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authorPatrick Rudolph <patrick.rudolph@9elements.com>2020-11-30 15:56:59 +0100
committerPatrick Georgi <pgeorgi@google.com>2020-12-05 08:19:17 +0000
commit7a359497cd83babdc5d3244a390cb775412105e6 (patch)
treeab346dffaa621ca95713f70b671126989aebc62e /src/cpu/x86/64bit
parent22b42a87de7cbc680857e512bcd0651a47b9fbdb (diff)
cpu/x86/64bit: Add code to call function in protected mode
This adds a helper function for long mode to call some code in protected mode and return back to long mode. The primary use case is to run binaries that have been compiled for protected mode, like the FSP or MRC binaries. Tested on Intel Skylake. The FSP-M runs and returns without error while coreboot runs in long mode. Change-Id: I22af2d224b546c0be9e7295330b4b6602df106d6 Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com> Reviewed-on: https://review.coreboot.org/c/coreboot/+/48175 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Diffstat (limited to 'src/cpu/x86/64bit')
-rw-r--r--src/cpu/x86/64bit/mode_switch.S70
1 files changed, 70 insertions, 0 deletions
diff --git a/src/cpu/x86/64bit/mode_switch.S b/src/cpu/x86/64bit/mode_switch.S
new file mode 100644
index 0000000000..eea104bcf3
--- /dev/null
+++ b/src/cpu/x86/64bit/mode_switch.S
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+.text
+.code64
+ .section ".text.protected_mode_call", "ax", @progbits
+ .globl protected_mode_call_narg
+protected_mode_call_narg:
+
+ push %rbp
+ mov %rsp, %rbp
+ /* Preserve registers */
+ push %rbx
+ push %r12
+ push %r13
+ push %r14
+ push %r15
+
+ /* Arguments to stack */
+ push %rdi
+ push %rsi
+ push %rdx
+ push %rcx
+
+ #include <cpu/x86/64bit/exit32.inc>
+
+ movl -48(%ebp), %eax /* Argument count */
+ movl -64(%ebp), %edx /* Argument 0 */
+ movl -72(%ebp), %ecx /* Argument 1 */
+
+ /* Align the stack */
+ andl $0xFFFFFFF0, %esp
+ test %eax, %eax
+ je 1f /* Zero arguments */
+
+ subl $1, %eax
+ test %eax, %eax
+ je 2f /* One argument */
+
+ /* Two arguments */
+ subl $8, %esp
+ pushl %ecx /* Argument 1 */
+ pushl %edx /* Argument 0 */
+ jmp 1f
+2:
+ subl $12, %esp
+ pushl %edx /* Argument 0 */
+
+1:
+ movl -56(%ebp), %ebx /* Function to call */
+ call *%ebx
+ movl %eax, %ebx
+
+ /* Preserves ebx */
+ #include <cpu/x86/64bit/entry64.inc>
+
+ /* Place return value in rax */
+ movl %ebx, %eax
+
+ /* Restore registers */
+ mov -40(%rbp), %r15
+ mov -32(%rbp), %r14
+ mov -24(%rbp), %r13
+ mov -16(%rbp), %r12
+ mov -8(%rbp), %rbx
+
+ /* Restore stack pointer */
+ mov %rbp, %rsp
+ pop %rbp
+
+ ret