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Date: Tue, 24 Nov 2009 02:51:00 -0000
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>, 	Ananth N Mavinakayanahalli <ananth@in.ibm.com>, 	lkml <linux-kernel@vger.kernel.org>, 	systemtap <systemtap@sources.redhat.com>, 	DLE <dle-develop@lists.sourceforge.net>, 	Jim Keniston <jkenisto@us.ibm.com>, 	Srikar Dronamraju <srikar@linux.vnet.ibm.com>, 	Christoph Hellwig <hch@infradead.org>, 	Steven Rostedt <rostedt@goodmis.org>, 	"H. Peter Anvin" <hpa@zytor.com>, 	Anders Kaseorg <andersk@ksplice.com>, 	Tim Abbott <tabbott@ksplice.com>, Andi Kleen <andi@firstfloor.org>, 	Jason Baron <jbaron@redhat.com>, 	Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Subject: Re: [PATCH -tip v5 06/10] kprobes/x86: Cleanup save/restore 	registers
Message-ID: <20091124025115.GB6752@nowhere>
References: <20091123232115.22071.71558.stgit@dhcp-100-2-132.bos.redhat.com> <20091123232204.22071.60562.stgit@dhcp-100-2-132.bos.redhat.com>
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On Mon, Nov 23, 2009 at 06:22:04PM -0500, Masami Hiramatsu wrote:
> +#ifdef CONFIG_X86_64
> +#define SAVE_REGS_STRING		\
> +	/* Skip cs, ip, orig_ax. */	\
> +	"	subq $24, %rsp\n"	\
> +	"	pushq %rdi\n"		\
> +	"	pushq %rsi\n"		\
> +	"	pushq %rdx\n"		\
> +	"	pushq %rcx\n"		\
> +	"	pushq %rax\n"		\
> +	"	pushq %r8\n"		\
> +	"	pushq %r9\n"		\
> +	"	pushq %r10\n"		\
> +	"	pushq %r11\n"		\
> +	"	pushq %rbx\n"		\
> +	"	pushq %rbp\n"		\
> +	"	pushq %r12\n"		\
> +	"	pushq %r13\n"		\
> +	"	pushq %r14\n"		\
> +	"	pushq %r15\n"
> +#define RESTORE_REGS_STRING		\
> +	"	popq %r15\n"		\
> +	"	popq %r14\n"		\
> +	"	popq %r13\n"		\
> +	"	popq %r12\n"		\
> +	"	popq %rbp\n"		\
> +	"	popq %rbx\n"		\
> +	"	popq %r11\n"		\
> +	"	popq %r10\n"		\
> +	"	popq %r9\n"		\
> +	"	popq %r8\n"		\
> +	"	popq %rax\n"		\
> +	"	popq %rcx\n"		\
> +	"	popq %rdx\n"		\
> +	"	popq %rsi\n"		\
> +	"	popq %rdi\n"		\


BTW, do you really need to push/pop every registers
before/after calling a probe handler?

Is it possible to only save/restore the scratch ones?