Re: [PATCH 1/2] riscv: mm: add support for CONFIG_DEBUG_VIRTUAL

[Palmer Dabbelt <palmerdabbelt@google.com>]

On Wed, 01 Jan 2020 19:12:39 PST (-0800), zong.li@sifive.com wrote:
> This patch implements CONFIG_DEBUG_VIRTUAL to do additional checks on
> virt_to_phys and __pa_symbol calls. virt_to_phys used for linear mapping
> check, and __pa_symbol used for kernel symbol check. In current RISC-V,
> kernel image maps to linear mapping area. If CONFIG_DEBUG_VIRTUAL is
> disable, these two functions calculate the offset on the address feded
> directly without any checks.
>
> The result of test_debug_virtual as follows:
>
> [    0.358456] ------------[ cut here ]------------
> [    0.358738] virt_to_phys used for non-linear address: (____ptrval____) (0xffffffd000000000)
> [    0.359174] WARNING: CPU: 0 PID: 1 at arch/riscv/mm/physaddr.c:16 __virt_to_phys+0x3c/0x50
> [    0.359409] Modules linked in:
> [    0.359630] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.5.0-rc3-00002-g5133c5c0ca13 #57
> [    0.359861] epc: ffffffe000253d1a ra : ffffffe000253d1a sp : ffffffe03aa87da0
> [    0.360019]  gp : ffffffe000ae03b0 tp : ffffffe03aa88000 t0 : ffffffe000af2660
> [    0.360175]  t1 : 0000000000000064 t2 : 00000000000000b7 s0 : ffffffe03aa87dc0
> [    0.360330]  s1 : ffffffd000000000 a0 : 000000000000004f a1 : 0000000000000000
> [    0.360492]  a2 : 0000000000000000 a3 : 0000000000000000 a4 : ffffffe000a84358
> [    0.360672]  a5 : 0000000000000000 a6 : 0000000000000000 a7 : 0000000000000000
> [    0.360876]  s2 : ffffffe000ae0600 s3 : ffffffe00000fc7c s4 : ffffffe0000224b0
> [    0.361067]  s5 : ffffffe000030890 s6 : ffffffe000022470 s7 : 0000000000000008
> [    0.361267]  s8 : ffffffe0000002c4 s9 : ffffffe000ae0640 s10: ffffffe000ae0630
> [    0.361453]  s11: 0000000000000000 t3 : 0000000000000000 t4 : 000000000001e6d0
> [    0.361636]  t5 : ffffffe000ae0a18 t6 : ffffffe000aee54e
> [    0.361806] status: 0000000000000120 badaddr: 0000000000000000 cause: 0000000000000003
> [    0.362056] ---[ end trace aec0bf78d4978122 ]---
> [    0.362404] PA: 0xfffffff080200000 for VA: 0xffffffd000000000
> [    0.362607] PA: 0x00000000baddd2d0 for VA: 0xffffffe03abdd2d0
>
> Signed-off-by: Zong Li <zong.li@sifive.com>

Thanks.  Looks like patch 2 landed in Linus' tree as part of 5.5, but this one
didn't.  I've taken it on to for-next.

> ---
>  arch/riscv/Kconfig            |  1 +
>  arch/riscv/include/asm/page.h | 16 +++++++++++++--
>  arch/riscv/mm/Makefile        |  2 ++
>  arch/riscv/mm/physaddr.c      | 37 +++++++++++++++++++++++++++++++++++
>  4 files changed, 54 insertions(+), 2 deletions(-)
>  create mode 100644 arch/riscv/mm/physaddr.c
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index d8efbaa78d67..7f268816be5b 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -57,6 +57,7 @@ config RISCV
>  	select GENERIC_ARCH_TOPOLOGY if SMP
>  	select ARCH_HAS_PTE_SPECIAL
>  	select ARCH_HAS_MMIOWB
> +	select ARCH_HAS_DEBUG_VIRTUAL
>  	select HAVE_EBPF_JIT if 64BIT
>  	select EDAC_SUPPORT
>  	select ARCH_HAS_GIGANTIC_PAGE
> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> index ac699246ae7e..8ca1930caa44 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -100,8 +100,20 @@ extern unsigned long pfn_base;
>  extern unsigned long max_low_pfn;
>  extern unsigned long min_low_pfn;
>
> -#define __pa(x)		((unsigned long)(x) - va_pa_offset)
> -#define __va(x)		((void *)((unsigned long) (x) + va_pa_offset))
> +#define __pa_to_va_nodebug(x)	((void *)((unsigned long) (x) + va_pa_offset))
> +#define __va_to_pa_nodebug(x)	((unsigned long)(x) - va_pa_offset)
> +
> +#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)	__va_to_pa_nodebug(x)
> +#define __phys_addr_symbol(x)	__va_to_pa_nodebug(x)
> +#endif /* CONFIG_DEBUG_VIRTUAL */
> +
> +#define __pa_symbol(x)	__phys_addr_symbol(RELOC_HIDE((unsigned long)(x), 0))
> +#define __pa(x)		__virt_to_phys((unsigned long)(x))
> +#define __va(x)		((void *)__pa_to_va_nodebug((phys_addr_t)(x)))
>
>  #define phys_to_pfn(phys)	(PFN_DOWN(phys))
>  #define pfn_to_phys(pfn)	(PFN_PHYS(pfn))
> diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
> index a1bd95c8047a..7de157ecfb77 100644
> --- a/arch/riscv/mm/Makefile
> +++ b/arch/riscv/mm/Makefile
> @@ -15,3 +15,5 @@ ifeq ($(CONFIG_MMU),y)
>  obj-$(CONFIG_SMP) += tlbflush.o
>  endif
>  obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
> +
> +obj-$(CONFIG_DEBUG_VIRTUAL) += physaddr.o
> diff --git a/arch/riscv/mm/physaddr.c b/arch/riscv/mm/physaddr.c
> new file mode 100644
> index 000000000000..e8e4dcd39fed
> --- /dev/null
> +++ b/arch/riscv/mm/physaddr.c
> @@ -0,0 +1,37 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/types.h>
> +#include <linux/mmdebug.h>
> +#include <linux/mm.h>
> +#include <asm/page.h>
> +#include <asm/sections.h>
> +
> +phys_addr_t __virt_to_phys(unsigned long x)
> +{
> +	phys_addr_t y = x - PAGE_OFFSET;
> +
> +	/*
> +	 * Boundary checking aginst the kernel linear mapping space.
> +	 */
> +	WARN(y >= KERN_VIRT_SIZE,
> +	     "virt_to_phys used for non-linear address: %pK (%pS)\n",
> +	     (void *)x, (void *)x);
> +
> +	return __va_to_pa_nodebug(x);
> +}
> +EXPORT_SYMBOL(__virt_to_phys);
> +
> +phys_addr_t __phys_addr_symbol(unsigned long x)
> +{
> +	unsigned long kernel_start = (unsigned long)PAGE_OFFSET;
> +	unsigned long kernel_end = (unsigned long)_end;
> +
> +	/*
> +	 * Boundary checking aginst the kernel image mapping.
> +	 * __pa_symbol should only be used on kernel symbol addresses.
> +	 */
> +	VIRTUAL_BUG_ON(x < kernel_start || x > kernel_end);
> +
> +	return __va_to_pa_nodebug(x);
> +}
> +EXPORT_SYMBOL(__phys_addr_symbol);