lkml.org 
[lkml]   [2014]   [Apr]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2 6/9] uprobes/x86: Introduce uprobe_xol_ops and arch_uprobe->ops
(2014/04/05 3:51), Oleg Nesterov wrote:
> Introduce arch_uprobe->ops pointing to the "struct uprobe_xol_ops",
> move the current UPROBE_FIX_{RIP*,IP,CALL} code into the default
> set of methods and change arch_uprobe_pre/post_xol() accordingly.
>
> This way we can add the new uprobe_xol_ops's to handle the insns
> which need the special processing (rip-relative jmp/call at least).
>
> TODO: An error from adjust_ret_addr() shouldn't be silently ignored,
> we should teach arch_uprobe_post_xol() or handle_singlestep() paths
> to restart the probed insn in this case. And probably "adjust" can
> be simplified and turned into set_ret_addr(). It seems that we do
> not really need copy_from_user(), we can always calculate the value
> we need to write into *regs->sp.

It seems that you fixed this in 8/9, we don't need the TODO list in
the description.

>
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>
> Reviewed-by: Jim Keniston <jkenisto@us.ibm.com>
> ---
> arch/x86/include/asm/uprobes.h | 7 ++-
> arch/x86/kernel/uprobes.c | 107 +++++++++++++++++++++++++--------------
> 2 files changed, 74 insertions(+), 40 deletions(-)
>
> diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
> index 3087ea9..9f8210b 100644
> --- a/arch/x86/include/asm/uprobes.h
> +++ b/arch/x86/include/asm/uprobes.h
> @@ -33,12 +33,17 @@ typedef u8 uprobe_opcode_t;
> #define UPROBE_SWBP_INSN 0xcc
> #define UPROBE_SWBP_INSN_SIZE 1
>
> +struct uprobe_xol_ops;
> +
> struct arch_uprobe {
> - u16 fixups;
> union {
> u8 insn[MAX_UINSN_BYTES];
> u8 ixol[MAX_UINSN_BYTES];
> };
> +
> + u16 fixups;
> + const struct uprobe_xol_ops *ops;
> +
> #ifdef CONFIG_X86_64
> unsigned long rip_rela_target_address;
> #endif
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index 3bb4198..13ad8a3 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -402,6 +402,64 @@ static int validate_insn_bits(struct arch_uprobe *auprobe, struct mm_struct *mm,
> }
> #endif /* CONFIG_X86_64 */
>
> +struct uprobe_xol_ops {
> + bool (*emulate)(struct arch_uprobe *, struct pt_regs *);
> + int (*pre_xol)(struct arch_uprobe *, struct pt_regs *);
> + int (*post_xol)(struct arch_uprobe *, struct pt_regs *);
> +};
> +
> +static int default_pre_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
> +{
> + pre_xol_rip_insn(auprobe, regs, &current->utask->autask);
> + 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, ncopied;
> + long ra = 0;
> +
> + if (is_ia32_task())
> + rasize = 4;
> + else
> + rasize = 8;
> +
> + ncopied = copy_from_user(&ra, (void __user *)sp, rasize);
> + if (unlikely(ncopied))
> + return -EFAULT;
> +
> + ra += correction;
> + ncopied = copy_to_user((void __user *)sp, &ra, rasize);
> + if (unlikely(ncopied))
> + return -EFAULT;
> +
> + return 0;
> +}
> +
> +static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs)
> +{
> + struct uprobe_task *utask = current->utask;
> + long correction = (long)(utask->vaddr - utask->xol_vaddr);
> + int ret = 0;
> +
> + handle_riprel_post_xol(auprobe, regs, &correction);
> + if (auprobe->fixups & UPROBE_FIX_IP)
> + regs->ip += correction;
> +
> + if (auprobe->fixups & UPROBE_FIX_CALL)
> + ret = adjust_ret_addr(regs->sp, correction);
> +
> + return ret;
> +}
> +
> +static struct uprobe_xol_ops default_xol_ops = {
> + .pre_xol = default_pre_xol_op,
> + .post_xol = default_post_xol_op,
> +};
> +
> /**
> * arch_uprobe_analyze_insn - instruction analysis including validity and fixups.
> * @mm: the probed address space.
> @@ -464,6 +522,7 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
> if (fix_call)
> auprobe->fixups |= UPROBE_FIX_CALL;
>
> + auprobe->ops = &default_xol_ops;
> return 0;
> }
>
> @@ -485,33 +544,8 @@ int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> if (test_tsk_thread_flag(current, TIF_BLOCKSTEP))
> set_task_blockstep(current, false);
>
> - pre_xol_rip_insn(auprobe, regs, &utask->autask);
> - return 0;
> -}
> -
> -/*
> - * This function is called by arch_uprobe_post_xol() to adjust the return
> - * address pushed by a call instruction executed out of line.
> - */
> -static int adjust_ret_addr(unsigned long sp, long correction)
> -{
> - int rasize, ncopied;
> - long ra = 0;
> -
> - if (is_ia32_task())
> - rasize = 4;
> - else
> - rasize = 8;
> -
> - ncopied = copy_from_user(&ra, (void __user *)sp, rasize);
> - if (unlikely(ncopied))
> - return -EFAULT;
> -
> - ra += correction;
> - ncopied = copy_to_user((void __user *)sp, &ra, rasize);
> - if (unlikely(ncopied))
> - return -EFAULT;
> -
> + if (auprobe->ops->pre_xol)
> + return auprobe->ops->pre_xol(auprobe, regs);
> return 0;
> }
>
> @@ -560,11 +594,8 @@ bool arch_uprobe_xol_was_trapped(struct task_struct *t)
> int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> {
> struct uprobe_task *utask = current->utask;
> - long correction;
> - int result = 0;
>
> WARN_ON_ONCE(current->thread.trap_nr != UPROBE_TRAP_NR);
> -
> current->thread.trap_nr = utask->autask.saved_trap_nr;
> /*
> * arch_uprobe_pre_xol() doesn't save the state of TIF_BLOCKSTEP
> @@ -576,15 +607,9 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> else if (!(auprobe->fixups & UPROBE_FIX_SETF))
> regs->flags &= ~X86_EFLAGS_TF;
>
> - correction = (long)(utask->vaddr - utask->xol_vaddr);
> - handle_riprel_post_xol(auprobe, regs, &correction);
> - if (auprobe->fixups & UPROBE_FIX_IP)
> - regs->ip += correction;
> -
> - if (auprobe->fixups & UPROBE_FIX_CALL)
> - result = adjust_ret_addr(regs->sp, correction);
> -
> - return result;
> + if (auprobe->ops->post_xol)
> + return auprobe->ops->post_xol(auprobe, regs);
> + return 0;
> }
>
> /* callback routine for handling exceptions. */
> @@ -642,6 +667,10 @@ static bool __skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
> {
> int i;
>
> + if (auprobe->ops->emulate)
> + return auprobe->ops->emulate(auprobe, regs);
> +
> + /* TODO: move this code into ->emulate() hook */

If you think this can move into the emulate(), you should do in this
patch. Since the following code runs by default, there should be
no problem to do that.

> for (i = 0; i < MAX_UINSN_BYTES; i++) {
> if (auprobe->insn[i] == 0x66)
> continue;
>

Thank you,

--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com




\
 
 \ /
  Last update: 2014-04-08 11:41    [W:0.308 / U:11.268 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site