linux-kernel - Re: [PATCH 1/3] powerpc: kprobes: fix handling of function offsets on ABIv2

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Date:   Tue, 14 Feb 2017 14:11:34 +0530
From:   Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>
To:     "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/3] powerpc: kprobes: fix handling of function offsets
 on ABIv2

On Tue, Feb 14, 2017 at 02:08:01PM +0530, Naveen N. Rao wrote:
> commit 239aeba76409 ("perf powerpc: Fix kprobe and kretprobe handling
> with kallsyms on ppc64le") changed how we use the offset field in struct
> kprobe on ABIv2. perf now offsets from the GEP (Global entry point) if an
> offset is specified and otherwise chooses the LEP (Local entry point).
> 
> Fix the same in kernel for kprobe API users. We do this by extending
> kprobe_lookup_name() to accept an additional parameter to indicate the
> offset specified with the kprobe registration. If offset is 0, we return
> the local function entry and return the global entry point otherwise.
> 
> With:
> 	# cd /sys/kernel/debug/tracing/
> 	# echo "p _do_fork" >> kprobe_events
> 	# echo "p _do_fork+0x10" >> kprobe_events
> 
> before this patch:
> 	# cat ../kprobes/list
> 	c0000000000d0748  k  _do_fork+0x8    [DISABLED]
> 	c0000000000d0758  k  _do_fork+0x18    [DISABLED]
> 	c0000000000412b0  k  kretprobe_trampoline+0x0    [OPTIMIZED]
> 
> and after:
> 	# cat ../kprobes/list
> 	c0000000000d04c8  k  _do_fork+0x8    [DISABLED]
> 	c0000000000d04d0  k  _do_fork+0x10    [DISABLED]
> 	c0000000000412b0  k  kretprobe_trampoline+0x0    [OPTIMIZED]
> 
> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

Acked-by: Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>