From: Mark Brown Date: Wed, 16 Feb 2022 17:32:22 +0000 (+0000) Subject: arm64/mte: Add a little bit of documentation for mte_update_sctlr_user() X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=cb627397e02bc65e44912daebfe0bbe6b0ecd384;p=linux.git arm64/mte: Add a little bit of documentation for mte_update_sctlr_user() 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 Reviewed-by: Catalin Marinas Reviewed-by: Vincenzo Frascino Tested-by: Branislav Rankov Link: https://lore.kernel.org/r/20220216173224.2342152-3-broonie@kernel.org Signed-off-by: Will Deacon --- diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index f983795b5eda2..b9a2d13e85f6d 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -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)