arm64: mte: Allow {set,get}_tagged_addr_ctrl() on non-current tasks

In preparation for ptrace() access to the prctl() value, allow calling
these functions on non-current tasks.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>

arch/arm64/include/asm/mte.h

@@ -23,8 +23,8 @@ 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(unsigned long arg);
-long get_mte_ctrl(void);
+long set_mte_ctrl(struct task_struct *task, unsigned long arg);
+long get_mte_ctrl(struct task_struct *task);
 
 #else
 
@@ -46,11 +46,11 @@ static inline void mte_thread_switch(struct task_struct *next)
 static inline void mte_suspend_exit(void)
 {
 }
-static inline long set_mte_ctrl(unsigned long arg)
+static inline long set_mte_ctrl(struct task_struct *task, unsigned long arg)
 {
 	return 0;
 }
-static inline long get_mte_ctrl(void)
+static inline long get_mte_ctrl(struct task_struct *task)
 {
 	return 0;
 }

arch/arm64/include/asm/processor.h

@@ -319,10 +319,10 @@ extern void __init minsigstksz_setup(void);
 
 #ifdef CONFIG_ARM64_TAGGED_ADDR_ABI
 /* PR_{SET,GET}_TAGGED_ADDR_CTRL prctl */
-long set_tagged_addr_ctrl(unsigned long arg);
-long get_tagged_addr_ctrl(void);
-#define SET_TAGGED_ADDR_CTRL(arg)	set_tagged_addr_ctrl(arg)
-#define GET_TAGGED_ADDR_CTRL()		get_tagged_addr_ctrl()
+long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg);
+long get_tagged_addr_ctrl(struct task_struct *task);
+#define SET_TAGGED_ADDR_CTRL(arg)	set_tagged_addr_ctrl(current, arg)
+#define GET_TAGGED_ADDR_CTRL()		get_tagged_addr_ctrl(current)
 #endif
 
 /*

arch/arm64/kernel/mte.c

@@ -124,9 +124,10 @@ void mte_suspend_exit(void)
 	update_gcr_el1_excl(current->thread.gcr_user_incl);
 }
 
-long set_mte_ctrl(unsigned long arg)
+long set_mte_ctrl(struct task_struct *task, unsigned long arg)
 {
 	u64 tcf0;
+	u64 gcr_incl = (arg & PR_MTE_TAG_MASK) >> PR_MTE_TAG_SHIFT;
 
 	if (!system_supports_mte())
 		return 0;
@@ -145,22 +146,27 @@ long set_mte_ctrl(unsigned long arg)
 		return -EINVAL;
 	}
 
+	if (task != current) {
+		task->thread.sctlr_tcf0 = tcf0;
+		task->thread.gcr_user_incl = gcr_incl;
+	} else {
 		set_sctlr_el1_tcf0(tcf0);
-	set_gcr_el1_excl((arg & PR_MTE_TAG_MASK) >> PR_MTE_TAG_SHIFT);
+		set_gcr_el1_excl(gcr_incl);
+	}
 
 	return 0;
 }
 
-long get_mte_ctrl(void)
+long get_mte_ctrl(struct task_struct *task)
 {
 	unsigned long ret;
 
 	if (!system_supports_mte())
 		return 0;
 
-	ret = current->thread.gcr_user_incl << PR_MTE_TAG_SHIFT;
+	ret = task->thread.gcr_user_incl << PR_MTE_TAG_SHIFT;
 
-	switch (current->thread.sctlr_tcf0) {
+	switch (task->thread.sctlr_tcf0) {
 	case SCTLR_EL1_TCF0_NONE:
 		return PR_MTE_TCF_NONE;
 	case SCTLR_EL1_TCF0_SYNC:

arch/arm64/kernel/process.c

@@ -641,11 +641,12 @@ void arch_setup_new_exec(void)
  */
 static unsigned int tagged_addr_disabled;
 
-long set_tagged_addr_ctrl(unsigned long arg)
+long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg)
 {
 	unsigned long valid_mask = PR_TAGGED_ADDR_ENABLE;
+	struct thread_info *ti = task_thread_info(task);
 
-	if (is_compat_task())
+	if (is_compat_thread(ti))
 		return -EINVAL;
 
 	if (system_supports_mte())
@@ -661,25 +662,26 @@ long set_tagged_addr_ctrl(unsigned long arg)
 	if (arg & PR_TAGGED_ADDR_ENABLE && tagged_addr_disabled)
 		return -EINVAL;
 
-	if (set_mte_ctrl(arg) != 0)
+	if (set_mte_ctrl(task, arg) != 0)
 		return -EINVAL;
 
-	update_thread_flag(TIF_TAGGED_ADDR, arg & PR_TAGGED_ADDR_ENABLE);
+	update_ti_thread_flag(ti, TIF_TAGGED_ADDR, arg & PR_TAGGED_ADDR_ENABLE);
 
 	return 0;
 }
 
-long get_tagged_addr_ctrl(void)
+long get_tagged_addr_ctrl(struct task_struct *task)
 {
 	long ret = 0;
+	struct thread_info *ti = task_thread_info(task);
 
-	if (is_compat_task())
+	if (is_compat_thread(ti))
 		return -EINVAL;
 
-	if (test_thread_flag(TIF_TAGGED_ADDR))
+	if (test_ti_thread_flag(ti, TIF_TAGGED_ADDR))
 		ret = PR_TAGGED_ADDR_ENABLE;
 
-	ret |= get_mte_ctrl();
+	ret |= get_mte_ctrl(task);
 
 	return ret;
 }