diff options
Diffstat (limited to 'arch/mips/tools/loongson3-llsc-check.c')
| -rw-r--r-- | arch/mips/tools/loongson3-llsc-check.c | 309 |
1 files changed, 309 insertions, 0 deletions
diff --git a/arch/mips/tools/loongson3-llsc-check.c b/arch/mips/tools/loongson3-llsc-check.c new file mode 100644 index 000000000..5f68a4fa8 --- /dev/null +++ b/arch/mips/tools/loongson3-llsc-check.c @@ -0,0 +1,309 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <byteswap.h> +#include <elf.h> +#include <endian.h> +#include <errno.h> +#include <fcntl.h> +#include <inttypes.h> +#include <stdbool.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <sys/mman.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <unistd.h> + +#ifdef be32toh +/* If libc provides le{16,32,64}toh() then we'll use them */ +#elif BYTE_ORDER == LITTLE_ENDIAN +# define le16toh(x) (x) +# define le32toh(x) (x) +# define le64toh(x) (x) +#elif BYTE_ORDER == BIG_ENDIAN +# define le16toh(x) bswap_16(x) +# define le32toh(x) bswap_32(x) +# define le64toh(x) bswap_64(x) +#endif + +/* MIPS opcodes, in bits 31:26 of an instruction */ +#define OP_SPECIAL 0x00 +#define OP_REGIMM 0x01 +#define OP_BEQ 0x04 +#define OP_BNE 0x05 +#define OP_BLEZ 0x06 +#define OP_BGTZ 0x07 +#define OP_BEQL 0x14 +#define OP_BNEL 0x15 +#define OP_BLEZL 0x16 +#define OP_BGTZL 0x17 +#define OP_LL 0x30 +#define OP_LLD 0x34 +#define OP_SC 0x38 +#define OP_SCD 0x3c + +/* Bits 20:16 of OP_REGIMM instructions */ +#define REGIMM_BLTZ 0x00 +#define REGIMM_BGEZ 0x01 +#define REGIMM_BLTZL 0x02 +#define REGIMM_BGEZL 0x03 +#define REGIMM_BLTZAL 0x10 +#define REGIMM_BGEZAL 0x11 +#define REGIMM_BLTZALL 0x12 +#define REGIMM_BGEZALL 0x13 + +/* Bits 5:0 of OP_SPECIAL instructions */ +#define SPECIAL_SYNC 0x0f + +static void usage(FILE *f) +{ + fprintf(f, "Usage: loongson3-llsc-check /path/to/vmlinux\n"); +} + +static int se16(uint16_t x) +{ + return (int16_t)x; +} + +static bool is_ll(uint32_t insn) +{ + switch (insn >> 26) { + case OP_LL: + case OP_LLD: + return true; + + default: + return false; + } +} + +static bool is_sc(uint32_t insn) +{ + switch (insn >> 26) { + case OP_SC: + case OP_SCD: + return true; + + default: + return false; + } +} + +static bool is_sync(uint32_t insn) +{ + /* Bits 31:11 should all be zeroes */ + if (insn >> 11) + return false; + + /* Bits 5:0 specify the SYNC special encoding */ + if ((insn & 0x3f) != SPECIAL_SYNC) + return false; + + return true; +} + +static bool is_branch(uint32_t insn, int *off) +{ + switch (insn >> 26) { + case OP_BEQ: + case OP_BEQL: + case OP_BNE: + case OP_BNEL: + case OP_BGTZ: + case OP_BGTZL: + case OP_BLEZ: + case OP_BLEZL: + *off = se16(insn) + 1; + return true; + + case OP_REGIMM: + switch ((insn >> 16) & 0x1f) { + case REGIMM_BGEZ: + case REGIMM_BGEZL: + case REGIMM_BGEZAL: + case REGIMM_BGEZALL: + case REGIMM_BLTZ: + case REGIMM_BLTZL: + case REGIMM_BLTZAL: + case REGIMM_BLTZALL: + *off = se16(insn) + 1; + return true; + + default: + return false; + } + + default: + return false; + } +} + +static int check_ll(uint64_t pc, uint32_t *code, size_t sz) +{ + ssize_t i, max, sc_pos; + int off; + + /* + * Every LL must be preceded by a sync instruction in order to ensure + * that instruction reordering doesn't allow a prior memory access to + * execute after the LL & cause erroneous results. + */ + if (!is_sync(le32toh(code[-1]))) { + fprintf(stderr, "%" PRIx64 ": LL