OvmfPkg/Csm/LegacyBiosDxe: Fix Legacy16GetTableAddress call for E820 data

The DX register is supposed to contain the required alignment for the
allocation. It was zero, and SeaBIOS doesn't (well, didn't) cope well
with that. Set it appropriately.

Also set BX to indicate the regions it's OK to allocate in too. That
wasn't being initialised and was just using whatever the previous user
of the structure had left there.

Finally, actually return an error if the allocation fails. Instead of
going all the way through into the CSM and just letting it have a bogus
pointer to the E820 data.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Reviewed-by: Hao A Wu <hao.a.wu@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>

diff --git a/OvmfPkg/Csm/LegacyBiosDxe/LegacyBootSupport.c b/OvmfPkg/Csm/LegacyBiosDxe/LegacyBootSupport.c
index 211750c0123b936a38b9895efaa0a156118b0838..cd4cd24f4246ff51b673e8b0fca92a3b408b544e 100644 (file)
--- a/OvmfPkg/Csm/LegacyBiosDxe/LegacyBootSupport.c
+++ b/OvmfPkg/Csm/LegacyBiosDxe/LegacyBootSupport.c
@@ -928,7 +928,9 @@ GenericLegacyBoot (
   if (CopySize > Private->Legacy16Table->E820Length) {\r
     ZeroMem (&Regs, sizeof (EFI_IA32_REGISTER_SET));\r
     Regs.X.AX = Legacy16GetTableAddress;\r
   if (CopySize > Private->Legacy16Table->E820Length) {\r
     ZeroMem (&Regs, sizeof (EFI_IA32_REGISTER_SET));\r
     Regs.X.AX = Legacy16GetTableAddress;\r

+    Regs.X.BX = (UINT16) 0x0; // Any region\r

     Regs.X.CX = (UINT16) CopySize;\r
     Regs.X.CX = (UINT16) CopySize;\r

+    Regs.X.DX = (UINT16) 0x4; // Alignment\r

     Private->LegacyBios.FarCall86 (\r
       &Private->LegacyBios,\r
       Private->Legacy16Table->Compatibility16CallSegment,\r
     Private->LegacyBios.FarCall86 (\r
       &Private->LegacyBios,\r
       Private->Legacy16Table->Compatibility16CallSegment,\r


@@ -942,6 +944,7 @@ GenericLegacyBoot (
     Private->Legacy16Table->E820Length  = (UINT32) CopySize;\r
     if (Regs.X.AX != 0) {\r
       DEBUG ((EFI_D_ERROR, "Legacy16 E820 length insufficient\n"));\r
     Private->Legacy16Table->E820Length  = (UINT32) CopySize;\r
     if (Regs.X.AX != 0) {\r
       DEBUG ((EFI_D_ERROR, "Legacy16 E820 length insufficient\n"));\r

+      return EFI_OUT_OF_RESOURCES;\r

     } else {\r
       CopyMem (\r
         (VOID *)(UINTN) Private->Legacy16Table->E820Pointer,\r
     } else {\r
       CopyMem (\r
         (VOID *)(UINTN) Private->Legacy16Table->E820Pointer,\r