lkml.org 
[lkml]   [2017]   [Oct]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v9 12/29] x86/insn-eval: Add utility function to identify string instructions
    Date
    String instructions are special because, in protected mode, the linear
    address is always obtained via the ES segment register in operands that
    use the (E)DI register; the DS segment register in operands that use
    the (E)SI register. Furthermore, segment override prefixes are ignored
    when calculating a linear address involving the (E)DI register; segment
    override prefixes can be used when calculating linear addresses involving
    the (E)SI register.

    It follows that linear addresses are calculated differently for the case of
    string instructions. The purpose of this utility function is to identify
    such instructions for callers to determine a linear address correctly.

    Note that this function only identifies string instructions; it does not
    determine what segment register to use in the address computation. That is
    left to callers. A subsequent commmit introduces a function to determine
    the segment register to use given the instruction, operands and
    segment override prefixes.

    Cc: Dave Hansen <dave.hansen@linux.intel.com>
    Cc: Adam Buchbinder <adam.buchbinder@gmail.com>
    Cc: Colin Ian King <colin.king@canonical.com>
    Cc: Lorenzo Stoakes <lstoakes@gmail.com>
    Cc: Qiaowei Ren <qiaowei.ren@intel.com>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Masami Hiramatsu <mhiramat@kernel.org>
    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: Kees Cook <keescook@chromium.org>
    Cc: Thomas Garnier <thgarnie@google.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Borislav Petkov <bp@suse.de>
    Cc: Dmitry Vyukov <dvyukov@google.com>
    Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
    Cc: x86@kernel.org
    Reviewed-by: Borislav Petkov <bp@suse.de>
    Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
    ---
    arch/x86/lib/insn-eval.c | 28 ++++++++++++++++++++++++++++
    1 file changed, 28 insertions(+)

    diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c
    index 405ffeb..ac7b87c 100644
    --- a/arch/x86/lib/insn-eval.c
    +++ b/arch/x86/lib/insn-eval.c
    @@ -19,6 +19,34 @@ enum reg_type {
    REG_TYPE_BASE,
    };

    +/**
    + * is_string_insn() - Determine if instruction is a string instruction
    + * @insn: Instruction containing the opcode to inspect
    + *
    + * Returns:
    + *
    + * true if the instruction, determined by the opcode, is any of the
    + * string instructions as defined in the Intel Software Development manual.
    + * False otherwise.
    + */
    +static bool is_string_insn(struct insn *insn)
    +{
    + insn_get_opcode(insn);
    +
    + /* All string instructions have a 1-byte opcode. */
    + if (insn->opcode.nbytes != 1)
    + return false;
    +
    + switch (insn->opcode.bytes[0]) {
    + case 0x6c ... 0x6f: /* INS, OUTS */
    + case 0xa4 ... 0xa7: /* MOVS, CMPS */
    + case 0xaa ... 0xaf: /* STOS, LODS, SCAS */
    + return true;
    + default:
    + return false;
    + }
    +}
    +
    static int get_reg_offset(struct insn *insn, struct pt_regs *regs,
    enum reg_type type)
    {
    --
    2.7.4
    \
     
     \ /
      Last update: 2017-10-04 06:01    [W:2.639 / U:0.448 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site