x86: Add implementations of setjmp() and longjmp()

Bring in these functions from Linux v4.4. They will be needed for EFI loader
support.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/Makefile

@@ -10,7 +10,7 @@
 
 extra-y	= start.o
 obj-$(CONFIG_X86_RESET_VECTOR) += resetvec.o start16.o
-obj-y	+= interrupts.o cpu.o cpu_x86.o call64.o
+obj-y	+= interrupts.o cpu.o cpu_x86.o call64.o setjmp.o
 
 AFLAGS_REMOVE_call32.o := -mregparm=3 \
 	$(if $(CONFIG_EFI_STUB_64BIT),-march=i386 -m32)

arch/x86/cpu/setjmp.S

@@ -0,0 +1,61 @@
+/*
+ * Written by H. Peter Anvin <hpa@zytor.com>
+ * Brought in from Linux v4.4 and modified for U-Boot
+ * From Linux arch/um/sys-i386/setjmp.S
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ */
+
+#define _REGPARM
+
+/*
+ * The jmp_buf is assumed to contain the following, in order:
+ *	%ebx
+ *	%esp
+ *	%ebp
+ *	%esi
+ *	%edi
+ *	<return address>
+ */
+
+	.text
+	.align 4
+	.globl setjmp
+	.type setjmp, @function
+setjmp:
+#ifdef _REGPARM
+	movl %eax, %edx
+#else
+	movl 4(%esp), %edx
+#endif
+	popl %ecx		/* Return address, and adjust the stack */
+	xorl %eax, %eax		/* Return value */
+	movl %ebx, (%edx)
+	movl %esp, 4(%edx)	/* Post-return %esp! */
+	pushl %ecx		/* Make the call/return stack happy */
+	movl %ebp, 8(%edx)
+	movl %esi, 12(%edx)
+	movl %edi, 16(%edx)
+	movl %ecx, 20(%edx)	/* Return address */
+	ret
+
+	/* Provide function size if needed */
+	.size setjmp, .-setjmp
+
+	.align 4
+	.globl longjmp
+	.type longjmp, @function
+longjmp:
+#ifdef _REGPARM
+	xchgl %eax, %edx
+#else
+	movl 4(%esp), %edx	/* jmp_ptr address */
+#endif
+	movl (%edx), %ebx
+	movl 4(%edx), %esp
+	movl 8(%edx), %ebp
+	movl 12(%edx), %esi
+	movl 16(%edx), %edi
+	jmp *20(%edx)
+
+	.size longjmp, .-longjmp

arch/x86/include/asm/setjmp.h

@@ -0,0 +1,24 @@
+/*
+ * Written by H. Peter Anvin <hpa@zytor.com>
+ * Brought in from Linux v4.4 and modified for U-Boot
+ * From Linux arch/um/sys-i386/setjmp.S
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ */
+
+#ifndef __setjmp_h
+#define __setjmp_h
+
+struct jmp_buf_data {
+	unsigned int __ebx;
+	unsigned int __esp;
+	unsigned int __ebp;
+	unsigned int __esi;
+	unsigned int __edi;
+	unsigned int __eip;
+};
+
+int setjmp(struct jmp_buf_data *jmp_buf);
+void longjmp(struct jmp_buf_data *jmp_buf, int val);
+
+#endif