[PATCH 0/4] Fix runtime issue in XenBusDxe when compiled with GCC5

[Anthony PERARD <anthony.perard@citrix.com>]

Hi,

That might be only with the Xen part of OVMF but now that the GCC5
toolchains is used with my gcc (6.2.1 20160830, Arch Linux), OVMF fail
to boot in Xen guests.

Here is the result:
!!!! X64 Exception Type - 06(#UD - Invalid Opcode)  CPU Apic ID - 00000000 !!!!
RIP  - 000000001F26AF6B, CS  - 0000000000000038, RFLAGS - 0000000000010202
RAX  - 0000000000000001, RCX - 000000001F26AF51, RDX - 0000000000000004
RBX  - 0000000000000000, RSP - 000000001F43C510, RBP - 000000001E583D18
RSI  - 0000000000000003, RDI - 0000000000000001
R8   - 0000000000000000, R9  - 0000000000000000, R10 - 000000001E58DB98
R11  - 0000000000000002, R12 - 000000001E58D898, R13 - 0000000000000000
R14  - 000000001E58D8A0, R15 - 000000001F26D001
DS   - 0000000000000030, ES  - 0000000000000030, FS  - 0000000000000030
GS   - 0000000000000030, SS  - 0000000000000030
CR0  - 0000000080000033, CR2 - 0000000000000000, CR3 - 000000001F3DB000
CR4  - 0000000000000668, CR8 - 0000000000000000
DR0  - 0000000000000000, DR1 - 0000000000000000, DR2 - 0000000000000000
DR3  - 0000000000000000, DR6 - 00000000FFFF0FF0, DR7 - 0000000000000400
GDTR - 000000001F3C9A98 0000000000000047, LDTR - 0000000000000000
IDTR - 000000001EB0A018 0000000000000FFF,   TR - 0000000000000000
FXSAVE_STATE - 000000001F43C170
!!!! Find PE image ./Build/OvmfX64/DEBUG_GCC5/X64/OvmfPkg/XenBusDxe/XenBusDxe/DEBUG/XenBusDxe.dll (ImageBase=000000001F266000, EntryPoint=000000001F2669D5) !!!!

Removing the gcc option -flto in only the XenBusDxe module makes OVMF
boot.

While trying to debug that, I've added some debug prints (in this module
and in XenPvBlkDxe), and the exception could change and become a "page
fault" instead, or even an assert failure in the PrintLib, that was the
ASSERT(Buffer != NULL) at I think
MdePkg/Library/BasePrintLib/PrintLibInternal.c:366

Adding EFIAPI to internal functions in XenBusDxe makes things work
again.  My guest is that gcc would bypass (optimise) an exported
functions and call directly an internal one but without reordering the
arguments (EFIAPI vs nothing).

Does that make sense?

Anthony PERARD (4):
  OvmfPkg/XenHypercallLib: Add EFIAPI
  OvmfPkg/XenBusDxe: Add EFIAPI to XenEventChannelNotify
  OvmfPkg/XenBusDxe: Add EFIAPI to XenStore functions
  OvmfPkg/XenBusDxe: Add EFIAPI to XenGrantTable{Grant,End}Access

 OvmfPkg/Include/Library/XenHypercallLib.h      |  3 +++
 OvmfPkg/Library/XenHypercallLib/XenHypercall.c |  3 +++
 OvmfPkg/XenBusDxe/EventChannel.c               |  1 +
 OvmfPkg/XenBusDxe/EventChannel.h               |  1 +
 OvmfPkg/XenBusDxe/GrantTable.c                 |  2 ++
 OvmfPkg/XenBusDxe/XenStore.c                   | 13 +++++++++++++
 OvmfPkg/XenBusDxe/XenStore.h                   | 10 ++++++++++
 7 files changed, 33 insertions(+)

-- 
Anthony PERARD