Change in coreboot[master]: arch/x86: Save resume vector to stack in x86_64 mode

[Patrick Georgi (Code Review)]

Patrick Georgi has submitted this change. ( https://review.coreboot.org/c/coreboot/+/55947 )

Change subject: arch/x86: Save resume vector to stack in x86_64 mode
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arch/x86: Save resume vector to stack in x86_64 mode

In x86_64, the first function parameter is passed in rdi register, and
the 32-bit code after exiting long mode reads the resume vector in
4(%esp), so it's needed to save the resume vector from rdi to 4(%rsp).

Also note that the function attribute "regparm" only works on x86-32
targets according to the GCC manual, so "asmlinkage" doesn't change
the ABI of an x86_64 function.

Tested on HP EliteBook 2560p. The laptop can resume from S3 in x86_64
mode after this change.

Change-Id: I45f2678071b2511c0af5dce9d9b73ac70dfd7252
Signed-off-by: Iru Cai 
Reviewed-on: https://review.coreboot.org/c/coreboot/+/55947
Reviewed-by: Arthur Heymans 
Tested-by: build bot (Jenkins) 
---
M src/arch/x86/wakeup.S
1 file changed, 7 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Arthur Heymans: Looks good to me, approved

diff --git a/src/arch/x86/wakeup.S b/src/arch/x86/wakeup.S
index dc9510b..7462dad 100644
--- a/src/arch/x86/wakeup.S
+++ b/src/arch/x86/wakeup.S
@@ -15,6 +15,13 @@
    .globl __wakeup
 __wakeup:
 #if ENV_X86_64
+	/* When called in x86_64 mode, the resume vector is in %rdi
+	 * instead of the stack, save it in 4(%rsp) for the 32-bit code.
+	 * It's OK to overwrite the return address at (%rsp) because this
+	 * function doesn't return.
+	 */
+	mov	%edi, 4(%rsp)
+
    xor	%rax,%rax
    mov	%ss, %ax
    push	%rax