[PATCH v4 05/21] arm64: entry.S: Remove disable_dbg

James Morse
2017-10-19T14:59:03Z

enable_step_tsk is the only user of disable_dbg, which doesn't respect
our 'dai' order for exception masking. enable_step_tsk may enable
single-step, so previously needed to mask debug exceptions to prevent us
from single-stepping kernel_exit. enable_step_tsk is called at the end
of the ret_to_user loop, which has already masked all exceptions so this
is no longer needed.

Remove disable_dbg, add a comment that enable_step_tsk's caller should
have masked debug.

Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Julien Thierry <julien.thierry@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm64/include/asm/assembler.h | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index 114e741ca873..1b0972046a72 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -68,13 +68,6 @@
msr daif, \flags
.endm

-/*
- * Enable and disable debug exceptions.
- */
- .macro disable_dbg
- msr daifset, #8
- .endm
-
.macro enable_dbg
msr daifclr, #8
.endm
@@ -88,9 +81,9 @@
9990:
.endm

+ /* call with daif masked */
.macro enable_step_tsk, flgs, tmp
tbz \flgs, #TIF_SINGLESTEP, 9990f
- disable_dbg
mrs \tmp, mdscr_el1
orr \tmp, \tmp, #1
msr mdscr_el1, \tmp
--
2.13.3