[M] Change in coreboot[main]: libpayload/x86: Extend exception handling to x86_64 architecture

[Subrata Banik (Code Review)]

Attention is currently required from: Julius Werner, Paul Menzel.

Hello Julius Werner, Paul Menzel, build bot (Jenkins),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/83036?usp=email

to look at the new patch set (#5).

The following approvals got outdated and were removed:
Verified+1 by build bot (Jenkins)

Change subject: libpayload/x86: Extend exception handling to x86_64 architecture
......................................................................

libpayload/x86: Extend exception handling to x86_64 architecture

Adds 64-bit (x86_64) support to libpayload's exception handler,
previously limited to x86_32.

Ensures `exception_init_asm` is called when building with
LP_ARCH_X86_64 Kconfig.

BUG=b:336265399
TEST=Successful build and boot of google/rex and google/rex64 on
ChromeOS.

Verified correct x86_64 exception handling by triggering "Debug
Exception" using firmware-shell as below:

firmware-shell: mm.l -0
Debug Exception
Error code: n/a
REG_IP:    0x0000000030023e9f
REG_FLAGS: 0x0000000000000046
REG_AX:    0x0000000000000009
REG_BX:    0x0000000000000000
REG_CX:    0x0000002000000000
REG_DX:    0x0000000000000001
REG_SP:    0x0000000034072ec0
REG_BP:    0x0000000000000009
REG_SI:    0x0000000000000029
REG_DI:    0x0000000034072eef
REG_R8:    0x0000000000000009
REG_R9:    0x0000000000000000
REG_R10:   0x0000000000000000
REG_R11:   0x0000000034072d70
REG_R12:   0x0000000000000004
REG_R13:   0x0000000000000001
REG_R14:   0x0000000034072ee6
REG_R15:   0x0000000000000004
Dumping stack:
0x340730c0:
0x340730a0: 30034bc6 00000000 ... 0000002a 00000000
0x34073080: 34073234 00000000 ... 00002e65 00000000
...
...
0x34072ee0: 340730ed 30300000 ... 34073000 00000000
0x34072ec0: 34072ed8 00000000 ... 00000000 00000008
Ready for GDB connection.

Change-Id: I8f0aa1da8d179a760e8d49c3764dfd5a69d06887
Signed-off-by: Subrata Banik 
---
M payloads/libpayload/arch/x86/exception.c
M payloads/libpayload/arch/x86/exception_asm_64.S
2 files changed, 127 insertions(+), 28 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/36/83036/5