path: root/arch/powerpc/lib/feature-fixups.c

/*
 *  Copyright (C) 2001 Ben. Herrenschmidt (benh@kernel.crashing.org)
 *
 *  Modifications for ppc64:
 *      Copyright (C) 2003 Dave Engebretsen <engebret@us.ibm.com>
 *
 *  Copyright 2008 Michael Ellerman, IBM Corporation.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/init.h>
#include <asm/cputable.h>
#include <asm/code-patching.h>


struct fixup_entry {
	unsigned long	mask;
	unsigned long	value;
	long		start_off;
	long		end_off;
	long		alt_start_off;
	long		alt_end_off;
};

static unsigned int *calc_addr(struct fixup_entry *fcur, long offset)
{
	/*
	 * We store the offset to the code as a negative offset from
	 * the start of the alt_entry, to support the VDSO. This
	 * routine converts that back into an actual address.
	 */
	return (unsigned int *)((unsigned long)fcur + offset);
}

static int patch_alt_instruction(unsigned int *src, unsigned int *dest,
				 unsigned int *alt_start, unsigned int *alt_end)
{
	unsigned int instr;

	instr = *src;

	if (instr_is_relative_branch(*src)) {
		unsigned int *target = (unsigned int *)branch_target(src);

		/* Branch within the section doesn't need translating */
		if (target < alt_start || target >= alt_end) {
			instr = translate_branch(dest, src);
			if (!instr)
				return 1;
		}
	}

	patch_instruction(dest, instr);

	return 0;
}

static int patch_feature_section(unsigned long value, struct fixup_entry *fcur)
{
	unsigned int *start, *end, *alt_start, *alt_end, *src, *dest;

	start = calc_addr(fcur, fcur->start_off);
	end = calc_addr(fcur, fcur->end_off);
	alt_start = calc_addr(fcur, fcur->alt_start_off);
	alt_end = calc_addr(fcur, fcur->alt_end_off);

	if ((alt_end - alt_start) > (end - start))
		return 1;

	if ((value & fcur->mask) == fcur->value)
		return 0;

	src = alt_start;
	dest = start;

	for (; src < alt_end; src++, dest++) {
		if (patch_alt_instruction(src, dest, alt_start, alt_end))
			return 1;
	}

	for (; dest < end; dest++)
		patch_instruction(dest, PPC_NOP_INSTR);

	return 0;
}

void do_feature_fixups(unsigned long value, void *fixup_start, void *fixup_end)
{
	struct fixup_entry *fcur, *fend;

	fcur = fixup_start;
	fend = fixup_end;

	for (; fcur < fend; fcur++) {
		if (patch_feature_section(value, fcur)) {
			__WARN();
			printk("Unable to patch feature section at %p - %p" \
				" with %p - %p\n",
				calc_addr(fcur, fcur->start_off),
				calc_addr(fcur, fcur->end_off),
				calc_addr(fcur, fcur->alt_start_off),
				calc_addr(fcur, fcur->alt_end_off));
		}
	}
}

#ifdef CONFIG_FTR_FIXUP_SELFTEST

#define check(x)	\
	if (!(x)) printk("feature-fixups: test failed at line %d\n", __LINE__);

/* This must be after the text it fixes up, vmlinux.lds.S enforces that atm */
static struct fixup_entry fixup;

static long calc_offset(struct fixup_entry *entry, unsigned int *p)
{
	return (unsigned long)p - (unsigned long)entry;
}

void test_basic_patching(void)
{
	extern unsigned int ftr_fixup_test1;
	extern unsigned int end_ftr_fixup_test1;
	extern unsigned int ftr_fixup_test1_orig;
	extern unsigned int ftr_fixup_test1_expected;
	int size = &end_ftr_fixup_test1 - &ftr_fixup_test1;

	fixup.value = fixup.mask = 8;
	fixup.start_off = calc_offset(&fixup, &ftr_fixup_test1 + 1);
	fixup.end_off = calc_offset(&fixup, &ftr_fixup_test1 + 2);
	fixup.alt_start_off = fixup.alt_end_off = 0;

