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Date: Tue, 01 Apr 2014 11:00:58 +0900
From: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: Ingo Molnar <mingo@...e.hu>,
Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
Ananth N Mavinakayanahalli <ananth@...ibm.com>,
David Long <dave.long@...aro.org>,
Denys Vlasenko <dvlasenk@...hat.com>,
"Frank Ch. Eigler" <fche@...hat.com>,
Jim Keniston <jkenisto@...ibm.com>,
Jonathan Lebon <jlebon@...hat.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] uprobes/x86: Fold prepare_fixups() into arch_uprobe_analyze_insn()
(2014/04/01 4:43), Oleg Nesterov wrote:
> No functional changes, preparation.
>
> Shift the code from prepare_fixups() to arch_uprobe_analyze_insn()
> with the following modifications:
>
> - Do not call insn_get_opcode() again, it was already called
> by validate_insn_bits().
>
> - Move "case 0xea" up. This way "case 0xff" can fall through
> to default case.
>
> - change "case 0xff" to use the nested "switch (MODRM_REG)",
> this way the code looks a bit simpler.
>
> - Make the comments look consistent.
Interesting. Similar cleanup should be applied to kprobes too. :)
>
> While at it, kill the initialization of rip_rela_target_address and
> ->fixups, we can rely on kzalloc(). We will add the new members into
> arch_uprobe, it would be better to assume that everything is zero by
> default.
>
> TODO: cleanup/fix the mess in validate_insn_bits() paths:
>
> - validate_insn_64bits() and validate_insn_32bits() should be
> unified.
>
> - "ifdef" is not used consistently; if good_insns_64 depends
> on CONFIG_X86_64, then probably good_insns_32 should depend
> on CONFIG_X86_32/EMULATION
>
> - the usage of mm->context.ia32_compat looks wrong if the task
> is TIF_X32.
>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> ---
> arch/x86/kernel/uprobes.c | 110 +++++++++++++++++++--------------------------
> 1 files changed, 47 insertions(+), 63 deletions(-)
>
> diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
> index 2ed8459..098e56e 100644
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -53,7 +53,7 @@
> #define OPCODE1(insn) ((insn)->opcode.bytes[0])
> #define OPCODE2(insn) ((insn)->opcode.bytes[1])
> #define OPCODE3(insn) ((insn)->opcode.bytes[2])
> -#define MODRM_REG(insn) X86_MODRM_REG(insn->modrm.value)
> +#define MODRM_REG(insn) X86_MODRM_REG((insn)->modrm.value)
>
> #define W(row, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9, ba, bb, bc, bd, be, bf)\
> (((b0##UL << 0x0)|(b1##UL << 0x1)|(b2##UL << 0x2)|(b3##UL << 0x3) | \
> @@ -229,63 +229,6 @@ static int validate_insn_32bits(struct arch_uprobe *auprobe, struct insn *insn)
> return -ENOTSUPP;
> }
>
> -/*
> - * Figure out which fixups arch_uprobe_post_xol() will need to perform, and
> - * annotate arch_uprobe->fixups accordingly. To start with,
> - * arch_uprobe->fixups is either zero or it reflects rip-related fixups.
> - */
> -static void prepare_fixups(struct arch_uprobe *auprobe, struct insn *insn)
> -{
> - bool fix_ip = true, fix_call = false; /* defaults */
> - int reg;
> -
> - insn_get_opcode(insn); /* should be a nop */
> -
> - switch (OPCODE1(insn)) {
> - case 0x9d:
> - /* popf */
> - auprobe->fixups |= UPROBE_FIX_SETF;
> - break;
> - case 0xc3: /* ret/lret */
> - case 0xcb:
> - case 0xc2:
> - case 0xca:
> - /* ip is correct */
> - fix_ip = false;
> - break;
> - case 0xe8: /* call relative - Fix return addr */
> - fix_call = true;
> - break;
> - case 0x9a: /* call absolute - Fix return addr, not ip */
> - fix_call = true;
> - fix_ip = false;
> - break;
> - case 0xff:
> - insn_get_modrm(insn);
> - reg = MODRM_REG(insn);
> - if (reg == 2 || reg == 3) {
> - /* call or lcall, indirect */
> - /* Fix return addr; ip is correct. */
> - fix_call = true;
> - fix_ip = false;
> - } else if (reg == 4 || reg == 5) {
> - /* jmp or ljmp, indirect */
> - /* ip is correct. */
> - fix_ip = false;
> - }
> - break;
> - case 0xea: /* jmp absolute -- ip is correct */
> - fix_ip = false;
> - break;
> - default:
> - break;
> - }
> - if (fix_ip)
> - auprobe->fixups |= UPROBE_FIX_IP;
> - if (fix_call)
> - auprobe->fixups |= UPROBE_FIX_CALL;
> -}
> -
> #ifdef CONFIG_X86_64
> /*
> * If arch_uprobe->insn doesn't use rip-relative addressing, return
> @@ -318,7 +261,6 @@ handle_riprel_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, struct ins
> if (mm->context.ia32_compat)
> return;
>
> - auprobe->rip_rela_target_address = 0x0;
> if (!insn_rip_relative(insn))
> return;
>
> @@ -421,16 +363,58 @@ static int validate_insn_bits(struct arch_uprobe *auprobe, struct mm_struct *mm,
> */
> int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm, unsigned long addr)
> {
> - int ret;
> struct insn insn;
> + bool fix_ip = true, fix_call = false;
> + int ret;
>
> - auprobe->fixups = 0;
> ret = validate_insn_bits(auprobe, mm, &insn);
> - if (ret != 0)
> + if (ret)
> return ret;
>
> + /*
> + * Figure out which fixups arch_uprobe_post_xol() will need to perform,
> + * and annotate arch_uprobe->fixups accordingly. To start with, ->fixups
> + * is either zero or it reflects rip-related fixups.
> + */
> handle_riprel_insn(auprobe, mm, &insn);
> - prepare_fixups(auprobe, &insn);
> +
> + switch (OPCODE1(&insn)) {
> + case 0x9d: /* popf */
> + auprobe->fixups |= UPROBE_FIX_SETF;
> + break;
> + case 0xc3: /* ret or lret -- ip is correct */
> + case 0xcb:
> + case 0xc2:
> + case 0xca:
> + fix_ip = false;
> + break;
> + case 0xe8: /* call relative - Fix return addr */
> + fix_call = true;
> + break;
> + case 0x9a: /* call absolute - Fix return addr, not ip */
> + fix_call = true;
> + fix_ip = false;
> + break;
> + case 0xea: /* jmp absolute -- ip is correct */
> + fix_ip = false;
> + break;
> + case 0xff:
> + insn_get_modrm(&insn);
> + switch (MODRM_REG(&insn)) {
> + case 2: case 3: /* call or lcall, indirect */
> + fix_call = true;
> + case 4: case 5: /* jmp or ljmp, indirect */
> + fix_ip = false;
> + }
> + break;
> + default:
> + break;
> + }
> +
> + if (fix_ip)
> + auprobe->fixups |= UPROBE_FIX_IP;
> + if (fix_call)
> + auprobe->fixups |= UPROBE_FIX_CALL;
>
> return 0;
> }
>
--
Masami HIRAMATSU
IT Management Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@...achi.com
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