Re: [ARM/FDPIC v5 01/21] [ARM] FDPIC: Add -mfdpic option support

[Richard Sandiford <richard.sandiford@arm.com>]

Christophe Lyon <christophe.lyon@st.com> writes:
> On 16/07/2019 12:11, Richard Sandiford wrote:
>> [This isn't really something that should be reviewed under global
>> reviewership, but if it's either that or nothing, I'll do it anyway...]
>> 
>> Christophe Lyon <christophe.lyon@st.com> writes:
>>> 2019-XX-XX  Christophe Lyon  <christophe.lyon@st.com>
>>> 	Mickaël Guêné  <mickael.guene@st.com>
>>>
>>> 	gcc/
>>> 	* config/arm/arm.opt: Add -mfdpic option.
>>> 	* doc/invoke.texi: Add documentation for -mfdpic.
>>>
>>> Change-Id: I0eabd1d11c9406fd4a43c4333689ebebbfcc4fe8
>>>
>>> diff --git a/gcc/config/arm/arm.opt b/gcc/config/arm/arm.opt
>>> index 9067d49..2ed3bd5 100644
>>> --- a/gcc/config/arm/arm.opt
>>> +++ b/gcc/config/arm/arm.opt
>>> @@ -306,3 +306,7 @@ Cost to assume for a branch insn.
>>>   mgeneral-regs-only
>>>   Target Report RejectNegative Mask(GENERAL_REGS_ONLY) Save
>>>   Generate code which uses the core registers only (r0-r14).
>>> +
>>> +mfdpic
>>> +Target Report Mask(FDPIC)
>>> +Enable Function Descriptor PIC mode.
>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>> index 29585cf..805d7cc 100644
>>> --- a/gcc/doc/invoke.texi
>>> +++ b/gcc/doc/invoke.texi
>>> @@ -703,7 +703,8 @@ Objective-C and Objective-C++ Dialects}.
>>>   -mrestrict-it @gol
>>>   -mverbose-cost-dump @gol
>>>   -mpure-code @gol
>>> --mcmse}
>>> +-mcmse @gol
>>> +-mfdpic}
>>>   
>>>   @emph{AVR Options}
>>>   @gccoptlist{-mmcu=@var{mcu}  -mabsdata  -maccumulate-args @gol
>>> @@ -17912,6 +17913,23 @@ MOVT instruction.
>>>   Generate secure code as per the "ARMv8-M Security Extensions: Requirements on
>>>   Development Tools Engineering Specification", which can be found on
>>>   @url{http://infocenter.arm.com/help/topic/com.arm.doc.ecm0359818/ECM0359818_armv8m_security_extensions_reqs_on_dev_tools_1_0.pdf}.
>>> +
>>> +@item -mfdpic
>>> +@itemx -mno-fdpic
>>> +@opindex mfdpic
>>> +@opindex mno-fdpic
>>> +Select the FDPIC ABI, which uses function descriptors to represent
>> 
>> Maybe "64-bit function descriptors"?  Just a suggestion, might not be useful.
>> 
>> OK with that change, thanks.
>
> OK, here is a new version, where I added a few words to explain that -static
> is not supported.
>
> Thanks,
> Christophe
>
>> 
>> Richard
>> 
>>> +pointers to functions.  When the compiler is configured for
>>> +@code{arm-*-uclinuxfdpiceabi} targets, this option is on by default
>>> +and implies @option{-fPIE} if none of the PIC/PIE-related options is
>>> +provided.  On other targets, it only enables the FDPIC-specific code
>>> +generation features, and the user should explicitly provide the
>>> +PIC/PIE-related options as needed.
>>> +
>>> +The opposite @option{-mno-fdpic} option is useful (and required) to
>>> +build the Linux kernel using the same (@code{arm-*-uclinuxfdpiceabi})
>>> +toolchain as the one used to build the userland programs.
>>> +
>>>   @end table
>>>   
>>>   @node AVR Options
>> .
>> 
>
> From c936684e2b77ff5716bd8b67c617dcad088c72e0 Mon Sep 17 00:00:00 2001
> From: Christophe Lyon <christophe.lyon@linaro.org>
> Date: Thu, 8 Feb 2018 10:44:32 +0100
> Subject: [ARM/FDPIC v6 01/24] [ARM] FDPIC: Add -mfdpic option support
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> 2019-XX-XX  Christophe Lyon  <christophe.lyon@st.com>
> 	Micka«l Guªn©  <mickael.guene@st.com>
>
> 	gcc/
> 	* config/arm/arm.opt: Add -mfdpic option.
> 	* doc/invoke.texi: Add documentation for -mfdpic.
>
> Change-Id: I05b98d6ae87c2b3fc04dd7fba415c730accdf33e
>
> diff --git a/gcc/config/arm/arm.opt b/gcc/config/arm/arm.opt
> index 9067d49..2ed3bd5 100644
> --- a/gcc/config/arm/arm.opt
> +++ b/gcc/config/arm/arm.opt
> @@ -306,3 +306,7 @@ Cost to assume for a branch insn.
>  mgeneral-regs-only
>  Target Report RejectNegative Mask(GENERAL_REGS_ONLY) Save
>  Generate code which uses the core registers only (r0-r14).
> +
> +mfdpic
> +Target Report Mask(FDPIC)
> +Enable Function Descriptor PIC mode.
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 29585cf..b77fa06 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -703,7 +703,8 @@ Objective-C and Objective-C++ Dialects}.
>  -mrestrict-it @gol
>  -mverbose-cost-dump @gol
>  -mpure-code @gol
> --mcmse}
> +-mcmse @gol
> +-mfdpic}
>  
>  @emph{AVR Options}
>  @gccoptlist{-mmcu=@var{mcu}  -mabsdata  -maccumulate-args @gol
> @@ -17912,6 +17913,27 @@ MOVT instruction.
>  Generate secure code as per the "ARMv8-M Security Extensions: Requirements on
>  Development Tools Engineering Specification", which can be found on
>  @url{http://infocenter.arm.com/help/topic/com.arm.doc.ecm0359818/ECM0359818_armv8m_security_extensions_reqs_on_dev_tools_1_0.pdf}.
> +
> +@item -mfdpic
> +@itemx -mno-fdpic
> +@opindex mfdpic
> +@opindex mno-fdpic
> +Select the FDPIC ABI, which uses 64-bit function descriptors to
> +represent pointers to functions.  When the compiler is configured for
> +@code{arm-*-uclinuxfdpiceabi} targets, this option is on by default
> +and implies @option{-fPIE} if none of the PIC/PIE-related options is
> +provided.  On other targets, it only enables the FDPIC-specific code
> +generation features, and the user should explicitly provide the
> +PIC/PIE-related options as needed.
> +
> +Note that static linking is not supported because it would still
> +involve the dynamic linker when the program self-relocates.  If such
> +behaviour is acceptable, use -static and -Wl,-dynamic-linker options.

"behavior".  (To correct correct spelling :-/)

OK with that change if there are no objections before the rest of
the series is approved.

> +
> +The opposite @option{-mno-fdpic} option is useful (and required) to
> +build the Linux kernel using the same (@code{arm-*-uclinuxfdpiceabi})
> +toolchain as the one used to build the userland programs.
> +
>  @end table
>  
>  @node AVR Options