drivers/base: cacheinfo: handle absence of caches
authorSudeep Holla <sudeep.holla@arm.com>
Wed, 27 May 2015 10:26:13 +0000 (11:26 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 1 Jun 2015 01:34:24 +0000 (10:34 +0900)
On some simulators like GEM5, caches may not be simulated. In those
cases, the cache levels and leaves will be zero and will result in
following exception:

Unable to handle kernel NULL pointer dereference at virtual address 0040
pgd = ffffffc0008fa000
[00000040] *pgd=00000009f6807003, *pud=00000009f6807003,
   *pmd=00000009f6808003, *pte=006000002c010707
Internal error: Oops: 96000005 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.1.0-rc5 #198
task: ffffffc9768a0000 ti: ffffffc9768a8000 task.ti: ffffffc9768a8000
PC is at detect_cache_attributes+0x98/0x2c8
LR is at detect_cache_attributes+0x88/0x2c8

kcalloc(0) returns a special value ZERO_SIZE_PTR which is non-NULL value
but results in fault only on any attempt to dereferencing it. So
checking for the non-NULL pointer will not suffice.

This patch checks for non-zero cache leaf nodes and returns error if
there are no cache leaves in detect_cache_attributes.

Cc: <stable@vger.kernel.org> # 3.19.x
Cc: Will Deacon <will.deacon@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reported-by: William Wang <william.wang@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/base/cacheinfo.c

index 9c2ba1c97c4257016503a8ed4d2166ac19dea9c0..df0c66cb7ad3719016436dd7eb16ab1d3234568d 100644 (file)
@@ -179,7 +179,7 @@ static int detect_cache_attributes(unsigned int cpu)
 {
        int ret;
 
-       if (init_cache_level(cpu))
+       if (init_cache_level(cpu) || !cache_leaves(cpu))
                return -ENOENT;
 
        per_cpu_cacheinfo(cpu) = kcalloc(cache_leaves(cpu),