linux-kernel - Re: [PATCH 1/3] powerpc: Emulation support for load/store instructions on LE

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Date:   Sun, 6 Nov 2016 06:31:51 +1100
From:   Anton Blanchard <anton@...ba.org>
To:     Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Cc:     Andrew Donnellan <andrew.donnellan@....ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>, chris@...troguy.com,
        aneesh.kumar@...ux.vnet.ibm.com, ast@...nel.org,
        linux-kernel@...r.kernel.org, oss@...error.net,
        paul.gortmaker@...driver.com, duwe@....de,
        lsorense@...lub.uwaterloo.ca, bauerman@...ux.vnet.ibm.com,
        oohall@...il.com, naveen.n.rao@...ux.vnet.ibm.com,
        linuxppc-dev@...ts.ozlabs.org, paulus@...ba.org,
        viro@...iv.linux.org.uk
Subject: Re: [PATCH 1/3] powerpc: Emulation support for load/store
 instructions on LE

Hi,

> kprobe, uprobe, hw-breakpoint and xmon are the only user of
> emulate_step.
> 
> Kprobe / uprobe single-steps instruction if they can't emulate it, so
> there is no problem with them. As I mention, hw-breakpoint is broken.
> However I'm not sure about xmon, I need to check that.

I was mostly concerned that it would impact kprobes. Sounds like we are
ok there.

> So yes, there is no user-visible feature that depends on this.

Aren't hardware breakpoints exposed via perf? I'd call perf
user-visible.

Anton