[M] Change in coreboot[master]: cpu/x86/64bit/mode_switch2: The reverse function to mode_switch

[Patrick Rudolph (Code Review)]

Attention is currently required from: Jérémy Compostella.

Patrick Rudolph has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/79749?usp=email )

Change subject: cpu/x86/64bit/mode_switch2: The reverse function to mode_switch
......................................................................

cpu/x86/64bit/mode_switch2: The reverse function to mode_switch

Add another mode_switch assembly function to call x86_64 code from
x86_32 code. This is particullary useful for BLOBs like mrc.bin or
FSP that calls back into coreboot.

Tested:
- Called x86_64 code from x86_32 code in qemu.
- Booted Lenovo X220 using x86_32 MRC using x86_64 console.

Change-Id: Ib625233e5f673eae9f3dcb2d03004c06bb07b149
Signed-off-by: Patrick Rudolph 
---
M src/arch/x86/include/mode_switch.h
M src/cpu/x86/64bit/Makefile.inc
A src/cpu/x86/64bit/mode_switch2.S
3 files changed, 114 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/49/79749/1

diff --git a/src/arch/x86/include/mode_switch.h b/src/arch/x86/include/mode_switch.h
index 4235db9..c2cbbf5 100644
--- a/src/arch/x86/include/mode_switch.h
+++ b/src/arch/x86/include/mode_switch.h
@@ -3,6 +3,27 @@
 #include <stdint.h>

#if ENV_X86_64
+static inline int long_mode_call(void *func)
+{
+	int (*doit)(void) = func;
+
+	return doit();
+}
+
+static inline int long_mode_call_1arg(void *func, uint32_t arg1)
+{
+	int (*doit)(uint32_t arg1) = func;
+
+	return doit(arg1);
+}
+
+static inline int long_mode_call_2arg(void *func, uint32_t arg1, uint32_t arg2)
+{
+	int (*doit)(uint32_t arg1, uint32_t arg2) = func;
+
+	return doit(arg1, arg2);
+}
+
 /*
  * Assembly code that drops into protected mode and calls the function
  * specified as first argument, which must have been compiled for x86_32.
@@ -54,6 +75,55 @@
    return protected_mode_call_3arg((uintptr_t)func, arg1, arg2, 0);
 }
 #else
+/*
+ * Assembly function that elevates into long mode and calls the function
+ * specified as first argument, which must have been compiled for x86_64.
+ * After the function returns it enters protected mode again.
+ * The function pointer destination must be below 4GiB in physical memory.
+ *
+ * The called function has three arguments and returns an int.
+ */
+int long_mode_call_3arg(uint32_t func_ptr,
+			uint32_t opt_arg1,
+			uint32_t opt_arg2,
+			uint32_t opt_arg3);
+
+/*
+ * Elevates into long mode and calls the function, which must have been compiled for x86_64.
+ * After the function returns it enters protected mode again.
+ * The function pointer destination must be below 4GiB in physical memory.
+ *
+ * The called function doesn't have arguments and returns an int.
+ */
+static inline int long_mode_call(void *func)
+{
+	return long_mode_call_3arg((uintptr_t)func, 0, 0, 0);
+}
+
+/*
+ * Elevates into long mode and calls the function, which must have been compiled for x86_64.
+ * After the function returns it enters protected mode again.
+ * The function pointer destination must be below 4GiB in physical memory.
+ *
+ * The called function has one argument and returns an int.
+ */
+static inline int long_mode_call_1arg(void *func, uint32_t arg1)
+{
+	return long_mode_call_3arg((uintptr_t)func, arg1, 0, 0);
+}
+
+/*
+ * Elevates into long mode and calls the function, which must have been compiled for x86_64.
+ * After the function returns it enters protected mode again.
+ * The function pointer destination must be below 4GiB in physical memory.
+ *
+ * The called function has two arguments and returns an int.
+ */
+static inline int long_mode_call_2arg(void *func, uint32_t arg1, uint32_t arg2)
+{
+	return long_mode_call_3arg((uintptr_t)func, arg1, arg2, 0);
+}
+
 static inline int protected_mode_call(void *func)
 {
    int (*doit)(void) = func;
diff --git a/src/cpu/x86/64bit/Makefile.inc b/src/cpu/x86/64bit/Makefile.inc
index e1cf743..24a5a96 100644
--- a/src/cpu/x86/64bit/Makefile.inc
+++ b/src/cpu/x86/64bit/Makefile.inc
@@ -1,6 +1,7 @@
 ## SPDX-License-Identifier: GPL-2.0-only

all_x86-y += mode_switch.S
+all_x86-y += mode_switch2.S

# Add --defsym=_start=0 to suppress a linker warning.
 $(objcbfs)/pt: $(dir)/pt.S $(obj)/config.h
diff --git a/src/cpu/x86/64bit/mode_switch2.S b/src/cpu/x86/64bit/mode_switch2.S
new file mode 100644
index 0000000..0d39f50
--- /dev/null
+++ b/src/cpu/x86/64bit/mode_switch2.S
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Calls a x86_64 function from x86_32 context */
+
+.text
+.code32
+	.section ".text.long_mode_call_3arg", "ax", @progbits
+	.globl long_mode_call_3arg
+long_mode_call_3arg:
+
+	/* Backup registers */
+	pushal
+
+	/* Backup stack pointer */
+	mov	%esp, %ebp
+
+	/* Enter long mode, preserves ebx */
+	#include <cpu/x86/64bit/entry64.inc>
+
+	/* Align stack */
+	movabs	$0xfffffffffffffff0, %rax
+	andq	%rax, %rsp
+
+	movl	36(%rbp), %ebx	/* Function to call */
+	movl	40(%rbp), %edi	/* 1st arg */
+	movl	44(%rbp), %esi	/* 2nd arg */
+	movl	48(%rbp), %edx	/* 3rd arg */
+
+	call	*%rbx
+
+	/* Store return value on stack. popal will fetch it. */
+	mov	%eax, 28(%rbp)
+	shr	$32, %rax
+	movl	%eax, 24(%rbp)
+
+	#include <cpu/x86/64bit/exit32.inc>
+
+	/* Restore stack pointer */
+	mov	%ebp, %esp
+
+	/* Restore registers */
+	popal
+
+	ret