From: Jeff Law <law@redhat.com>
To: "H.J. Lu" <hjl.tools@gmail.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Jakub Jelinek <jakub@redhat.com>,
Richard Biener <richard.guenther@gmail.com>,
Richard Sandiford <richard.sandiford@arm.com>
Subject: Re: PING^5 [PATCH] Use the section flag 'o' for __patchable_function_entries
Date: Tue, 1 Dec 2020 22:23:10 -0700 [thread overview]
Message-ID: <8193889c-5f8a-62f9-b064-f28ab8aa030e@redhat.com> (raw)
In-Reply-To: <CAMe9rOrFxRwW8Q=05N8L-9S7iPZm_nJMwp7XN6PRK3jLn=UwTQ@mail.gmail.com>
On 11/18/20 7:00 AM, H.J. Lu wrote:
> On Sat, Nov 7, 2020 at 7:47 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>> On Sat, Oct 31, 2020 at 5:01 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>>> On Fri, Oct 23, 2020 at 5:41 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>>>> On Fri, Oct 2, 2020 at 6:00 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>>>>> On Thu, Feb 6, 2020 at 6:57 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>>>>>> This commit in GNU binutils 2.35:
>>>>>>
>>>>>> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=b7d072167715829eed0622616f6ae0182900de3e
>>>>>>
>>>>>> added the section flag 'o' to .section directive:
>>>>>>
>>>>>> .section __patchable_function_entries,"awo",@progbits,foo
>>>>>>
>>>>>> which specifies the symbol name which the section references. Assembler
>>>>>> creates a unique __patchable_function_entries section with the section,
>>>>>> where foo is defined, as its linked-to section. Linker keeps a section
>>>>>> if its linked-to section is kept during garbage collection.
>>>>>>
>>>>>> This patch checks assembler support for the section flag 'o' and uses
>>>>>> it to implement __patchable_function_entries section. Since Solaris may
>>>>>> use GNU assembler with Solairs ld. Even if GNU assembler supports the
>>>>>> section flag 'o', it doesn't mean that Solairs ld supports it. This
>>>>>> feature is disabled for Solairs targets.
>>>>>>
>>>>>> gcc/
>>>>>>
>>>>>> PR middle-end/93195
>>>>>> PR middle-end/93197
>>>>>> * configure.ac (HAVE_GAS_SECTION_LINK_ORDER): New. Define if
>>>>>> the assembler supports the section flag 'o' for specifying
>>>>>> section with link-order.
>>>>>> * dwarf2out.c (output_comdat_type_unit): Pass 0 as flags2
>>>>>> to targetm.asm_out.named_section.
>>>>>> * config/sol2.c (solaris_elf_asm_comdat_section): Likewise.
>>>>>> * output.h (SECTION2_LINK_ORDER): New.
>>>>>> (switch_to_section): Add an unsigned int argument.
>>>>>> (default_no_named_section): Likewise.
>>>>>> (default_elf_asm_named_section): Likewise.
>>>>>> * target.def (asm_out.named_section): Likewise.
>>>>>> * targhooks.c (default_print_patchable_function_entry): Pass
>>>>>> current_function_decl to get_section and SECTION2_LINK_ORDER
>>>>>> to switch_to_section.
>>>>>> * varasm.c (default_no_named_section): Add an unsigned int
>>>>>> argument.
>>>>>> (default_elf_asm_named_section): Add an unsigned int argument,
>>>>>> flags2. Use 'o' flag for SECTION2_LINK_ORDER if assembler
>>>>>> supports it.
>>>>>> (switch_to_section): Add an unsigned int argument and pass it
>>>>>> to targetm.asm_out.named_section.
>>>>>> (handle_vtv_comdat_section): Pass 0 to
>>>>>> targetm.asm_out.named_section.
>>>>>> * config.in: Regenerated.
>>>>>> * configure: Likewise.
>>>>>> * doc/tm.texi: Likewise.
>>>>>>
>>>>>> gcc/testsuite/
>>>>>>
>>>>>> PR middle-end/93195
>>>>>> * g++.dg/pr93195a.C: New test.
>>>>>> * g++.dg/pr93195b.C: Likewise.
>>>>>> * lib/target-supports.exp
>>>>>> (check_effective_target_o_flag_in_section): New proc.
>>>>> PING
>>>>>
>>>>> https://gcc.gnu.org/pipermail/gcc-patches/2020-February/539963.html
>>>> PING.
>>>>
>>> PING.
>>>
>> PING.
> Here is a simpler patch. OK for master?
>
> This commit in GNU binutils 2.35:
>
> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=b7d072167715
> 829eed0622616f6ae0182900de3e
>
> added the section flag 'o' to .section directive:
>
> .section __patchable_function_entries,"awo",@progbits,foo
>
> which specifies the symbol name which the section references. Assembler
> creates a unique __patchable_function_entries section with the section,
> where foo is defined, as its linked-to section. Linker keeps a section
> if its linked-to section is kept during garbage collection.
>
> This patch checks assembler support for the section flag 'o' and uses
> it to implement __patchable_function_entries section. Since Solaris may
> use GNU assembler with Solairs ld. Even if GNU assembler supports the
> section flag 'o', it doesn't mean that Solairs ld supports it. This
> feature is disabled for Solairs targets.
>
> gcc/
>
> PR middle-end/93195
> PR middle-end/93197
> * configure.ac (HAVE_GAS_SECTION_LINK_ORDER): New. Define 1 if
> the assembler supports the section flag 'o' for specifying
> section with link-order.
> * output.h (SECTION_LINK_ORDER): New. Defined to 0x4000000.
> (SECTION_MACH_DEP): Changed from 0x4000000 to 0x8000000.
> * targhooks.c (default_print_patchable_function_entry): Pass
> SECTION_LINK_ORDER to switch_to_section if the section flag 'o'
> works. Pass current_function_decl to switch_to_section.
> * varasm.c (default_elf_asm_named_section): Use 'o' flag for
> SECTION_LINK_ORDER if assembler supports it.
> * config.in: Regenerated.
> * configure: Likewise.
>
> gcc/testsuite/
>
> PR middle-end/93195
> * g++.dg/pr93195a.C: New test.
> * g++.dg/pr93195b.C: Likewise.
> * lib/target-supports.exp
> (check_effective_target_o_flag_in_section): New proc.
So you need to document the new effective target test in
sourcebuild.texi. I see new #if in targhooks.c. If that could be made
a if (...) it'd be greatly appreciated.
OK with those changes.
jeff
next prev parent reply other threads:[~2020-12-02 5:23 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-07 2:57 H.J. Lu
2020-10-02 13:00 ` PING: " H.J. Lu
2020-10-23 12:41 ` PING^2 " H.J. Lu
2020-10-31 12:01 ` PING^3 " H.J. Lu
2020-11-07 15:47 ` PING^4 " H.J. Lu
2020-11-18 14:00 ` PING^5 " H.J. Lu
2020-12-02 5:23 ` Jeff Law [this message]
2020-12-02 13:15 ` V2 " H.J. Lu
2020-12-15 20:48 ` [PATCH] varasm: Fix up __patchable_function_entries handling Jakub Jelinek
2020-12-16 13:36 ` H.J. Lu
2020-12-16 13:47 ` Jakub Jelinek
2020-12-16 14:18 ` Jeff Law
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