ARM: kernel: Get rid of thread_info::used_cp[] array

We keep track of which coprocessor triggered a fault in the used_cp[]
array in thread_info, but this data is never used anywhere. So let's
remove it.

Linus did some digging and found out that the last user of this field
was removed in commit bb1a773 ("kill unused dump_fpu() instances").

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Author: ardbiesheuvel

arch/arm/include/asm/thread_info.h

@@ -66,7 +66,6 @@ struct thread_info {
 	__u32			cpu_domain;	/* cpu domain */
 	struct cpu_context_save	cpu_context;	/* cpu context */
 	__u32			abi_syscall;	/* ABI type and syscall nr */
-	__u8			used_cp[16];	/* thread used copro */
 	unsigned long		tp_value[2];	/* TLS registers */
 	union fp_state		fpstate __attribute__((aligned(8)));
 	union vfp_state		vfpstate;

arch/arm/kernel/asm-offsets.c

@@ -47,7 +47,6 @@ int main(void)
   DEFINE(TI_CPU_DOMAIN,		offsetof(struct thread_info, cpu_domain));
   DEFINE(TI_CPU_SAVE,		offsetof(struct thread_info, cpu_context));
   DEFINE(TI_ABI_SYSCALL,	offsetof(struct thread_info, abi_syscall));
-  DEFINE(TI_USED_CP,		offsetof(struct thread_info, used_cp));
   DEFINE(TI_TP_VALUE,		offsetof(struct thread_info, tp_value));
   DEFINE(TI_FPSTATE,		offsetof(struct thread_info, fpstate));
 #ifdef CONFIG_VFP

arch/arm/kernel/entry-armv.S

@@ -591,19 +591,13 @@ call_fpe:
 	and	r8, r0, r5
 	cmp	r8, r7				@ NEON instruction?
 	bne	2b
-	mov	r7, #1
-	strb	r7, [r10, #TI_USED_CP + 10]	@ mark CP#10 as used
-	strb	r7, [r10, #TI_USED_CP + 11]	@ mark CP#11 as used
 	b	do_vfp				@ let VFP handler handle this
 1:
 #endif
 	tst	r0, #0x08000000			@ only CDP/CPRT/LDC/STC have bit 27
 	tstne	r0, #0x04000000			@ bit 26 set on both ARM and Thumb-2
 	reteq	lr
 	and	r8, r0, #0x00000f00		@ mask out CP number
-	mov	r7, #1
-	add	r6, r10, r8, lsr #8		@ add used_cp[] array offset first
-	strb	r7, [r6, #TI_USED_CP]		@ set appropriate used_cp[]
 #ifdef CONFIG_IWMMXT
 	@ Test if we need to give access to iWMMXt coprocessors
 	ldr	r5, [r10, #TI_FLAGS]

arch/arm/kernel/process.c

@@ -222,7 +222,6 @@ void flush_thread(void)
 
 	flush_ptrace_hw_breakpoint(tsk);
 
-	memset(thread->used_cp, 0, sizeof(thread->used_cp));
 	memset(&tsk->thread.debug, 0, sizeof(struct debug_info));
 	memset(&thread->fpstate, 0, sizeof(union fp_state));
 

arch/arm/kernel/ptrace.c

@@ -584,8 +584,6 @@ static int fpa_set(struct task_struct *target,
 {
 	struct thread_info *thread = task_thread_info(target);
 
-	thread->used_cp[1] = thread->used_cp[2] = 1;
-
 	return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
 		&thread->fpstate,
 		0, sizeof(struct user_fp));