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arm64: entry.S: Remove disable_dbg

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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>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
James Morse 2017-11-02 12:12:38 +00:00 committed by Will Deacon
parent 8d66772e86
commit 84d0fb1bb6
1 changed files with 1 additions and 8 deletions
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9
arch/arm64/include/asm/assembler.h
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@ -69,13 +69,6 @@
msr daif, \flags
.endm
/*
* Enable and disable debug exceptions.
*/
.macro disable_dbg
msr daifset, #8
.endm
.macro enable_dbg
msr daifclr, #8
.endm
@ -89,9 +82,9 @@
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, #DBG_MDSCR_SS
msr mdscr_el1, \tmp