not preceded by sync\n", pc); + return -EINVAL; + } + + /* Find the matching SC instruction */ + max = sz / 4; + for (sc_pos = 0; sc_pos < max; sc_pos++) { + if (is_sc(le32toh(code[sc_pos]))) + break; + } + if (sc_pos >= max) { + fprintf(stderr, "%" PRIx64 ": LL has no matching SC\n", pc); + return -EINVAL; + } + + /* + * Check branches within the LL/SC loop target sync instructions, + * ensuring that speculative execution can't generate memory accesses + * due to instructions outside of the loop. + */ + for (i = 0; i < sc_pos; i++) { + if (!is_branch(le32toh(code[i]), &off)) + continue; + + /* + * If the branch target is within the LL/SC loop then we don't + * need to worry about it. + */ + if ((off >= -i) && (off <= sc_pos)) + continue; + + /* If the branch targets a sync instruction we're all good... */ + if (is_sync(le32toh(code[i + off]))) + continue; + + /* ...but if not, we have a problem */ + fprintf(stderr, "%" PRIx64 ": Branch target not a sync\n", + pc + (i * 4)); + return -EINVAL; + } + + return 0; +} + +static int check_code(uint64_t pc, uint32_t *code, size_t sz) +{ + int err = 0; + + if (sz % 4) { + fprintf(stderr, "%" PRIx64 ": Section size not a multiple of 4\n", + pc); + err = -EINVAL; + sz -= (sz % 4); + } + + if (is_ll(le32toh(code[0]))) { + fprintf(stderr, "%" PRIx64 ": First instruction in section is an LL\n", + pc); + err = -EINVAL; + } + +#define advance() ( \ + code++, \ + pc += 4, \ + sz -= 4 \ +) + + /* + * Skip the first instruction, allowing check_ll to look backwards + * unconditionally. + */ + advance(); + + /* Now scan through the code looking for LL instructions */ + for (; sz; advance()) { + if (is_ll(le32toh(code[0]))) + err |= check_ll(pc, code, sz); + } + + return err; +} + +int main(int argc, char *argv[]) +{ + int vmlinux_fd, status, err, i; + const char *vmlinux_path; + struct stat st; + Elf64_Ehdr *eh; + Elf64_Shdr *sh; + void *vmlinux; + + status = EXIT_FAILURE; + + if (argc < 2) { + usage(stderr); + goto out_ret; + } + + vmlinux_path = argv[1]; + vmlinux_fd = open(vmlinux_path, O_RDONLY); + if (vmlinux_fd == -1) { + perror("Unable to open vmlinux"); + goto out_ret; + } + + err = fstat(vmlinux_fd, &st); + if (err) { + perror("Unable to stat vmlinux"); + goto out_close; + } + + vmlinux = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, vmlinux_fd, 0); + if (vmlinux == MAP_FAILED) { + perror("Unable to mmap vmlinux"); + goto out_close; + } + + eh = vmlinux; + if (memcmp(eh->e_ident, ELFMAG, SELFMAG)) { + fprintf(stderr, "vmlinux is not an ELF?\n"); + goto out_munmap; + } + + if (eh->e_ident[EI_CLASS] != ELFCLASS64) { + fprintf(stderr, "vmlinux is not 64b?\n"); + goto out_munmap; + } + + if (eh->e_ident[EI_DATA] != ELFDATA2LSB) { + fprintf(stderr, "vmlinux is not little endian?\n"); + goto out_munmap; + } + + for (i = 0; i < le16toh(eh->e_shnum); i++) { + sh = vmlinux + le64toh(eh->e_shoff) + (i * le16toh(eh->e_shentsize)); + + if (sh->sh_type != SHT_PROGBITS) + continue; + if (!(sh->sh_flags & SHF_EXECINSTR)) + continue; + + err = check_code(le64toh(sh->sh_addr), + vmlinux + le64toh(sh->sh_offset), + le64toh(sh->sh_size)); + if (err) + goto out_munmap; + } + + status = EXIT_SUCCESS; +out_munmap: + munmap(vmlinux, st.st_size); +out_close: + close(vmlinux_fd); +out_ret: + fprintf(stdout, "loongson3-llsc-check returns %s\n", + status ? "failure" : "success"); + return status; +} |