| Message ID | 20190812033120.43013-2-natechancellor@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | Clang build fixes for MIPS | expand |
Hello, Nathan Chancellor wrote: > clang warns: > > arch/mips/kernel/branch.c:148:8: error: variable 'bc_false' is used > uninitialized whenever switch case is taken > [-Werror,-Wsometimes-uninitialized] > case mm_bc2t_op: > ^~~~~~~~~~ > arch/mips/kernel/branch.c:157:8: note: uninitialized use occurs here > if (bc_false) > ^~~~~~~~ > arch/mips/kernel/branch.c:149:8: error: variable 'bc_false' is used > uninitialized whenever switch case is taken > [-Werror,-Wsometimes-uninitialized] > case mm_bc1t_op: > ^~~~~~~~~~ > arch/mips/kernel/branch.c:157:8: note: uninitialized use occurs here > if (bc_false) > ^~~~~~~~ > arch/mips/kernel/branch.c:142:4: note: variable 'bc_false' is declared > here > int bc_false = 0; > ^ > 2 errors generated. > > When mm_bc1t_op and mm_bc2t_op are taken, the bc_false initialization > does not happen, which leads to a garbage value upon use, as illustrated > below with a small sample program. > > $ mipsel-linux-gnu-gcc --version | head -n1 > mipsel-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0 > > $ clang --version | head -n1 > ClangBuiltLinux clang version 9.0.0 (git://github.com/llvm/llvm-project > 544315b4197034a3be8acd12cba56a75fb1f08dc) (based on LLVM 9.0.0svn) > > $ cat test.c > #include <stdio.h> > > static void switch_scoped(int opcode) > { > switch (opcode) { > case 1: > case 2: { > int bc_false = 0; > > bc_false = 4; > case 3: > case 4: > printf("\t* switch scoped bc_false = %d\n", bc_false); > } > } > } > > static void function_scoped(int opcode) > { > int bc_false = 0; > > switch (opcode) { > case 1: > case 2: { > bc_false = 4; > case 3: > case 4: > printf("\t* function scoped bc_false = %d\n", bc_false); > } > } > } > > int main(void) > { > int opcode; > > for (opcode = 1; opcode < 5; opcode++) { > printf("opcode = %d:\n", opcode); > switch_scoped(opcode); > function_scoped(opcode); > printf("\n"); > } > > return 0; > } > > $ mipsel-linux-gnu-gcc -std=gnu89 -static test.c && \ > qemu-mipsel a.out > opcode = 1: > * switch scoped bc_false = 4 > * function scoped bc_false = 4 > > opcode = 2: > * switch scoped bc_false = 4 > * function scoped bc_false = 4 > > opcode = 3: > * switch scoped bc_false = 2147483004 > * function scoped bc_false = 0 > > opcode = 4: > * switch scoped bc_false = 2147483004 > * function scoped bc_false = 0 > > $ clang -std=gnu89 --target=mipsel-linux-gnu -m32 -static test.c && \ > qemu-mipsel a.out > opcode = 1: > * switch scoped bc_false = 4 > * function scoped bc_false = 4 > > opcode = 2: > * switch scoped bc_false = 4 > * function scoped bc_false = 4 > > opcode = 3: > * switch scoped bc_false = 2147483004 > * function scoped bc_false = 0 > > opcode = 4: > * switch scoped bc_false = 2147483004 > * function scoped bc_false = 0 > > Move the definition up so that we get the right behavior and mark it > __maybe_unused as it will not be used when CONFIG_MIPS_FP_SUPPORT > isn't enabled. Applied to mips-next. > commit c2869aafe719 > https://git.kernel.org/mips/c/c2869aafe719 > > Fixes: 6a1cc218b9cc ("MIPS: branch: Remove FP branch handling when CONFIG_MIPS_FP_SUPPORT=n") > Link: https://github.com/ClangBuiltLinux/linux/issues/603 > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> > Signed-off-by: Paul Burton <paul.burton@mips.com> Thanks, Paul [ This message was auto-generated; if you believe anything is incorrect then please email paul.burton@mips.com to report it. ]
