[PATCH] mips: irq: Use DECLARE_BITMAP

[PATCH] mips: irq: Use DECLARE_BITMAP

[Joe Perches]

Use the generic mechanism to declare a bitmap instead of unsigned long.

This could fix an overwrite defect of whatever follows irq_map.

Not all "#define NR_IRQS <value>" are a multiple of BITS_PER_LONG so
using DECLARE_BITMAP allocates the proper number of longs required
for the possible bits.

For instance:

arch/mips/include/asm/mach-ath79/irq.h:#define NR_IRQS                  51
arch/mips/include/asm/mach-db1x00/irq.h:#define NR_IRQS 152
arch/mips/include/asm/mach-lantiq/falcon/irq.h:#define NR_IRQS 328

Signed-off-by: Joe Perches <joe@perches.com>
---
 arch/mips/kernel/irq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/irq.c b/arch/mips/kernel/irq.c
index d2bfbc2..51f57d8 100644
--- a/arch/mips/kernel/irq.c
+++ b/arch/mips/kernel/irq.c
@@ -29,7 +29,7 @@
 int kgdb_early_setup;
 #endif
 
-static unsigned long irq_map[NR_IRQS / BITS_PER_LONG];
+static DECLARE_BITMAP(irq_map, NR_IRQS);
 
 int allocate_irqno(void)
 {

Re: [PATCH] mips: irq: Use DECLARE_BITMAP

[Ralf Baechle]

On Wed, May 20, 2015 at 05:44:54AM -0700, Joe Perches wrote:

> Use the generic mechanism to declare a bitmap instead of unsigned long.
> 
> This could fix an overwrite defect of whatever follows irq_map.
> 
> Not all "#define NR_IRQS <value>" are a multiple of BITS_PER_LONG so
> using DECLARE_BITMAP allocates the proper number of longs required
> for the possible bits.
> 
> For instance:
> 
> arch/mips/include/asm/mach-ath79/irq.h:#define NR_IRQS                  51
> arch/mips/include/asm/mach-db1x00/irq.h:#define NR_IRQS 152
> arch/mips/include/asm/mach-lantiq/falcon/irq.h:#define NR_IRQS 328

This only matters to user of the allocate_irqno() API and there is only
on such platform, the IP27 which fortunately uses a NR_IRQS value that
is a multiple of 64, so no impact.

Thanks anyway!

  Ralf

Re: [PATCH] mips: irq: Use DECLARE_BITMAP

[Joe Perches]

On Thu, 2015-05-21 at 15:14 +0200, Ralf Baechle wrote:
> On Wed, May 20, 2015 at 05:44:54AM -0700, Joe Perches wrote:
> 
> > Use the generic mechanism to declare a bitmap instead of unsigned long.
> > 
> > This could fix an overwrite defect of whatever follows irq_map.
> > 
> > Not all "#define NR_IRQS <value>" are a multiple of BITS_PER_LONG so
> > using DECLARE_BITMAP allocates the proper number of longs required
> > for the possible bits.
> > 
> > For instance:
> > 
> > arch/mips/include/asm/mach-ath79/irq.h:#define NR_IRQS                  51
> > arch/mips/include/asm/mach-db1x00/irq.h:#define NR_IRQS 152
> > arch/mips/include/asm/mach-lantiq/falcon/irq.h:#define NR_IRQS 328
> 
> This only matters to user of the allocate_irqno() API and there is only
> on such platform, the IP27 which fortunately uses a NR_IRQS value that
> is a multiple of 64, so no impact.
> 
> Thanks anyway!

I think you should apply it anyway as it's an
error-prone style.

There are 3 mechanisms used today in the kernel
to declare bitmap arrays.

	DECLARE_BITMAP(array, size)
	unsigned long array[BITS_TO_LONGS(size)]
	unsigned long array[size/BITS_PER_LONG]

The first 2 are fine, the last has this defect
possible whenever size % BITS_PER_LONG != 0.

The series I sent converts all the uses of the
the possibly defective style.

cheers, Joe