| Message ID | 1456908433-27149-1-git-send-email-ard.biesheuvel@linaro.org |
|---|---|
| State | Accepted |
| Commit | 6d2aa549de1fc998581d216de3853aa131aa4446 |
| Headers | show |
On Wed, Mar 02, 2016 at 09:47:13AM +0100, Ard Biesheuvel wrote: > Commit 8439e62a1561 ("arm64: mm: use bit ops rather than arithmetic in > pa/va translations") changed the boundary check against PAGE_OFFSET from > an arithmetic comparison to a bit test. This means we now silently assume > that PAGE_OFFSET is a power of 2 that divides the kernel virtual address > space into two equal halves. So make that assumption explicit. Applied. Thanks. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 9cfe94b41b54..ea136b904f56 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -171,6 +171,13 @@ void __init arm64_memblock_init(void) const s64 linear_region_size = -(s64)PAGE_OFFSET; /* + * Ensure that the linear region takes up exactly half of the kernel + * virtual address space. This way, we can distinguish a linear address + * from a kernel/module/vmalloc address by testing a single bit. + */ + BUILD_BUG_ON(linear_region_size != BIT(VA_BITS - 1)); + + /* * Select a suitable value for the base of physical memory. */ memstart_addr = round_down(memblock_start_of_DRAM(),
Commit 8439e62a1561 ("arm64: mm: use bit ops rather than arithmetic in pa/va translations") changed the boundary check against PAGE_OFFSET from an arithmetic comparison to a bit test. This means we now silently assume that PAGE_OFFSET is a power of 2 that divides the kernel virtual address space into two equal halves. So make that assumption explicit. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> --- arch/arm64/mm/init.c | 7 +++++++ 1 file changed, 7 insertions(+) -- 2.5.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel