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Date: Mon, 02 Jun 2014 08:27:59 -0700
From: Jim Keniston <jkenisto@...ux.vnet.ibm.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Ingo Molnar <mingo@...e.hu>, Denys Vlasenko <dvlasenk@...hat.com>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uprobes/x86: Rename arch_uprobe->def into ->dflt,
minor comment updates
On Sun, 2014-06-01 at 21:25 +0200, Oleg Nesterov wrote:
> Purely cosmetic, no changes in .o,
>
> 1. As Jim pointed out arch_uprobe->def looks ambiguous, rename it to
> ->dflt.
>
> 2. Add the comment into default_post_xol_op() to explain "regs->sp +=".
>
> 3. Remove the stale part of the comment in arch_uprobe_analyze_insn().
>
> Suggested-by: Jim Keniston <jkenisto@...ibm.com>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Looks good. Thanks.
Reviewed-by: Jim Keniston <jkenisto@...ibm.com>
> ---
> arch/x86/include/asm/uprobes.h | 2 +-
> arch/x86/kernel/uprobes.c | 37 ++++++++++++++++++-------------------
> 2 files changed, 19 insertions(+), 20 deletions(-)
>
> diff --git a/arch/x86/include/asm/uprobes.h b/arch/x86/include/asm/uprobes.h
> index 7be3c07..b3d9442 100644
> --- a/arch/x86/include/asm/uprobes.h
> +++ b/arch/x86/include/asm/uprobes.h
> @@ -52,7 +52,7 @@ struct arch_uprobe {
> struct {
> u8 fixups;
> u8 ilen;
> - } def;
> + } dflt;
> };
> };
>
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index fcf6279..33e239f 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -254,7 +254,7 @@ static inline bool is_64bit_mm(struct mm_struct *mm)
> * If arch_uprobe->insn doesn't use rip-relative addressing, return
> * immediately. Otherwise, rewrite the instruction so that it accesses
> * its memory operand indirectly through a scratch register. Set
> - * def->fixups accordingly. (The contents of the scratch register
> + * dflt->fixups accordingly. (The contents of the scratch register
> * will be saved before we single-step the modified instruction,
> * and restored afterward).
> *
> @@ -372,14 +372,14 @@ static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
> */
> if (reg != 6 && reg2 != 6) {
> reg2 = 6;
> - auprobe->def.fixups |= UPROBE_FIX_RIP_SI;
> + auprobe->dflt.fixups |= UPROBE_FIX_RIP_SI;
> } else if (reg != 7 && reg2 != 7) {
> reg2 = 7;
> - auprobe->def.fixups |= UPROBE_FIX_RIP_DI;
> + auprobe->dflt.fixups |= UPROBE_FIX_RIP_DI;
> /* TODO (paranoia): force maskmovq to not use di */
> } else {
> reg2 = 3;
> - auprobe->def.fixups |= UPROBE_FIX_RIP_BX;
> + auprobe->dflt.fixups |= UPROBE_FIX_RIP_BX;
> }
> /*
> * Point cursor at the modrm byte. The next 4 bytes are the
> @@ -398,9 +398,9 @@ static void riprel_analyze(struct arch_uprobe *auprobe, struct insn *insn)
> static inline unsigned long *
> scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)
> {
> - if (auprobe->def.fixups & UPROBE_FIX_RIP_SI)
> + if (auprobe->dflt.fixups & UPROBE_FIX_RIP_SI)
> return ®s->si;
> - if (auprobe->def.fixups & UPROBE_FIX_RIP_DI)
> + if (auprobe->dflt.fixups & UPROBE_FIX_RIP_DI)
> return ®s->di;
> return ®s->bx;
> }
> @@ -411,18 +411,18 @@ scratch_reg(struct arch_uprobe *auprobe, struct pt_regs *regs)
> */
> static void riprel_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> {
> - if (auprobe->def.fixups & UPROBE_FIX_RIP_MASK) {
> + if (auprobe->dflt.fixups & UPROBE_FIX_RIP_MASK) {
> struct uprobe_task *utask = current->utask;
> unsigned long *sr = scratch_reg(auprobe, regs);
>
> utask->autask.saved_scratch_register = *sr;
> - *sr = utask->vaddr + auprobe->def.ilen;
> + *sr = utask->vaddr + auprobe->dflt.ilen;
> }
> }
>
> static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
> {
> - if (auprobe->def.fixups & UPROBE_FIX_RIP_MASK) {
> + if (auprobe->dflt.fixups & UPROBE_FIX_RIP_MASK) {
> struct uprobe_task *utask = current->utask;
> unsigned long *sr = scratch_reg(auprobe, regs);
>
> @@ -499,16 +499,16 @@ static int default_post_xol_op(struct arch_uprobe *auprobe, struct pt_regs *regs
> struct uprobe_task *utask = current->utask;
>
> riprel_post_xol(auprobe, regs);
> - if (auprobe->def.fixups & UPROBE_FIX_IP) {
> + if (auprobe->dflt.fixups & UPROBE_FIX_IP) {
> long correction = utask->vaddr - utask->xol_vaddr;
> regs->ip += correction;
> - } else if (auprobe->def.fixups & UPROBE_FIX_CALL) {
> - regs->sp += sizeof_long();
> - if (push_ret_address(regs, utask->vaddr + auprobe->def.ilen))
> + } else if (auprobe->dflt.fixups & UPROBE_FIX_CALL) {
> + regs->sp += sizeof_long(); /* Pop incorrect return address */
> + if (push_ret_address(regs, utask->vaddr + auprobe->dflt.ilen))
> return -ERESTART;
> }
> /* popf; tell the caller to not touch TF */
> - if (auprobe->def.fixups & UPROBE_FIX_SETF)
> + if (auprobe->dflt.fixups & UPROBE_FIX_SETF)
> utask->autask.saved_tf = true;
>
> return 0;
> @@ -711,12 +711,11 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
>
> /*
> * Figure out which fixups default_post_xol_op() will need to perform,
> - * and annotate def->fixups accordingly. To start with, ->fixups is
> - * either zero or it reflects rip-related fixups.
> + * and annotate dflt->fixups accordingly.
> */
> switch (OPCODE1(&insn)) {
> case 0x9d: /* popf */
> - auprobe->def.fixups |= UPROBE_FIX_SETF;
> + auprobe->dflt.fixups |= UPROBE_FIX_SETF;
> break;
> case 0xc3: /* ret or lret -- ip is correct */
> case 0xcb:
> @@ -742,8 +741,8 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
> riprel_analyze(auprobe, &insn);
> }
>
> - auprobe->def.ilen = insn.length;
> - auprobe->def.fixups |= fix_ip_or_call;
> + auprobe->dflt.ilen = insn.length;
> + auprobe->dflt.fixups |= fix_ip_or_call;
>
> auprobe->ops = &default_xol_ops;
> return 0;
--
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