Hi Changbin, Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on linus/master] [also build test WARNING on v4.17-rc3 next-20180504] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system] url: https://github.com/0day-ci/linux/commits/changbin-du-intel-com/kernel-hacking-GCC-optimization-for-better-debug-experience-Og/20180506-110946 config: x86_64-allmodconfig (attached as .config) compiler: gcc-7 (Debian 7.3.0-16) 7.3.0 reproduce: # save the attached .config to linux build tree make ARCH=x86_64 Note: it may well be a FALSE warning. FWIW you are at least aware of it now. http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings All warnings (new ones prefixed by >>): arch/x86/entry/vsyscall/vsyscall_64.c: In function 'emulate_vsyscall': >> arch/x86/entry/vsyscall/vsyscall_64.c:127:19: warning: 'syscall_nr' may be >> used uninitialized in this function [-Wmaybe-uninitialized] int vsyscall_nr, syscall_nr, tmp; ^~~~~~~~~~ vim +/syscall_nr +127 arch/x86/entry/vsyscall/vsyscall_64.c 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 122 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 123 bool emulate_vsyscall(struct pt_regs *regs, unsigned long address) 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 124 { 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 125 struct task_struct *tsk; 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 126 unsigned long caller; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 @127 int vsyscall_nr, syscall_nr, tmp; 2a53ccbc arch/x86/entry/vsyscall/vsyscall_64.c Ingo Molnar 2016-07-15 128 int prev_sig_on_uaccess_err; 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 129 long ret; fa697140 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-05 130 unsigned long orig_dx; 7460ed28 arch/x86_64/kernel/vsyscall.c John Stultz 2007-02-16 131 c9712944 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-07-13 132 /* 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 133 * No point in checking CS -- the only way to get here is a user mode 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 134 * trap to a high address, which means that we're in 64-bit user code. c9712944 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-07-13 135 */ 7460ed28 arch/x86_64/kernel/vsyscall.c John Stultz 2007-02-16 136 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 137 WARN_ON_ONCE(address != regs->ip); 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 138 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 139 if (vsyscall_mode == NONE) { 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 140 warn_bad_vsyscall(KERN_INFO, regs, 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 141 "vsyscall attempted with vsyscall=none"); 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 142 return false; c9712944 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-07-13 143 } 7460ed28 arch/x86_64/kernel/vsyscall.c John Stultz 2007-02-16 144 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 145 vsyscall_nr = addr_to_vsyscall_nr(address); c149a665 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-03 146 c149a665 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-03 147 trace_emulate_vsyscall(vsyscall_nr); c149a665 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-03 148 c9712944 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-07-13 149 if (vsyscall_nr < 0) { c9712944 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-07-13 150 warn_bad_vsyscall(KERN_WARNING, regs, 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 151 "misaligned vsyscall (exploit attempt or buggy program) -- look up the vsyscall kernel parameter if you need a workaround"); 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 152 goto sigsegv; 7460ed28 arch/x86_64/kernel/vsyscall.c John Stultz 2007-02-16 153 } 7460ed28 arch/x86_64/kernel/vsyscall.c John Stultz 2007-02-16 154 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 155 if (get_user(caller, (unsigned long __user *)regs->sp) != 0) { 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 156 warn_bad_vsyscall(KERN_WARNING, regs, 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 157 "vsyscall with bad stack (exploit attempt?)"); 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 158 goto sigsegv; ^1da177e arch/x86_64/kernel/vsyscall.c Linus Torvalds 2005-04-16 159 } ^1da177e arch/x86_64/kernel/vsyscall.c Linus Torvalds 2005-04-16 160 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 161 tsk = current; 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 162 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 163 /* 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 164 * Check for access_ok violations and find the syscall nr. 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 165 * 46ed99d1 arch/x86/kernel/vsyscall_64.c Emil Goode 2012-04-01 166 * NULL is a valid user pointer (in the access_ok sense) on 32-bit and 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 167 * 64-bit, so we don't need to special-case it here. For all the 46ed99d1 arch/x86/kernel/vsyscall_64.c Emil Goode 2012-04-01 168 * vsyscalls, NULL means "don't write anything" not "write it at 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 169 * address 0". 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 170 */ 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 171 switch (vsyscall_nr) { 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 172 case 0: 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 173 if (!write_ok_or_segv(regs->di, sizeof(struct timeval)) || 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 174 !write_ok_or_segv(regs->si, sizeof(struct timezone))) { 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 175 ret = -EFAULT; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 176 goto check_fault; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 177 } 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 178 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 179 syscall_nr = __NR_gettimeofday; 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 180 break; 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 181 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 182 case 1: 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 183 if (!write_ok_or_segv(regs->di, sizeof(time_t))) { 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 184 ret = -EFAULT; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 185 goto check_fault; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 186 } 5651721e arch/x86/kernel/vsyscall_64.c Will Drewry 2012-07-13 187 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 188 syscall_nr = __NR_time; 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 189 break; 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 190 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 191 case 2: 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 192 if (!write_ok_or_segv(regs->di, sizeof(unsigned)) || 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 193 !write_ok_or_segv(regs->si, sizeof(unsigned))) { 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 194 ret = -EFAULT; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 195 goto check_fault; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 196 } 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 197 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 198 syscall_nr = __NR_getcpu; 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 199 break; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 200 } 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 201 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 202 /* 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 203 * Handle seccomp. regs->ip must be the original value. 