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    Subject[RFC PATCH v2 2/6] uprobes/x86: Emulate unconditional rip-relative jmp's
    0xeb and 0xe9. Anything else?

    TODO: move ->fixup into the union along with rip_rela_target_address.

    Reported-by: Jonathan Lebon <jlebon@redhat.com>
    Signed-off-by: Oleg Nesterov <oleg@redhat.com>
    ---
    arch/x86/include/asm/uprobes.h | 8 +++++++-
    arch/x86/kernel/uprobes.c | 38 ++++++++++++++++++++++++++++++++++++++
    2 files changed, 45 insertions(+), 1 deletions(-)

    diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
    index 9f8210b..cca62c5 100644
    --- a/arch/x86/include/asm/uprobes.h
    +++ b/arch/x86/include/asm/uprobes.h
    @@ -44,9 +44,15 @@ struct arch_uprobe {
    u16 fixups;
    const struct uprobe_xol_ops *ops;

    + union {
    #ifdef CONFIG_X86_64
    - unsigned long rip_rela_target_address;
    + unsigned long rip_rela_target_address;
    #endif
    + struct {
    + s32 disp;
    + u8 ilen;
    + } ttt;
    + };
    };

    struct arch_uprobe_task {
    diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
    index ef59ef9..1cdc379 100644
    --- a/arch/x86/kernel/uprobes.c
    +++ b/arch/x86/kernel/uprobes.c
    @@ -461,6 +461,40 @@ static struct uprobe_xol_ops default_xol_ops = {
    .post_xol = default_post_xol_op,
    };

    +static bool ttt_emulate_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
    +{
    + regs->ip += auprobe->ttt.ilen + auprobe->ttt.disp;
    + return true;
    +}
    +
    +static struct uprobe_xol_ops ttt_xol_ops = {
    + .emulate = ttt_emulate_op,
    +};
    +
    +/* Returns -ENOSYS if ttt_xol_ops doesn't handle this insn */
    +static int ttt_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn)
    +{
    +
    + switch (OPCODE1(insn)) {
    + case 0xeb: /* jmp 8 */
    + case 0xe9: /* jmp 32 */
    + break;
    + default:
    + return -ENOSYS;
    + }
    +
    + /* has the side-effect of processing the entire instruction */
    + insn_get_length(insn);
    + if (WARN_ON_ONCE(!insn_complete(insn)))
    + return -ENOEXEC;
    +
    + auprobe->ttt.ilen = insn->length;
    + auprobe->ttt.disp = insn->immediate.value;
    +
    + auprobe->ops = &ttt_xol_ops;
    + return 0;
    +}
    +
    /**
    * arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
    * @mm: the probed address space.
    @@ -478,6 +512,10 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
    if (ret)
    return ret;

    + ret = ttt_setup_xol_ops(auprobe, &insn);
    + if (ret != -ENOSYS)
    + return ret;
    +
    /*
    * Figure out which fixups arch_uprobe_post_xol() will need to perform,
    * and annotate arch_uprobe->fixups accordingly. To start with, ->fixups
    --
    1.5.5.1


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