powerpc/64: Avoid panic during boot due to divide by zero in init_cache_info()

I see a panic in early boot when building with a recent gcc toolchain.
The issue is a divide by zero, which is undefined. Older toolchains
let us get away with it:

int foo(int a) { return a / 0; }

foo:
	li 9,0
	divw 3,3,9
	extsw 3,3
	blr

But newer ones catch it:

foo:
	trap

Add a check to avoid the divide by zero.

Fixes: e2827fe5c156 ("powerpc/64: Clean up ppc64_caches using a struct per cache")
Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
index adf2084f214b2bd01d5aa3ef2a613e66b7b66a05..9cfaa8b69b5f32eb64d7adcd8504ccdb6cd87b32 100644 (file)
--- a/arch/powerpc/kernel/setup_64.c
+++ b/arch/powerpc/kernel/setup_64.c
@@ -408,7 +408,10 @@ static void init_cache_info(struct ppc_cache_info *info, u32 size, u32 lsize,
        info->line_size = lsize;
        info->block_size = bsize;
        info->log_block_size = __ilog2(bsize);
-       info->blocks_per_page = PAGE_SIZE / bsize;
+       if (bsize)
+               info->blocks_per_page = PAGE_SIZE / bsize;
+       else
+               info->blocks_per_page = 0;
 
        if (sets == 0)
                info->assoc = 0xffff;