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 204 * See seccomp_send_sigsys and Documentation/prctl/seccomp_filter.txt. 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 205 * 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 206 * We could optimize the seccomp disabled case, but performance 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 207 * here doesn't matter. 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 208 */ 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 209 regs->orig_ax = syscall_nr; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 210 regs->ax = -ENOSYS; 2f275de5 arch/x86/entry/vsyscall/vsyscall_64.c Andy Lutomirski 2016-05-27 211 tmp = secure_computing(NULL); 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 212 if ((!tmp && regs->orig_ax != syscall_nr) || regs->ip != address) { 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 213 warn_bad_vsyscall(KERN_DEBUG, regs, 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 214 "seccomp tried to change syscall nr or ip"); 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 215 do_exit(SIGSYS); 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 216 } 26893107 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2014-11-04 217 regs->orig_ax = -1; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 218 if (tmp) 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 219 goto do_ret; /* skip requested */ 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 220 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 221 /* 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 222 * With a real vsyscall, page faults cause SIGSEGV. We want to 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 223 * preserve that behavior to make writing exploits harder. 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 224 */ 2a53ccbc arch/x86/entry/vsyscall/vsyscall_64.c Ingo Molnar 2016-07-15 225 prev_sig_on_uaccess_err = current->thread.sig_on_uaccess_err; 2a53ccbc arch/x86/entry/vsyscall/vsyscall_64.c Ingo Molnar 2016-07-15 226 current->thread.sig_on_uaccess_err = 1; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 227 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 228 ret = -EFAULT; 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 229 switch (vsyscall_nr) { 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 230 case 0: fa697140 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-05 231 /* this decodes regs->di and regs->si on its own */ d5a00528 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-09 232 ret = __x64_sys_gettimeofday(regs); 5651721e arch/x86/kernel/vsyscall_64.c Will Drewry 2012-07-13 233 break; 5651721e arch/x86/kernel/vsyscall_64.c Will Drewry 2012-07-13 234 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 235 case 1: fa697140 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-05 236 /* this decodes regs->di on its own */ d5a00528 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-09 237 ret = __x64_sys_time(regs); 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 238 break; 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 239 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 240 case 2: fa697140 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-05 241 /* while we could clobber regs->dx, we didn't in the past... */ fa697140 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-05 242 orig_dx = regs->dx; fa697140 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-05 243 regs->dx = 0; fa697140 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-05 244 /* this decodes regs->di, regs->si and regs->dx on its own */ d5a00528 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-09 245 ret = __x64_sys_getcpu(regs); fa697140 arch/x86/entry/vsyscall/vsyscall_64.c Dominik Brodowski 2018-04-05 246 regs->dx = orig_dx; 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 247 break; 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 248 } 8c73626a arch/x86/kernel/vsyscall_64.c John Stultz 2010-07-13 249 2a53ccbc arch/x86/entry/vsyscall/vsyscall_64.c Ingo Molnar 2016-07-15 250 current->thread.sig_on_uaccess_err = prev_sig_on_uaccess_err; 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 251 87b526d3 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2012-10-01 252 check_fault: 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 253 if (ret == -EFAULT) { 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 254 /* Bad news -- userspace fed a bad pointer to a vsyscall. */ 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 255 warn_bad_vsyscall(KERN_INFO, regs, 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 256 "vsyscall fault (exploit attempt?)"); 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 257 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 258 /* 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 259 * If we failed to generate a signal for any reason, 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 260 * generate one here. (This should be impossible.) 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 261 */ 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 262 if (WARN_ON_ONCE(!sigismember(&tsk->pending.signal, SIGBUS) && 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 263 !sigismember(&tsk->pending.signal, SIGSEGV))) 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 264 goto sigsegv; 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 265 4fc34901 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-11-07 266 return true; /* Don't emulate the ret. */ 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 267 } 8c73626a arch/x86/kernel/vsyscall_64.c John Stultz 2010-07-13 268 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 269 regs->ax = ret; 8c73626a arch/x86/kernel/vsyscall_64.c John Stultz 2010-07-13 270 5651721e arch/x86/kernel/vsyscall_64.c Will Drewry 2012-07-13 271 do_ret: 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 272 /* Emulate a ret instruction. */ 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 273 regs->ip = caller; 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 274 regs->sp += 8; 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 275 return true; c08c8205 arch/x86_64/kernel/vsyscall.c Vojtech Pavlik 2006-09-26 276 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 277 sigsegv: 5cec93c2 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-06-05 278 force_sig(SIGSEGV, current); 3ae36655 arch/x86/kernel/vsyscall_64.c Andy Lutomirski 2011-08-10 279 return true; ^1da177e arch/x86_64/kernel/vsyscall.c Linus Torvalds 2005-04-16 280 } ^1da177e arch/x86_64/kernel/vsyscall.c Linus Torvalds 2005-04-16 281 :::::: The code at line 127 was first introduced by commit :::::: 87b526d349b04c31d7b3a40b434eb3f825d22305 seccomp: Make syscall skipping and nr changes more consistent :::::: TO: Andy Lutomirski <l...@amacapital.net> :::::: CC: James Morris <james.l.mor...@oracle.com> --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
.config.gz
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