Hi Larry, On 05/22/2014 03:27 PM, Larry Bassel wrote: > To implement the context tracker properly on arm64, > a function call needs to be made after debugging and > interrupts are turned on, but before the lr is changed > to point to ret_to_user(). If the function call > is made after the lr is changed the function will not > return to the correct place. > > For similar reasons, defer the setting of x0 so that > it doesn't need to be saved around the function call > (save far_el1 in x26 temporarily instead). > > Signed-off-by: Larry Bassel <larry.bas...@linaro.org> > --- > arch/arm64/kernel/entry.S | 24 +++++++++++++++++------- > 1 file changed, 17 insertions(+), 7 deletions(-) > > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index e8b23a3..20b336e 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -354,7 +354,6 @@ el0_sync: > lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class > cmp x24, #ESR_EL1_EC_SVC64 // SVC in 64-bit state > b.eq el0_svc > - adr lr, ret_to_user > cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0 > b.eq el0_da > cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0 > @@ -383,7 +382,6 @@ el0_sync_compat: > lsr x24, x25, #ESR_EL1_EC_SHIFT // exception class > cmp x24, #ESR_EL1_EC_SVC32 // SVC in 32-bit state > b.eq el0_svc_compat > - adr lr, ret_to_user > cmp x24, #ESR_EL1_EC_DABT_EL0 // data abort in EL0 > b.eq el0_da > cmp x24, #ESR_EL1_EC_IABT_EL0 // instruction abort in EL0 > @@ -426,22 +424,26 @@ el0_da: > /* > * Data abort handling > */ > - mrs x0, far_el1 > - bic x0, x0, #(0xff << 56) > + mrs x26, far_el1 > // enable interrupts before calling the main handler > enable_dbg_and_irq > + mov x0, x26 > + bic x0, x0, #(0xff << 56)
Nit: I believe you can bit clear with x26 as the source register and omit the move instruction. Regards, Christopher -- Employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by the Linux Foundation. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
