From 09ec66de840c6542d60ebd6a256ba0ea38307777 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Wed, 14 Jul 2021 15:38:41 +0100 Subject: [PATCH] UPSTREAM: arm64: mte: fix restoration of GCR_EL1 from suspend Since commit: bad1e1c663e0a72f ("arm64: mte: switch GCR_EL1 in kernel entry and exit") we saved/restored the user GCR_EL1 value at exception boundaries, and update_gcr_el1_excl() is no longer used for this. However it is used to restore the kernel's GCR_EL1 value when returning from a suspend state. Thus, the comment is misleading (and an ISB is necessary). When restoring the kernel's GCR value, we need an ISB to ensure this is used by subsequent instructions. We don't necessarily get an ISB by other means (e.g. if the kernel is built without support for pointer authentication). As __cpu_setup() initialised GCR_EL1.Exclude to 0xffff, until a context synchronization event, allocation tag 0 may be used rather than the desired set of tags. This patch drops the misleading comment, adds the missing ISB, and for clarity folds update_gcr_el1_excl() into its only user. Fixes: bad1e1c663e0 ("arm64: mte: switch GCR_EL1 in kernel entry and exit") Signed-off-by: Mark Rutland Cc: Andrey Konovalov Cc: Catalin Marinas Cc: Vincenzo Frascino Cc: Will Deacon Link: https://lore.kernel.org/r/20210714143843.56537-2-mark.rutland@arm.com Signed-off-by: Will Deacon (cherry picked from commit 59f44069e0527523f27948da7b77599a73dab157) Bug: 187129171 Signed-off-by: Connor O'Brien Change-Id: I1be6e588f9796ca5f01d2e9bd5e9743c40dc0778 --- arch/arm64/kernel/mte.c | 15 ++------------- 1 file changed, 2 insertions(+), 13 deletions(-) diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index 50ae1a7435ae..859c1fcefdf4 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -188,18 +188,6 @@ void mte_check_tfsr_el1(void) } #endif -static void update_gcr_el1_excl(u64 excl) -{ - - /* - * Note that the mask controlled by the user via prctl() is an - * include while GCR_EL1 accepts an exclude mask. - * No need for ISB since this only affects EL0 currently, implicit - * with ERET. - */ - sysreg_clear_set_s(SYS_GCR_EL1, SYS_GCR_EL1_EXCL_MASK, excl); -} - static void mte_update_sctlr_user(struct task_struct *task) { /* @@ -271,7 +259,8 @@ void mte_suspend_exit(void) if (!system_supports_mte()) return; - update_gcr_el1_excl(gcr_kernel_excl); + sysreg_clear_set_s(SYS_GCR_EL1, SYS_GCR_EL1_EXCL_MASK, gcr_kernel_excl); + isb(); } long set_mte_ctrl(struct task_struct *task, unsigned long arg)