| Message ID | c8311f9b759e254308a8e57d9f6eb17728a686a7.1559649879.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] uaccess: add noop untagged_addr definition | expand |
On Tue, Jun 04, 2019 at 02:04:47PM +0200, Andrey Konovalov wrote: > Architectures that support memory tagging have a need to perform untagging > (stripping the tag) in various parts of the kernel. This patch adds an > untagged_addr() macro, which is defined as noop for architectures that do > not support memory tagging. The oncoming patch series will define it at > least for sparc64 and arm64. > > Acked-by: Catalin Marinas <catalin.marinas@arm.com> > Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com> > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > include/linux/mm.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 0e8834ac32b7..dd0b5f4e1e45 100644 > +++ b/include/linux/mm.h > @@ -99,6 +99,17 @@ extern int mmap_rnd_compat_bits __read_mostly; > #include <asm/pgtable.h> > #include <asm/processor.h> > > +/* > + * Architectures that support memory tagging (assigning tags to memory regions, > + * embedding these tags into addresses that point to these memory regions, and > + * checking that the memory and the pointer tags match on memory accesses) > + * redefine this macro to strip tags from pointers. > + * It's defined as noop for arcitectures that don't support memory tagging. > + */ > +#ifndef untagged_addr > +#define untagged_addr(addr) (addr) Can you please make this a static inline instead of this macro? Then we can actually know what the input/output types are supposed to be. Is it static inline unsigned long untagged_addr(void __user *ptr) {return ptr;} ? Which would sort of make sense to me. Jason
On Tue, Jun 4, 2019 at 2:28 PM Jason Gunthorpe <jgg@ziepe.ca> wrote: > > On Tue, Jun 04, 2019 at 02:04:47PM +0200, Andrey Konovalov wrote: > > Architectures that support memory tagging have a need to perform untagging > > (stripping the tag) in various parts of the kernel. This patch adds an > > untagged_addr() macro, which is defined as noop for architectures that do > > not support memory tagging. The oncoming patch series will define it at > > least for sparc64 and arm64. > > > > Acked-by: Catalin Marinas <catalin.marinas@arm.com> > > Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com> > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > > include/linux/mm.h | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 0e8834ac32b7..dd0b5f4e1e45 100644 > > +++ b/include/linux/mm.h > > @@ -99,6 +99,17 @@ extern int mmap_rnd_compat_bits __read_mostly; > > #include <asm/pgtable.h> > > #include <asm/processor.h> > > > > +/* > > + * Architectures that support memory tagging (assigning tags to memory regions, > > + * embedding these tags into addresses that point to these memory regions, and > > + * checking that the memory and the pointer tags match on memory accesses) > > + * redefine this macro to strip tags from pointers. > > + * It's defined as noop for arcitectures that don't support memory tagging. > > + */ > > +#ifndef untagged_addr > > +#define untagged_addr(addr) (addr) > > Can you please make this a static inline instead of this macro? Then > we can actually know what the input/output types are supposed to be. > > Is it > > static inline unsigned long untagged_addr(void __user *ptr) {return ptr;} > > ? > > Which would sort of make sense to me. Hm, I'm not sure. arm64 specifically defines this as a macro that works on different kinds of pointer compatible types to avoid casting everywhere it's used: https://elixir.bootlin.com/linux/v5.1.7/source/arch/arm64/include/asm/memory.h#L214 > > Jason
On Tue, Jun 04, 2019 at 09:28:41AM -0300, Jason Gunthorpe wrote: > On Tue, Jun 04, 2019 at 02:04:47PM +0200, Andrey Konovalov wrote: > > Architectures that support memory tagging have a need to perform untagging > > (stripping the tag) in various parts of the kernel. This patch adds an > > untagged_addr() macro, which is defined as noop for architectures that do > > not support memory tagging. The oncoming patch series will define it at > > least for sparc64 and arm64. > > > > Acked-by: Catalin Marinas <catalin.marinas@arm.com> > > Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com> > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > > include/linux/mm.h | 11 +++++++++++ > > 1 file changed, 11 insertions(+) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 0e8834ac32b7..dd0b5f4e1e45 100644 > > +++ b/include/linux/mm.h > > @@ -99,6 +99,17 @@ extern int mmap_rnd_compat_bits __read_mostly; > > #include <asm/pgtable.h> > > #include <asm/processor.h> > > > > +/* > > + * Architectures that support memory tagging (assigning tags to memory regions, > > + * embedding these tags into addresses that point to these memory regions, and > > + * checking that the memory and the pointer tags match on memory accesses) > > + * redefine this macro to strip tags from pointers. > > + * It's defined as noop for arcitectures that don't support memory tagging. > > + */ > > +#ifndef untagged_addr > > +#define untagged_addr(addr) (addr) > > Can you please make this a static inline instead of this macro? Then > we can actually know what the input/output types are supposed to be. > > Is it > > static inline unsigned long untagged_addr(void __user *ptr) {return ptr;} > > ? > > Which would sort of make sense to me. This macro is used mostly on unsigned long since for __user ptr we can deference them in the kernel even if tagged. So if we are to use types here, I'd rather have: static inline unsigned long untagged_addr(unsigned long addr); In addition I'd like to avoid the explicit casting to (unsigned long) and use some userptr_to_ulong() or something. We are investigating in parallel on how to leverage static checking (sparse, smatch) for better tracking these conversions.
