[PATCH v1 7/8] powerpc/uaccess: Add unsafe_clear_user()
From: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Date: 2026-05-22 09:56:56
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
Implement unsafe_clear_user() for powerpc. It's a copy/paste of unsafe_copy_to_user() with value 0 as source. It may be improved in a later patch by using 'dcbz' instruction to zeroize full cache lines at once. Signed-off-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org> --- arch/powerpc/include/asm/uaccess.h | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+)
diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h
index e98c628e3899..ef6711d1278b 100644
--- a/arch/powerpc/include/asm/uaccess.h
+++ b/arch/powerpc/include/asm/uaccess.h@@ -588,6 +588,26 @@ do { \ unsafe_put_user(*(u8*)(_src + _i), (u8 __user *)(_dst + _i), e); \ } while (0) +#define unsafe_clear_user(d, l, e) \ +do { \ + u8 __user *_dst = (u8 __user *)(d); \ + size_t _len = (l); \ + int _i; \ + \ + for (_i = 0; _i < (_len & ~(sizeof(u64) - 1)); _i += sizeof(u64)) \ + unsafe_put_user(0, (u64 __user *)(_dst + _i), e); \ + if (_len & 4) { \ + unsafe_put_user(0, (u32 __user *)(_dst + _i), e); \ + _i += 4; \ + } \ + if (_len & 2) { \ + unsafe_put_user(0, (u16 __user *)(_dst + _i), e); \ + _i += 2; \ + } \ + if (_len & 1) \ + unsafe_put_user(0, (u8 __user *)(_dst + _i), e); \ +} while (0) + #define arch_get_kernel_nofault(dst, src, type, err_label) \ __get_user_size_goto(*((type *)(dst)), \ (__force type __user *)(src), sizeof(type), err_label)
--
2.54.0