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

[Zied Guermazi <zied.guermazi@trande.de>]

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 set 
https://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)

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.

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.


Kind Regards

Zied Guermazi


On 02.05.22 18:46, Pedro Alves wrote:
> On 2022-04-30 14:33, Andreas Schwab wrote:
>> On Apr 30 2022, Zied Guermazi wrote:
>>
>>> PAGE_SIZE for target system was not defined, in other cases PAGE_SIZE of
>>> the host system was used etc... :).
>> This file is only used in a native configuration.
>>
> Zied, when you said:
>
>    "the issue was first observed when activating this code while compiling on an x86 for an arm target."
>
> are you talking about:
>
>    --build=x86_64-linux --host=aarch64-linux
>
> or:
>    --host=x86_64-linux --target=aarch64-linux
>
> ?
>
> I agree with Andreas -- linux-btrace.c is only included in the build on x86 hosts, so why are you seeing
> this?  Did you tweak gdb/configure.nat to include linux-btrace.c in other configurations?  Or gdb/configure.tgt?
> What exactly did you do?