Commit 6b0f68e3 authored Sep 08, 2015 by Mark Salter Committed by Linus Torvalds Sep 08, 2015

mm: add utility for early copy from unmapped ram



When booting an arm64 kernel w/initrd using UEFI/grub, use of mem= will
likely cut off part or all of the initrd.  This leaves it outside the
kernel linear map which leads to failure when unpacking.  The x86 code
has a similar need to relocate an initrd outside of mapped memory in
some cases.

The current x86 code uses early_memremap() to copy the original initrd
from unmapped to mapped RAM.  This patchset creates a generic
copy_from_early_mem() utility based on that x86 code and has arm64 and
x86 share it in their respective initrd relocation code.

This patch (of 3):

In some early boot circumstances, it may be necessary to copy from RAM
outside the kernel linear mapping to mapped RAM.  The need to relocate
an initrd is one example in the x86 code.  This patch creates a helper
function based on current x86 code.

Signed-off-by: Mark Salter <msalter@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e6590740

include/asm-generic/early_ioremap.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -33,6 +33,12 @@ extern void early_ioremap_setup(void);
		*/
		extern void early_ioremap_reset(void);

		/*
		* Early copy from unmapped memory to kernel mapped memory.
		*/
		extern void copy_from_early_mem(void *dest, phys_addr_t src,
		unsigned long size);

		#else
		static inline void early_ioremap_init(void) { }
		static inline void early_ioremap_setup(void) { }

mm/early_ioremap.c

+22 −0

Original line number	Diff line number	Diff line
		@@ -217,6 +217,28 @@ early_memremap(resource_size_t phys_addr, unsigned long size)
		return (__force void *)__early_ioremap(phys_addr, size,
		FIXMAP_PAGE_NORMAL);
		}

		#define MAX_MAP_CHUNK (NR_FIX_BTMAPS << PAGE_SHIFT)

		void __init copy_from_early_mem(void *dest, phys_addr_t src, unsigned long size)
		{
		unsigned long slop, clen;
		char *p;

		while (size) {
		slop = src & ~PAGE_MASK;
		clen = size;
		if (clen > MAX_MAP_CHUNK - slop)
		clen = MAX_MAP_CHUNK - slop;
		p = early_memremap(src & PAGE_MASK, clen + slop);
		memcpy(dest, p + slop, clen);
		early_memunmap(p, clen + slop);
		dest += clen;
		src += clen;
		size -= clen;
		}
		}

		#else /* CONFIG_MMU */

		void __init __iomem *

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