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cpu/intel/car/romstage: Fix false-positive stack corruption

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Fix regression introduced in commit 0351872731
("arch/x86: Add breakpoint to stack canary").

romstage_main writes to the stack-canary, but since that's expected
temporarily disable the breakpoint. This only caused a warning on
platforms that do select IDT_IN_EVERY_STAGE, since those install the
stack canary breakpoint.

TEST: No more exceptions are printed in romstage when IDT_IN_EVERY_STAGE
      is enabled.

Change-Id: I7ebf0a5e8eaad49af77ab4d5f6b58fc849013b14
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/85568
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Shuo Liu <shuo.liu@intel.com>
Reviewed-by: Lean Sheng Tan <sheng.tan@9elements.com>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
This commit is contained in:
Patrick Rudolph 2024-12-12 10:42:17 +01:00 • committed by Lean Sheng Tan
commit c3dee9eaba
1 changed files with 18 additions and 0 deletions
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18
src/cpu/intel/car/romstage.c
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@ -3,6 +3,7 @@
#include <adainit.h>
#include <arch/romstage.h>
#include <arch/symbols.h>
#include <arch/stack_canary_breakpoint.h>
#include <commonlib/helpers.h>
#include <console/console.h>
#include <cpu/x86/smm.h>
@ -35,9 +36,26 @@ void __noreturn romstage_main(void)
stack_base = (u32 *)(_ecar_stack - size);
/* Disable breakpoint since stack is intentionally corrupted */
stack_canary_breakpoint_remove();
/*
* The "stack guard" and the "stack canary breakpoint" can both detect excessive
* stack usage. Excessive stack usage can corrupt data and lead to undefined
* (and thus hard to debug) behaviour.
* The stack guard will be checked later on, assuming the corruption wasn't to
* severe and allowed romstage to run. It's useful to detect problems when
* HW breakpoints were disabled.
*
* When HW breakpoints are used and enabled, the stack canary breakpoint will
* report the instruction pointer immediately, which can hint at which function
* may be using too much stack. FSP might disable HW breakpoints, though.
*/
for (i = 0; i < num_guards; i++)
stack_base[i] = stack_guard;
stack_canary_breakpoint_init();
if (CONFIG(VBOOT_EARLY_EC_SYNC))
vboot_sync_ec();