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arm64/mte: Add a little bit of documentation for mte_update_sctlr_user()

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The code isn't that obscure but it probably won't hurt to have a little
bit more documentation for anyone trying to find out where everything
actually takes effect.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Vincenzo Frascino <Vincenzo.Frascino@arm.com>
Tested-by: Branislav Rankov <branislav.rankov@arm.com>
Link: https://lore.kernel.org/r/20220216173224.2342152-3-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Mark Brown 2022-02-16 17:32:22 +00:00 committed by Will Deacon
parent 3f9ab2a698
commit cb627397e0
1 changed files with 14 additions and 0 deletions
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14
arch/arm64/kernel/mte.c
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@ -186,6 +186,11 @@ void mte_check_tfsr_el1(void)
}
#endif
/*
* This is where we actually resolve the system and process MTE mode
* configuration into an actual value in SCTLR_EL1 that affects
* userspace.
*/
static void mte_update_sctlr_user(struct task_struct *task)
{
/*
@ -199,8 +204,17 @@ static void mte_update_sctlr_user(struct task_struct *task)
unsigned long pref, resolved_mte_tcf;
pref = __this_cpu_read(mte_tcf_preferred);
/*
* If there is no overlap between the system preferred and
* program requested values go with what was requested.
*/
resolved_mte_tcf = (mte_ctrl & pref) ? pref : mte_ctrl;
sctlr &= ~SCTLR_EL1_TCF0_MASK;
/*
* Pick an actual setting. The order in which we check for
* set bits and map into register values determines our
* default order.
*/
if (resolved_mte_tcf & MTE_CTRL_TCF_ASYNC)
sctlr |= SCTLR_EL1_TCF0_ASYNC;
else if (resolved_mte_tcf & MTE_CTRL_TCF_SYNC)