| Message ID | 2d821f2c32e6cdca252a80451f38429ef49b6984.1689151537.git.kai.huang@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Unify TDCALL/SEAMCALL and TDVMCALL assembly | expand |
On 7/12/23 1:55 AM, Kai Huang wrote: > In the TDX_HYPERCALL asm, after the TDCALL instruction returns from the > untrusted VMM, the registers that the TDX guest shares to the VMM need > to be cleared to avoid speculative execution of VMM-provided values. > > RSI is specified in the bitmap of those registers, but it is missing > when zeroing out those registers in the current TDX_HYPERCALL. > > It was there when it was originally added in commit 752d13305c78 > ("x86/tdx: Expand __tdx_hypercall() to handle more arguments"), but was > later removed in commit 1e70c680375a ("x86/tdx: Do not corrupt > frame-pointer in __tdx_hypercall()"), which was correct because %rsi is > later restored in the "pop %rsi". However a later commit 7a3a401874be > ("x86/tdx: Drop flags from __tdx_hypercall()") removed that "pop %rsi" > but forgot to add the "xor %rsi, %rsi" back. > > Fix by adding it back. > > Fixes: 7a3a401874be ("x86/tdx: Drop flags from __tdx_hypercall()") > Signed-off-by: Kai Huang <kai.huang@intel.com> > --- Looks fine to me. Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> > arch/x86/coco/tdx/tdcall.S | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S > index b193c0a1d8db..2eca5f43734f 100644 > --- a/arch/x86/coco/tdx/tdcall.S > +++ b/arch/x86/coco/tdx/tdcall.S > @@ -195,6 +195,7 @@ SYM_FUNC_END(__tdx_module_call) > xor %r10d, %r10d > xor %r11d, %r11d > xor %rdi, %rdi > + xor %rsi, %rsi > xor %rdx, %rdx > > /* Restore callee-saved GPRs as mandated by the x86_64 ABI */
diff --git a/arch/x86/coco/tdx/tdcall.S b/arch/x86/coco/tdx/tdcall.S index b193c0a1d8db..2eca5f43734f 100644 --- a/arch/x86/coco/tdx/tdcall.S +++ b/arch/x86/coco/tdx/tdcall.S @@ -195,6 +195,7 @@ SYM_FUNC_END(__tdx_module_call) xor %r10d, %r10d xor %r11d, %r11d xor %rdi, %rdi + xor %rsi, %rsi xor %rdx, %rdx /* Restore callee-saved GPRs as mandated by the x86_64 ABI */
In the TDX_HYPERCALL asm, after the TDCALL instruction returns from the untrusted VMM, the registers that the TDX guest shares to the VMM need to be cleared to avoid speculative execution of VMM-provided values. RSI is specified in the bitmap of those registers, but it is missing when zeroing out those registers in the current TDX_HYPERCALL. It was there when it was originally added in commit 752d13305c78 ("x86/tdx: Expand __tdx_hypercall() to handle more arguments"), but was later removed in commit 1e70c680375a ("x86/tdx: Do not corrupt frame-pointer in __tdx_hypercall()"), which was correct because %rsi is later restored in the "pop %rsi". However a later commit 7a3a401874be ("x86/tdx: Drop flags from __tdx_hypercall()") removed that "pop %rsi" but forgot to add the "xor %rsi, %rsi" back. Fix by adding it back. Fixes: 7a3a401874be ("x86/tdx: Drop flags from __tdx_hypercall()") Signed-off-by: Kai Huang <kai.huang@intel.com> --- arch/x86/coco/tdx/tdcall.S | 1 + 1 file changed, 1 insertion(+)