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authorMichael Ellerman <mpe@ellerman.id.au>2018-07-10 16:20:56 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2018-08-10 22:26:10 +1000
commitf7a6947cd49b7ff4e03f1b4f7e7b223003d752ca (patch)
tree86107043996f10e9a662cea876f1b54c47354c6d /arch/powerpc
parentf405b510c93eeb7390d0e2c6ef8d12af9a33021a (diff)
downloadlinux-f7a6947cd49b7ff4e03f1b4f7e7b223003d752ca.tar.bz2
powerpc/uaccess: Enable get_user(u64, *p) on 32-bit
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>
Diffstat (limited to 'arch/powerpc')
-rw-r--r--arch/powerpc/include/asm/uaccess.h13
1 files changed, 10 insertions, 3 deletions
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index 643cfbd5bcb5..bac225bb7f64 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h
@@ -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(); \