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uaccess: generalize access_ok()

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There are many different ways that access_ok() is defined across
architectures, but in the end, they all just compare against the
user_addr_max() value or they accept anything.

Provide one definition that works for most architectures, checking
against TASK_SIZE_MAX for user processes or skipping the check inside
of uaccess_kernel() sections.

For architectures without CONFIG_SET_FS(), this should be the fastest
check, as it comes down to a single comparison of a pointer against a
compile-time constant, while the architecture specific versions tend to
do something more complex for historic reasons or get something wrong.

Type checking for __user annotations is handled inconsistently across
architectures, but this is easily simplified as well by using an inline
function that takes a 'const void __user *' argument. A handful of
callers need an extra __user annotation for this.

Some architectures had trick to use 33-bit or 65-bit arithmetic on the
addresses to calculate the overflow, however this simpler version uses
fewer registers, which means it can produce better object code in the
end despite needing a second (statically predicted) branch.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mark Rutland <mark.rutland@arm.com> [arm64, asm-generic]
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Stafford Horne <shorne@gmail.com>
Acked-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
This commit is contained in:
Arnd Bergmann
2022-02-15 17:55:04 +01:00
parent 23fc539e81
commit 12700c17fc
32 changed files with 110 additions and 362 deletions
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31
arch/riscv/include/asm/uaccess.h
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@@ -21,42 +21,13 @@
#include <asm/byteorder.h>
#include <asm/extable.h>
#include <asm/asm.h>
#include <asm-generic/access_ok.h>
#define __enable_user_access() \
__asm__ __volatile__ ("csrs sstatus, %0" : : "r" (SR_SUM) : "memory")
#define __disable_user_access() \
__asm__ __volatile__ ("csrc sstatus, %0" : : "r" (SR_SUM) : "memory")
/**
* access_ok: - Checks if a user space pointer is valid
* @addr: User space pointer to start of block to check
* @size: Size of block to check
*
* Context: User context only. This function may sleep.
*
* Checks if a pointer to a block of memory in user space is valid.
*
* Returns true (nonzero) if the memory block may be valid, false (zero)
* if it is definitely invalid.
*
* Note that, depending on architecture, this function probably just
* checks that the pointer is in the user space range - after calling
* this function, memory access functions may still return -EFAULT.
*/
#define access_ok(addr, size) ({ \
__chk_user_ptr(addr); \
likely(__access_ok((unsigned long __force)(addr), (size))); \
})
/*
* Ensure that the range [addr, addr+size) is within the process's
* address space
*/
static inline int __access_ok(unsigned long addr, unsigned long size)
{
return size <= TASK_SIZE && addr <= TASK_SIZE - size;
}
/*
* The exception table consists of pairs of addresses: the first is the
* address of an instruction that is allowed to fault, and the second is