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.bassel@linaro.org --- arch/arm64/kernel/entry.S | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index e8b23a3..b0101b9 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 +424,25 @@ 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 + bic x0, x26, #(0xff << 56) mov x1, x25 mov x2, sp + adr lr, ret_to_user b do_mem_abort el0_ia: /* * Instruction abort handling */ - mrs x0, far_el1 + mrs x26, far_el1 // enable interrupts before calling the main handler enable_dbg_and_irq + mov x0, x26 orr x1, x25, #1 << 24 // use reserved ISS bit for instruction aborts mov x2, sp + adr lr, ret_to_user b do_mem_abort el0_fpsimd_acc: /* @@ -450,6 +451,7 @@ el0_fpsimd_acc: enable_dbg mov x0, x25 mov x1, sp + adr lr, ret_to_user b do_fpsimd_acc el0_fpsimd_exc: /* @@ -458,16 +460,19 @@ el0_fpsimd_exc: enable_dbg mov x0, x25 mov x1, sp + adr lr, ret_to_user b do_fpsimd_exc el0_sp_pc: /* * Stack or PC alignment exception handling */ - mrs x0, far_el1 + mrs x26, far_el1 // enable interrupts before calling the main handler enable_dbg_and_irq + mov x0, x26 mov x1, x25 mov x2, sp + adr lr, ret_to_user b do_sp_pc_abort el0_undef: /* @@ -476,6 +481,7 @@ el0_undef: // enable interrupts before calling the main handler enable_dbg_and_irq mov x0, sp + adr lr, ret_to_user b do_undefinstr el0_dbg: /* @@ -493,6 +499,7 @@ el0_inv: mov x0, sp mov x1, #BAD_SYNC mrs x2, esr_el1 + adr lr, ret_to_user b bad_mode ENDPROC(el0_sync)