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authorArd Biesheuvel <ardb@kernel.org>2022-10-28 16:39:14 +0200
committerArd Biesheuvel <ardb@kernel.org>2022-11-03 18:01:15 +0100
commit23715a26c8d812912a70c6ac1ce67af649b95914 (patch)
tree8fdd241a7d36495e386b6fc22ff8b6c25e0e68c9 /arch/arm64/mm/fault.c
parentefi: efivars: Fix variable writes with unsupported query_variable_store() (diff)
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arm64: efi: Recover from synchronous exceptions occurring in firmware
Unlike x86, which has machinery to deal with page faults that occur during the execution of EFI runtime services, arm64 has nothing like that, and a synchronous exception raised by firmware code brings down the whole system. With more EFI based systems appearing that were not built to run Linux (such as the Windows-on-ARM laptops based on Qualcomm SOCs), as well as the introduction of PRM (platform specific firmware routines that are callable just like EFI runtime services), we are more likely to run into issues of this sort, and it is much more likely that we can identify and work around such issues if they don't bring down the system entirely. Since we already use a EFI runtime services call wrapper in assembler, we can quite easily add some code that captures the execution state at the point where the call is made, allowing us to revert to this state and proceed execution if the call triggered a synchronous exception. Given that the kernel and the firmware don't share any data structures that could end up in an indeterminate state, we can happily continue running, as long as we mark the EFI runtime services as unavailable from that point on. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to '')
-rw-r--r--arch/arm64/mm/fault.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 5b391490e045..3e9cf9826417 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -30,6 +30,7 @@
#include <asm/bug.h>
#include <asm/cmpxchg.h>
#include <asm/cpufeature.h>
+#include <asm/efi.h>
#include <asm/exception.h>
#include <asm/daifflags.h>
#include <asm/debug-monitors.h>
@@ -391,6 +392,9 @@ static void __do_kernel_fault(unsigned long addr, unsigned long esr,
msg = "paging request";
}
+ if (efi_runtime_fixup_exception(regs, msg))
+ return;
+
die_kernel_fault(msg, addr, esr, regs);
}