[ARM] 3168/1: Update ARM signal delivery and masking

Patch from Daniel Jacobowitz

After delivering a signal (creating its stack frame) we must check for
additional pending unblocked signals before returning to userspace.
Otherwise signals may be delayed past the next syscall or reschedule.

Once that was fixed it became obvious that the ARM signal mask manipulation
was broken.  It was a little bit broken before the recent SA_NODEFER
changes, and then very broken after them.  We must block the requested
signals before starting the handler or the same signal can be delivered
again before the handler even gets a chance to run.
Signed-off-by: Daniel Jacobowitz <dan@codesourcery.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/entry-common.S

@@ -48,8 +48,7 @@ work_pending:
 	mov	r0, sp				@ 'regs'
 	mov	r2, why				@ 'syscall'
 	bl	do_notify_resume
-	disable_irq				@ disable interrupts
-	b	no_work_pending
+	b	ret_slow_syscall		@ Check work again
 
 work_resched:
 	bl	schedule

arch/arm/kernel/signal.c

@@ -595,23 +595,22 @@ handle_signal(unsigned long sig, struct k_sigaction *ka,
 	 */
 	ret |= !valid_user_regs(regs);
 
-	/*
-	 * Block the signal if we were unsuccessful.
-	 */
 	if (ret != 0) {
-		spin_lock_irq(&tsk->sighand->siglock);
-		sigorsets(&tsk->blocked, &tsk->blocked,
-			  &ka->sa.sa_mask);
-		if (!(ka->sa.sa_flags & SA_NODEFER))
-			sigaddset(&tsk->blocked, sig);
-		recalc_sigpending();
-		spin_unlock_irq(&tsk->sighand->siglock);
+		force_sigsegv(sig, tsk);
+		return;
 	}
 
-	if (ret == 0)
-		return;
+	/*
+	 * Block the signal if we were successful.
+	 */
+	spin_lock_irq(&tsk->sighand->siglock);
+	sigorsets(&tsk->blocked, &tsk->blocked,
+		  &ka->sa.sa_mask);
+	if (!(ka->sa.sa_flags & SA_NODEFER))
+		sigaddset(&tsk->blocked, sig);
+	recalc_sigpending();
+	spin_unlock_irq(&tsk->sighand->siglock);
 
-	force_sigsegv(sig, tsk);
 }
 
 /*

arch/arm/mm/Makefile

@@ -51,4 +51,4 @@ obj-$(CONFIG_CPU_ARM1026)	+= proc-arm1026.o
 obj-$(CONFIG_CPU_SA110)		+= proc-sa110.o
 obj-$(CONFIG_CPU_SA1100)	+= proc-sa1100.o
 obj-$(CONFIG_CPU_XSCALE)	+= proc-xscale.o
-obj-$(CONFIG_CPU_V6)		+= proc-v6.o blockops.o
+obj-$(CONFIG_CPU_V6)		+= proc-v6.o

