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Commit fcfd2c79 authored by Laura Abbott's avatar Laura Abbott Committed by Rohit Vaswani
Browse files

arm64: use fixmap for text patching 



When kernel text is marked as read only, it cannot be modified directly.
Use a fixmap to modify the text instead in a similar manner to
x86 and arm.

Change-Id: I466a1d3cdab4f5cbb940710f613526cf31cf9387
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Tested-by: default avatarKees Cook <keescook@chromium.org>
Tested-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarLaura Abbott <lauraa@codeaurora.org>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Git-commit: 2f896d5866107e2926dcdec34a7d40bc56dd2951)
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[rvaswani@codeaurora.org: fixed merge conflicts]
Signed-off-by: default avatarRohit Vaswani <rvaswani@codeaurora.org>
parent b2474b6c

arch/arm64/include/asm/fixmap.h

+1 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ enum fixed_addresses { 


	FIX_BTMAP_END = __end_of_permanent_fixed_addresses,

	FIX_BTMAP_BEGIN = FIX_BTMAP_END + TOTAL_FIX_BTMAPS - 1,

	FIX_TEXT_POKE0,

	__end_of_fixed_addresses

};

arch/arm64/kernel/insn.c

+46 −1
Original line number Diff line number Diff line
@@ -17,14 +17,19 @@ 
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */

#include <linux/bitops.h>

#include <linux/bug.h>

#include <linux/compiler.h>

#include <linux/kernel.h>

#include <linux/mm.h>

#include <linux/smp.h>

#include <linux/spinlock.h>

#include <linux/stop_machine.h>

#include <linux/types.h>

#include <linux/uaccess.h>



#include <asm/cacheflush.h>

#include <asm/debug-monitors.h>

#include <asm/fixmap.h>

#include <asm/insn.h>



#define AARCH64_INSN_SF_BIT	BIT(31)
@@ -72,6 +77,29 @@ bool __kprobes aarch64_insn_is_nop(u32 insn) 
	}

}



static DEFINE_SPINLOCK(patch_lock);



static void __kprobes *patch_map(void *addr, int fixmap)

{

	unsigned long uintaddr = (uintptr_t) addr;

	bool module = !core_kernel_text(uintaddr);

	struct page *page;



	if (module && IS_ENABLED(CONFIG_DEBUG_SET_MODULE_RONX))

		page = vmalloc_to_page(addr);

	else

		page = virt_to_page(addr);



	BUG_ON(!page);

	set_fixmap(fixmap, page_to_phys(page));



	return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));

}



static void __kprobes patch_unmap(int fixmap)

{

	clear_fixmap(fixmap);

}

/*

 * In ARMv8-A, A64 instructions have a fixed length of 32 bits and are always

 * little-endian.
@@ -88,10 +116,27 @@ int __kprobes aarch64_insn_read(void *addr, u32 *insnp) 
	return ret;

}



static int __kprobes __aarch64_insn_write(void *addr, u32 insn)

{

	void *waddr = addr;

	unsigned long flags = 0;

	int ret;



	spin_lock_irqsave(&patch_lock, flags);

	waddr = patch_map(addr, FIX_TEXT_POKE0);



	ret = probe_kernel_write(waddr, &insn, AARCH64_INSN_SIZE);



	patch_unmap(FIX_TEXT_POKE0);

	spin_unlock_irqrestore(&patch_lock, flags);



	return ret;

}



int __kprobes aarch64_insn_write(void *addr, u32 insn)

{

	insn = cpu_to_le32(insn);

	return probe_kernel_write(addr, &insn, AARCH64_INSN_SIZE);

	return __aarch64_insn_write(addr, insn);

}



static bool __kprobes __aarch64_insn_hotpatch_safe(u32 insn)