arch/x86/boot: Jump to payload in protected mode

*   On ARCH_RAMSTAGE_X86_64 jump to the payload in protected mode.
*   Add a helper function to jump to arbitrary code in protected mode,
    similar to the real mode call handler.
*   Doesn't affect existing x86_32 code.
*   Add a macro to cast pointer to uint32_t that dies if it would overflow
    on conversion

Tested on QEMU Q35 using SeaBIOS as payload.
Tested on Lenovo T410 with additional x86_64 patches.

Change-Id: I6552ac30f1b6205e08e16d251328e01ce3fbfd14
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/30118
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

1 files changed, 38 insertions, 0 deletions

diff --git a/src/arch/x86/c_exit.S b/src/arch/x86/c_exit.S
new file mode 100644
index 0000000000..e5b9bf8d74
--- /dev/null
+++ b/src/arch/x86/c_exit.S
@@ -0,0 +1,38 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <arch/ram_segs.h>
+#include <cpu/x86/msr.h>
+#include <cpu/x86/cr.h>
+
+
+#ifdef __x86_64__
+
+	/*
+	 * Functions to handle mode switches from long mode to protected
+	 * mode.
+	 */
+.text
+.code64
+	.section ".text.protected_mode_jump", "ax", @progbits
+	.globl protected_mode_jump
+protected_mode_jump:
+
+	push %rbp
+	mov %rsp, %rbp
+
+	/* Arguments to stack */
+	push	%rdi
+	push	%rsi
+
+	#include <cpu/x86/64bit/exit32.inc>
+
+	movl	-8(%ebp), %eax	/* Function to call */
+	movl	-16(%ebp), %ebx	/* Argument 0 */
+
+	/* Align the stack */
+	andl	$0xFFFFFFF0, %esp
+	subl	$12, %esp
+	pushl	%ebx	/* Argument 0 */
+
+	jmp	*%eax
+#endif