From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Michael Ellerman <mpe@ellerman.id.au>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
ruscur@russell.cc,
Segher Boessenkool <segher@kernel.crashing.org>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: GCC bug ? Re: [PATCH v2 10/10] powerpc/32s: Implement Kernel Userspace Access Protection
Date: Tue, 21 Jan 2020 17:22:32 +0000 [thread overview]
Message-ID: <a008a182-f1db-073c-7d38-27bfd1fd8676@c-s.fr> (raw)
In-Reply-To: <87ftqfu7j1.fsf@concordia.ellerman.id.au>
On 04/18/2019 06:55 AM, Michael Ellerman wrote:
> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>> diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
>> index 5f97c742ca71..b3560b2de435 100644
>> --- a/arch/powerpc/include/asm/book3s/32/kup.h
>> +++ b/arch/powerpc/include/asm/book3s/32/kup.h
>> @@ -37,6 +37,113 @@
> ...
>> +
>> +static inline void allow_user_access(void __user *to, const void __user *from, u32 size)
>> +{
>> + u32 addr = (__force u32)to;
>> + u32 end = min(addr + size, TASK_SIZE);
>> +
>> + if (!addr || addr >= TASK_SIZE || !size)
>> + return;
>> +
>> + current->thread.kuap = (addr & 0xf0000000) | ((((end - 1) >> 28) + 1) & 0xf);
>> + kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end); /* Clear Ks */
>> +}
>
> When rebasing on my v6 I changed the above to:
>
> static inline void allow_user_access(void __user *to, const void __user *from, u32 size)
> {
> u32 addr, end;
>
> if (__builtin_constant_p(to) && to == NULL)
> return;
Look like the above doesn't work: gcc bug ?
#define NULL (void*)0
static inline int f1(void *to)
{
if (__builtin_constant_p(to) && to == NULL)
return 3;
return 5;
}
int g1(void)
{
return f1(NULL);
}
static inline int f2(int x)
{
if (__builtin_constant_p(x) && x == 0)
return 7;
return 9;
}
int g2(void)
{
return f2(0);
}
toto.o: file format elf32-powerpc
Disassembly of section .text:
00000000 <g1>:
0: 38 60 00 05 li r3,5
4: 4e 80 00 20 blr
00000008 <g2>:
8: 38 60 00 07 li r3,7
c: 4e 80 00 20 blr
It works for the int const, but not for the pointer const:
g1() should return 3, not 5. GCC bug ?
Christophe
next prev parent reply other threads:[~2020-01-21 17:25 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-11 8:30 [PATCH v2 00/10] Kernel Userspace protection for PPC32 Christophe Leroy
2019-03-11 8:30 ` [PATCH v2 01/10] powerpc/6xx: fix setup and use of SPRN_SPRG_PGDIR for hash32 Christophe Leroy
2019-03-20 13:04 ` [v2, " Michael Ellerman
2019-03-11 8:30 ` [PATCH v2 02/10] powerpc/mm: Detect bad KUAP faults (Squash of v5 series) Christophe Leroy
2019-03-11 8:30 ` [PATCH v2 03/10] powerpc/32: Remove MSR_PR test when returning from syscall Christophe Leroy
2019-04-21 14:18 ` [v2, " Michael Ellerman
2019-03-11 8:30 ` [PATCH v2 04/10] powerpc/32: Prepare for Kernel Userspace Access Protection Christophe Leroy
2019-03-11 8:30 ` [PATCH v2 05/10] powerpc/8xx: Only define APG0 and APG1 Christophe Leroy
2019-03-11 8:30 ` [PATCH v2 06/10] powerpc/8xx: Add Kernel Userspace Execution Prevention Christophe Leroy
2019-03-11 8:30 ` [PATCH v2 07/10] powerpc/8xx: Add Kernel Userspace Access Protection Christophe Leroy
2019-04-18 6:53 ` Michael Ellerman
2019-03-11 8:30 ` [PATCH v2 08/10] powerpc/32s: Implement Kernel Userspace Execution Prevention Christophe Leroy
2019-03-11 8:30 ` [PATCH v2 09/10] powerpc/32s: Prepare Kernel Userspace Access Protection Christophe Leroy
2019-03-11 8:30 ` [PATCH v2 10/10] powerpc/32s: Implement " Christophe Leroy
2019-04-18 6:55 ` Michael Ellerman
2019-04-23 9:26 ` Christophe Leroy
2020-01-21 17:22 ` Christophe Leroy [this message]
2020-01-21 19:55 ` GCC bug ? " Segher Boessenkool
2020-01-22 6:52 ` Christophe Leroy
2020-01-22 13:36 ` Segher Boessenkool
2020-01-22 14:45 ` Christophe Leroy
2020-01-22 6:57 ` Christophe Leroy
2020-01-22 13:18 ` Segher Boessenkool
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