	/* Sanity check */
	check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_orig, size) == 0);

	/* Check we don't patch if the value matches */
	patch_feature_section(8, &fixup);
	check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_orig, size) == 0);

	/* Check we do patch if the value doesn't match */
	patch_feature_section(0, &fixup);
	check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_expected, size) == 0);

	/* Check we do patch if the mask doesn't match */
	memcpy(&ftr_fixup_test1, &ftr_fixup_test1_orig, size);
	check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_orig, size) == 0);
	patch_feature_section(~8, &fixup);
	check(memcmp(&ftr_fixup_test1, &ftr_fixup_test1_expected, size) == 0);
}

static void test_alternative_patching(void)
{
	extern unsigned int ftr_fixup_test2;
	extern unsigned int end_ftr_fixup_test2;
	extern unsigned int ftr_fixup_test2_orig;
	extern unsigned int ftr_fixup_test2_alt;
	extern unsigned int ftr_fixup_test2_expected;
	int size = &end_ftr_fixup_test2 - &ftr_fixup_test2;

	fixup.value = fixup.mask = 0xF;
	fixup.start_off = calc_offset(&fixup, &ftr_fixup_test2 + 1);
	fixup.end_off = calc_offset(&fixup, &ftr_fixup_test2 + 2);
	fixup.alt_start_off = calc_offset(&fixup, &ftr_fixup_test2_alt);
	fixup.alt_end_off = calc_offset(&fixup, &ftr_fixup_test2_alt + 1);

	/* Sanity check */
	check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_orig, size) == 0);

	/* Check we don't patch if the value matches */
	patch_feature_section(0xF, &fixup);
	check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_orig, size) == 0);

	/* Check we do patch if the value doesn't match */
	patch_feature_section(0, &fixup);
	check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_expected, size) == 0);

	/* Check we do patch if the mask doesn't match */
	memcpy(&ftr_fixup_test2, &ftr_fixup_test2_orig, size);
	check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_orig, size) == 0);
	patch_feature_section(~0xF, &fixup);
	check(memcmp(&ftr_fixup_test2, &ftr_fixup_test2_expected, size) == 0);
}

static void test_alternative_case_too_big(void)
{
	extern unsigned int ftr_fixup_test3;
	extern unsigned int end_ftr_fixup_test3;
	extern unsigned int ftr_fixup_test3_orig;
	extern unsigned int ftr_fixup_test3_alt;
	int size = &end_ftr_fixup_test3 - &ftr_fixup_test3;

	fixup.value = fixup.mask = 0xC;
	fixup.start_off = calc_offset(&fixup, &ftr_fixup_test3 + 1);
	fixup.end_off = calc_offset(&fixup, &ftr_fixup_test3 + 2);
	fixup.alt_start_off = calc_offset(&fixup, &ftr_fixup_test3_alt);
	fixup.alt_end_off = calc_offset(&fixup, &ftr_fixup_test3_alt + 2);

	/* Sanity check */
	check(memcmp(&ftr_fixup_test3, &ftr_fixup_test3_orig, size) == 0);

	/* Expect nothing to be patched, and the error returned to us */
	check(patch_feature_section(0xF, &fixup) == 1);
	check(memcmp(&ftr_fixup_test3, &ftr_fixup_test3_orig, size) == 0);
	check(patch_feature_section(0, &fixup) == 1);
	check(memcmp(&ftr_fixup_test3, &ftr_fixup_test3_orig, size) == 0);
	check(patch_feature_section(~0xF, &fixup) == 1);
	check(memcmp(&ftr_fixup_test3, &ftr_fixup_test3_orig, size) == 0);
}

static void test_alternative_case_too_small(void)
{
	extern unsigned int ftr_fixup_test4;
	extern unsigned int end_ftr_fixup_test4;
	extern unsigned int ftr_fixup_test4_orig;
	extern unsigned int ftr_fixup_test4_alt;
	extern unsigned int ftr_fixup_test4_expected;
	int size = &end_ftr_fixup_test4 - &ftr_fixup_test4;
	unsigned long flag;

