From: Sai Praneeth <sai.praneeth.prakhya@xxxxxxxxx>
During early boot phase EFI_BOOT_SERVICES_<CODE/DATA> regions are marked
as reserved by kernel (see efi_reserve_boot_services()) and hence are
not used by kernel for boot purposes. When EFI_WARN_ON_ILLEGAL_ACCESSES
is enabled, page faults triggered by firmware due to illegal accesses to
EFI_BOOT_SERVICES_<CODE/DATA> regions are dynamically fixed by kernel by
mapping these regions on demand. This resolution assumes that
EFI_BOOT_SERVICES_<CODE/DATA> regions are intact i.e. no one has ever
used these regions except firmware. Hence, to make this assumption true,
don't call efi_free_boot_services() if EFI_WARN_ON_ILLEGAL_ACCESSES is
enabled.
Signed-off-by: Sai Praneeth Prakhya <sai.praneeth.prakhya@xxxxxxxxx>
Suggested-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Based-on-code-from: Ricardo Neri <ricardo.neri@xxxxxxxxx>
Cc: Al Stone <astone@xxxxxxxxxx>
Cc: Lee Chun-Yi <jlee@xxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Bhupesh Sharma <bhsharma@xxxxxxxxxx>
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
---
init/main.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/init/main.c b/init/main.c
index 3b4ada11ed52..dce0520861a1 100644
--- a/init/main.c
+++ b/init/main.c
@@ -730,7 +730,8 @@ asmlinkage __visible void __init start_kernel(void)
arch_post_acpi_subsys_init();
sfi_init_late();
- if (efi_enabled(EFI_RUNTIME_SERVICES)) {
+ if (efi_enabled(EFI_RUNTIME_SERVICES) &&
+ !IS_ENABLED(CONFIG_EFI_WARN_ON_ILLEGAL_ACCESSES)) {
efi_free_boot_services();
}
--
2.7.4
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