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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2016-02-16 15:52:42 +0300
committerCatalin Marinas <catalin.marinas@arm.com>2016-02-18 21:16:53 +0300
commita7f8de168ace487fa7b88cb154e413cf40e87fc6 (patch)
tree870a068dba048cdf795c241e97f1e8684fed2208 /arch/arm64/include/asm/kernel-pgtable.h
parenta89dea585371a9d5d85499db47c93f129be8e0c4 (diff)
downloadlinux-a7f8de168ace487fa7b88cb154e413cf40e87fc6.tar.xz
arm64: allow kernel Image to be loaded anywhere in physical memory
This relaxes the kernel Image placement requirements, so that it may be placed at any 2 MB aligned offset in physical memory. This is accomplished by ignoring PHYS_OFFSET when installing memblocks, and accounting for the apparent virtual offset of the kernel Image. As a result, virtual address references below PAGE_OFFSET are correctly mapped onto physical references into the kernel Image regardless of where it sits in memory. Special care needs to be taken for dealing with memory limits passed via mem=, since the generic implementation clips memory top down, which may clip the kernel image itself if it is loaded high up in memory. To deal with this case, we simply add back the memory covering the kernel image, which may result in more memory to be retained than was passed as a mem= parameter. Since mem= should not be considered a production feature, a panic notifier handler is installed that dumps the memory limit at panic time if one was set. Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/kernel-pgtable.h')
-rw-r--r--arch/arm64/include/asm/kernel-pgtable.h12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/kernel-pgtable.h b/arch/arm64/include/asm/kernel-pgtable.h
index a459714ee29e..5c6375d8528b 100644
--- a/arch/arm64/include/asm/kernel-pgtable.h
+++ b/arch/arm64/include/asm/kernel-pgtable.h
@@ -79,5 +79,17 @@
#define SWAPPER_MM_MMUFLAGS (PTE_ATTRINDX(MT_NORMAL) | SWAPPER_PTE_FLAGS)
#endif
+/*
+ * To make optimal use of block mappings when laying out the linear
+ * mapping, round down the base of physical memory to a size that can
+ * be mapped efficiently, i.e., either PUD_SIZE (4k granule) or PMD_SIZE
+ * (64k granule), or a multiple that can be mapped using contiguous bits
+ * in the page tables: 32 * PMD_SIZE (16k granule)
+ */
+#ifdef CONFIG_ARM64_64K_PAGES
+#define ARM64_MEMSTART_ALIGN SZ_512M
+#else
+#define ARM64_MEMSTART_ALIGN SZ_1G
+#endif
#endif /* __ASM_KERNEL_PGTABLE_H */