Message-ID: <4B0BFE21.7000102@redhat.com>
Date: Tue, 24 Nov 2009 10:39:13 -0500
From: Masami Hiramatsu <mhiramat@redhat.com>
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To: Frederic Weisbecker <fweisbec@gmail.com>
CC: Ingo Molnar <mingo@elte.hu>,
       Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
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       Christoph Hellwig <hch@infradead.org>,
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Subject: Re: [PATCH -tip v5 06/10] kprobes/x86: Cleanup save/restore	registers
References: <20091123232115.22071.71558.stgit@dhcp-100-2-132.bos.redhat.com> <20091123232204.22071.60562.stgit@dhcp-100-2-132.bos.redhat.com> <20091124025115.GB6752@nowhere>
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Frederic Weisbecker wrote:
> 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?

Yes, in both cases (kretprobe/optprpbe) it needs to
emulate kprobes behavior. kprobes can be used as
fault injection, it should pop pt_regs.

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

Hmm, what code did you mean?

Thank you,

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com

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