
+  UINT32                            HiPermanentMemorySize;
 } EFI_COMPATIBILITY16_TABLE;
 
 ///
-- 
1.9.0


-- 
dwmw2

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