linux-kernel - [PATCH v3 07/15] uprobes/x86: Conditionalize the usage of handle_riprel

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Message-ID: <20140413174546.GA11859@redhat.com>
Date:	Sun, 13 Apr 2014 19:45:46 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Anton Arapov <aarapov@...hat.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>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 07/15] uprobes/x86: Conditionalize the usage of
	handle_riprel_insn()

arch_uprobe_analyze_insn() calls handle_riprel_insn() at the start,
but only "0xff" and "default" cases need the UPROBE_FIX_RIP_ logic.
Move the callsite into "default" case and change the "0xff" case to
fall-through.

We are going to add the various hooks to handle the rip-relative
jmp/call instructions (and more), we need this change to enforce the
fact that the new code can not conflict with is_riprel_insn() logic
which, after this change, can only be used by default_xol_ops.

Note: arch_uprobe_abort_xol() still calls handle_riprel_post_xol()
directly. This is fine unless another _xol_ops we may add later will
need to reuse "UPROBE_FIX_RIP_AX|UPROBE_FIX_RIP_CX" bits in ->fixup.
In this case we can add uprobe_xol_ops->abort() hook, which (perhaps)
we will need anyway in the long term.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Reviewed-by: Jim Keniston <jkenisto@...ibm.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
---
 arch/x86/kernel/uprobes.c |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 6ba6705..f4b436b 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -482,8 +482,6 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
 	 * and annotate arch_uprobe->fixups accordingly. To start with, ->fixups
 	 * is either zero or it reflects rip-related fixups.
 	 */
-	handle_riprel_insn(auprobe, &insn);
-
 	switch (OPCODE1(&insn)) {
 	case 0x9d:		/* popf */
 		auprobe->fixups |= UPROBE_FIX_SETF;
@@ -512,9 +510,9 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
 		case 4: case 5:			/* jmp or ljmp, indirect */
 			fix_ip = false;
 		}
-		break;
+		/* fall through */
 	default:
-		break;
+		handle_riprel_insn(auprobe, &insn);
 	}
 
 	if (fix_ip)
-- 
1.5.5.1

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