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Mon, 20 Jan 2020 09:35:05 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id j-6E-PTjA8J5; Mon, 20 Jan 2020 09:35:05 +0100 (CET) Received: from [172.25.230.100] (po15451.idsi0.si.c-s.fr [172.25.230.100]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 2A21C8B752; Mon, 20 Jan 2020 09:35:05 +0100 (CET) Subject: Re: [PATCH v6 1/5] powerpc/mm: Implement set_memory() routines To: Russell Currey , linuxppc-dev@lists.ozlabs.org References: <20191224055545.178462-1-ruscur@russell.cc> <20191224055545.178462-2-ruscur@russell.cc> From: Christophe Leroy Message-ID: Date: Mon, 20 Jan 2020 09:35:04 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <20191224055545.178462-2-ruscur@russell.cc> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ajd@linux.ibm.com, kernel-hardening@lists.openwall.com, npiggin@gmail.com, joel@jms.id.au, dja@axtens.net Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Le 24/12/2019 à 06:55, Russell Currey a écrit : > The set_memory_{ro/rw/nx/x}() functions are required for STRICT_MODULE_RWX, > and are generally useful primitives to have. This implementation is > designed to be completely generic across powerpc's many MMUs. > > It's possible that this could be optimised to be faster for specific > MMUs, but the focus is on having a generic and safe implementation for > now. > > This implementation does not handle cases where the caller is attempting > to change the mapping of the page it is executing from, or if another > CPU is concurrently using the page being altered. These cases likely > shouldn't happen, but a more complex implementation with MMU-specific code > could safely handle them, so that is left as a TODO for now. > > Signed-off-by: Russell Currey > --- > arch/powerpc/Kconfig | 1 + > arch/powerpc/include/asm/set_memory.h | 32 +++++++++++ > arch/powerpc/mm/Makefile | 1 + > arch/powerpc/mm/pageattr.c | 83 +++++++++++++++++++++++++++ > 4 files changed, 117 insertions(+) > create mode 100644 arch/powerpc/include/asm/set_memory.h > create mode 100644 arch/powerpc/mm/pageattr.c > > +static int __change_page_attr(pte_t *ptep, unsigned long addr, void *data) > +{ > + int action = *((int *)data); > + pte_t pte_val; pte_val is really not a good naming, because pte_val() is already a function which returns the value of a pte_t var. Here you should name it 'pte' as usual. Christophe > + > + // invalidate the PTE so it's safe to modify > + pte_val = ptep_get_and_clear(&init_mm, addr, ptep); > + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); > + > + // modify the PTE bits as desired, then apply > + switch (action) { > + case SET_MEMORY_RO: > + pte_val = pte_wrprotect(pte_val); > + break; > + case SET_MEMORY_RW: > + pte_val = pte_mkwrite(pte_val); > + break; > + case SET_MEMORY_NX: > + pte_val = pte_exprotect(pte_val); > + break; > + case SET_MEMORY_X: > + pte_val = pte_mkexec(pte_val); > + break; > + default: > + WARN_ON(true); > + return -EINVAL; > + } > + > + set_pte_at(&init_mm, addr, ptep, pte_val); > + > + return 0; > +} > +