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Groups > linux.kernel > #1320239 > unrolled thread
| Started by | Balbir Singh <bsingharora@gmail.com> |
|---|---|
| First post | 2016-01-28 03:50 +0100 |
| Last post | 2016-01-28 12:20 +0100 |
| Articles | 3 — 3 participants |
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Re: [PATCH v6 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2) Balbir Singh <bsingharora@gmail.com> - 2016-01-28 03:50 +0100
Re: [PATCH v6 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2) Michael Ellerman <mpe@ellerman.id.au> - 2016-01-28 04:40 +0100
Re: [PATCH v6 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2) Torsten Duwe <duwe@lst.de> - 2016-01-28 12:20 +0100
| From | Balbir Singh <bsingharora@gmail.com> |
|---|---|
| Date | 2016-01-28 03:50 +0100 |
| Subject | Re: [PATCH v6 0/9] ftrace with regs + live patching for ppc64 LE (ABI v2) |
| Message-ID | <qVKOK-4TF-11@gated-at.bofh.it> |
On Wed, 27 Jan 2016 13:19:04 +0100 Torsten Duwe <duwe@lst.de> wrote: > Thanks! Make sure you use a compiler that can disable -mprofile-kernel with "notrace". gcc-6? I have gcc-5.2.1 Balbir Singh.
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| From | Michael Ellerman <mpe@ellerman.id.au> |
|---|---|
| Date | 2016-01-28 04:40 +0100 |
| Message-ID | <qVLB7-5Fa-3@gated-at.bofh.it> |
| In reply to | #1320239 |
On Thu, 2016-01-28 at 13:41 +1100, Balbir Singh wrote: > On Wed, 27 Jan 2016 13:19:04 +0100 > Torsten Duwe <duwe@lst.de> wrote: > > > Thanks! Make sure you use a compiler that can disable -mprofile-kernel with "notrace". > > gcc-6? I have gcc-5.2.1 That should work. But that's a good point. We need to have some Makefile logic to only enable -mprofile-kernel when it's known to work, ie. for versions where the notrace fix is in. Looking at GCC history it looks like the fix is in 4.9.0 and anything later. But a version check doesn't work with patched distro/vendor toolchains. So we probably need some sort of runtime check. cheers
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| From | Torsten Duwe <duwe@lst.de> |
|---|---|
| Date | 2016-01-28 12:20 +0100 |
| Message-ID | <qVSMi-2B1-19@gated-at.bofh.it> |
| In reply to | #1320270 |
On Thu, Jan 28, 2016 at 02:31:58PM +1100, Michael Ellerman wrote:
>
> Looking at GCC history it looks like the fix is in 4.9.0 and anything later.
Good. But 4.8.5 has a buggy -mprofile-kernel, and there will be no 4.8.6, Bad.
> But a version check doesn't work with patched distro/vendor toolchains. So we
> probably need some sort of runtime check.
Agreed.
/bin/echo -e '#include <linux/compiler.h>\nnotrace int func() { return 0; }' |
gcc -D__KERNEL__ -Iinclude -p -mprofile-kernel -x c -O2 - -S -o - | grep mcount
should be empty. If it yields "bl _mcount" your compiler is buggy.
I haven't looked at the kernel's "autoconf" yet, but it's probably capable
of testing this.
Torsten
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