From ff0f90c107bdde8a0c9333379f3ff1662089e91f Mon Sep 17 00:00:00 2001 From: Neeraj Upadhyay Date: Mon, 20 Mar 2017 19:46:36 +0530 Subject: arm64: kaslr: Fix up the kernel image alignment If kernel image extends across alignment boundary, existing code increases the KASLR offset by size of kernel image. The offset is masked after resizing. There are cases, where after masking, we may still have kernel image extending across boundary. This eventually results in only 2MB block getting mapped while creating the page tables. This results in data aborts while accessing unmapped regions during second relocation (with kaslr offset) in __primary_switch. To fix this problem, round up the kernel image size, by swapper block size, before adding it for correction. For example consider below case, where kernel image still crosses 1GB alignment boundary, after masking the offset, which is fixed by rounding up kernel image size. SWAPPER_TABLE_SHIFT = 30 Swapper using section maps with section size 2MB. CONFIG_PGTABLE_LEVELS = 3 VA_BITS = 39 _text : 0xffffff8008080000 _end : 0xffffff800aa1b000 offset : 0x1f35600000 mask = ((1UL << (VA_BITS - 2)) - 1) & ~(SZ_2M - 1) (_text + offset) >> SWAPPER_TABLE_SHIFT = 0x3fffffe7c (_end + offset) >> SWAPPER_TABLE_SHIFT = 0x3fffffe7d offset after existing correction (before mask) = 0x1f37f9b000 (_text + offset) >> SWAPPER_TABLE_SHIFT = 0x3fffffe7d (_end + offset) >> SWAPPER_TABLE_SHIFT = 0x3fffffe7d offset (after mask) = 0x1f37e00000 (_text + offset) >> SWAPPER_TABLE_SHIFT = 0x3fffffe7c (_end + offset) >> SWAPPER_TABLE_SHIFT = 0x3fffffe7d new offset w/ rounding up = 0x1f38000000 (_text + offset) >> SWAPPER_TABLE_SHIFT = 0x3fffffe7d (_end + offset) >> SWAPPER_TABLE_SHIFT = 0x3fffffe7d Change-Id: I6de9019cffe5e730a505fba1fd1168bb13fb10af Fixes: f80fb3a3d508 ("arm64: add support for kernel ASLR") Signed-off-by: Neeraj Upadhyay Signed-off-by: Srinivas Ramana --- arch/arm64/kernel/kaslr.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c index b05469173ba5..310f2f463cd4 100644 --- a/arch/arm64/kernel/kaslr.c +++ b/arch/arm64/kernel/kaslr.c @@ -130,11 +130,15 @@ u64 __init kaslr_early_init(u64 dt_phys, u64 modulo_offset) /* * The kernel Image should not extend across a 1GB/32MB/512MB alignment * boundary (for 4KB/16KB/64KB granule kernels, respectively). If this - * happens, increase the KASLR offset by the size of the kernel image. + * happens, increase the KASLR offset by the size of the kernel image + * rounded up by SWAPPER_BLOCK_SIZE. */ if ((((u64)_text + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT) != - (((u64)_end + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT)) - offset = (offset + (u64)(_end - _text)) & mask; + (((u64)_end + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT)) { + u64 kimg_sz = _end - _text; + offset = (offset + round_up(kimg_sz, SWAPPER_BLOCK_SIZE)) + & mask; + } if (IS_ENABLED(CONFIG_KASAN)) /* -- cgit v1.2.3