| Message ID | 29b174a1-bd4f-b030-23b7-ff6a7b4c9e83@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Vladimir, On 08/03/17 19:56, Vladimir Murzin wrote: > On 08/03/17 03:21, Greg Ungerer wrote: >> On 21/01/17 19:20, afzal mohammed write: >>> No-MMU dynamic exception base address configuration on CP15 >>> processors. In the case of low vectors, decision based on whether >>> security extensions are enabled & whether remap vectors to RAM >>> CONFIG option is selected. >>> >>> For no-MMU without CP15, current default value of 0x0 is retained. >>> >>> Signed-off-by: afzal mohammed <afzal.mohd.ma at gmail.com> >> >> This patch (which is in mainline now as commit f8300a0b5d) breaks >> my patch series to support running the Versatile QEMU target with >> a nommu configured linux kernel. This series can be found here: >> >> http://lists.infradead.org/pipermail/linux-arm-kernel/2017-February/490653.html >> >> The problem is that QEMU is failing out with: >> >> qemu: fatal: Trying to execute code outside RAM or ROM at 0x41069264 >> >> when this your patch is applied. >> >> >>> diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c >>> index 2740967727e2..20ac52579952 100644 >>> --- a/arch/arm/mm/nommu.c >>> +++ b/arch/arm/mm/nommu.c >>> @@ -11,6 +11,7 @@ >>> #include <linux/kernel.h> >>> >>> #include <asm/cacheflush.h> >>> +#include <asm/cp15.h> >>> #include <asm/sections.h> >>> #include <asm/page.h> >>> #include <asm/setup.h> >>> @@ -22,6 +23,8 @@ >>> >>> #include "mm.h" >>> >>> +unsigned long vectors_base; >>> + >>> #ifdef CONFIG_ARM_MPU >>> struct mpu_rgn_info mpu_rgn_info; >>> >>> @@ -278,15 +281,60 @@ static void sanity_check_meminfo_mpu(void) {} >>> static void __init mpu_setup(void) {} >>> #endif /* CONFIG_ARM_MPU */ >>> >>> +#ifdef CONFIG_CPU_CP15 >>> +#ifdef CONFIG_CPU_HIGH_VECTOR >>> +static unsigned long __init setup_vectors_base(void) >>> +{ >>> + unsigned long reg = get_cr(); >>> + >>> + set_cr(reg | CR_V); >>> + return 0xffff0000; >>> +} >>> +#else /* CONFIG_CPU_HIGH_VECTOR */ >>> +/* Write exception base address to VBAR */ >>> +static inline void set_vbar(unsigned long val) >>> +{ >>> + asm("mcr p15, 0, %0, c12, c0, 0" : : "r" (val) : "cc"); >>> +} >>> + >>> +/* >>> + * Security extensions, bits[7:4], permitted values, >>> + * 0b0000 - not implemented, 0b0001/0b0010 - implemented >>> + */ >>> +static inline bool security_extensions_enabled(void) >>> +{ >>> + return !!cpuid_feature_extract(CPUID_EXT_PFR1, 4); >> >> The problem is here. This ends up generating the asm code: >> >> 2ebacc: ee103f31 mrc 15, 0, r3, cr0, cr1, {1} >> >> QEMU loses it on running this (confirmed by single stepping here). >> >> Is this valid for an ARM926EJ? >> Or is it QEMU that is at fault here... >> >> I can see that this would be valid for an ARM11 for example >> (http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0360f/CHDGIJFB.html) >> >> But I could not see that it is valid on an ARM926 >> (http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0198e/I1003211.html) >> >> Maybe I am looking in the wrong place though. >> >> Thoughts? > > I'm wondering if something like bellow would help? > > diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c > index 3b5c7aa..25542ec 100644 > --- a/arch/arm/mm/nommu.c > +++ b/arch/arm/mm/nommu.c > @@ -303,7 +303,11 @@ static inline void set_vbar(unsigned long val) > */ > static inline bool security_extensions_enabled(void) > { > +#if __LINUX_ARM_ARCH__ < 6 > + return 0; > +#else > return !!cpuid_feature_extract(CPUID_EXT_PFR1, 4); > +#endif > } > > static unsigned long __init setup_vectors_base(void) Yes, that fixes the problem. Boots up fine with that applied. Regards Greg
diff --git a/arch/arm/mm/nommu.c b/arch/arm/mm/nommu.c index 3b5c7aa..25542ec 100644 --- a/arch/arm/mm/nommu.c +++ b/arch/arm/mm/nommu.c @@ -303,7 +303,11 @@ static inline void set_vbar(unsigned long val) */ static inline bool security_extensions_enabled(void) { +#if __LINUX_ARM_ARCH__ < 6 + return 0; +#else return !!cpuid_feature_extract(CPUID_EXT_PFR1, 4); +#endif } static unsigned long __init setup_vectors_base(void)