arch/arm/mm/blockops.c

-#include <linux/kernel.h>
-#include <linux/init.h>
-#include <linux/errno.h>
-#include <linux/mm.h>
-
-#include <asm/memory.h>
-#include <asm/ptrace.h>
-#include <asm/cacheflush.h>
-#include <asm/traps.h>
-
-extern struct cpu_cache_fns blk_cache_fns;
-
-#define HARVARD_CACHE
-
-/*
- *	blk_flush_kern_dcache_page(kaddr)
- *
- *	Ensure that the data held in the page kaddr is written back
- *	to the page in question.
- *
- *	- kaddr   - kernel address (guaranteed to be page aligned)
- */
-static void __attribute__((naked))
-blk_flush_kern_dcache_page(void *kaddr)
-{
-	asm(
-	"add	r1, r0, %0							\n\
-	sub	r1, r1, %1							\n\
-1:	.word	0xec401f0e	@ mcrr	p15, 0, r0, r1, c14, 0	@ blocking	\n\
-	mov	r0, #0								\n\
-	mcr	p15, 0, r0, c7, c5, 0						\n\
-	mcr	p15, 0, r0, c7, c10, 4						\n\
-	mov	pc, lr"
-	:
-	: "I" (PAGE_SIZE), "I" (L1_CACHE_BYTES));
-}
-
-/*
- *	blk_dma_inv_range(start,end)
- *
- *	Invalidate the data cache within the specified region; we will
- *	be performing a DMA operation in this region and we want to
- *	purge old data in the cache.
- *
- *	- start   - virtual start address of region
- *	- end     - virtual end address of region
- */
-static void __attribute__((naked))
-blk_dma_inv_range_unified(unsigned long start, unsigned long end)
-{
-	asm(
-	"tst	r0, %0								\n\
-	mcrne	p15, 0, r0, c7, c11, 1		@ clean unified line		\n\
-	tst	r1, %0								\n\
-	mcrne	p15, 0, r1, c7, c15, 1		@ clean & invalidate unified line\n\
-	.word	0xec401f06	@ mcrr	p15, 0, r1, r0, c6, 0	@ blocking	\n\
-	mov	r0, #0								\n\
-	mcr	p15, 0, r0, c7, c10, 4		@ drain write buffer		\n\
-	mov	pc, lr"
-	:
-	: "I" (L1_CACHE_BYTES - 1));
-}
-
-static void __attribute__((naked))
-blk_dma_inv_range_harvard(unsigned long start, unsigned long end)
-{
-	asm(
-	"tst	r0, %0								\n\
-	mcrne	p15, 0, r0, c7, c10, 1		@ clean D line			\n\
-	tst	r1, %0								\n\
-	mcrne	p15, 0, r1, c7, c14, 1		@ clean & invalidate D line	\n\
-	.word	0xec401f06	@ mcrr	p15, 0, r1, r0, c6, 0	@ blocking	\n\
-	mov	r0, #0								\n\
-	mcr	p15, 0, r0, c7, c10, 4		@ drain write buffer		\n\
-	mov	pc, lr"
-	:
-	: "I" (L1_CACHE_BYTES - 1));
-}
-
-/*
- *	blk_dma_clean_range(start,end)
- *	- start   - virtual start address of region
- *	- end     - virtual end address of region
- */
-static void __attribute__((naked))
-blk_dma_clean_range(unsigned long start, unsigned long end)
-{
-	asm(
-	".word	0xec401f0c	@ mcrr	p15, 0, r1, r0, c12, 0	@ blocking	\n\
-	mov	r0, #0								\n\
-	mcr	p15, 0, r0, c7, c10, 4		@ drain write buffer		\n\
-	mov	pc, lr");
-}
-
-/*
- *	blk_dma_flush_range(start,end)
- *	- start   - virtual start address of region
- *	- end     - virtual end address of region
- */
-static void __attribute__((naked))
-blk_dma_flush_range(unsigned long start, unsigned long end)
-{
-	asm(
-	".word	0xec401f0e	@ mcrr	p15, 0, r1, r0, c14, 0	@ blocking	\n\
-	mov	pc, lr");
-}
-
-static int blockops_trap(struct pt_regs *regs, unsigned int instr)
-{
-	regs->ARM_r4 |= regs->ARM_r2;
-	regs->ARM_pc += 4;
-	return 0;
-}
-
-static char *func[] = {
-	"Prefetch data range",
-	"Clean+Invalidate data range",
-	"Clean data range",
-	"Invalidate data range",
-	"Invalidate instr range"
-};
-
-static struct undef_hook blockops_hook __initdata = {
-	.instr_mask	= 0x0fffffd0,
-	.instr_val	= 0x0c401f00,
-	.cpsr_mask	= PSR_T_BIT,
-	.cpsr_val	= 0,
-	.fn		= blockops_trap,
-};
-
-static int __init blockops_check(void)
-{
-	register unsigned int err asm("r4") = 0;
-	unsigned int err_pos = 1;
-	unsigned int cache_type;
-	int i;
-
-	asm("mrc p15, 0, %0, c0, c0, 1" : "=r" (cache_type));
-
-	printk("Checking V6 block cache operations:\n");
-	register_undef_hook(&blockops_hook);
-
-	__asm__ ("mov	r0, %0\n\t"
-		"mov	r1, %1\n\t"
-		"mov	r2, #1\n\t"
-		".word	0xec401f2c @ mcrr p15, 0, r1, r0, c12, 2\n\t"
-		"mov	r2, #2\n\t"
-		".word	0xec401f0e @ mcrr p15, 0, r1, r0, c14, 0\n\t"
-		"mov	r2, #4\n\t"
-		".word	0xec401f0c @ mcrr p15, 0, r1, r0, c12, 0\n\t"
-		"mov	r2, #8\n\t"
-		".word	0xec401f06 @ mcrr p15, 0, r1, r0, c6, 0\n\t"
-		"mov	r2, #16\n\t"
-		".word	0xec401f05 @ mcrr p15, 0, r1, r0, c5, 0\n\t"
-		:
-		: "r" (PAGE_OFFSET), "r" (PAGE_OFFSET + 128)
-		: "r0", "r1", "r2");
-
-	unregister_undef_hook(&blockops_hook);
-
-	for (i = 0; i < ARRAY_SIZE(func); i++, err_pos <<= 1)
-		printk("%30s: %ssupported\n", func[i], err & err_pos ? "not " : "");
-
-	if ((err & 8) == 0) {
-		printk(" --> Using %s block cache invalidate\n",
-			cache_type & (1 << 24) ? "harvard" : "unified");
-		if (cache_type & (1 << 24))
-			cpu_cache.dma_inv_range = blk_dma_inv_range_harvard;
-		else
-			cpu_cache.dma_inv_range = blk_dma_inv_range_unified;
-	}
-	if ((err & 4) == 0) {
-		printk(" --> Using block cache clean\n");
-		cpu_cache.dma_clean_range        = blk_dma_clean_range;
-	}
-	if ((err & 2) == 0) {
-		printk(" --> Using block cache clean+invalidate\n");
-		cpu_cache.dma_flush_range        = blk_dma_flush_range;
-		cpu_cache.flush_kern_dcache_page = blk_flush_kern_dcache_page;
-	}
-
-	return 0;
-}
-
-__initcall(blockops_check);