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Violators will be prosecuted for from ; Wed, 18 Oct 2017 15:10:50 -0600 Date: Wed, 18 Oct 2017 14:10:41 -0700 From: Ram Pai To: Balbir Singh Cc: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, benh@kernel.crashing.org, paulus@samba.org, khandual@linux.vnet.ibm.com, aneesh.kumar@linux.vnet.ibm.com, hbabu@us.ibm.com, mhocko@kernel.org, bauerman@linux.vnet.ibm.com, ebiederm@xmission.com Subject: Re: [PATCH 13/25] powerpc: implementation for arch_override_mprotect_pkey() Reply-To: Ram Pai References: <1504910713-7094-1-git-send-email-linuxram@us.ibm.com> <1504910713-7094-22-git-send-email-linuxram@us.ibm.com> <20171018153635.1ab9765d@firefly.ozlabs.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20171018153635.1ab9765d@firefly.ozlabs.ibm.com> Message-Id: <20171018211041.GI5617@ram.oc3035372033.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Oct 18, 2017 at 03:36:35PM +1100, Balbir Singh wrote: > On Fri, 8 Sep 2017 15:45:01 -0700 > Ram Pai wrote: > > > arch independent code calls arch_override_mprotect_pkey() > > to return a pkey that best matches the requested protection. > > > > This patch provides the implementation. > > > > Signed-off-by: Ram Pai > > --- > > arch/powerpc/include/asm/mmu_context.h | 5 +++ > > arch/powerpc/include/asm/pkeys.h | 17 ++++++++++- > > arch/powerpc/mm/pkeys.c | 47 ++++++++++++++++++++++++++++++++ > > 3 files changed, 67 insertions(+), 2 deletions(-) > > > > diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h > > index c705a5d..8e5a87e 100644 > > --- a/arch/powerpc/include/asm/mmu_context.h > > +++ b/arch/powerpc/include/asm/mmu_context.h > > @@ -145,6 +145,11 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, > > #ifndef CONFIG_PPC64_MEMORY_PROTECTION_KEYS > > #define pkey_initialize() > > #define pkey_mm_init(mm) > > + > > +static inline int vma_pkey(struct vm_area_struct *vma) > > +{ > > + return 0; > > +} > > #endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */ > > > > #endif /* __KERNEL__ */ > > diff --git a/arch/powerpc/include/asm/pkeys.h b/arch/powerpc/include/asm/pkeys.h > > index f13e913..d2fffef 100644 > > --- a/arch/powerpc/include/asm/pkeys.h > > +++ b/arch/powerpc/include/asm/pkeys.h > > @@ -41,6 +41,16 @@ static inline u64 pkey_to_vmflag_bits(u16 pkey) > > ((pkey & 0x10UL) ? VM_PKEY_BIT4 : 0x0UL)); > > } > > > > +#define ARCH_VM_PKEY_FLAGS (VM_PKEY_BIT0 | VM_PKEY_BIT1 | VM_PKEY_BIT2 | \ > > + VM_PKEY_BIT3 | VM_PKEY_BIT4) > > + > > +static inline int vma_pkey(struct vm_area_struct *vma) > > +{ > > + if (!pkey_inited) > > + return 0; > > We don't want pkey_inited to be present in all functions, why do we need > a conditional branch for all functions. Even if we do, it should be a jump > label. I would rather we just removed !pkey_inited unless really really > required. No. we really really need it. For example when we build a kernel with PROTECTION_KEYS config enabled and run that kernel on a older processor or on a system where the key feature is not enabled in the device tree, we have fail all the calls that get called-in by the arch-neutral code. Hence we need this check. BTW: jump labels are awkward IMHO, unless absolutely needed. > > > + return (vma->vm_flags & ARCH_VM_PKEY_FLAGS) >> VM_PKEY_SHIFT; > > +} > > + > > #define arch_max_pkey() pkeys_total > > #define AMR_RD_BIT 0x1UL > > #define AMR_WR_BIT 0x2UL > > @@ -142,11 +152,14 @@ static inline int execute_only_pkey(struct mm_struct *mm) > > return __execute_only_pkey(mm); > > } > > > > - > > +extern int __arch_override_mprotect_pkey(struct vm_area_struct *vma, > > + int prot, int pkey); > > static inline int arch_override_mprotect_pkey(struct vm_area_struct *vma, > > int prot, int pkey) > > { > > - return 0; > > + if (!pkey_inited) > > + return 0; > > + return __arch_override_mprotect_pkey(vma, prot, pkey); > > } > > > > extern int __arch_set_user_pkey_access(struct task_struct *tsk, int pkey, > > diff --git a/arch/powerpc/mm/pkeys.c b/arch/powerpc/mm/pkeys.c > > index 8a24983..fb1a76a 100644 > > --- a/arch/powerpc/mm/pkeys.c > > +++ b/arch/powerpc/mm/pkeys.c > > @@ -245,3 +245,50 @@ int __execute_only_pkey(struct mm_struct *mm) > > mm->context.execute_only_pkey = execute_only_pkey; > > return execute_only_pkey; > > } > > + > > +static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma) > > +{ > > + /* Do this check first since the vm_flags should be hot */ > > + if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC) > > + return false; > > + > > + return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey); > > +} > > + > > +/* > > + * This should only be called for *plain* mprotect calls. > > What's a plain mprotect call? there is sys_mprotect() and now there is a sys_pkey_mprotect() call. The 'plain' one is the former. > > > + */ > > +int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot, > > + int pkey) > > +{ > > + /* > > + * Is this an mprotect_pkey() call? If so, never > > + * override the value that came from the user. > > + */ > > + if (pkey != -1) > > + return pkey; > > If the user specified a key, we always use it? Presumably the user > got it from pkey_alloc(), in other cases, the user was lazy and used > -1 in the mprotect call? in the plain sys_mprotect() key is not specified. In that case this function gets called with a -1. > > > + > > + /* > > + * If the currently associated pkey is execute-only, > > + * but the requested protection requires read or write, > > + * move it back to the default pkey. > > + */ > > + if (vma_is_pkey_exec_only(vma) && > > + (prot & (PROT_READ|PROT_WRITE))) > > + return 0; > > + > > + /* > > + * the requested protection is execute-only. Hence > > + * lets use a execute-only pkey. > > + */ > > + if (prot == PROT_EXEC) { > > + pkey = execute_only_pkey(vma->vm_mm); > > + if (pkey > 0) > > + return pkey; > > + } > > + > > + /* > > + * nothing to override. > > + */ > > + return vma_pkey(vma); > > +} > > Balbir Singh. -- Ram Pai