tree: https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git x86/kentry head: fb951a475a1cd1e5e280ee8b4ce64a6a68c77b64 commit: 5c61d03b2b823992b0e8eba73d2be61947f00323 [6/11] kentry: Simplify the common syscall API config: i386-randconfig-r035-20210519 (attached as .config) compiler: gcc-9 (Debian 9.3.0-22) 9.3.0 reproduce (this is a W=1 build): # https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?id... git remote add luto https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git git fetch --no-tags luto x86/kentry git checkout 5c61d03b2b823992b0e8eba73d2be61947f00323 # save the attached .config to linux build tree make W=1 ARCH=i386 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All warnings (new ones prefixed by >>): arch/x86/entry/common.c:90:24: warning: no previous prototype for 'do_int80_syscall_32' [-Wmissing-prototypes] 90 | __visible noinstr void do_int80_syscall_32(struct pt_regs *regs) | ^~~~~~~~~~~~~~~~~~~ arch/x86/entry/common.c: In function '__do_fast_syscall_32': 116 | bool ret; | ^~~ arch/x86/entry/common.c: At top level: arch/x86/entry/common.c:161:24: warning: no previous prototype for 'do_fast_syscall_32' [-Wmissing-prototypes] 161 | __visible noinstr long do_fast_syscall_32(struct pt_regs *regs) | ^~~~~~~~~~~~~~~~~~ arch/x86/entry/common.c:213:24: warning: no previous prototype for 'do_SYSENTER_32' [-Wmissing-prototypes] 213 | __visible noinstr long do_SYSENTER_32(struct pt_regs *regs) | ^~~~~~~~~~~~~~ vim +/ret +116 arch/x86/entry/common.c 112 113 static noinstr bool __do_fast_syscall_32(struct pt_regs *regs) 114 { 115 unsigned int nr = syscall_32_enter(regs); 117 int res; 118 119 add_random_kstack_offset(); 120 kentry_enter_from_user_mode(regs); 121 instrumentation_begin(); 122 local_irq_enable(); 123 124 /* Fetch EBP from where the vDSO stashed it. */ 125 if (IS_ENABLED(CONFIG_X86_64)) { 126 /* 127 * Micro-optimization: the pointer we're following is 128 * explicitly 32 bits, so it can't be out of range. 129 */ 130 res = __get_user(*(u32 *)&regs->bp, 131 (u32 __user __force *)(unsigned long)(u32)regs->sp); 132 } else { 133 res = get_user(*(u32 *)&regs->bp, 134 (u32 __user __force *)(unsigned long)(u32)regs->sp); 135 } 136 137 if (res) { 138 /* User code screwed up. */ 139 regs->ax = -EFAULT; 140 ret = false; 141 goto out; 142 } 143 144 /* The case truncates any ptrace induced syscall nr > 2^32 -1 */ 145 nr = (unsigned int)kentry_syscall_begin(regs, nr); 146 147 /* Now this is just like a normal syscall. */ 148 do_syscall_32_irqs_on(regs, nr); 149 150 kentry_syscall_end(regs); 151 ret = true; 152 153 out: 154 local_irq_disable(); 155 instrumentation_end(); 156 kentry_exit_to_user_mode(regs); 157 return true; 158 } 159 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org