From: Nathan Chancellor <nathan@kernel.org> To: Michael Ellerman <mpe@ellerman.id.au> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, Nick Desaulniers <ndesaulniers@google.com>, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, Nathan Chancellor <nathan@kernel.org> Subject: [PATCH] powerpc: Avoid clang uninitialized warning in __get_user_size_allowed Date: Mon, 26 Apr 2021 13:35:18 -0700 [thread overview] Message-ID: <20210426203518.981550-1-nathan@kernel.org> (raw) 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. Link: https://github.com/ClangBuiltLinux/linux/issues/1359 Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- arch/powerpc/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index a4e791bcd3fe..a09e4240c5b1 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -232,7 +232,7 @@ do { \ case 2: __get_user_asm(x, (u16 __user *)ptr, retval, "lhz"); break; \ case 4: __get_user_asm(x, (u32 __user *)ptr, retval, "lwz"); break; \ case 8: __get_user_asm2(x, (u64 __user *)ptr, retval); break; \ - default: BUILD_BUG(); \ + default: x = 0; BUILD_BUG(); \ } \ } while (0) base-commit: ee6b25fa7c037e42cc5f3b5c024b2a779edab6dd -- 2.31.1.362.g311531c9de
WARNING: multiple messages have this Message-ID (diff)
From: Nathan Chancellor <nathan@kernel.org> To: Michael Ellerman <mpe@ellerman.id.au> Cc: Nick Desaulniers <ndesaulniers@google.com>, linux-kernel@vger.kernel.org, Nathan Chancellor <nathan@kernel.org>, clang-built-linux@googlegroups.com, Paul Mackerras <paulus@samba.org>, linuxppc-dev@lists.ozlabs.org Subject: [PATCH] powerpc: Avoid clang uninitialized warning in __get_user_size_allowed Date: Mon, 26 Apr 2021 13:35:18 -0700 [thread overview] Message-ID: <20210426203518.981550-1-nathan@kernel.org> (raw) 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. Link: https://github.com/ClangBuiltLinux/linux/issues/1359 Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- arch/powerpc/include/asm/uaccess.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index a4e791bcd3fe..a09e4240c5b1 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -232,7 +232,7 @@ do { \ case 2: __get_user_asm(x, (u16 __user *)ptr, retval, "lhz"); break; \ case 4: __get_user_asm(x, (u32 __user *)ptr, retval, "lwz"); break; \ case 8: __get_user_asm2(x, (u64 __user *)ptr, retval); break; \ - default: BUILD_BUG(); \ + default: x = 0; BUILD_BUG(); \ } \ } while (0) base-commit: ee6b25fa7c037e42cc5f3b5c024b2a779edab6dd -- 2.31.1.362.g311531c9de
next reply other threads:[~2021-04-26 20:35 UTC|newest] Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-26 20:35 Nathan Chancellor [this message] 2021-04-26 20:35 ` [PATCH] powerpc: Avoid clang uninitialized warning in __get_user_size_allowed Nathan Chancellor 2021-04-27 5:05 ` Christophe Leroy 2021-04-27 5:05 ` Christophe Leroy 2021-04-28 21:41 ` Nathan Chancellor 2021-04-28 21:41 ` Nathan Chancellor 2021-04-29 14:01 ` Michael Ellerman 2021-04-29 14:01 ` Michael Ellerman
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