linux-kernel - Re: [BUGFIX PATCH v2 1/5] selftests: proc: Make va

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Message-Id: <20191023135141.77aef5dc41182e069676d27e@kernel.org>
Date:   Wed, 23 Oct 2019 13:51:41 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Alexey Dobriyan <adobriyan@...il.com>,
        Shuah Khan <shuah@...nel.org>, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org, jaswinder.singh@...aro.org
Subject: Re: [BUGFIX PATCH v2 1/5] selftests: proc: Make va_max 1GB on 32bit
 arch

On Wed, 23 Oct 2019 10:56:18 +0900
Masami Hiramatsu <mhiramat@...nel.org> wrote:

> On Mon, 21 Oct 2019 20:30:53 +0300
> Alexey Dobriyan <adobriyan@...il.com> wrote:
> 
> > On Mon, Oct 21, 2019 at 05:28:09PM +0900, Masami Hiramatsu wrote:
> > > Currently proc-self-map-files-002.c sets va_max (max test address
> > > of user virtual address) to 4GB, but it is too big for 32bit
> > > arch and 1UL << 32 is overflow on 32bit long.
> > > 
> > > Make va_max 1GB on 32bit arch like i386 and arm.
> > 
> > > +#if __BITS_PER_LONG == 32
> > > +# define VA_MAX (1UL << 30)
> > > +#elif __BITS_PER_LONG == 64
> > > +# define VA_MAX (1UL << 32)
> > > +#else
> > > +# define VA_MAX 0
> > > +#endif
> > > +
> > >  int main(void)
> > >  {
> > >  	const int PAGE_SIZE = sysconf(_SC_PAGESIZE);
> > > -	const unsigned long va_max = 1UL << 32;
> > > +	const unsigned long va_max = VA_MAX;
> > 
> > No, just make it like 1MB unconditionally.
> 
> Ah, I sse. BTW, would you mean 1GB?

I understand that 1MB will be good enough, since vm.mmap_min_addr is
64KB by default (except for arm/arm64 which is 32KB).
OK, I'll update and resend.

Thank you,

> 
> > This is not intended to cover all address space, just large enough part
> > (larger than reasonable vm.mmap_min_addr)
> 
> Then, should we better to check the /proc/sys/vm/mmap_min_addr?
> 
> Thank you,
> 
> -- 
> Masami Hiramatsu <mhiramat@...nel.org>


-- 
Masami Hiramatsu <mhiramat@...nel.org>