linux-kernel - [PATCH AUTOSEL 4.19 3/8] selftests: sigaltstack: fix -Wuninitialized

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Message-Id: <20230406113400.649038-3-sashal@kernel.org>
Date:   Thu,  6 Apr 2023 07:33:55 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux Kernel Functional Testing <lkft@...aro.org>,
        Kees Cook <keescook@...omium.org>,
        Anders Roxell <anders.roxell@...aro.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Sasha Levin <sashal@...nel.org>, shuah@...nel.org,
        paul.walmsley@...ive.com, palmer@...belt.com,
        aou@...s.berkeley.edu, guoren@...nel.org, nathan@...nel.org,
        linux-kselftest@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-csky@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH AUTOSEL 4.19 3/8] selftests: sigaltstack: fix -Wuninitialized

From: Nick Desaulniers <ndesaulniers@...gle.com>

[ Upstream commit 05107edc910135d27fe557267dc45be9630bf3dd ]

Building sigaltstack with clang via:
$ ARCH=x86 make LLVM=1 -C tools/testing/selftests/sigaltstack/

produces the following warning:
  warning: variable 'sp' is uninitialized when used here [-Wuninitialized]
  if (sp < (unsigned long)sstack ||
      ^~

Clang expects these to be declared at global scope; we've fixed this in
the kernel proper by using the macro `current_stack_pointer`. This is
defined in different headers for different target architectures, so just
create a new header that defines the arch-specific register names for
the stack pointer register, and define it for more targets (at least the
ones that support current_stack_pointer/ARCH_HAS_CURRENT_STACK_POINTER).

Reported-by: Linux Kernel Functional Testing <lkft@...aro.org>
Link: https://lore.kernel.org/lkml/CA+G9fYsi3OOu7yCsMutpzKDnBMAzJBCPimBp86LhGBa0eCnEpA@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
Reviewed-by: Kees Cook <keescook@...omium.org>
Tested-by: Linux Kernel Functional Testing <lkft@...aro.org>
Tested-by: Anders Roxell <anders.roxell@...aro.org>
Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 .../sigaltstack/current_stack_pointer.h       | 23 +++++++++++++++++++
 tools/testing/selftests/sigaltstack/sas.c     |  7 +-----
 2 files changed, 24 insertions(+), 6 deletions(-)
 create mode 100644 tools/testing/selftests/sigaltstack/current_stack_pointer.h

diff --git a/tools/testing/selftests/sigaltstack/current_stack_pointer.h b/tools/testing/selftests/sigaltstack/current_stack_pointer.h
new file mode 100644
index 0000000000000..ea9bdf3a90b16
--- /dev/null
+++ b/tools/testing/selftests/sigaltstack/current_stack_pointer.h
@@ -0,0 +1,23 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#if __alpha__
+register unsigned long sp asm("$30");
+#elif __arm__ || __aarch64__ || __csky__ || __m68k__ || __mips__ || __riscv
+register unsigned long sp asm("sp");
+#elif __i386__
+register unsigned long sp asm("esp");
+#elif __loongarch64
+register unsigned long sp asm("$sp");
+#elif __ppc__
+register unsigned long sp asm("r1");
+#elif __s390x__
+register unsigned long sp asm("%15");
+#elif __sh__
+register unsigned long sp asm("r15");
+#elif __x86_64__
+register unsigned long sp asm("rsp");
+#elif __XTENSA__
+register unsigned long sp asm("a1");
+#else
+#error "implement current_stack_pointer equivalent"
+#endif
diff --git a/tools/testing/selftests/sigaltstack/sas.c b/tools/testing/selftests/sigaltstack/sas.c
index 228c2ae47687d..6069d97bf5063 100644
--- a/tools/testing/selftests/sigaltstack/sas.c
+++ b/tools/testing/selftests/sigaltstack/sas.c
@@ -19,6 +19,7 @@
 #include <errno.h>
 
 #include "../kselftest.h"
+#include "current_stack_pointer.h"
 
 #ifndef SS_AUTODISARM
 #define SS_AUTODISARM  (1U << 31)
@@ -40,12 +41,6 @@ void my_usr1(int sig, siginfo_t *si, void *u)
 	stack_t stk;
 	struct stk_data *p;
 
-#if __s390x__
-	register unsigned long sp asm("%15");
-#else
-	register unsigned long sp asm("sp");
-#endif
-
 	if (sp < (unsigned long)sstack ||
 			sp >= (unsigned long)sstack + SIGSTKSZ) {
 		ksft_exit_fail_msg("SP is not on sigaltstack\n");
-- 
2.39.2