[PATCH v4 11/12] ARM: iwmmxt: Use undef hook to enable coprocessor for task

From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org, linux@armlinux.org.uk
Cc: Ard Biesheuvel <ardb@kernel.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Guenter Roeck <linux@roeck-us.net>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>
Subject: [PATCH v4 11/12] ARM: iwmmxt: Use undef hook to enable coprocessor for task
Date: Mon, 20 Mar 2023 14:18:44 +0100	[thread overview]
Message-ID: <20230320131845.3138015-12-ardb@kernel.org> (raw)
In-Reply-To: <20230320131845.3138015-1-ardb@kernel.org>

Define a undef hook to deal with undef exceptions triggered by iwmmxt
instructions that were issued with the coprocessor disabled. This
removes the dependency on the coprocessor dispatch code in entry-armv.S,
which will be made NWFPE-only in a subsequent patch.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm/include/asm/thread_info.h | 16 ++++++++++++++++
 arch/arm/kernel/iwmmxt.S           |  9 +++++++++
 arch/arm/kernel/pj4-cp0.c          |  1 +
 arch/arm/kernel/xscale-cp0.c       |  1 +
 4 files changed, 27 insertions(+)

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 85c5f1e02ebf83ca..943ffcf069d29cf4 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -40,6 +40,7 @@ struct task_struct;
 DECLARE_PER_CPU(struct task_struct *, __entry_task);
 
 #include <asm/types.h>
+#include <asm/traps.h>
 
 struct cpu_context_save {
 	__u32	r4;
@@ -104,6 +105,21 @@ extern void iwmmxt_task_restore(struct thread_info *, void *);
 extern void iwmmxt_task_release(struct thread_info *);
 extern void iwmmxt_task_switch(struct thread_info *);
 
+extern int iwmmxt_undef_handler(struct pt_regs *, u32);
+
+static inline void register_iwmmxt_undef_handler(void)
+{
+	static struct undef_hook iwmmxt_undef_hook = {
+		.instr_mask	= 0x0c000e00,
+		.instr_val	= 0x0c000000,
+		.cpsr_mask	= MODE_MASK | PSR_T_BIT,
+		.cpsr_val	= USR_MODE,
+		.fn		= iwmmxt_undef_handler,
+	};
+
+	register_undef_hook(&iwmmxt_undef_hook);
+}
+
 extern void vfp_sync_hwstate(struct thread_info *);
 extern void vfp_flush_hwstate(struct thread_info *);
 
diff --git a/arch/arm/kernel/iwmmxt.S b/arch/arm/kernel/iwmmxt.S
index d2b4ac06e4ed8c67..f8ea2c0ee19bd3d7 100644
--- a/arch/arm/kernel/iwmmxt.S
+++ b/arch/arm/kernel/iwmmxt.S
@@ -58,6 +58,15 @@
 	.text
 	.arm
 
+ENTRY(iwmmxt_undef_handler)
+	push		{r9, r10, lr}
+	get_thread_info	r10
+	mov		r9, pc
+	b		iwmmxt_task_enable
+	mov		r0, #0
+	pop		{r9, r10, pc}
+ENDPROC(iwmmxt_undef_handler)
+
 /*
  * Lazy switching of Concan coprocessor context
  *
diff --git a/arch/arm/kernel/pj4-cp0.c b/arch/arm/kernel/pj4-cp0.c
index 1d1fb22f44f37e3b..4bca8098c4ff5583 100644
--- a/arch/arm/kernel/pj4-cp0.c
+++ b/arch/arm/kernel/pj4-cp0.c
@@ -126,6 +126,7 @@ static int __init pj4_cp0_init(void)
 	pr_info("PJ4 iWMMXt v%d coprocessor enabled.\n", vers);
 	elf_hwcap |= HWCAP_IWMMXT;
 	thread_register_notifier(&iwmmxt_notifier_block);
+	register_iwmmxt_undef_handler();
 #endif
 
 	return 0;
diff --git a/arch/arm/kernel/xscale-cp0.c b/arch/arm/kernel/xscale-cp0.c
index ed4f6e77616da1c2..00d00d3aae972d1e 100644
--- a/arch/arm/kernel/xscale-cp0.c
+++ b/arch/arm/kernel/xscale-cp0.c
@@ -166,6 +166,7 @@ static int __init xscale_cp0_init(void)
 		pr_info("XScale iWMMXt coprocessor detected.\n");
 		elf_hwcap |= HWCAP_IWMMXT;
 		thread_register_notifier(&iwmmxt_notifier_block);
+		register_iwmmxt_undef_handler();
 #endif
 	} else {
 		pr_info("XScale DSP coprocessor detected.\n");
-- 
2.39.2


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