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    Subject[PATCH 3/4] uprobes/x86: Kill adjust_ret_addr(), simplify UPROBE_FIX_CALL logic
    The only insn which could have both UPROBE_FIX_IP and UPROBE_FIX_CALL
    was 0xe8 "call relative", and now it is handled by branch_xol_ops.

    So we can change default_post_xol_op(UPROBE_FIX_CALL) to simply push
    the address of next insn == utask->vaddr + insn.length, just we need
    to record insn.length into the new auprobe->def.ilen member.

    Note: if/when we teach branch_xol_ops to support jcxz/loopz we can
    remove the "correction" logic, UPROBE_FIX_IP can use the same address.

    Signed-off-by: Oleg Nesterov <oleg@redhat.com>
    ---
    arch/x86/include/asm/uprobes.h | 1 +
    arch/x86/kernel/uprobes.c | 24 +++---------------------
    2 files changed, 4 insertions(+), 21 deletions(-)

    diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
    index 9ce25ce..a040d49 100644
    --- a/arch/x86/include/asm/uprobes.h
    +++ b/arch/x86/include/asm/uprobes.h
    @@ -54,6 +54,7 @@ struct arch_uprobe {
    long riprel_target;
    #endif
    u8 fixups;
    + u8 ilen;
    } def;
    };
    };
    diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
    index 48d2623..4c60b7a 100644
    --- a/arch/x86/kernel/uprobes.c
    +++ b/arch/x86/kernel/uprobes.c
    @@ -418,24 +418,6 @@ static int push_ret_address(struct pt_regs *regs, unsigned long ip)
    return 0;
    }

    -/*
    - * Adjust the return address pushed by a call insn executed out of line.
    - */
    -static int adjust_ret_addr(unsigned long sp, long correction)
    -{
    - int rasize = sizeof_long();
    - long ra;
    -
    - if (copy_from_user(&ra, (void __user *)sp, rasize))
    - return -EFAULT;
    -
    - ra += correction;
    - if (copy_to_user((void __user *)sp, &ra, rasize))
    - return -EFAULT;
    -
    - return 0;
    -}
    -
    static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
    {
    struct uprobe_task *utask = current->utask;
    @@ -446,10 +428,9 @@ static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs
    regs->ip += correction;

    if (auprobe->def.fixups & UPROBE_FIX_CALL) {
    - if (adjust_ret_addr(regs->sp, correction)) {
    - regs->sp += sizeof_long();
    + regs->sp += sizeof_long();
    + if (push_ret_address(regs, utask->vaddr + auprobe->def.ilen))
    return -ERESTART;
    - }
    }
    /* popf; tell the caller to not touch TF */
    if (auprobe->def.fixups & UPROBE_FIX_SETF)
    @@ -676,6 +657,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
    handle_riprel_insn(auprobe, &insn);
    }

    + auprobe->def.ilen = insn.length;
    if (fix_ip)
    auprobe->def.fixups |= UPROBE_FIX_IP;
    if (fix_call)
    --
    1.5.5.1


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