Messages in this thread | | | Subject | Re: [PATCH v1 01/15] powerpc/uaccess: Remove __get_user_allowed() and unsafe_op_wrap() | From | Christophe Leroy <> | Date | Wed, 10 Mar 2021 09:14:23 +0100 |
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Le 01/03/2021 à 23:02, Daniel Axtens a écrit : > > > Christophe Leroy <christophe.leroy@csgroup.eu> writes: > >> Those two macros have only one user which is unsafe_get_user(). >> >> Put everything in one place and remove them. >> >> Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> >> --- >> arch/powerpc/include/asm/uaccess.h | 10 +++++----- >> 1 file changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h >> index 78e2a3990eab..8cbf3e3874f1 100644 >> --- a/arch/powerpc/include/asm/uaccess.h >> +++ b/arch/powerpc/include/asm/uaccess.h >> @@ -53,9 +53,6 @@ static inline bool __access_ok(unsigned long addr, unsigned long size) >> #define __put_user(x, ptr) \ >> __put_user_nocheck((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr))) >> >> -#define __get_user_allowed(x, ptr) \ >> - __get_user_nocheck((x), (ptr), sizeof(*(ptr)), false) >> - >> #define __get_user_inatomic(x, ptr) \ >> __get_user_nosleep((x), (ptr), sizeof(*(ptr))) >> #define __put_user_inatomic(x, ptr) \ >> @@ -482,8 +479,11 @@ user_write_access_begin(const void __user *ptr, size_t len) >> #define user_write_access_begin user_write_access_begin >> #define user_write_access_end prevent_current_write_to_user >> >> -#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0) >> -#define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e) >> +#define unsafe_get_user(x, p, e) do { \ >> + if (unlikely(__get_user_nocheck((x), (p), sizeof(*(p)), false)))\ >> + goto e; \ >> +} while (0) >> + > > This seems correct to me. > > Checkpatch does have one check that is relevant: > > CHECK: Macro argument reuse 'p' - possible side-effects? > #36: FILE: arch/powerpc/include/asm/uaccess.h:482: > +#define unsafe_get_user(x, p, e) do { \ > + if (unlikely(__get_user_nocheck((x), (p), sizeof(*(p)), false)))\ > + goto e; \ > +} while (0) > > Given that we are already creating a new block, should we do something > like this (completely untested): > > #define unsafe_get_user(x, p, e) do { \ > __typeof__(p) __p = (p); > if (unlikely(__get_user_nocheck((x), (__p), sizeof(*(__p)), false)))\ > goto e; \ > } while (0) >
As mentioned by Segher, this is not needed, sizeof(p) doesn't evaluate (p) so (p) is only evaluated once in the macro, so no risk of side-effects with that.
Christophe
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