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[for_v37,1/6] x86/vdso: x86/sgx: Explicitly force 8-byte CMP for detecting user handler

Message ID 20200904104437.29555-2-sean.j.christopherson@intel.com (mailing list archive)
State New, archived
Headers show
Series x86/vdso: x86/sgx: Rework SGX vDSO API | expand

Commit Message

Sean Christopherson Sept. 4, 2020, 10:44 a.m. UTC 
Use 'cmpq' to force an 8-byte CMP when checking for a user provided exit
handler.  The handler is a pointer, which is guaranteed to be an 8-byte
value since SGX is 64-bit mode only, and gcc defaults to 'cmpl' given a
bare 'cmp', i.e. is only checking the lower 32 bits.  This could cause
a false negative when detecting a user exit handler.

Acked-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Acked-by: Jethro Beekman <jethro@fortanix.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/entry/vdso/vsgx_enter_enclave.S | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/x86/entry/vdso/vsgx_enter_enclave.S b/arch/x86/entry/vdso/vsgx_enter_enclave.S
index be7e467e1efb3..2d88acd408d4e 100644
--- a/arch/x86/entry/vdso/vsgx_enter_enclave.S
+++ b/arch/x86/entry/vdso/vsgx_enter_enclave.S
@@ -48,7 +48,7 @@  SYM_FUNC_START(__vdso_sgx_enter_enclave)
 
 	/* Invoke userspace's exit handler if one was provided. */
 .Lhandle_exit:
-	cmp	$0, 0x20(%rbp)
+	cmpq	$0, 0x20(%rbp)
 	jne	.Linvoke_userspace_handler
 
 .Lout: