diff options
Diffstat (limited to 'arch/arc/kernel/jump_label.c')
| -rw-r--r-- | arch/arc/kernel/jump_label.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/arch/arc/kernel/jump_label.c b/arch/arc/kernel/jump_label.c new file mode 100644 index 000000000000..b8600dc325b5 --- /dev/null +++ b/arch/arc/kernel/jump_label.c @@ -0,0 +1,170 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <linux/kernel.h> +#include <linux/jump_label.h> + +#include "asm/cacheflush.h" + +#define JUMPLABEL_ERR "ARC: jump_label: ERROR: " + +/* Halt system on fatal error to make debug easier */ +#define arc_jl_fatal(format...) \ +({ \ + pr_err(JUMPLABEL_ERR format); \ + BUG(); \ +}) + +static inline u32 arc_gen_nop(void) +{ + /* 1x 32bit NOP in middle endian */ + return 0x7000264a; +} + +/* + * Atomic update of patched instruction is only available if this + * instruction doesn't cross L1 cache line boundary. You can read about + * the way we achieve this in arc/include/asm/jump_label.h + */ +static inline void instruction_align_assert(void *addr, int len) +{ + unsigned long a = (unsigned long)addr; + + if ((a >> L1_CACHE_SHIFT) != ((a + len - 1) >> L1_CACHE_SHIFT)) + arc_jl_fatal("instruction (addr %px) cross L1 cache line border", + addr); +} + +/* + * ARCv2 'Branch unconditionally' instruction: + * 00000ssssssssss1SSSSSSSSSSNRtttt + * s S[n:0] lower bits signed immediate (number is bitfield size) + * S S[m:n+1] upper bits signed immediate (number is bitfield size) + * t S[24:21] upper bits signed immediate (branch unconditionally far) + * N N <.d> delay slot mode + * R R Reserved + */ +static inline u32 arc_gen_branch(jump_label_t pc, jump_label_t target) +{ + u32 instruction_l, instruction_r; + u32 pcl = pc & GENMASK(31, 2); + u32 u_offset = target - pcl; + u32 s, S, t; + + /* + * Offset in 32-bit branch instruction must to fit into s25. + * Something is terribly broken if we get such huge offset within one + * function. + */ + if ((s32)u_offset < -16777216 || (s32)u_offset > 16777214) + arc_jl_fatal("gen branch with offset (%d) not fit in s25", + (s32)u_offset); + + /* + * All instructions are aligned by 2 bytes so we should never get offset + * here which is not 2 bytes aligned. + */ + if (u_offset & 0x1) + arc_jl_fatal("gen branch with offset (%d) unaligned to 2 bytes", + (s32)u_offset); + + s = (u_offset >> 1) & GENMASK(9, 0); + S = (u_offset >> 11) & GENMASK(9, 0); + t = (u_offset >> 21) & GENMASK(3, 0); + + /* 00000ssssssssss1 */ + instruction_l = (s << 1) | 0x1; + /* SSSSSSSSSSNRtttt */ + instruction_r = (S << 6) | t; + + return (instruction_r << 16) | (instruction_l & GENMASK(15, 0)); +} + +void arch_jump_label_transform(struct jump_entry *entry, + enum jump_label_type type) +{ + jump_label_t *instr_addr = (jump_label_t *)entry->code; + u32 instr; + + instruction_align_assert(instr_addr, JUMP_LABEL_NOP_SIZE); + + if (type == JUMP_LABEL_JMP) + instr = arc_gen_branch(entry->code, entry->target); + else + instr = arc_gen_nop(); + + WRITE_ONCE(*instr_addr, instr); + flush_icache_range(entry->code, entry->code + JUMP_LABEL_NOP_SIZE); +} + +void arch_jump_label_transform_static(struct jump_entry *entry, + enum jump_label_type type) +{ + /* + * We use only one NOP type (1x, 4 byte) in arch_static_branch, so + * there's no need to patch an identical NOP over the top of it here. + * The generic code calls 'arch_jump_label_transform' if the NOP needs + * to be replaced by a branch, so 'arch_jump_label_transform_static' is + * never called with type other than JUMP_LABEL_NOP. + */ + BUG_ON(type != JUMP_LABEL_NOP); +} + +#ifdef CONFIG_ARC_DBG_JUMP_LABEL +#define SELFTEST_MSG "ARC: instruction generation self-test: " + +struct arc_gen_branch_testdata { + jump_label_t pc; + jump_label_t target_address; + u32 expected_instr; +}; + +static __init int branch_gen_test(const struct arc_gen_branch_testdata *test) +{ + u32 instr_got; + + instr_got = arc_gen_branch(test->pc, test->target_address); + if (instr_got == test->expected_instr) + return 0; + + pr_err(SELFTEST_MSG "FAIL:\n arc_gen_branch(0x%08x, 0x%08x) != 0x%08x, got 0x%08x\n", + test->pc, test->target_address, + test->expected_instr, instr_got); + + return -EFAULT; +} + +/* + * Offset field in branch instruction is not continuous. Test all + * available offset field and sign combinations. Test data is generated + * from real working code. + */ +static const struct arc_gen_branch_testdata arcgenbr_test_data[] __initconst = { + {0x90007548, 0x90007514, 0xffcf07cd}, /* tiny (-52) offs */ + {0x9000c9c0, 0x9000c782, 0xffcf05c3}, /* tiny (-574) offs */ + {0x9000cc1c, 0x9000c782, 0xffcf0367}, /* tiny (-1178) offs */ + {0x9009dce0, 0x9009d106, 0xff8f0427}, /* small (-3034) offs */ + {0x9000f5de, 0x90007d30, 0xfc0f0755}, /* big (-30892) offs */ + {0x900a2444, 0x90035f64, 0xc9cf0321}, /* huge (-443616) offs */ + {0x90007514, 0x9000752c, 0x00000019}, /* tiny (+24) offs */ + {0x9001a578, 0x9001a77a, 0x00000203}, /* tiny (+514) offs */ + {0x90031ed8, 0x90032634, 0x0000075d}, /* tiny (+1884) offs */ + {0x9008c7f2, 0x9008d3f0, 0x00400401}, /* small (+3072) offs */ + {0x9000bb38, 0x9003b340, 0x17c00009}, /* big (+194568) offs */ + {0x90008f44, 0x90578d80, 0xb7c2063d} /* huge (+5701180) offs */ +}; + +static __init int instr_gen_test(void) +{ + int i; + + for (i = 0; i < ARRAY_SIZE(arcgenbr_test_data); i++) + if (branch_gen_test(&arcgenbr_test_data[i])) + return -EFAULT; + + pr_info(SELFTEST_MSG "OK\n"); + + return 0; +} +early_initcall(instr_gen_test); + +#endif /* CONFIG_ARC_DBG_JUMP_LABEL */ |