efi/libstub: x86/mixed: increase supported argument count

Increase the number of arguments supported by mixed mode calls, so that
we will be able to call into the TCG2 protocol to measure the initrd
and extend the associated PCR. This involves the TCG2 protocol's
hash_log_extend_event() method, which takes five arguments, three of
which are u64 and need to be split, producing a total of 8 outgoing
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Link: https://lore.kernel.org/r/20211119114745.1560453-3-ilias.apalodimas@linaro.orgSigned-off-by: Ard Biesheuvel <ardb@kernel.org>

arch/x86/boot/compressed/efi_thunk_64.S

@@ -26,8 +26,6 @@ SYM_FUNC_START(__efi64_thunk)
 	push	%rbp
 	push	%rbx
 
-	leaq	1f(%rip), %rbp
-
 	movl	%ds, %eax
 	push	%rax
 	movl	%es, %eax
@@ -35,6 +33,11 @@ SYM_FUNC_START(__efi64_thunk)
 	movl	%ss, %eax
 	push	%rax
 
+	/* Copy args passed on stack */
+	movq	0x30(%rsp), %rbp
+	movq	0x38(%rsp), %rbx
+	movq	0x40(%rsp), %rax
+
 	/*
 	 * Convert x86-64 ABI params to i386 ABI
 	 */
@@ -44,13 +47,18 @@ SYM_FUNC_START(__efi64_thunk)
 	movl	%ecx, 0x8(%rsp)
 	movl	%r8d, 0xc(%rsp)
 	movl	%r9d, 0x10(%rsp)
+	movl	%ebp, 0x14(%rsp)
+	movl	%ebx, 0x18(%rsp)
+	movl	%eax, 0x1c(%rsp)
 
-	leaq	0x14(%rsp), %rbx
+	leaq	0x20(%rsp), %rbx
 	sgdt	(%rbx)
 
 	addq	$16, %rbx
 	sidt	(%rbx)
 
+	leaq	1f(%rip), %rbp
+
 	/*
 	 * Switch to IDT and GDT with 32-bit segments. This is the firmware GDT
 	 * and IDT that was installed when the kernel started executing. The

arch/x86/include/asm/efi.h

@@ -46,13 +46,14 @@ extern unsigned long efi_mixed_mode_stack_pa;
 
 #define __efi_nargs(...) __efi_nargs_(__VA_ARGS__)
 #define __efi_nargs_(...) __efi_nargs__(0, ##__VA_ARGS__,	\
+	__efi_arg_sentinel(9), __efi_arg_sentinel(8),		\
 	__efi_arg_sentinel(7), __efi_arg_sentinel(6),		\
 	__efi_arg_sentinel(5), __efi_arg_sentinel(4),		\
 	__efi_arg_sentinel(3), __efi_arg_sentinel(2),		\
 	__efi_arg_sentinel(1), __efi_arg_sentinel(0))
-#define __efi_nargs__(_0, _1, _2, _3, _4, _5, _6, _7, n, ...)	\
+#define __efi_nargs__(_0, _1, _2, _3, _4, _5, _6, _7, _8, _9, n, ...)	\
 	__take_second_arg(n,					\
-		({ BUILD_BUG_ON_MSG(1, "__efi_nargs limit exceeded"); 8; }))
+		({ BUILD_BUG_ON_MSG(1, "__efi_nargs limit exceeded"); 10; }))
 #define __efi_arg_sentinel(n) , n
 
 /*
@@ -176,8 +177,9 @@ extern u64 efi_setup;
 extern efi_status_t __efi64_thunk(u32, ...);
 
 #define efi64_thunk(...) ({						\
-	__efi_nargs_check(efi64_thunk, 6, __VA_ARGS__);			\
-	__efi64_thunk(__VA_ARGS__);					\
+	u64 __pad[3]; /* must have space for 3 args on the stack */	\
+	__efi_nargs_check(efi64_thunk, 9, __VA_ARGS__);			\
+	__efi64_thunk(__VA_ARGS__, __pad);				\
 })
 
 static inline bool efi_is_mixed(void)

arch/x86/platform/efi/efi_thunk_64.S

@@ -36,6 +36,17 @@ SYM_CODE_START(__efi64_thunk)
 	movq	efi_mixed_mode_stack_pa(%rip), %rsp
 	push	%rax
 
+	/*
+	 * Copy args passed via the stack
+	 */
+	subq	$0x24, %rsp
+	movq	0x18(%rax), %rbp
+	movq	0x20(%rax), %rbx
+	movq	0x28(%rax), %rax
+	movl	%ebp, 0x18(%rsp)
+	movl	%ebx, 0x1c(%rsp)
+	movl	%eax, 0x20(%rsp)
+
 	/*
 	 * Calculate the physical address of the kernel text.
 	 */
@@ -47,7 +58,6 @@ SYM_CODE_START(__efi64_thunk)
 	subq	%rax, %rbp
 	subq	%rax, %rbx
 
-	subq	$28, %rsp
 	movl	%ebx, 0x0(%rsp)		/* return address */
 	movl	%esi, 0x4(%rsp)
 	movl	%edx, 0x8(%rsp)
@@ -60,7 +70,7 @@ SYM_CODE_START(__efi64_thunk)
 	pushq	%rdi			/* EFI runtime service address */
 	lretq
 
-1:	movq	24(%rsp), %rsp
+1:	movq	0x20(%rsp), %rsp
 	pop	%rbx
 	pop	%rbp
 	retq