Interrupt must be disabled before we storing ELR and other system registers, or else ELR will be overridden by interrupt reentrance.
This bug is critical as we may get occasional exception or dead loop when interrupt reentrance occurs: After increasing SP ... Before popping out registers Or After restoring ELR The 1st circumstance could also be resolved by optimizing SP operation (Pop out registers before adding SP back), but the 2nd could not be resolved by disabling interrupt. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Heyi Guo <heyi....@linaro.org> Cc: Leif Lindholm <leif.lindh...@linaro.org> Cc: Ard Biesheuvel <ard.biesheu...@linaro.org> --- ArmPkg/Drivers/CpuDxe/AArch64/ExceptionSupport.S | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/ArmPkg/Drivers/CpuDxe/AArch64/ExceptionSupport.S b/ArmPkg/Drivers/CpuDxe/AArch64/ExceptionSupport.S index 2682f4f..ca6c9a1 100644 --- a/ArmPkg/Drivers/CpuDxe/AArch64/ExceptionSupport.S +++ b/ArmPkg/Drivers/CpuDxe/AArch64/ExceptionSupport.S @@ -358,6 +358,14 @@ ASM_PFX(AsmCommonExceptionEntry): #define REG_PAIR(REG1, REG2, OFFSET, CONTEXT_SIZE) ldp REG1, REG2, [sp, #(OFFSET-CONTEXT_SIZE)] #define REG_ONE(REG1, OFFSET, CONTEXT_SIZE) ldur REG1, [sp, #(OFFSET-CONTEXT_SIZE)] + // + // Disable interrupt(IRQ and FIQ) before restoring context, + // or else the context will be corrupted by interrupt reentrance. + // Interrupt mask will be restored from spsr by hardware when we call eret + // + msr daifset, #3 + isb + // Adjust SP to pop system registers add sp, sp, #(GP_CONTEXT_SIZE + FP_CONTEXT_SIZE + SYS_CONTEXT_SIZE) ALL_SYS_REGS -- 2.1.4 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
