LXR linux/arch/arc/kernel/jump

   1// SPDX-License-Identifier: GPL-2.0
   2
   3#include <linux/kernel.h>
   4#include <linux/jump_label.h>
   5
   6#include "asm/cacheflush.h"
   7
   8#define JUMPLABEL_ERR   "ARC: jump_label: ERROR: "
   9
  10/* Halt system on fatal error to make debug easier */
  11#define arc_jl_fatal(format...)                                         \
  12({                                                                      \
  13        pr_err(JUMPLABEL_ERR format);                                   \
  14        BUG();                                                          \
  15})
  16
  17static inline u32 arc_gen_nop(void)
  18{
  19        /* 1x 32bit NOP in middle endian */
  20        return 0x7000264a;
  21}
  22
  23/*
  24 * Atomic update of patched instruction is only available if this
  25 * instruction doesn't cross L1 cache line boundary. You can read about
  26 * the way we achieve this in arc/include/asm/jump_label.h
  27 */
  28static inline void instruction_align_assert(void *addr, int len)
  29{
  30        unsigned long a = (unsigned long)addr;
  31
  32        if ((a >> L1_CACHE_SHIFT) != ((a + len - 1) >> L1_CACHE_SHIFT))
  33                arc_jl_fatal("instruction (addr %px) cross L1 cache line border",
  34                             addr);
  35}
  36
  37/*
  38 * ARCv2 'Branch unconditionally' instruction:
  39 * 00000ssssssssss1SSSSSSSSSSNRtttt
  40 * s S[n:0] lower bits signed immediate (number is bitfield size)
  41 * S S[m:n+1] upper bits signed immediate (number is bitfield size)
  42 * t S[24:21] upper bits signed immediate (branch unconditionally far)
  43 * N N <.d> delay slot mode
  44 * R R Reserved
  45 */
  46static inline u32 arc_gen_branch(jump_label_t pc, jump_label_t target)
  47{
  48        u32 instruction_l, instruction_r;
  49        u32 pcl = pc & GENMASK(31, 2);
  50        u32 u_offset = target - pcl;
  51        u32 s, S, t;
  52
  53        /*
  54         * Offset in 32-bit branch instruction must to fit into s25.
  55         * Something is terribly broken if we get such huge offset within one
  56         * function.
  57         */
  58        if ((s32)u_offset < -16777216 || (s32)u_offset > 16777214)
  59                arc_jl_fatal("gen branch with offset (%d) not fit in s25",
  60                             (s32)u_offset);
  61
  62        /*
  63         * All instructions are aligned by 2 bytes so we should never get offset
  64         * here which is not 2 bytes aligned.
  65         */
  66        if (u_offset & 0x1)
  67                arc_jl_fatal("gen branch with offset (%d) unaligned to 2 bytes",
  68                             (s32)u_offset);
  69
  70        s = (u_offset >> 1)  & GENMASK(9, 0);
  71        S = (u_offset >> 11) & GENMASK(9, 0);
  72        t = (u_offset >> 21) & GENMASK(3, 0);
  73
  74        /* 00000ssssssssss1 */
  75        instruction_l = (s << 1) | 0x1;
  76        /* SSSSSSSSSSNRtttt */
  77        instruction_r = (S << 6) | t;
  78
  79        return (instruction_r << 16) | (instruction_l & GENMASK(15, 0));
  80}
  81
  82void arch_jump_label_transform(struct jump_entry *entry,
  83                               enum jump_label_type type)
  84{
  85        jump_label_t *instr_addr = (jump_label_t *)entry->code;
  86        u32 instr;
  87
  88        instruction_align_assert(instr_addr, JUMP_LABEL_NOP_SIZE);
  89
  90        if (type == JUMP_LABEL_JMP)
  91                instr = arc_gen_branch(entry->code, entry->target);
  92        else
  93                instr = arc_gen_nop();
  94
  95        WRITE_ONCE(*instr_addr, instr);
  96        flush_icache_range(entry->code, entry->code + JUMP_LABEL_NOP_SIZE);
  97}
  98
  99void arch_jump_label_transform_static(struct jump_entry *entry,
 100                                      enum jump_label_type type)
 101{
 102        /*
 103         * We use only one NOP type (1x, 4 byte) in arch_static_branch, so
 104         * there's no need to patch an identical NOP over the top of it here.
 105         * The generic code calls 'arch_jump_label_transform' if the NOP needs
 106         * to be replaced by a branch, so 'arch_jump_label_transform_static' is
 107         * never called with type other than JUMP_LABEL_NOP.
 108         */
 109        BUG_ON(type != JUMP_LABEL_NOP);
 110}
 111
 112#ifdef CONFIG_ARC_DBG_JUMP_LABEL
 113#define SELFTEST_MSG    "ARC: instruction generation self-test: "
 114
 115struct arc_gen_branch_testdata {
 116        jump_label_t pc;
 117        jump_label_t target_address;
 118        u32 expected_instr;
 119};
 120
 121static __init int branch_gen_test(const struct arc_gen_branch_testdata *test)
 122{
 123        u32 instr_got;
 124
 125        instr_got = arc_gen_branch(test->pc, test->target_address);
 126        if (instr_got == test->expected_instr)
 127                return 0;
 128
 129        pr_err(SELFTEST_MSG "FAIL:\n arc_gen_branch(0x%08x, 0x%08x) != 0x%08x, got 0x%08x\n",
 130               test->pc, test->target_address,
 131               test->expected_instr, instr_got);
 132
 133        return -EFAULT;
 134}
 135
 136/*
 137 * Offset field in branch instruction is not continuous. Test all
 138 * available offset field and sign combinations. Test data is generated
 139 * from real working code.
 140 */
 141static const struct arc_gen_branch_testdata arcgenbr_test_data[] __initconst = {
 142        {0x90007548, 0x90007514, 0xffcf07cd}, /* tiny (-52) offs */
 143        {0x9000c9c0, 0x9000c782, 0xffcf05c3}, /* tiny (-574) offs */
 144        {0x9000cc1c, 0x9000c782, 0xffcf0367}, /* tiny (-1178) offs */
 145        {0x9009dce0, 0x9009d106, 0xff8f0427}, /* small (-3034) offs */
 146        {0x9000f5de, 0x90007d30, 0xfc0f0755}, /* big  (-30892) offs */
 147        {0x900a2444, 0x90035f64, 0xc9cf0321}, /* huge (-443616) offs */
 148        {0x90007514, 0x9000752c, 0x00000019}, /* tiny (+24) offs */
 149        {0x9001a578, 0x9001a77a, 0x00000203}, /* tiny (+514) offs */
 150        {0x90031ed8, 0x90032634, 0x0000075d}, /* tiny (+1884) offs */
 151        {0x9008c7f2, 0x9008d3f0, 0x00400401}, /* small (+3072) offs */
 152        {0x9000bb38, 0x9003b340, 0x17c00009}, /* big  (+194568) offs */
 153        {0x90008f44, 0x90578d80, 0xb7c2063d}  /* huge (+5701180) offs */
 154};
 155
 156static __init int instr_gen_test(void)
 157{
 158        int i;
 159
 160        for (i = 0; i < ARRAY_SIZE(arcgenbr_test_data); i++)
 161                if (branch_gen_test(&arcgenbr_test_data[i]))
 162                        return -EFAULT;
 163
 164        pr_info(SELFTEST_MSG "OK\n");
 165
 166        return 0;
 167}
 168early_initcall(instr_gen_test);
 169
 170#endif /* CONFIG_ARC_DBG_JUMP_LABEL */
 171