From: Anshuman Khandual <anshuman.khandual@arm.com>
To: Qian Cai <cai@lca.pw>, linux-mm@kvack.org
Cc: Mark Rutland <mark.rutland@arm.com>,
linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
James Hogan <jhogan@kernel.org>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Michal Hocko <mhocko@kernel.org>,
Dave Hansen <dave.hansen@intel.com>,
Paul Mackerras <paulus@samba.org>,
sparclinux@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
linux-s390@vger.kernel.org, Jason Gunthorpe <jgg@ziepe.ca>,
x86@kernel.org, Russell King - ARM Linux <linux@armlinux.org.uk>,
Matthew Wilcox <willy@infradead.org>,
Steven Price <Steven.Price@arm.com>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Gerald Schaefer <gerald.schaefer@de.ibm.com>,
linux-snps-arc@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
Kees Cook <keescook@chromium.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
Mark Brown <broonie@kernel.org>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Dan Williams <dan.j.williams@intel.com>,
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Sri Krishna chowdary <schowdary@nvidia.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
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linux-mips@vger.kernel.org, Ralf Baechle <ralf@linux-mips.org>,
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Mike Rapoport <rppt@linux.vnet.ibm.com>,
Vineet Gupta <vgupta@synopsys.com>,
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Andrew Morton <akpm@linux-foundation.org>,
linuxppc-dev@lists.ozlabs.org,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers
Date: Wed, 16 Oct 2019 15:24:23 +0530 [thread overview]
Message-ID: <7cd03155-6713-3116-1e88-f81f84dd794f@arm.com> (raw)
In-Reply-To: <1571162982.5937.42.camel@lca.pw>
On 10/15/2019 11:39 PM, Qian Cai wrote:
> On Tue, 2019-10-15 at 14:51 +0530, Anshuman Khandual wrote:
>> +static unsigned long __init get_random_vaddr(void)
>> +{
>> + unsigned long random_vaddr, random_pages, total_user_pages;
>> +
>> + total_user_pages = (TASK_SIZE - FIRST_USER_ADDRESS) / PAGE_SIZE;
>> +
>> + random_pages = get_random_long() % total_user_pages;
>> + random_vaddr = FIRST_USER_ADDRESS + random_pages * PAGE_SIZE;
>> +
>> + WARN_ON(random_vaddr > TASK_SIZE);
>> + WARN_ON(random_vaddr < FIRST_USER_ADDRESS);
>
> It would be nice if this patch does not introduce a new W=1 GCC warning here on
> x86 because FIRST_USER_ADDRESS is 0, and GCC think the code is dumb because
> "random_vaddr" is unsigned,
>
> In file included from ./arch/x86/include/asm/bug.h:83,
> from ./include/linux/bug.h:5,
> from ./include/linux/mmdebug.h:5,
> from ./include/linux/gfp.h:5,
> from mm/debug_vm_pgtable.c:13:
> mm/debug_vm_pgtable.c: In function ‘get_random_vaddr’:
> mm/debug_vm_pgtable.c:359:23: warning: comparison of unsigned expression < 0 is
> always false [-Wtype-limits]
> WARN_ON(random_vaddr < FIRST_USER_ADDRESS);
> ^
> ./include/asm-generic/bug.h:113:25: note: in definition of macro ‘WARN_ON’
> int __ret_warn_on = !!(condition); \
> ^~~~~~~~~
The test checks against an erroneous unsigned long overflow when
FIRST_USER_ADDRESS is not 0 but a positive number. Wondering if
the compiler will still complain if we merge both the WARN_ON()
checks as || on a single statement.
next prev parent reply other threads:[~2019-10-16 9:56 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-15 9:21 [PATCH V6 0/2] mm/debug: Add tests validating architecture page table helpers Anshuman Khandual
2019-10-15 9:21 ` [PATCH V6 1/2] mm/page_alloc: Make alloc_gigantic_page() available for general use Anshuman Khandual
2019-10-15 10:45 ` Michal Hocko
2019-10-15 11:07 ` Anshuman Khandual
2019-10-15 11:42 ` David Hildenbrand
2019-10-15 11:47 ` Michal Hocko
2019-10-15 11:50 ` David Hildenbrand
2019-10-15 12:01 ` David Hildenbrand
2019-10-15 12:09 ` Michal Hocko
2019-10-15 12:11 ` Michal Hocko
2019-10-15 9:21 ` [PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers Anshuman Khandual
2019-10-15 11:46 ` Michal Hocko
2019-10-15 12:27 ` Anshuman Khandual
2019-10-15 18:09 ` Qian Cai
2019-10-16 9:54 ` Anshuman Khandual [this message]
2019-10-15 14:41 ` [PATCH V6 0/2] " Qian Cai
2019-10-15 15:21 ` Anshuman Khandual
2019-10-15 18:42 ` Qian Cai
2019-10-16 8:59 ` Anshuman Khandual
2019-10-16 8:20 ` Michal Hocko
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