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Message-ID: <a50d7d1b-643f-cf17-b38f-475916c971c1@redhat.com>
Date: Tue, 6 Dec 2016 18:00:36 -0800
From: Laura Abbott <labbott@...hat.com>
To: Florian Fainelli <f.fainelli@...il.com>,
linux-arm-kernel@...ts.infradead.org
Cc: linux@...linux.org.uk, nicolas.pitre@...aro.org, panand@...hat.com,
chris.brandt@...esas.com, arnd@...db.de, jonathan.austin@....com,
pawel.moll@....com, vladimir.murzin@....com, mark.rutland@....com,
ard.biesheuvel@...aro.org, keescook@...omium.org,
matt@...eblueprint.co.uk, kirill.shutemov@...ux.intel.com,
ben@...adent.org.uk, js07.lee@...sung.com, stefan@...er.ch,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] ARM: Add support for CONFIG_DEBUG_VIRTUAL
On 12/06/2016 11:53 AM, Florian Fainelli wrote:
> x86 has an option: CONFIG_DEBUG_VIRTUAL to do additional checks on
> virt_to_phys calls. The goal is to catch users who are calling
> virt_to_phys on non-linear addresses immediately. This includes caller
> using __virt_to_phys() on image addresses instead of __pa_symbol(). This
> is a generally useful debug feature to spot bad code (particulary in
> drivers).
>
> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
> ---
> arch/arm/Kconfig | 1 +
> arch/arm/include/asm/memory.h | 16 ++++++++++++--
> arch/arm/mm/Makefile | 1 +
> arch/arm/mm/physaddr.c | 51 +++++++++++++++++++++++++++++++++++++++++++
> 4 files changed, 67 insertions(+), 2 deletions(-)
> create mode 100644 arch/arm/mm/physaddr.c
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index b5d529fdffab..5e66173c5787 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -2,6 +2,7 @@ config ARM
> bool
> default y
> select ARCH_CLOCKSOURCE_DATA
> + select ARCH_HAS_DEBUG_VIRTUAL
> select ARCH_HAS_DEVMEM_IS_ALLOWED
> select ARCH_HAS_ELF_RANDOMIZE
> select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
> diff --git a/arch/arm/include/asm/memory.h b/arch/arm/include/asm/memory.h
> index bee7511c5098..46f192218be7 100644
> --- a/arch/arm/include/asm/memory.h
> +++ b/arch/arm/include/asm/memory.h
> @@ -213,7 +213,7 @@ extern const void *__pv_table_begin, *__pv_table_end;
> : "r" (x), "I" (__PV_BITS_31_24) \
> : "cc")
>
> -static inline phys_addr_t __virt_to_phys(unsigned long x)
> +static inline phys_addr_t __virt_to_phys_nodebug(unsigned long x)
> {
> phys_addr_t t;
>
> @@ -245,7 +245,7 @@ static inline unsigned long __phys_to_virt(phys_addr_t x)
> #define PHYS_OFFSET PLAT_PHYS_OFFSET
> #define PHYS_PFN_OFFSET ((unsigned long)(PHYS_OFFSET >> PAGE_SHIFT))
>
> -static inline phys_addr_t __virt_to_phys(unsigned long x)
> +static inline phys_addr_t __virt_to_phys_nodebug(unsigned long x)
> {
> return (phys_addr_t)x - PAGE_OFFSET + PHYS_OFFSET;
> }
> @@ -261,6 +261,16 @@ static inline unsigned long __phys_to_virt(phys_addr_t x)
> ((((unsigned long)(kaddr) - PAGE_OFFSET) >> PAGE_SHIFT) + \
> PHYS_PFN_OFFSET)
>
> +#define __pa_symbol_nodebug(x) ((x) - (unsigned long)KERNEL_START)
On arm64 the kernel image lives in a separate linear offset. arm doesn't
do anything like that so __phys_addr_symbol should just be the regular
__virt_to_phys
> +
> +#ifdef CONFIG_DEBUG_VIRTUAL
> +extern phys_addr_t __virt_to_phys(unsigned long x);
> +extern phys_addr_t __phys_addr_symbol(unsigned long x);
> +#else
> +#define __virt_to_phys(x) __virt_to_phys_nodebug(x)
> +#define __phys_addr_symbol(x) __pa_symbol_nodebug(x)
> +#endif
> +
> /*
> * These are *only* valid on the kernel direct mapped RAM memory.
