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From: Florian Weimer <fweimer@redhat.com>
To: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: libc-alpha@sourceware.org, stli@linux.ibm.com
Subject: Re: [PATCH 00/12] S390: Implement __fentry__
Date: Thu, 02 Aug 2018 18:32:00 -0000	[thread overview]
Message-ID: <b2aa26cf-c469-fd7f-398a-b1bd94fad9ee@redhat.com> (raw)
In-Reply-To: <6FCC9B6F-312C-444B-B4A3-758539536264@linux.ibm.com>

On 08/02/2018 12:43 PM, Ilya Leoshkevich wrote:
> 
>> Am 02.08.2018 um 11:17 schrieb Florian Weimer <fweimer@redhat.com>:
>>
>> On 08/02/2018 09:57 AM, Ilya Leoshkevich wrote:
>>> This patch series adds the runtime support in glibc for the -mfentry
>>> gcc feature introduced in [1] and [2].
>>> Patches 1-9 deal with avoiding clobbering %r0 when calling lazily bound
>>> functions, so that the new __fentry__ symbol could be called with return
>>> address in that register.
>>
>> Should GCC arrange for suitable ABI markup if -mfentry is used?  I'm worried that unexpected clobbers of r0 could be quite difficult to figure out otherwise.
> 
> I don’t think we need to do anything ABI-related at this point.
> 
> __fentry__ itself is being newly introduced, so there is no old ABI to
> comply with. Instrumented functions’ ABI does not change, particularly,
> %r0, being a volatile register, used to be clobbered anyway.
> 
> Are there other cases that I’m missing?

Agreed, with the __fentry__ addition in the same release as the 
trampoline change, this should be safe and avoid the issue I was worried 
about.

Thanks,
Florian

  reply	other threads:[~2018-08-02 18:32 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-02  7:58 Ilya Leoshkevich
2018-08-02  7:58 ` [PATCH 03/12] S390: Use symbolic offsets for stack variables in 64-bit _dl_runtime_resolve Ilya Leoshkevich
2018-08-02  7:58 ` [PATCH 01/12] S390: Use symbolic offsets for stack variables in 32-bit _dl_runtime_resolve Ilya Leoshkevich
2018-08-02  7:58 ` [PATCH 02/12] S390: Use symbolic offsets for stack variables in 32-bit _dl_runtime_profile Ilya Leoshkevich
2018-08-02  7:59 ` [PATCH 05/12] S390: Do not clobber R0 in 32-bit _dl_runtime_resolve Ilya Leoshkevich
2018-08-02  7:59 ` [PATCH 08/12] S390: Do not clobber R0 in 64-bit _dl_runtime_profile Ilya Leoshkevich
2018-08-02  7:59 ` [PATCH 11/12] S390: Implement 64-bit __fentry__ Ilya Leoshkevich
2018-08-02  7:59 ` [PATCH 09/12] S390: Test that lazy binding does not clobber R0 Ilya Leoshkevich
2018-08-02  7:59 ` [PATCH 07/12] S390: Do not clobber R0 in 64-bit _dl_runtime_resolve Ilya Leoshkevich
2018-08-02  7:59 ` [PATCH 12/12] S390: Fix unwind in 32-bit _mcount Ilya Leoshkevich
2018-08-02  8:10 ` [PATCH 10/12] Move __fentry__ version definition to sysdeps/{i386,x86_64} Ilya Leoshkevich
2018-08-02  8:41 ` [PATCH 06/12] S390: Do not clobber R0 in 32-bit _dl_runtime_profile Ilya Leoshkevich
2018-08-02  9:00 ` [PATCH 04/12] S390: Use symbolic offsets for stack variables in 64-bit _dl_runtime_profile Ilya Leoshkevich
2018-08-02  9:17 ` [PATCH 00/12] S390: Implement __fentry__ Florian Weimer
2018-08-02 10:43   ` Ilya Leoshkevich
2018-08-02 18:32     ` Florian Weimer [this message]
2018-08-07  8:27 ` Stefan Liebler
2018-08-10  7:15   ` [COMMITTED] " Stefan Liebler

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