diff --git a/arch/mips/kernel/branch.c b/arch/mips/kernel/branch.c index 1db29957a931..2c38f75d87ff 100644 --- a/arch/mips/kernel/branch.c +++ b/arch/mips/kernel/branch.c @@ -58,6 +58,7 @@ int __mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn, unsigned long *contpc) { union mips_instruction insn = (union mips_instruction)dec_insn.insn; + int __maybe_unused bc_false = 0; if (!cpu_has_mmips) return 0; @@ -139,7 +140,6 @@ int __mm_isBranchInstr(struct pt_regs *regs, struct mm_decoded_insn dec_insn, #ifdef CONFIG_MIPS_FP_SUPPORT case mm_bc2f_op: case mm_bc1f_op: { - int bc_false = 0; unsigned int fcr31; unsigned int bit;
clang warns: arch/mips/kernel/branch.c:148:8: error: variable 'bc_false' is used uninitialized whenever switch case is taken [-Werror,-Wsometimes-uninitialized] case mm_bc2t_op: ^~~~~~~~~~ arch/mips/kernel/branch.c:157:8: note: uninitialized use occurs here if (bc_false) ^~~~~~~~ arch/mips/kernel/branch.c:149:8: error: variable 'bc_false' is used uninitialized whenever switch case is taken [-Werror,-Wsometimes-uninitialized] case mm_bc1t_op: ^~~~~~~~~~ arch/mips/kernel/branch.c:157:8: note: uninitialized use occurs here if (bc_false) ^~~~~~~~ arch/mips/kernel/branch.c:142:4: note: variable 'bc_false' is declared here int bc_false = 0; ^ 2 errors generated. When mm_bc1t_op and mm_bc2t_op are taken, the bc_false initialization does not happen, which leads to a garbage value upon use, as illustrated below with a small sample program. $ mipsel-linux-gnu-gcc --version | head -n1 mipsel-linux-gnu-gcc (Debian 8.3.0-2) 8.3.0 $ clang --version | head -n1 ClangBuiltLinux clang version 9.0.0 (git://github.com/llvm/llvm-project 544315b4197034a3be8acd12cba56a75fb1f08dc) (based on LLVM 9.0.0svn) $ cat test.c #include <stdio.h> static void switch_scoped(int opcode) { switch (opcode) { case 1: case 2: { int bc_false = 0; bc_false = 4; case 3: case 4: printf("\t* switch scoped bc_false = %d\n", bc_false); } } } static void function_scoped(int opcode) { int bc_false = 0; switch (opcode) { case 1: case 2: { bc_false = 4; case 3: case 4: printf("\t* function scoped bc_false = %d\n", bc_false); } } } int main(void) { int opcode; for (opcode = 1; opcode < 5; opcode++) { printf("opcode = %d:\n", opcode); switch_scoped(opcode); function_scoped(opcode); printf("\n"); } return 0; } $ mipsel-linux-gnu-gcc -std=gnu89 -static test.c && \ qemu-mipsel a.out opcode = 1: * switch scoped bc_false = 4 * function scoped bc_false = 4 opcode = 2: * switch scoped bc_false = 4 * function scoped bc_false = 4 opcode = 3: * switch scoped bc_false = 2147483004 * function scoped bc_false = 0 opcode = 4: * switch scoped bc_false = 2147483004 * function scoped bc_false = 0 $ clang -std=gnu89 --target=mipsel-linux-gnu -m32 -static test.c && \ qemu-mipsel a.out opcode = 1: * switch scoped bc_false = 4 * function scoped bc_false = 4 opcode = 2: * switch scoped bc_false = 4 * function scoped bc_false = 4 opcode = 3: * switch scoped bc_false = 2147483004 * function scoped bc_false = 0 opcode = 4: * switch scoped bc_false = 2147483004 * function scoped bc_false = 0 Move the definition up so that we get the right behavior and mark it __maybe_unused as it will not be used when CONFIG_MIPS_FP_SUPPORT isn't enabled. Fixes: 6a1cc218b9cc ("MIPS: branch: Remove FP branch handling when CONFIG_MIPS_FP_SUPPORT=n") Link: https://github.com/ClangBuiltLinux/linux/issues/603 Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> --- arch/mips/kernel/branch.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)