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Commit 4bdf4d31 authored by Alex Van Brunt's avatar Alex Van Brunt Committed by Ruchi Kandoi
Browse files

arm64: add fault handling to SWP emulation 



Add excpetion table and fixup for SWP/SWPB instruction emulation.
This prevents the kernel from panicing when emulating a SWP/SWPB
instruction that access unmapped memory.

Change-Id: I4a9ca34fa161a0f306cdb663827d9bee39cec733
Signed-off-by: default avatarAlex Van Brunt <avanbrunt@nvidia.com>
Reviewed-on: http://git-master/r/370278
parent 2ef02d44

arch/arm64/kernel/swp_emulate.c

+72 −6
Original line number Diff line number Diff line
@@ -32,6 +32,71 @@ 
#include <asm/system_misc.h>

#include <linux/debugfs.h>



/*

 * Error-checking SWP macros implemented using ldrex{b}/strex{b}

 */



static int swpb(u8 in, u8 *out, u8 *addr)

{

	u8 _out;

	int res;

	int err = 0;



	do {

		__asm__ __volatile__(

		"0:	ldxrb	%w1, %4\n"

		"1:	stxrb	%w0, %w3, %4\n"

		"2:\n"

		"	.section	 .fixup,\"ax\"\n"

		"	.align		2\n"

		"3:	mov	%w2, %5\n"

		"	b	2b\n"

		"	.previous\n"

		"	.section	 __ex_table,\"a\"\n"

		"	.align		3\n"

		"	.quad		0b, 3b\n"

		"	.quad		1b, 3b\n"

		"	.previous"

		: "=&r" (res), "=r" (_out), "=r" (err)

		: "r" (in), "Q" (addr), "i" (-EFAULT)

		: "cc", "memory");

	} while (err == 0 && res != 0);



	if (err == 0)

		*out = _out;

	return err;

}



static int swp(u32 in, u32 *out, u32 *addr)

{

	u32 _out;

	int res;

	int err = 0;



	do {

		__asm__ __volatile__(

		"0:	ldxr	%w1, %4\n"

		"1:	stxr	%w0, %w3, %4\n"

		"2:\n"

		"	.section	 .fixup,\"ax\"\n"

		"	.align		2\n"

		"3:	mov	%w2, %5\n"

		"	b	2b\n"

		"	.previous\n"

		"	.section	 __ex_table,\"a\"\n"

		"	.align		3\n"

		"	.quad		0b, 3b\n"

		"	.quad		1b, 3b\n"

		"	.previous"

		: "=&r" (res), "=r" (_out), "=r" (err)

		: "r" (in), "Q" (addr), "i" (-EFAULT)

		: "cc", "memory");

	} while (err == 0 && res != 0);



	if (err == 0)

		*out = _out;

	return err;

}

/*

 * Macros/defines for extracting register numbers from instruction.

 */
@@ -61,6 +126,7 @@ static int swp_handler(struct pt_regs *regs, unsigned int instr) 
	u32 destreg, data, type;

	uintptr_t address;

	unsigned int res = 0;

	int err;

	u32 temp32;

	u8 temp8;
@@ -100,9 +166,9 @@ static int swp_handler(struct pt_regs *regs, unsigned int instr) 
		res = -EFAULT;

	}

	if (type == TYPE_SWPB) {

		do {

			temp8 = ldax8((u8 *) address);

		} while (stlx8((u8 *) address, (u8) data));

		err = swpb((u8) data, &temp8, (u8 *) address);

		if (err)

			return err;

		regs->regs[destreg] = temp8;

		regs->pc += 4;

		swpb_count++;
@@ -111,9 +177,9 @@ static int swp_handler(struct pt_regs *regs, unsigned int instr) 
		pr_debug("SWP instruction on unaligned pointer!\n");

		return -EFAULT;

	} else {

		do {

			temp32 = ldax32((u32 *) address);

		} while (stlx32((u32 *) address, (u32) data));

		err = swp((u32) data, &temp32, (u32 *) address);

		if (err)

			return err;

		regs->regs[destreg] = temp32;

		regs->pc += 4;

		swp_count++;