	/* Check a high-bit flag */
	flag = 1UL << ((sizeof(unsigned long) - 1) * 8);
	fixup.value = fixup.mask = flag;
	fixup.start_off = calc_offset(&fixup, &ftr_fixup_test4 + 1);
	fixup.end_off = calc_offset(&fixup, &ftr_fixup_test4 + 5);
	fixup.alt_start_off = calc_offset(&fixup, &ftr_fixup_test4_alt);
	fixup.alt_end_off = calc_offset(&fixup, &ftr_fixup_test4_alt + 2);

	/* Sanity check */
	check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_orig, size) == 0);

	/* Check we don't patch if the value matches */
	patch_feature_section(flag, &fixup);
	check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_orig, size) == 0);

	/* Check we do patch if the value doesn't match */
	patch_feature_section(0, &fixup);
	check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_expected, size) == 0);

	/* Check we do patch if the mask doesn't match */
	memcpy(&ftr_fixup_test4, &ftr_fixup_test4_orig, size);
	check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_orig, size) == 0);
	patch_feature_section(~flag, &fixup);
	check(memcmp(&ftr_fixup_test4, &ftr_fixup_test4_expected, size) == 0);
}

static void test_alternative_case_with_branch(void)
{
	extern unsigned int ftr_fixup_test5;
	extern unsigned int end_ftr_fixup_test5;
	extern unsigned int ftr_fixup_test5_expected;
	int size = &end_ftr_fixup_test5 - &ftr_fixup_test5;

	check(memcmp(&ftr_fixup_test5, &ftr_fixup_test5_expected, size) == 0);
}

static void test_alternative_case_with_external_branch(void)
{
	extern unsigned int ftr_fixup_test6;
	extern unsigned int end_ftr_fixup_test6;
	extern unsigned int ftr_fixup_test6_expected;
	int size = &end_ftr_fixup_test6 - &ftr_fixup_test6;

	check(memcmp(&ftr_fixup_test6, &ftr_fixup_test6_expected, size) == 0);
}

static void test_cpu_macros(void)
{
	extern void ftr_fixup_test_FTR_macros;
	extern void ftr_fixup_test_FTR_macros_expected;
	unsigned long size = &ftr_fixup_test_FTR_macros_expected -
			     &ftr_fixup_test_FTR_macros;

	/* The fixups have already been done for us during boot */
	check(memcmp(&ftr_fixup_test_FTR_macros,
		     &ftr_fixup_test_FTR_macros_expected, size) == 0);
}

static void test_fw_macros(void)
{
#ifdef CONFIG_PPC64
	extern void ftr_fixup_test_FW_FTR_macros;
	extern void ftr_fixup_test_FW_FTR_macros_expected;
	unsigned long size = &ftr_fixup_test_FW_FTR_macros_expected -
			     &ftr_fixup_test_FW_FTR_macros;

	/* The fixups have already been done for us during boot */
	check(memcmp(&ftr_fixup_test_FW_FTR_macros,
		     &ftr_fixup_test_FW_FTR_macros_expected, size) == 0);
#endif
}

static int __init test_feature_fixups(void)
{
	printk(KERN_DEBUG "Running feature fixup self-tests ...\n");

	test_basic_patching();
	test_alternative_patching();
	test_alternative_case_too_big();
	test_alternative_case_too_small();
	test_alternative_case_with_branch();
	test_alternative_case_with_external_branch();
	test_cpu_macros();
	test_fw_macros();

	return 0;
}
late_initcall(test_feature_fixups);

#endif /* CONFIG_FTR_FIXUP_SELFTEST */