From: "sunceping" <cepingx.sun@intel.com>
To: devel@edk2.groups.io
Cc: Ceping Sun <cepingx.sun@intel.com>,
Erdem Aktas <erdemaktas@google.com>,
James Bottomley <jejb@linux.ibm.com>,
Jiewen Yao <jiewen.yao@intel.com>, Min Xu <min.m.xu@intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
Michael Roth <michael.roth@amd.com>,
Gerd Hoffmann <kraxel@redhat.com>,
Isaku Yamahata <isaku.yamahata@intel.com>
Subject: [edk2-devel] [PATCH V1 3/3] OvmfPkg/TdxDxe: Clear the registers before tdcall
Date: Tue, 27 Feb 2024 05:18:33 +0800 [thread overview]
Message-ID: <20240226211833.3156606-4-cepingx.sun@intel.com> (raw)
In-Reply-To: <20240226211833.3156606-1-cepingx.sun@intel.com>
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4696
Refer to the [GHCI] spec, TDVF should clear the BIT5 for RBP in the mask.
And TDVF should clear the regitsers to avoid leaking secrets to VMM.
Reference:
[GHCI]: TDX Guest-Host-Communication Interface v1.5
https://cdrdv2.intel.com/v1/dl/getContent/726792
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Ceping Sun <cepingx.sun@intel.com>
---
OvmfPkg/TdxDxe/X64/ApRunLoop.nasm | 30 ++++++++++++++++++++++++++----
1 file changed, 26 insertions(+), 4 deletions(-)
diff --git a/OvmfPkg/TdxDxe/X64/ApRunLoop.nasm b/OvmfPkg/TdxDxe/X64/ApRunLoop.nasm
index 0bef89c48552..57560015f491 100644
--- a/OvmfPkg/TdxDxe/X64/ApRunLoop.nasm
+++ b/OvmfPkg/TdxDxe/X64/ApRunLoop.nasm
@@ -20,7 +20,7 @@ SECTION .text
BITS 64
-%define TDVMCALL_EXPOSE_REGS_MASK 0xffec
+%define TDVMCALL_EXPOSE_REGS_MASK 0xffcc
%define TDVMCALL 0x0
%define EXIT_REASON_CPUID 0xa
@@ -28,6 +28,30 @@ BITS 64
db 0x66, 0x0f, 0x01, 0xcc
%endmacro
+%macro tdcall_regs_preamble 2
+ mov rax, %1
+
+ xor rcx, rcx
+ mov ecx, %2
+
+ ; R10 = 0 (standard TDVMCALL)
+
+ xor r10d, r10d
+
+ ; Zero out unused (for standard TDVMCALL) registers to avoid leaking
+ ; secrets to the VMM.
+
+ xor esi, esi
+ xor edi, edi
+
+ xor edx, edx
+ xor ebp, ebp
+ xor r8d, r8d
+ xor r9d, r9d
+ xor r14, r14
+ xor r15, r15
+%endmacro
+
;
; Relocated Ap Mailbox loop
;
@@ -40,11 +64,9 @@ global ASM_PFX(AsmRelocateApMailBoxLoop)
ASM_PFX(AsmRelocateApMailBoxLoop):
AsmRelocateApMailBoxLoopStart:
- mov rax, TDVMCALL
- mov rcx, TDVMCALL_EXPOSE_REGS_MASK
- xor r10, r10
mov r11, EXIT_REASON_CPUID
mov r12, 0xb
+ tdcall_regs_preamble TDVMCALL, TDVMCALL_EXPOSE_REGS_MASK
tdcall
test r10, r10
jnz Panic
--
2.34.1
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next prev parent reply other threads:[~2024-02-26 5:19 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 21:18 [edk2-devel] [PATCH V1 0/3] OvmfPkg: Update TDVMCALL to avoid leaking secrets to the VMM sunceping
2024-02-26 21:18 ` [edk2-devel] [PATCH V1 1/3] MdePkg/BaseLib: Update TDVMCALL_EXPOSE_REGS_MASK sunceping
2024-03-04 1:09 ` Min Xu
2024-03-04 3:22 ` sunceping
2024-03-13 7:32 ` sunceping
2024-03-14 14:33 ` 回复: " gaoliming via groups.io
2024-02-26 21:18 ` [edk2-devel] [PATCH V1 2/3] OvmfPkg/CcExitLib: " sunceping
2024-03-04 1:09 ` Min Xu
2024-02-26 21:18 ` sunceping [this message]
2024-02-27 12:25 ` [edk2-devel] [PATCH V1 3/3] OvmfPkg/TdxDxe: Clear the registers before tdcall Isaku Yamahata
2024-02-28 8:27 ` sunceping
2024-03-04 1:09 ` Min Xu
2024-02-27 6:48 ` [edk2-devel] [PATCH V1 0/3] OvmfPkg: Update TDVMCALL to avoid leaking secrets to the VMM Min Xu
2024-03-12 5:53 ` Yao, Jiewen
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