Messages in this thread | | | Date | Wed, 9 Aug 2023 16:38:01 +0200 | From | Christoph Hellwig <> | Subject | Re: [PATCH RFC] Introduce uniptr_t as a generic "universal" pointer |
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On Wed, Aug 09, 2023 at 04:35:47PM +0200, Takashi Iwai wrote: > Although sockptr_t is used already in several places as a "universal" > pointer, it's still too confusing to use it in other subsystems, since > people see it always as if it were a network-related stuff. > > This patch defines a more generic type, uniptr_t, that does exactly as > same as sockptr_t for a wider use. As of now, it's almost 1:1 copy > with renames (just with comprehensive header file inclusions).
The original set_fs removal series did that as uptr_t, and Linus hated it with passion. I somehow doubt he's going to like it more now.
> Signed-off-by: Takashi Iwai <tiwai@suse.de> > --- > > This is a RFC patch, or rather a material for bikeshedding. > > Initially the discussion started from the use of sockptr_t for the > sound driver in Andy's patch: > https://lore.kernel.org/r/20230721100146.67293-1-andriy.shevchenko@linux.intel.com > followed by a bigger series of patches by me: > https://lore.kernel.org/r/20230731154718.31048-1-tiwai@suse.de > > The first reaction to the patches (including my own) were > "why sockptr_t?" Yes, it's just confusing. So, here it is, a > proposal of defining the new type for the very purpose as sockptr_t. > > The name of uniptr_t is nothing but my random pick up, and we can > endlessly discuss for a better name (genptr_t or whatever). > I'm totally open for the name. > > After this introduction, sockptr_t can be alias of uniptr_t, > e.g. simply override with "#define sockptr_t uniptr_t" or such. > How can it be is another open question. > > Also, we can clean up the macro implementation along with it; > there seem a few (rather minor) issues as suggested by Andy: > https://lore.kernel.org/r/ZMlGKy7ibjkQ6ii7@smile.fi.intel.com > > Honestly speaking, I don't mind to keep using sockptr_t generically > despite of the name, if people agree. The rename might make sense, > though, if it's more widely used in other subsystems in future. > > > Takashi > > === > > include/linux/uniptr.h | 121 +++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 121 insertions(+) > create mode 100644 include/linux/uniptr.h > > diff --git a/include/linux/uniptr.h b/include/linux/uniptr.h > new file mode 100644 > index 000000000000..f7994d3a45eb > --- /dev/null > +++ b/include/linux/uniptr.h > @@ -0,0 +1,121 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +/* > + * Support for "universal" pointers that can point to either kernel or userspace > + * memory. > + * > + * Original code from sockptr.h > + * Copyright (c) 2020 Christoph Hellwig > + */ > +#ifndef _LINUX_UNIPTR_H > +#define _LINUX_UNIPTR_H > + > +#include <linux/err.h> > +#include <linux/slab.h> > +#include <linux/string.h> > +#include <linux/types.h> > +#include <linux/uaccess.h> > + > +typedef struct { > + union { > + void *kernel; > + void __user *user; > + }; > + bool is_kernel : 1; > +} uniptr_t; > + > +static inline bool uniptr_is_kernel(uniptr_t uniptr) > +{ > + return uniptr.is_kernel; > +} > + > +static inline uniptr_t KERNEL_UNIPTR(void *p) > +{ > + return (uniptr_t) { .kernel = p, .is_kernel = true }; > +} > + > +static inline uniptr_t USER_UNIPTR(void __user *p) > +{ > + return (uniptr_t) { .user = p }; > +} > + > +static inline bool uniptr_is_null(uniptr_t uniptr) > +{ > + if (uniptr_is_kernel(uniptr)) > + return !uniptr.kernel; > + return !uniptr.user; > +} > + > +static inline int copy_from_uniptr_offset(void *dst, uniptr_t src, > + size_t offset, size_t size) > +{ > + if (!uniptr_is_kernel(src)) > + return copy_from_user(dst, src.user + offset, size); > + memcpy(dst, src.kernel + offset, size); > + return 0; > +} > + > +static inline int copy_from_uniptr(void *dst, uniptr_t src, size_t size) > +{ > + return copy_from_uniptr_offset(dst, src, 0, size); > +} > + > +static inline int copy_to_uniptr_offset(uniptr_t dst, size_t offset, > + const void *src, size_t size) > +{ > + if (!uniptr_is_kernel(dst)) > + return copy_to_user(dst.user + offset, src, size); > + memcpy(dst.kernel + offset, src, size); > + return 0; > +} > + > +static inline int copy_to_uniptr(uniptr_t dst, const void *src, size_t size) > +{ > + return copy_to_uniptr_offset(dst, 0, src, size); > +} > + > +static inline void *memdup_uniptr(uniptr_t src, size_t len) > +{ > + void *p = kmalloc_track_caller(len, GFP_USER | __GFP_NOWARN); > + > + if (!p) > + return ERR_PTR(-ENOMEM); > + if (copy_from_uniptr(p, src, len)) { > + kfree(p); > + return ERR_PTR(-EFAULT); > + } > + return p; > +} > + > +static inline void *memdup_uniptr_nul(uniptr_t src, size_t len) > +{ > + char *p = kmalloc_track_caller(len + 1, GFP_KERNEL); > + > + if (!p) > + return ERR_PTR(-ENOMEM); > + if (copy_from_uniptr(p, src, len)) { > + kfree(p); > + return ERR_PTR(-EFAULT); > + } > + p[len] = '\0'; > + return p; > +} > + > +static inline long strncpy_from_uniptr(char *dst, uniptr_t src, size_t count) > +{ > + if (uniptr_is_kernel(src)) { > + size_t len = min(strnlen(src.kernel, count - 1) + 1, count); > + > + memcpy(dst, src.kernel, len); > + return len; > + } > + return strncpy_from_user(dst, src.user, count); > +} > + > +static inline int check_zeroed_uniptr(uniptr_t src, size_t offset, size_t size) > +{ > + if (!uniptr_is_kernel(src)) > + return check_zeroed_user(src.user + offset, size); > + return memchr_inv(src.kernel + offset, 0, size) == NULL; > +} > + > +#endif /* _LINUX_UNIPTR_H */ > -- > 2.35.3 ---end quoted text---
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