[PATCH 1/1] get page size using sysconf (_SC_PAGESIZE) instead of PAGE_SIZE

[Zied Guermazi]

hi Pedro,

the issue was observed twice: once when building on x86 using

"../binutils-gdb/configure --host aarch64-linux-gnu 
--target=aarch64-linux-gnu --disable-ld --disable-gold --disable-gas 
--disable-sim --disable-gprofng --with-arm-cs"

and once when building natively on Debian on aarch64 by using

"../binutils-gdb/configure --disable-ld --disable-gold --disable-gas 
--disable-sim --disable-gprofng --with-arm-cs"


I will change the comment and re-submit the patch


Kind Regards

Zied Guermazi.

On 02.05.22 20:55, Pedro Alves wrote:
> On 2022-05-02 19:01, Zied Guermazi wrote:
>> hi Pedro,
>>
>> I think I can clarify the situation here by giving more insight on the context. A short explanation is needed.
>>
>> In current build system linux-btrace.c is only included when the host is a Linux running of an i386 cpu. (see gdb/configure.nat).  so the point of Andreas is pertinent with no further explanations of additional planned changes.
>>
>> This patch is a preparation for another patch set for adding btrace on arm processors using ARM Coresight ETM traces. (see the patch sethttps://pi.simark.ca/gdb-patches/20210531213307.275079-1-zied.guermazi@trande.de/#r  ). Markus Metzger in his review recommended submitting this change in a separated patch.
>>
>> In the patch set for adding btrace on arm,  there is a need to build linux-btrace.c for hosts linux/aarch64 and linux/arm. gdb/configure.nat at line 233 looks now as following:
>>
>> "
>>
>>   /   linux)//
>> //    case ${gdb_host_cpu} in//
>> //        aarch64)//
>> //        #  Host: AArch64 based machine running GNU/Linux//
>> //        NATDEPFILES="${NATDEPFILES} aarch64-nat.o aarch64-linux-nat.o \//
>> //        aarch32-linux-nat.o nat/aarch64-hw-point.o \//
>> //        nat/aarch64-linux-hw-point.o \//
>> //        nat/aarch64-linux.o \//
>> //        *nat/linux-btrace.o* \//
>> //        nat/aarch64-sve-linux-ptrace.o \//
>> //        nat/aarch64-mte-linux-ptrace.o"//
>> //        ;;//
>> //        arc)//
>> //        # Host: ARC based machine running GNU/Linux//
>> //        NATDEPFILES="${NATDEPFILES} arc-linux-nat.o"//
>> //        ;;//
>> //        arm)//
>> //        # Host: ARM based machine running GNU/Linux//
>> //        NATDEPFILES="${NATDEPFILES} arm-linux-nat.o \//
>> //        aarch32-linux-nat.o *nat/linux-btrace.o*"//
>> //        ;;/
>>
>> "
>>
>> which means that the file is now included in the build for linux/aarch64 and linux/arm
>>
>>
>> I have observed this issue when the build machine was an intel x86,  host and target were both aarch64-linux (and also arm-linux)
> OK, thanks, that clarifies things.  I wasn't aware of that patch series.  The build and target machines (in autoconf terms) are
> really irrelevant here.  The only machine that matters here is the host one.
>
>> using following configuration
>>
>> "../binutils-gdb/configure --host aarch64-linux-gnu --target=aarch64-linux-gnu --disable-ld --disable-gold --disable-gas --disable-sim --disable-gprofng --with-arm-cs"
>>
>> and when building natively on Debian on aarch64 and Debian on arm.
> Did you really run configure on one machine, and then typed "make" on a different machine?
> Anyhow, doesn't matter.
>
>> I was getting following build error message
>>
>> "
>> /../../binutils-gdb/gdb/nat/linux-btrace.c:799:30: error: ‘PAGE_SIZE’ was not declared in this scope; did you mean ‘PTRACE_SEIZE’?//
>> //  799 |   scoped_mmap data (nullptr, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,//
>> //      |                              ^~~~~~~~~//
>> //      |                              PTRACE_SEIZE/
>>
>> "
>>
>> The issue was fixed with this patch.
> Right.
>
> So in the commit log, instead of:
>
>   "PAGE_SIZE is not defined in all build configurations, e.g cross compiling
>   for aarch64 GNU/Linux machine. This patch gets the value at runtime using
>   posix call sysconf (_SC_PAGESIZE)"
>
> don't mention cross compiling at all, as that just confuses things.
>
> I'd suggest instead:
>
>   "Currently, linux-btrace.c is only built when the host is x86 or x86_64 GNU/Linux.
>   Later patches will add btrace support on ARM processors using ARM Coresight ETM traces.
>   That ran into the fact that PAGE_SIZE is not defined on Aarch64.  This patch fixes that
>   by getting the page size value at runtime using POSIX sysconf(_SC_PAGESIZE) instead."
>
> Pedro Alves
-- 

*Zied Guermazi*
founder

Trande GmbH
Leuschnerstraße 2
69469 Weinheim/Germany

Mobile: +491722645127
mailto:zied.guermazi@trande.de <mailto:zied.guermazi@trande.de>

*Trande GmbH*
Leuschnerstraße 2, D-69469 Weinheim; Telefon: +491722645127
Sitz der Gesellschaft: Weinheim- Registergericht: AG Mannheim HRB 736209 
- Geschäftsführung: Zied Guermazi

*Confidentiality Note*
This message is intended only for the use of the named recipient(s) and 
may contain confidential and/or privileged information. If you are not 
the intended recipient, please contact the sender and delete the 
message. Any unauthorized use of the information contained in this 
message is prohibited.