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authorRaul E Rangel <rrangel@chromium.org>2021-09-21 10:17:24 -0600
committerFelix Held <felix-coreboot@felixheld.de>2021-09-29 14:12:58 +0000
commitea5c31138b7591efd68147b6ea12097ea98d98c9 (patch)
treeb5d08412fb9dd5146c97dfb3372369d3bf174c91 /src/arch/x86
parent326a2c4794e392df2803a22cbaca66dbb5ed58fd (diff)
arch/x86,cpu/x86: Disable the %gs and %fs segments
The %fs and %gs segment are typically used to implement thread local storage or cpu local storage. We don't currently use these in coreboot, so there is no reason to map them. By setting the segment index to 0, it disables the segment. If an instruction tries to read from one of these segments an exception will be raised. The end goal is to make cpu_info() use the %gs segment. This will remove the stack alignment requirements and fix smm_do_relocation. BUG=b:194391185, b:179699789 TEST=Boot guybrush to OS Signed-off-by: Raul E Rangel <rrangel@chromium.org> Change-Id: Iaa376e562acc6bd1dfffb7a23bdec82aa474c1d5 Reviewed-on: https://review.coreboot.org/c/coreboot/+/57860 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Eric Peers <epeers@google.com> Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Diffstat (limited to 'src/arch/x86')
-rw-r--r--src/arch/x86/c_start.S3
1 files changed, 2 insertions, 1 deletions
diff --git a/src/arch/x86/c_start.S b/src/arch/x86/c_start.S
index b6375b1243..a4a7b28cbb 100644
--- a/src/arch/x86/c_start.S
+++ b/src/arch/x86/c_start.S
@@ -39,8 +39,9 @@ _start:
movl %eax, %ds
movl %eax, %es
movl %eax, %ss
+ xor %eax, %eax /* zero out the gs and fs segment index */
movl %eax, %fs
- movl %eax, %gs
+ movl %eax, %gs /* Will be used for cpu_info */
#if ENV_X86_64
mov $RAM_CODE_SEG64, %ecx
call SetCodeSelector