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Re: [PATCH -tip v5 06/10] kprobes/x86: Cleanup save/restore registers
- From: Masami Hiramatsu <mhiramat at redhat dot com>
- To: Frederic Weisbecker <fweisbec at gmail dot com>
- Cc: Ingo Molnar <mingo at elte dot hu>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, lkml <linux-kernel at vger dot kernel dot org>, systemtap <systemtap at sources dot redhat dot com>, DLE <dle-develop at lists dot sourceforge dot net>, Jim Keniston <jkenisto at us dot ibm dot com>, Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>, Christoph Hellwig <hch at infradead dot org>, Steven Rostedt <rostedt at goodmis dot org>, "H. Peter Anvin" <hpa at zytor dot com>, Anders Kaseorg <andersk at ksplice dot com>, Tim Abbott <tabbott at ksplice dot com>, Andi Kleen <andi at firstfloor dot org>, Jason Baron <jbaron at redhat dot com>, Mathieu Desnoyers <mathieu dot desnoyers at polymtl dot ca>
- Date: Tue, 24 Nov 2009 10:39:13 -0500
- 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>
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