[U-Boot] [PATCH v2 2/3] arm: relocate the exception vectors

Georges Savoundararadj
2014-10-14T20:02:00Z

Hi Albert,

Hi Masahiro,

As my issue is related to Kconfig, I would like you to give me your
opinions.

Le 11/10/2014 12:47, Albert ARIBAUD a ?crit :
> Hi Georges,
>
> On Sat, 27 Sep 2014 21:48:10 +0200, Georges Savoundararadj
> <savoundg@gmail.com> wrote:
>
>> This commit relocates the exception vectors.
>> As ARM1176 and ARMv7 have the security extensions, it uses VBAR. For
>> the other ARM processors, it copies the relocated exception vectors to
>> the correct address: 0x00000000 or 0xFFFF0000.
>>
>> Signed-off-by: Georges Savoundararadj <savoundg@gmail.com>
>> Cc: Albert Aribaud <albert.u.boot@aribaud.net>
>> Cc: Tom Warren <twarren@nvidia.com>
>>
>> ---
>> This patch needs some tests because it impacts many boards. I have
>> tested it with my raspberry pi in the two cases: using VBAR and
>> using the copied exception vectors.
>>
>> Changes in v2:
>> - Relocate exception vectors also on processors which do not support
>> security extensions
>> - Reword the commit message
>>
>> arch/arm/cpu/armv7/start.S | 6 ------
>> arch/arm/lib/relocate.S | 30 ++++++++++++++++++++++++++++++
>> 2 files changed, 30 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
>> index fedd7c8..fdc05b9 100644
>> --- a/arch/arm/cpu/armv7/start.S
>> +++ b/arch/arm/cpu/armv7/start.S
>> @@ -81,12 +81,6 @@ ENTRY(c_runtime_cpu_setup)
>> mcr p15, 0, r0, c7, c10, 4 @ DSB
>> mcr p15, 0, r0, c7, c5, 4 @ ISB
>> #endif
>> -/*
>> - * Move vector table
>> - */
>> - /* Set vector address in CP15 VBAR register */
>> - ldr r0, =_start
>> - mcr p15, 0, r0, c12, c0, 0 @Set VBAR
>>
>> bx lr
>>
>> diff --git a/arch/arm/lib/relocate.S b/arch/arm/lib/relocate.S
>> index 8035251..88a478e 100644
>> --- a/arch/arm/lib/relocate.S
>> +++ b/arch/arm/lib/relocate.S
>> @@ -6,6 +6,8 @@
>> * SPDX-License-Identifier: GPL-2.0+
>> */
>>
>> +#include <asm-offsets.h>
>> +#include <config.h>
>> #include <linux/linkage.h>
>>
>> /*
>> @@ -52,6 +54,34 @@ fixnext:
>> cmp r2, r3
>> blo fixloop
>>
>> + /*
>> + * Relocate the exception vectors
>> + */
>> +#if (defined(CONFIG_ARM1176) || defined(CONFIG_ARMV7))
> I would prefer a single CONFIG_HAS_VBAR symbol defined through
> Kconfig.
1)
Actually, there is no Kconfig entry such as "config ARM1176" nor "config
ARMV7" in U-Boot,
unlike in Linux (arch/arm/mm/Kconfig).

If there were such entries, we would simply do like the following (in
arch/arm/Kconfig):

config HAS_VBAR
bool

config ARM1176
select HAS_VBAR

config ARMV7
select HAS_VBAR

Should we go in this direction?
It is the cleanest way to use Kconfig but it requires some work in order
to convert all
"#define CONFIG_<cpu>" into Kconfig entries.

2)
Otherwise, we can insert a "select HAS_VBAR" in all boards that have a
ARM1176 or a ARMv7
processor in arch/arm/Kconfig. It is not logical but this is what has
been done with the Kconfig
entry ARM64. And, it does not require much change.

3)
The last thing we can do is as follows:

config HAS_VBAR
bool
depends on SYS_CPU = "arm1176" || SYS_CPU = "armv7"
default y

CONFIG_HAS_VBAR will be defined if SYS_CPU are arm1176 or armv7. It does
not require much
change as well but, I think, it is bad code.

What do you think is the best way to introduce CONFIG_HAS_VBAR symbol?
(1, 2 or 3)

>> + /*
>> + * If the ARM processor has the security extensions,
>> + * use VBAR to relocate the exception vectors.
>> + */
>> + ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */
>> + mcr p15, 0, r0, c12, c0, 0 /* Set VBAR */
>> +#else
>> + /*
>> + * Copy the relocated exception vectors to the
>> + * correct address
>> + * CP15 c1 V bit gives us the location of the vectors:
>> + * 0x00000000 or 0xFFFF0000.
>> + */
>> + ldr r0, [r9, #GD_RELOCADDR] /* r0 = gd->relocaddr */
>> + mrc p15, 0, r2, c1, c0, 0 /* V bit (bit[13]) in CP15 c1 */
>> + ands r2, r2, #(1 << 13)
>> + ldreq r1, =0x00000000 /* If V=0 */
>> + ldrne r1, =0xFFFF0000 /* If V=1 */
>> + ldmia r0!, {r2-r8,r10}
>> + stmia r1!, {r2-r8,r10}
>> + ldmia r0!, {r2-r8,r10}
>> + stmia r1!, {r2-r8,r10}
>> +#endif
>> +
>> relocate_done:
>>
>> #ifdef __XSCALE__
>
> Amicalement,
Regards,

Georges