In an upcoming change we are going to introduce per-task SCTLR_EL1 bits for PAC. Move the existing per-task SCTLR_EL1 field out of the MTE-specific code so that we will be able to use it from both the PAC and MTE code paths and make the task switching code more efficient. Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> Link: https://linux-review.googlesource.com/id/Ic65fac78a7926168fa68f9e8da591c9e04ff7278 --- arch/arm64/Kconfig | 4 +++ arch/arm64/include/asm/mte.h | 4 --- arch/arm64/include/asm/processor.h | 10 ++++++- arch/arm64/kernel/mte.c | 47 ++++++------------------------ arch/arm64/kernel/process.c | 34 +++++++++++++++++---- 5 files changed, 50 insertions(+), 49 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index c35e73efd407..21a289dcdf7d 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -344,6 +344,9 @@ config KASAN_SHADOW_OFFSET default 0xeffffff900000000 if ARM64_VA_BITS_36 && KASAN_SW_TAGS default 0xffffffffffffffff +config ARM64_NEED_SCTLR_USER + bool + source "arch/arm64/Kconfig.platforms" menu "Kernel Features" @@ -1671,6 +1674,7 @@ config ARM64_MTE depends on ARM64_AS_HAS_MTE && ARM64_TAGGED_ADDR_ABI depends on AS_HAS_ARMV8_5 select ARCH_USES_HIGH_VMA_FLAGS + select ARM64_NEED_SCTLR_USER help Memory Tagging (part of the ARMv8.5 Extensions) provides architectural support for run-time, always-on detection of diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h index d02aff9f493d..4e807969e767 100644 --- a/arch/arm64/include/asm/mte.h +++ b/arch/arm64/include/asm/mte.h @@ -42,7 +42,6 @@ void mte_free_tag_storage(char *storage); void mte_sync_tags(pte_t *ptep, pte_t pte); void mte_copy_page_tags(void *kto, const void *kfrom); void flush_mte_state(void); -void mte_thread_switch(struct task_struct *next); void mte_suspend_exit(void); long set_mte_ctrl(struct task_struct *task, unsigned long arg); long get_mte_ctrl(struct task_struct *task); @@ -65,9 +64,6 @@ static inline void mte_copy_page_tags(void *kto, const void *kfrom) static inline void flush_mte_state(void) { } -static inline void mte_thread_switch(struct task_struct *next) -{ -} static inline void mte_suspend_exit(void) { } diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index e8cfc41a92d4..254c04b75879 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -153,11 +153,15 @@ struct thread_struct { struct ptrauth_keys_kernel keys_kernel; #endif #ifdef CONFIG_ARM64_MTE - u64 sctlr_tcf0; u64 gcr_user_excl; #endif +#ifdef CONFIG_ARM64_NEED_SCTLR_USER + u64 sctlr_user; +#endif }; +#define SCTLR_USER_MASK SCTLR_EL1_TCF0_MASK + static inline void arch_thread_struct_whitelist(unsigned long *offset, unsigned long *size) { @@ -249,6 +253,10 @@ extern void release_thread(struct task_struct *); unsigned long get_wchan(struct task_struct *p); +#ifdef CONFIG_ARM64_NEED_SCTLR_USER +void set_task_sctlr_el1(u64 sctlr); +#endif + /* Thread switching */ extern struct task_struct *cpu_switch_to(struct task_struct *prev, struct task_struct *next); diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index dbda6598c19d..8c5bf77a0b02 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -158,26 +158,6 @@ void mte_enable(void) isb(); } -static void update_sctlr_el1_tcf0(u64 tcf0) -{ - /* ISB required for the kernel uaccess routines */ - sysreg_clear_set(sctlr_el1, SCTLR_EL1_TCF0_MASK, tcf0); - isb(); -} - -static void set_sctlr_el1_tcf0(u64 tcf0) -{ - /* - * mte_thread_switch() checks current->thread.sctlr_tcf0 as an - * optimisation. Disable preemption so that it does not see - * the variable update