From: Michael Ellerman <mpe@ellerman•id.au>
To: Torsten Duwe <duwe@lst•de>, Balbir Singh <bsingharora@gmail•com>
Cc: linuxppc-dev@ozlabs•org, pmladek@suse•com, jeyu@redhat•com,
jkosina@suse•cz, linux-kernel@vger•kernel.org,
rostedt@goodmis•org, kamalesh@linux•vnet.ibm.com,
live-patching@vger•kernel.org, mbenes@suse•cz
Subject: Re: [PATCH 07/12] powerpc/ftrace: FTRACE_WITH_REGS implementation for ppc64le
Date: Fri, 26 Feb 2016 21:14:01 +1100 [thread overview]
Message-ID: <1456481641.25691.5.camel@ellerman.id.au> (raw)
In-Reply-To: <20160225151113.GK21932@lst.de>
On Thu, 2016-02-25 at 16:11 +0100, Torsten Duwe wrote:
> On Thu, Feb 25, 2016 at 11:48:59AM +1100, Balbir Singh wrote:
> > > @@ -608,6 +621,9 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
> > > return -ENOENT;
> > > if (!restore_r2((u32 *)location + 1, me))
> > > return -ENOEXEC;
> > > + /* Squash the TOC saver for profiler calls */
> > > + if (!strcmp("_mcount", strtab+sym->st_name))
> > > + SQUASH_TOC_SAVE_INSN(value);
> > I don't think we need this anymore, do we?
>
> I'm not sure. Once a module is loaded, are all the "bl _mcount"s NOPed out
> before any of its functions are run? If not, the _mcount trampoline will
> be used, and it must not save R2!
With dynamic ftrace, yes they are all nop'ed out before the module runs. See
ftrace_module_init() called from load_module().
But with static ftrace they are just left as-is.
As this series is currently written you can't enable mprofile-kernel with
static ftrace. But that's a bit fragile, someone could easily send a patch to
enable it for static ftrace and we'd probably merge it without thinking about
this code. So I'll leave this as is for now, and we will clean it up once the
series is in.
cheers
next prev parent reply other threads:[~2016-02-26 10:14 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-24 14:28 [PATCH 01/12] powerpc/module: Only try to generate the ftrace_caller() stub once Michael Ellerman
2016-02-24 14:28 ` [PATCH 02/12] powerpc/module: Mark module stubs with a magic value Michael Ellerman
2016-02-25 0:04 ` Balbir Singh
2016-02-25 6:43 ` Michael Ellerman
2016-02-25 13:17 ` Torsten Duwe
2016-02-26 10:37 ` Michael Ellerman
2016-02-24 14:28 ` [PATCH 03/12] powerpc/module: Create a special stub for ftrace_caller() Michael Ellerman
2016-02-25 0:08 ` Balbir Singh
2016-02-25 10:48 ` Michael Ellerman
2016-02-25 13:31 ` Torsten Duwe
2016-02-26 10:35 ` Michael Ellerman
2016-02-24 14:28 ` [PATCH 04/12] powerpc/ftrace: Prepare for -mprofile-kernel Michael Ellerman
2016-02-25 0:28 ` Balbir Singh
2016-02-25 10:37 ` Michael Ellerman
2016-02-25 13:52 ` Torsten Duwe
2016-02-26 10:14 ` Michael Ellerman
2016-02-24 14:28 ` [PATCH 05/12] powerpc/ftrace: ftrace_graph_caller() needs to save/restore toc Michael Ellerman
2016-02-25 0:30 ` Balbir Singh
2016-02-25 10:39 ` Michael Ellerman
2016-02-25 14:02 ` Torsten Duwe
2016-02-24 14:28 ` [PATCH 06/12] powerpc/module: Rework is_early_mcount_callsite() Michael Ellerman
2016-02-24 23:39 ` Balbir Singh
2016-02-25 10:28 ` Michael Ellerman
2016-02-25 14:06 ` Torsten Duwe
2016-02-24 14:28 ` [PATCH 07/12] powerpc/ftrace: FTRACE_WITH_REGS implementation for ppc64le Michael Ellerman
2016-02-25 0:48 ` Balbir Singh
2016-02-25 15:11 ` Torsten Duwe
2016-02-26 10:14 ` Michael Ellerman [this message]
2016-02-24 14:28 ` [PATCH 08/12] powerpc/ftrace: Rework ftrace_caller() Michael Ellerman
2016-02-25 1:06 ` Balbir Singh
2016-02-25 14:25 ` Torsten Duwe
2016-02-24 14:28 ` [PATCH 09/12] powerpc/ftrace: Use generic ftrace_modify_all_code() Michael Ellerman
2016-02-25 1:10 ` Balbir Singh
2016-02-24 14:28 ` [PATCH 10/12] powerpc/ftrace: FTRACE_WITH_REGS configuration variables Michael Ellerman
2016-02-25 1:11 ` Balbir Singh
2016-02-25 14:34 ` Torsten Duwe
2016-02-24 14:28 ` [PATCH 11/12] powerpc/ftrace: Rework __ftrace_make_nop() Michael Ellerman
2016-02-24 14:28 ` [PATCH 12/12] powerpc/ftrace: Disable profiling for some files Michael Ellerman
2016-02-25 1:13 ` Balbir Singh
2016-02-24 23:55 ` [PATCH 01/12] powerpc/module: Only try to generate the ftrace_caller() stub once Balbir Singh
2016-02-25 4:36 ` Balbir Singh
2016-02-25 13:08 ` Torsten Duwe
2016-02-25 14:38 ` Kamalesh Babulal
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