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author | Arnd Bergmann <arnd@arndb.de> | 2022-02-15 19:55:04 +0300 |
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committer | Arnd Bergmann <arnd@arndb.de> | 2022-02-25 11:36:05 +0300 |
commit | 12700c17fc286149324f92d6d380bc48e43f253d (patch) | |
tree | 63157067b99d0adec5db4058ab9235b4802d1e49 /arch/arc/include/asm | |
parent | 23fc539e81295b14b50c6ccc5baeb4f3d59d822d (diff) | |
download | linux-12700c17fc286149324f92d6d380bc48e43f253d.tar.xz |
uaccess: generalize access_ok()
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>
Diffstat (limited to 'arch/arc/include/asm')
-rw-r--r-- | arch/arc/include/asm/uaccess.h | 29 |
1 files changed, 0 insertions, 29 deletions
diff --git a/arch/arc/include/asm/uaccess.h b/arch/arc/include/asm/uaccess.h index 783bfdb3bfa3..30f80b4be2ab 100644 --- a/arch/arc/include/asm/uaccess.h +++ b/arch/arc/include/asm/uaccess.h @@ -23,35 +23,6 @@ #include <linux/string.h> /* for generic string functions */ - -#define __kernel_ok (uaccess_kernel()) - -/* - * Algorithmically, for __user_ok() we want do: - * (start < TASK_SIZE) && (start+len < TASK_SIZE) - * where TASK_SIZE could either be retrieved from thread_info->addr_limit or - * emitted directly in code. - * - * This can however be rewritten as follows: - * (len <= TASK_SIZE) && (start+len < TASK_SIZE) - * - * Because it essentially checks if buffer end is within limit and @len is - * non-ngeative, which implies that buffer start will be within limit too. - * - * The reason for rewriting being, for majority of cases, @len is generally - * compile time constant, causing first sub-expression to be compile time - * subsumed. - * - * The second part would generate weird large LIMMs e.g. (0x6000_0000 - 0x10), - * so we check for TASK_SIZE using get_fs() since the addr_limit load from mem - * would already have been done at this call site for __kernel_ok() - * - */ -#define __user_ok(addr, sz) (((sz) <= TASK_SIZE) && \ - ((addr) <= (get_fs() - (sz)))) -#define __access_ok(addr, sz) (unlikely(__kernel_ok) || \ - likely(__user_ok((addr), (sz)))) - /*********** Single byte/hword/word copies ******************/ #define __get_user_fn(sz, u, k) \ |