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From: Dmitry Osipenko <digetx@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
	linux-kernel@vger.kernel.org,
	Russell King <linux@armlinux.org.uk>,
	clang-built-linux@googlegroups.com,
	Ingo Molnar <mingo@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v1] ARM: vfp: Use long jump to fix THUMB2 kernel compilation error
Date: Thu, 22 Oct 2020 03:00:06 +0300	[thread overview]
Message-ID: <773fbdb0-5fc4-ab39-e72d-89845faa4c6d@gmail.com> (raw)
In-Reply-To: <202010211637.7CFD8435@keescook>

22.10.2020 02:40, Kees Cook пишет:
> On Thu, Oct 22, 2020 at 01:57:37AM +0300, Dmitry Osipenko wrote:
>> The vfp_kmode_exception() function now is unreachable using relative
>> branching in THUMB2 kernel configuration, resulting in a "relocation
>> truncated to fit: R_ARM_THM_JUMP19 against symbol `vfp_kmode_exception'"
>> linker error. Let's use long jump in order to fix the issue.
> 
> Eek. Is this with gcc or clang?

GCC 9.3.0

>> Fixes: eff8728fe698 ("vmlinux.lds.h: Add PGO and AutoFDO input sections")
> 
> Are you sure it wasn't 512dd2eebe55 ("arm/build: Add missing sections") ?
> That commit may have implicitly moved the location of .vfp11_veneer,
> though I thought I had chosen the correct position.

I re-checked that the fixes tag is correct.

>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>  arch/arm/vfp/vfphw.S | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
>> index 4fcff9f59947..6e2b29f0c48d 100644
>> --- a/arch/arm/vfp/vfphw.S
>> +++ b/arch/arm/vfp/vfphw.S
>> @@ -82,7 +82,8 @@ ENTRY(vfp_support_entry)
>>  	ldr	r3, [sp, #S_PSR]	@ Neither lazy restore nor FP exceptions
>>  	and	r3, r3, #MODE_MASK	@ are supported in kernel mode
>>  	teq	r3, #USR_MODE
>> -	bne	vfp_kmode_exception	@ Returns through lr
>> +	ldr	r1, =vfp_kmode_exception
>> +	bxne	r1			@ Returns through lr
>>  
>>  	VFPFMRX	r1, FPEXC		@ Is the VFP enabled?
>>  	DBGSTR1	"fpexc %08x", r1
> 
> This seems like a workaround though? I suspect the vfp11_veneer needs
> moving?
> 

I don't know where it needs to be moved. Please feel free to make a
patch if you have a better idea, I'll be glad to test it.

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WARNING: multiple messages have this Message-ID (diff)
From: Dmitry Osipenko <digetx@gmail.com>
To: Kees Cook <keescook@chromium.org>
Cc: Russell King <linux@armlinux.org.uk>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Ingo Molnar <mingo@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com
Subject: Re: [PATCH v1] ARM: vfp: Use long jump to fix THUMB2 kernel compilation error
Date: Thu, 22 Oct 2020 03:00:06 +0300	[thread overview]
Message-ID: <773fbdb0-5fc4-ab39-e72d-89845faa4c6d@gmail.com> (raw)
In-Reply-To: <202010211637.7CFD8435@keescook>

22.10.2020 02:40, Kees Cook пишет:
> On Thu, Oct 22, 2020 at 01:57:37AM +0300, Dmitry Osipenko wrote:
>> The vfp_kmode_exception() function now is unreachable using relative
>> branching in THUMB2 kernel configuration, resulting in a "relocation
>> truncated to fit: R_ARM_THM_JUMP19 against symbol `vfp_kmode_exception'"
>> linker error. Let's use long jump in order to fix the issue.
> 
> Eek. Is this with gcc or clang?

GCC 9.3.0

>> Fixes: eff8728fe698 ("vmlinux.lds.h: Add PGO and AutoFDO input sections")
> 
> Are you sure it wasn't 512dd2eebe55 ("arm/build: Add missing sections") ?
> That commit may have implicitly moved the location of .vfp11_veneer,
> though I thought I had chosen the correct position.

I re-checked that the fixes tag is correct.

>> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
>> ---
>>  arch/arm/vfp/vfphw.S | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/vfp/vfphw.S b/arch/arm/vfp/vfphw.S
>> index 4fcff9f59947..6e2b29f0c48d 100644
>> --- a/arch/arm/vfp/vfphw.S
>> +++ b/arch/arm/vfp/vfphw.S
>> @@ -82,7 +82,8 @@ ENTRY(vfp_support_entry)
>>  	ldr	r3, [sp, #S_PSR]	@ Neither lazy restore nor FP exceptions
>>  	and	r3, r3, #MODE_MASK	@ are supported in kernel mode
>>  	teq	r3, #USR_MODE
>> -	bne	vfp_kmode_exception	@ Returns through lr
>> +	ldr	r1, =vfp_kmode_exception
>> +	bxne	r1			@ Returns through lr
>>  
>>  	VFPFMRX	r1, FPEXC		@ Is the VFP enabled?
>>  	DBGSTR1	"fpexc %08x", r1
> 
> This seems like a workaround though? I suspect the vfp11_veneer needs
> moving?
> 

I don't know where it needs to be moved. Please feel free to make a
patch if you have a better idea, I'll be glad to test it.

  reply	other threads:[~2020-10-22  0:02 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-21 22:57 [PATCH v1] ARM: vfp: Use long jump to fix THUMB2 kernel compilation error Dmitry Osipenko
2020-10-21 22:57 ` Dmitry Osipenko
2020-10-21 23:40 ` Kees Cook
2020-10-21 23:40   ` Kees Cook
2020-10-22  0:00   ` Dmitry Osipenko [this message]
2020-10-22  0:00     ` Dmitry Osipenko
2020-10-22  3:28     ` Kees Cook
2020-10-22  3:28       ` Kees Cook
2020-10-22  7:06       ` Ard Biesheuvel
2020-10-22  7:06         ` Ard Biesheuvel
2020-10-22 15:57         ` Dmitry Osipenko
2020-10-22 15:57           ` Dmitry Osipenko
2020-10-22 16:06           ` Ard Biesheuvel
2020-10-22 16:06             ` Ard Biesheuvel
2020-10-22 16:11             ` Russell King - ARM Linux admin
2020-10-22 16:11               ` Russell King - ARM Linux admin
2020-10-22 16:20               ` Ard Biesheuvel
2020-10-22 16:20                 ` Ard Biesheuvel
2020-10-22 16:23                 ` Russell King - ARM Linux admin
2020-10-22 16:23                   ` Russell King - ARM Linux admin
2020-10-22 16:33                   ` Ard Biesheuvel
2020-10-22 16:33                     ` Ard Biesheuvel
2020-10-22 17:48                     ` Russell King - ARM Linux admin
2020-10-22 17:48                       ` Russell King - ARM Linux admin
2020-10-22 17:59                       ` Ard Biesheuvel
2020-10-22 17:59                         ` Ard Biesheuvel
2020-10-26  8:58                         ` Ard Biesheuvel
2020-10-26  8:58                           ` Ard Biesheuvel
2020-10-29  9:56                           ` Ard Biesheuvel
2020-10-29  9:56                             ` Ard Biesheuvel
2020-11-03  7:24                             ` Ard Biesheuvel
2020-11-03  7:24                               ` Ard Biesheuvel
2020-11-03  8:43                               ` Dmitry Osipenko
2020-11-03  8:43                                 ` Dmitry Osipenko
2020-11-09  7:25                                 ` Ard Biesheuvel
2020-11-09  7:25                                   ` Ard Biesheuvel
2020-11-10  7:44                                   ` Dmitry Osipenko
2020-11-10  7:44                                     ` Dmitry Osipenko
2020-11-10  7:45                                     ` Ard Biesheuvel
2020-11-10  7:45                                       ` Ard Biesheuvel
2020-10-22 16:34                   ` Dmitry Osipenko
2020-10-22 16:34                     ` Dmitry Osipenko
2020-10-22 17:38                     ` Russell King - ARM Linux admin
2020-10-22 17:38                       ` Russell King - ARM Linux admin
2020-10-22 17:47                       ` Ard Biesheuvel
2020-10-22 17:47                         ` Ard Biesheuvel
2020-10-22 17:50                         ` Russell King - ARM Linux admin
2020-10-22 17:50                           ` Russell King - ARM Linux admin
2020-10-22 17:51                           ` Ard Biesheuvel
2020-10-22 17:51                             ` Ard Biesheuvel
2020-10-22 19:05                       ` Dmitry Osipenko
2020-10-22 19:05                         ` Dmitry Osipenko
2020-10-22 14:57 ` Russell King - ARM Linux admin
2020-10-22 14:57   ` Russell King - ARM Linux admin
2020-10-22 15:56   ` Dmitry Osipenko
2020-10-22 15:56     ` Dmitry Osipenko

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