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Feedback-ID: i56a14606:Fastmail Received: by mailuser.nyi.internal (Postfix, from userid 501) id C40F3B60089; Fri, 30 Sep 2022 10:10:15 -0400 (EDT) X-Mailer: MessagingEngine.com Webmail Interface User-Agent: Cyrus-JMAP/3.7.0-alpha0-968-g04df58079d-fm-20220921.001-g04df5807 Mime-Version: 1.0 Message-Id: In-Reply-To: <87h70pov7x.fsf@mpe.ellerman.id.au> References: <20220921065605.1051927-1-rmclure@linux.ibm.com> <20220921065605.1051927-14-rmclure@linux.ibm.com> <87k05ng0fq.fsf@mpe.ellerman.id.au> <2be2c0f2-9b4b-46e7-a10e-1c17026e8f79@www.fastmail.com> <87h70pov7x.fsf@mpe.ellerman.id.au> Date: Fri, 30 Sep 2022 16:09:54 +0200 From: "Arnd Bergmann" To: "Michael Ellerman" , "Rohan McLure" , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH v6 13/25] powerpc: Remove direct call to mmap2 syscall handlers Content-Type: text/plain 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: Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Fri, Sep 30, 2022, at 3:19 PM, Michael Ellerman wrote: > "Arnd Bergmann" writes: >> >> While sys_mmap_pgoff() was meant to replace the various sys_mmap2() >> implementations, I think it was ultimately a mistake, and we later >> converged on the sys_mmap2() calling conventions with 12 bits >> offset for almost all 32-bit architectures. > > I only see 3 compat mmap2s: > > $ gg "COMPAT_SYSCALL.*mmap2" > arch/arm64/kernel/sys32.c:COMPAT_SYSCALL_DEFINE6(aarch32_mmap2, > unsigned long, addr, unsigned long, len, > arch/powerpc/kernel/syscalls.c:COMPAT_SYSCALL_DEFINE6(mmap2, unsigned > long, addr, size_t, len, > arch/s390/kernel/compat_linux.c:COMPAT_SYSCALL_DEFINE1(s390_mmap2, > struct mmap_arg_struct_emu31 __user *, arg) They are all inconsistently named, and some are shared with the 64-bit implementation on architectures that provide mmap2 for both 32-bit and 64-bit mode, rather than only for 32-bit. arch/mips/kernel/syscall.c:SYSCALL_DEFINE6(mips_mmap2, unsigned long, addr, unsigned long, len, arch/sparc/kernel/sys32.S: .globl sys32_mmap2 arch/parisc/kernel/sys_parisc.c:asmlinkage unsigned long sys_mmap2(unsigned long addr, unsigned long len, > s390 is weird. Right, they used to be limited to 5 register arguments > The arm64 one and ours are similar, but we have the additional call to > arch_validate_prot(prot, addr). arm64 does implement arch_validate_prot(). > > Similar with mmap2, we call arch_validate_prot() but no one else does > (why not?). This looks like it was added in ef3d3246a0d0 ("powerpc/mm: Add Strong Access Ordering support"), which is powerpc specific. It looks like this should correspond to a custom arch_calc_vm_prot_bits() implementation, which exists on arm64, powerpc, sparc and x86. I suppose it should be there for those four. Arnd