> * Note: Drivers should NOT use these. They are the wrong
> @@ -283,9 +293,11 @@ static inline void *phys_to_virt(phys_addr_t x)
> * Drivers should NOT use these either.
> */
> #define __pa(x) __virt_to_phys((unsigned long)(x))
> +#define __pa_symbol(x) __phys_addr_symbol(RELOC_HIDE((unsigned long)(x), 0))
> #define __va(x) ((void *)__phys_to_virt((phys_addr_t)(x)))
> #define pfn_to_kaddr(pfn) __va((phys_addr_t)(pfn) << PAGE_SHIFT)
>
> +
> extern long long arch_phys_to_idmap_offset;
>
> /*
> diff --git a/arch/arm/mm/Makefile b/arch/arm/mm/Makefile
> index e8698241ece9..b3dea80715b4 100644
> --- a/arch/arm/mm/Makefile
> +++ b/arch/arm/mm/Makefile
> @@ -14,6 +14,7 @@ endif
>
> obj-$(CONFIG_ARM_PTDUMP) += dump.o
> obj-$(CONFIG_MODULES) += proc-syms.o
> +obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o
>
> obj-$(CONFIG_ALIGNMENT_TRAP) += alignment.o
> obj-$(CONFIG_HIGHMEM) += highmem.o
> diff --git a/arch/arm/mm/physaddr.c b/arch/arm/mm/physaddr.c
> new file mode 100644
> index 000000000000..00f6dcffab8b
> --- /dev/null
> +++ b/arch/arm/mm/physaddr.c
> @@ -0,0 +1,51 @@
> +#include <linux/bug.h>
> +#include <linux/export.h>
> +#include <linux/types.h>
> +#include <linux/mmdebug.h>
> +#include <linux/mm.h>
> +
> +#include <asm/sections.h>
> +#include <asm/memory.h>
> +#include <asm/fixmap.h>
> +
> +#include "mm.h"
> +
> +static inline bool __virt_addr_valid(unsigned long x)
> +{
> + if (x < PAGE_OFFSET)
> + return false;
> + if (arm_lowmem_limit && is_vmalloc_or_module_addr((void *)x))
> + return false;
> + if (x >= FIXADDR_START && x < FIXADDR_END)
> + return false;
> + return true;
> +}
I'd rather see this return true for only the linear range and
reject everything else. asm/memory.h already has
#define virt_addr_valid(kaddr) (((unsigned long)(kaddr) >= PAGE_OFFSET && (unsigned long)(kaddr) < (unsigned long)high_memory) \
&& pfn_valid(virt_to_pfn(kaddr)))
So we can make the check x >= PAGE_OFFSET && x < high_memory
> +
> +phys_addr_t __virt_to_phys(unsigned long x)
> +{
> + WARN(!__virt_addr_valid(x),
> + "virt_to_phys used for non-linear address :%pK\n", (void *)x);
> +
> + return __virt_to_phys_nodebug(x);
> +}
> +EXPORT_SYMBOL(__virt_to_phys);
> +
> +static inline bool __phys_addr_valid(unsigned long x)
> +{
> + /* This is bounds checking against the kernel image only.
> + * __pa_symbol should only be used on kernel symbol addresses.
> + */
> + if (x < (unsigned long)KERNEL_START ||
> + x > (unsigned long)KERNEL_END)
> + return false;
> +
> + return true;
> +}
This is a confusing name for this function, it's not checking if
a physical address is valid, it's checking if a virtual address
corresponding to a kernel symbol is valid.
> +
> +phys_addr_t __phys_addr_symbol(unsigned long x)
> +{
> + VIRTUAL_BUG_ON(!__phys_addr_valid(x));
> +
> + return __pa_symbol_nodebug(x);
> +}
> +EXPORT_SYMBOL(__phys_addr_symbol);
>
Thanks,
Laura
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