On Tue, Jun 04, 2019 at 01:38:00PM +0100, Catalin Marinas wrote: > On Tue, Jun 04, 2019 at 09:28:41AM -0300, Jason Gunthorpe wrote: > > On Tue, Jun 04, 2019 at 02:04:47PM +0200, Andrey Konovalov wrote: > > > Architectures that support memory tagging have a need to perform untagging > > > (stripping the tag) in various parts of the kernel. This patch adds an > > > untagged_addr() macro, which is defined as noop for architectures that do > > > not support memory tagging. The oncoming patch series will define it at > > > least for sparc64 and arm64. > > > > > > Acked-by: Catalin Marinas <catalin.marinas@arm.com> > > > Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com> > > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > > > include/linux/mm.h | 11 +++++++++++ > > > 1 file changed, 11 insertions(+) > > > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > > index 0e8834ac32b7..dd0b5f4e1e45 100644 > > > +++ b/include/linux/mm.h > > > @@ -99,6 +99,17 @@ extern int mmap_rnd_compat_bits __read_mostly; > > > #include <asm/pgtable.h> > > > #include <asm/processor.h> > > > > > > +/* > > > + * Architectures that support memory tagging (assigning tags to memory regions, > > > + * embedding these tags into addresses that point to these memory regions, and > > > + * checking that the memory and the pointer tags match on memory accesses) > > > + * redefine this macro to strip tags from pointers. > > > + * It's defined as noop for arcitectures that don't support memory tagging. > > > + */ > > > +#ifndef untagged_addr > > > +#define untagged_addr(addr) (addr) > > > > Can you please make this a static inline instead of this macro? Then > > we can actually know what the input/output types are supposed to be. > > > > Is it > > > > static inline unsigned long untagged_addr(void __user *ptr) {return ptr;} > > > > ? > > > > Which would sort of make sense to me. > > This macro is used mostly on unsigned long since for __user ptr we can > deference them in the kernel even if tagged. What does that mean? Do all kernel apis that accept 'void __user *' already untag due to other patches? > So if we are to use types here, I'd rather have: > > static inline unsigned long untagged_addr(unsigned long addr); > > In addition I'd like to avoid the explicit casting to (unsigned long) > and use some userptr_to_ulong() or something. Personally I think it is a very bad habit we have in the kernel to store a 'void __user *' as a u64 or an unsigned long all over the place. AFAIK a u64 passed in from userpace is supposed to be converted to the 'void __user *' via u64_to_user_ptr() before it can be used. (IIRC Some arches require this..) So, if I have a ioctl that takes a user pointer as a u64, and I want to pass it to find_vma, then I do need to write: find_vma(untagged_addr(u64_to_user_ptr(ioctl_u64))) Right? So, IMHO, not accepting a 'void __user *' is just encouraging drivers to skip the needed u64_to_user_ptr() step. At the very worst we should have at least a 2nd function, but, IMHO, it would be better to do a bit more work on adding missing u64_to_user_ptr() calls to get the 'void __user *', and maybe a bit more work on swapping unsigned long for 'void __user *' in various places. Jason
On Tue, Jun 4, 2019 at 5:04 AM Andrey Konovalov <andreyknvl@google.com> wrote: > > Architectures that support memory tagging have a need to perform untagging > (stripping the tag) in various parts of the kernel. This patch adds an > untagged_addr() macro, which is defined as noop for architectures that do > not support memory tagging. Ok, applied directly to my tree so that people can use this independently starting with rc4 (which I might release tomorrow rather than Sunday because I have some travel). Linus
diff --git a/include/linux/mm.h b/include/linux/mm.h index 0e8834ac32b7..dd0b5f4e1e45 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -99,6 +99,17 @@ extern int mmap_rnd_compat_bits __read_mostly; #include <asm/pgtable.h> #include <asm/processor.h> +/* + * Architectures that support memory tagging (assigning tags to memory regions, + * embedding these tags into addresses that point to these memory regions, and + * checking that the memory and the pointer tags match on memory accesses) + * redefine this macro to strip tags from pointers. + * It's defined as noop for arcitectures that don't support memory tagging. + */ +#ifndef untagged_addr +#define untagged_addr(addr) (addr) +#endif + #ifndef __pa_symbol #define __pa_symbol(x) __pa(RELOC_HIDE((unsigned long)(x), 0)) #endif