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powerpc/uaccess: Enable get_user(u64, *p) on 32-bit

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Currently if you build a 32-bit powerpc kernel and use get_user() to
load a u64 value it will fail to build with eg:

  kernel/rseq.o: In function `rseq_get_rseq_cs':
  kernel/rseq.c:123: undefined reference to `__get_user_bad'

This is hitting the check in __get_user_size() that makes sure the
size we're copying doesn't exceed the size of the destination:

  #define __get_user_size(x, ptr, size, retval)
  do {
  	retval = 0;
  	__chk_user_ptr(ptr);
  	if (size > sizeof(x))
  		(x) = __get_user_bad();

Which doesn't immediately make sense because the size of the
destination is u64, but it's not really, because __get_user_check()
etc. internally create an unsigned long and copy into that:

  #define __get_user_check(x, ptr, size)
  ({
  	long __gu_err = -EFAULT;
  	unsigned long  __gu_val = 0;

The problem being that on 32-bit unsigned long is not big enough to
hold a u64. We can fix this with a trick from hpa in the x86 code, we
statically check the type of x and set the type of __gu_val to either
unsigned long or unsigned long long.

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Michael Ellerman 2018-07-10 16:20:56 +10:00
parent f405b510c9
commit f7a6947cd4
1 changed files with 10 additions and 3 deletions
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13
arch/powerpc/include/asm/uaccess.h
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@ -249,10 +249,17 @@ do { \
} \
} while (0)
/*
* This is a type: either unsigned long, if the argument fits into
* that type, or otherwise unsigned long long.
*/
#define __long_type(x) \
__typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
#define __get_user_nocheck(x, ptr, size) \
({ \
long __gu_err; \
unsigned long __gu_val; \
__long_type(*(ptr)) __gu_val; \
const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \
__chk_user_ptr(ptr); \
if (!is_kernel_addr((unsigned long)__gu_addr)) \
@ -266,7 +273,7 @@ do { \
#define __get_user_check(x, ptr, size) \
({ \
long __gu_err = -EFAULT; \
unsigned long __gu_val = 0; \
__long_type(*(ptr)) __gu_val = 0; \
const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \
might_fault(); \
if (access_ok(VERIFY_READ, __gu_addr, (size))) { \
@ -280,7 +287,7 @@ do { \
#define __get_user_nosleep(x, ptr, size) \
({ \
long __gu_err; \
unsigned long __gu_val; \
__long_type(*(ptr)) __gu_val; \
const __typeof__(*(ptr)) __user *__gu_addr = (ptr); \
__chk_user_ptr(ptr); \
barrier_nospec(); \