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)
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 +452,7 @@ 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 +461,19 @@ 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:
/*
@@ -476,23 +482,27 @@ 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:
/*
* Debug exception handling
*/
tbnz x24, #0, el0_inv // EL0 only
- mrs x0, far_el1
+ mrs x26, far_el1
+ mov x0, x26
mov x1, x25
mov x2, sp
bl do_debug_exception
enable_dbg
+ mov x0, x26
b ret_to_user
el0_inv:
enable_dbg
mov x0, sp
mov x1, #BAD_SYNC
mrs x2, esr_el1
+ adr lr, ret_to_user
b bad_mode
ENDPROC(el0_sync)
--
1.8.3.2
--
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