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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_ON(1);
                  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));
            }
      }
}

void do_lwsync_fixups(unsigned long value, void *fixup_start, void *fixup_end)
{
      unsigned int *start, *end, *dest;

      if (!(value & CPU_FTR_LWSYNC))
            return ;

      start = fixup_start;
      end = fixup_end;

      for (; start < end; start++) {
            dest = (void *)start + *start;
            patch_instruction(dest, PPC_LWSYNC_INSTR);
      }
}

#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 void test_lwsync_macros(void)
{
      extern void lwsync_fixup_test;
      extern void end_lwsync_fixup_test;
      extern void lwsync_fixup_test_expected_LWSYNC;
      extern void lwsync_fixup_test_expected_SYNC;
      unsigned long size = &end_lwsync_fixup_test -
                       &lwsync_fixup_test;

      /* The fixups have already been done for us during boot */
      if (cur_cpu_spec->cpu_features & CPU_FTR_LWSYNC) {
            check(memcmp(&lwsync_fixup_test,
                       &lwsync_fixup_test_expected_LWSYNC, size) == 0);
      } else {
            check(memcmp(&lwsync_fixup_test,
                       &lwsync_fixup_test_expected_SYNC, size) == 0);
      }
}

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();
      test_lwsync_macros();

      return 0;
}
late_initcall(test_feature_fixups);

#endif /* CONFIG_FTR_FIXUP_SELFTEST */

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