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[114.34.229.221]) by smtp.gmail.com with ESMTPSA id i22sm15948250pfo.92.2020.06.16.00.45.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 16 Jun 2020 00:45:55 -0700 (PDT) From: Zong Li To: paul.walmsley@sifive.com, palmer@dabbelt.com, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Zong Li Subject: [PATCH 2/2] riscv: Support CONFIG_STRICT_DEVMEM Date: Tue, 16 Jun 2020 15:45:47 +0800 Message-Id: <7faa60aa4a606b5c5c1ae374d82a7eee6c764b38.1592292685.git.zong.li@sifive.com> X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Implement the 'devmem_is_allowed()' interface for RISC-V, like some of other architectures have done. It will be called from range_is_allowed() when userpsace attempts to access /dev/mem. Access to exclusive IOMEM and kernel RAM is denied unless CONFIG_STRICT_DEVMEM is set to 'n'. Test it by devmem, the result as follows: - CONFIG_STRICT_DEVMEM=y $ devmem 0x10010000 0x00000000 $ devmem 0x80200000 0x0000106F - CONFIG_STRICT_DEVMEM is not set $ devmem 0x10010000 devmem: mmap: Operation not permitted $ devmem 0x80200000 devmem: mmap: Operation not permitted Signed-off-by: Zong Li --- arch/riscv/Kconfig | 1 + arch/riscv/include/asm/io.h | 2 ++ arch/riscv/mm/init.c | 19 +++++++++++++++++++ 3 files changed, 22 insertions(+) diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 128192e14ff2..ffd7841ede4c 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -16,6 +16,7 @@ config RISCV select ARCH_HAS_BINFMT_FLAT select ARCH_HAS_DEBUG_VIRTUAL if MMU select ARCH_HAS_DEBUG_WX + select ARCH_HAS_DEVMEM_IS_ALLOWED select ARCH_HAS_GCOV_PROFILE_ALL select ARCH_HAS_GIGANTIC_PAGE select ARCH_HAS_MMIOWB diff --git a/arch/riscv/include/asm/io.h b/arch/riscv/include/asm/io.h index 3835c3295dc5..04ac65ab93ce 100644 --- a/arch/riscv/include/asm/io.h +++ b/arch/riscv/include/asm/io.h @@ -147,4 +147,6 @@ __io_writes_outs(outs, u64, q, __io_pbr(), __io_paw()) #include +extern int devmem_is_allowed(unsigned long pfn); + #endif /* _ASM_RISCV_IO_H */ diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index bbe816e03b2f..5e7e61519acc 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -517,6 +517,25 @@ void mark_rodata_ro(void) } #endif +#ifdef CONFIG_STRICT_DEVMEM +#include +/* + * devmem_is_allowed() checks to see if /dev/mem access to a certain address + * is valid. The argument is a physical page number. + * + * Disallow access to system RAM as well as device-exclusive MMIO regions. + * This effectively disable read()/write() on /dev/mem. + */ +int devmem_is_allowed(unsigned long pfn) +{ + if (iomem_is_exclusive(pfn << PAGE_SHIFT)) + return 0; + if (!page_is_ram(pfn)) + return 1; + return 0; +} +#endif + void __init resource_init(void) { struct memblock_region *region; -- 2.27.0