before the SCTLR_EL1.TCF0 one. - */ - preempt_disable(); - current->thread.sctlr_tcf0 = tcf0; - update_sctlr_el1_tcf0(tcf0); - preempt_enable(); -} - static void update_gcr_el1_excl(u64 excl) { @@ -210,21 +190,12 @@ void flush_mte_state(void) write_sysreg_s(0, SYS_TFSRE0_EL1); clear_thread_flag(TIF_MTE_ASYNC_FAULT); /* disable tag checking */ - set_sctlr_el1_tcf0(SCTLR_EL1_TCF0_NONE); + set_task_sctlr_el1((current->thread.sctlr_user & ~SCTLR_EL1_TCF0_MASK) | + SCTLR_EL1_TCF0_NONE); /* reset tag generation mask */ set_gcr_el1_excl(SYS_GCR_EL1_EXCL_MASK); } -void mte_thread_switch(struct task_struct *next) -{ - if (!system_supports_mte()) - return; - - /* avoid expensive SCTLR_EL1 accesses if no change */ - if (current->thread.sctlr_tcf0 != next->thread.sctlr_tcf0) - update_sctlr_el1_tcf0(next->thread.sctlr_tcf0); -} - void mte_suspend_exit(void) { if (!system_supports_mte()) @@ -235,7 +206,7 @@ void mte_suspend_exit(void) long set_mte_ctrl(struct task_struct *task, unsigned long arg) { - u64 tcf0; + u64 sctlr = task->thread.sctlr_user & ~SCTLR_EL1_TCF0_MASK; u64 gcr_excl = ~((arg & PR_MTE_TAG_MASK) >> PR_MTE_TAG_SHIFT) & SYS_GCR_EL1_EXCL_MASK; @@ -244,23 +215,23 @@ long set_mte_ctrl(struct task_struct *task, unsigned long arg) switch (arg & PR_MTE_TCF_MASK) { case PR_MTE_TCF_NONE: - tcf0 = SCTLR_EL1_TCF0_NONE; + sctlr |= SCTLR_EL1_TCF0_NONE; break; case PR_MTE_TCF_SYNC: - tcf0 = SCTLR_EL1_TCF0_SYNC; + sctlr |= SCTLR_EL1_TCF0_SYNC; break; case PR_MTE_TCF_ASYNC: - tcf0 = SCTLR_EL1_TCF0_ASYNC; + sctlr |= SCTLR_EL1_TCF0_ASYNC; break; default: return -EINVAL; } if (task != current) { - task->thread.sctlr_tcf0 = tcf0; + task->thread.sctlr_user = sctlr; task->thread.gcr_user_excl = gcr_excl; } else { - set_sctlr_el1_tcf0(tcf0); + set_task_sctlr_el1(sctlr); set_gcr_el1_excl(gcr_excl); } @@ -277,7 +248,7 @@ long get_mte_ctrl(struct task_struct *task) ret = incl << PR_MTE_TAG_SHIFT; - switch (task->thread.sctlr_tcf0) { + switch (task->thread.sctlr_user & SCTLR_EL1_TCF0_MASK) { case SCTLR_EL1_TCF0_NONE: return PR_MTE_TCF_NONE; case SCTLR_EL1_TCF0_SYNC: diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 4784011cecac..47e3dfb5d4a9 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -542,6 +542,29 @@ static void erratum_1418040_thread_switch(struct task_struct *prev, write_sysreg(val, cntkctl_el1); } +#ifdef CONFIG_ARM64_NEED_SCTLR_USER +static void update_sctlr_el1(u64 sctlr) +{ + sysreg_clear_set(sctlr_el1, SCTLR_USER_MASK, sctlr); + + /* ISB required for the kernel uaccess routines when setting TCF0. */ + isb(); +} + +void set_task_sctlr_el1(u64 sctlr) +{ + /* + * __switch_to() checks current->thread.sctlr as an + * optimisation. Disable preemption so that it does not see + * the variable update before the SCTLR_EL1 one. + */ + preempt_disable(); + current->thread.sctlr_user = sctlr; + update_sctlr_el1(sctlr); + preempt_enable(); +} +#endif /* CONFIG_ARM64_NEED_SCTLR_USER */ + /* * Thread switching. */ @@ -567,12 +590,11 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, */ dsb(ish); - /* - * MTE thread switching must happen after the DSB above to ensure that - * any asynchronous tag check faults have been logged in the TFSR*_EL1 - * registers. - */ - mte_thread_switch(next); +#ifdef CONFIG_ARM64_NEED_SCTLR_USER + /* avoid expensive SCTLR_EL1 accesses if no change */ + if (prev->thread.sctlr_user != next->thread.sctlr_user) + update_sctlr_el1(next->thread.sctlr_user); +#endif /* the actual thread switch */ last = cpu_switch_to(prev, next); -- 2.29.2.454.gaff20da3a2-goog
