kernel.git/arch/powerpc/include/asm/uaccess.h, branch linux-5.13.y

powerpc/uaccess: Fix __get_user() with CONFIG_CC_HAS_ASM_GOTO_OUTPUT

2021-05-12T01:07:39Z

Building kernel mainline with GCC 11 leads to following failure when starting 'init': init[1]: bad frame in sys_sigreturn: 7ff5a900 nip 001083cc lr 001083c4 Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b This is an issue due to a segfault happening in __unsafe_restore_general_regs() in a loop copying registers from user to kernel: 10: 7d 09 03 a6 mtctr r8 14: 80 ca 00 00 lwz r6,0(r10) 18: 80 ea 00 04 lwz r7,4(r10) 1c: 90 c9 00 08 stw r6,8(r9) 20: 90 e9 00 0c stw r7,12(r9) 24: 39 0a 00 08 addi r8,r10,8 28: 39 29 00 08 addi r9,r9,8 2c: 81 4a 00 08 lwz r10,8(r10) <== r10 is clobbered here 30: 81 6a 00 0c lwz r11,12(r10) 34: 91 49 00 08 stw r10,8(r9) 38: 91 69 00 0c stw r11,12(r9) 3c: 39 48 00 08 addi r10,r8,8 40: 39 29 00 08 addi r9,r9,8 44: 42 00 ff d0 bdnz 14 <__unsafe_restore_general_regs+0x14> As shown above, this is due to r10 being re-used by GCC. This didn't happen with CLANG. This is fixed by tagging 'x' output as an earlyclobber operand in __get_user_asm2_goto(). Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/cf0a050d124d4f426cdc7a74009d17b01d8d8969.1620465917.git.christophe.leroy@csgroup.eu

powerpc: Avoid clang uninitialized warning in __get_user_size_allowed

2021-04-28T13:34:50Z

Commit 9975f852ce1b ("powerpc/uaccess: Remove calls to __get_user_bad() and __put_user_bad()") switch to BUILD_BUG() in the default case, which leaves x uninitialized. This will not be an issue because the build will be broken in that case but clang does static analysis before it realizes the default case will be done so it warns about x being uninitialized (trimmed for brevity): In file included from mm/mprotect.c:13: In file included from ./include/linux/hugetlb.h:28: In file included from ./include/linux/mempolicy.h:16: ./include/linux/pagemap.h:772:16: warning: variable '__gu_val' is used uninitialized whenever switch default is taken [-Wsometimes-uninitialized] if (unlikely(__get_user(c, uaddr) != 0)) ^~~~~~~~~~~~~~~~~~~~ ./arch/powerpc/include/asm/uaccess.h:266:2: note: expanded from macro '__get_user' __get_user_size_allowed(__gu_val, __gu_addr, __gu_size, __gu_err); \ ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ./arch/powerpc/include/asm/uaccess.h:235:2: note: expanded from macro '__get_user_size_allowed' default: BUILD_BUG(); \ ^~~~~~~ Commit 5cd29b1fd3e8 ("powerpc/uaccess: Use asm goto for get_user when compiler supports it") added an initialization for x because of the same reason. Do the same thing here so there is no warning across all versions of clang. Signed-off-by: Nathan Chancellor Acked-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://github.com/ClangBuiltLinux/linux/issues/1359 Link: https://lore.kernel.org/r/20210426203518.981550-1-nathan@kernel.org

powerpc/uaccess: Also perform 64 bits copies in unsafe_copy_from_user() on ppc32

2021-04-03T10:22:18Z

Similarly to commit 5cf773fc8f37 ("powerpc/uaccess: Also perform 64 bits copies in unsafe_copy_to_user() on ppc32") ppc32 has an efficiant 64 bits unsafe_get_user(), so also use it in order to unroll loops more. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/308e65d9237a14e8c0e3b22919fcf0b5e5592608.1616151715.git.christophe.leroy@csgroup.eu

powerpc/uaccess: Use asm goto for get_user when compiler supports it

2021-04-03T10:22:16Z

clang 11 and future GCC are supporting asm goto with outputs. Use it to implement get_user in order to get better generated code. Note that clang requires to set x in the default branch of __get_user_size_goto() otherwise is compliant about x not being initialised :puzzled: Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/403745b5aaa1b315bb4e8e46c1ba949e77eecec0.1615398265.git.christophe.leroy@csgroup.eu

powerpc/uaccess: Introduce __get_user_size_goto()

2021-04-03T10:22:13Z

We have got two places doing a goto based on the result of __get_user_size_allowed(). Refactor that into __get_user_size_goto(). Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/def8a39289e02653cfb1583b3b19837de9efed3a.1615398265.git.christophe.leroy@csgroup.eu

powerpc/uaccess: Refactor get/put_user() and __get/put_user()

2021-04-03T10:22:10Z

Make get_user() do the access_ok() check then call __get_user(). Make put_user() do the access_ok() check then call __put_user(). Then embed __get_user_size() and __put_user_size() in __get_user() and __put_user(). Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/eebc554f6a81f570c46ea3551000ff5b886e4faa.1615398265.git.christophe.leroy@csgroup.eu

powerpc/uaccess: Rename __get/put_user_check/nocheck

2021-04-03T10:22:08Z

__get_user_check() becomes get_user() __put_user_check() becomes put_user() __get_user_nocheck() becomes __get_user() __put_user_nocheck() becomes __put_user() Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/41d7e45f4733f0e61e63824e4865b4e049db74d6.1615398265.git.christophe.leroy@csgroup.eu

powerpc/uaccess: Split out __get_user_nocheck()

2021-04-03T10:22:05Z

One part of __get_user_nocheck() is used for __get_user(), the other part for unsafe_get_user(). Move the part dedicated to unsafe_get_user() in it. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/618fe2e0626b308a5a063d5baac827b968e85c32.1615398265.git.christophe.leroy@csgroup.eu

powerpc/uaccess: Remove calls to __get_user_bad() and __put_user_bad()

2021-04-03T10:22:02Z

__get_user_bad() and __put_user_bad() are functions that are declared but not defined, in order to make the link fail in case they are called. Nowadays, we have BUILD_BUG() and BUILD_BUG_ON() for that, and they have the advantage to break the build earlier as it breaks it at compile time instead of link time. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/d7d839e994f49fae4ff7b70fac72bd951272436b.1615398265.git.christophe.leroy@csgroup.eu

powerpc/uaccess: Remove __chk_user_ptr() in __get/put_user

2021-04-03T10:21:59Z

Commit d02f6b7dab82 ("powerpc/uaccess: Evaluate macro arguments once, before user access is allowed") changed the __chk_user_ptr() argument from the passed ptr pointer to the locally declared __gu_addr. But __gu_addr is locally defined as __user so the check is pointless. During kernel build __chk_user_ptr() voids and is only evaluated during sparse checks so it should have been armless to leave the original pointer check there. Nevertheless, this check is indeed redundant with the assignment above which casts the ptr pointer to the local __user __gu_addr. In case of mismatch, sparse will detect it there, so the __check_user_ptr() is not needed anywhere else than in access_ok(). Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/69f17d75046733b891ab2e668dbf464787cdf598.1615398265.git.christophe.leroy@csgroup.eu