Messages in this thread | | | Subject | Re: arch/powerpc/kernel/signal_32.c:297:2: warning: Value stored to 'msr' is never read [clang-analyzer-deadcode.DeadStores] | From | Christophe Leroy <> | Date | Mon, 23 Aug 2021 16:35:18 +0200 |
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Le 23/08/2021 à 12:59, kernel test robot a écrit : > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master > head: e22ce8eb631bdc47a4a4ea7ecf4e4ba499db4f93 > commit: ef75e73182949a94bde169a774de1b62ae21fbbc powerpc/signal32: Transform save_user_regs() and save_tm_user_regs() in 'unsafe' version > date: 9 months ago > config: powerpc-randconfig-c003-20210821 (attached as .config) > compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project d9c5613e856cf2addfbf892fc4c1ce9ef9feceaa) > reproduce (this is a W=1 build): > wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross > chmod +x ~/bin/make.cross > # install powerpc cross compiling tool for clang build > # apt-get install binutils-powerpc-linux-gnu > # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ef75e73182949a94bde169a774de1b62ae21fbbc > git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > git fetch --no-tags linus master > git checkout ef75e73182949a94bde169a774de1b62ae21fbbc > # save the attached .config to linux build tree > COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=powerpc clang-analyzer > > If you fix the issue, kindly add following tag as appropriate > Reported-by: kernel test robot <lkp@intel.com> > > > clang-analyzer warnings: (new ones prefixed by >>) > ^ >>> arch/powerpc/kernel/signal_32.c:297:2: warning: Value stored to 'msr' is never read [clang-analyzer-deadcode.DeadStores] > msr &= ~MSR_VSX; > ^ ~~~~~~~~ > arch/powerpc/kernel/signal_32.c:297:2: note: Value stored to 'msr' is never read > msr &= ~MSR_VSX; > ^ ~~~~~~~~
This is wrong.
msr is used at line 326:
ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 326 unsafe_put_user(msr, &frame->mc_gregs[PT_MSR], failed);
> arch/powerpc/kernel/signal_32.c:765:16: warning: Value stored to 'msr' during its initialization is never read [clang-analyzer-deadcode.DeadStores] > unsigned long msr = regs->msr; > ^~~ ~~~~~~~~~ > arch/powerpc/kernel/signal_32.c:765:16: note: Value stored to 'msr' during its initialization is never read > unsigned long msr = regs->msr; > ^~~ ~~~~~~~~~ > arch/powerpc/kernel/signal_32.c:869:16: warning: Value stored to 'msr' during its initialization is never read [clang-analyzer-deadcode.DeadStores] > unsigned long msr = regs->msr; > ^~~ ~~~~~~~~~ > arch/powerpc/kernel/signal_32.c:869:16: note: Value stored to 'msr' during its initialization is never read > unsigned long msr = regs->msr; > ^~~ ~~~~~~~~~ > > vim +/msr +297 arch/powerpc/kernel/signal_32.c > > 968c4fccd1bb8b arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 262 > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 263 static int save_user_regs_unsafe(struct pt_regs *regs, struct mcontext __user *frame, > 8d33001dd650b8 arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 264 struct mcontext __user *tm_frame, int ctx_has_vsx_region) > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 265 { > 9e7511861c4f8d arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 266 unsigned long msr = regs->msr; > 9e7511861c4f8d arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 267 > c6e6771b87d4e3 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 268 /* save general registers */ > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 269 unsafe_save_general_regs(regs, frame, failed); > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 270 > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 271 #ifdef CONFIG_ALTIVEC > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 272 /* save altivec registers */ > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 273 if (current->thread.used_vr) { > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 274 unsafe_copy_to_user(&frame->mc_vregs, ¤t->thread.vr_state, > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 275 ELF_NVRREG * sizeof(vector128), failed); > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 276 /* set MSR_VEC in the saved MSR value to indicate that > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 277 frame->mc_vregs contains valid data */ > 9e7511861c4f8d arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 278 msr |= MSR_VEC; > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 279 } > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 280 /* else assert((regs->msr & MSR_VEC) == 0) */ > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 281 > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 282 /* We always copy to/from vrsave, it's 0 if we don't have or don't > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 283 * use altivec. Since VSCR only contains 32 bits saved in the least > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 284 * significant bits of a vector, we "cheat" and stuff VRSAVE in the > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 285 * most significant bits of that same vector. --BenH > 408a7e08b2112f arch/powerpc/kernel/signal_32.c Paul Mackerras 2013-08-05 286 * Note that the current VRSAVE value is in the SPR at this point. > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 287 */ > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 288 unsafe_put_user(current->thread.vrsave, (u32 __user *)&frame->mc_vregs[32], > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 289 failed); > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 290 #endif /* CONFIG_ALTIVEC */ > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 291 unsafe_copy_fpr_to_user(&frame->mc_fregs, current, failed); > ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling 2013-11-25 292 > ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling 2013-11-25 293 /* > ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling 2013-11-25 294 * Clear the MSR VSX bit to indicate there is no valid state attached > ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling 2013-11-25 295 * to this context, except in the specific case below where we set it. > ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling 2013-11-25 296 */ > ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling 2013-11-25 @297 msr &= ~MSR_VSX; > 6a274c08f2f4df arch/powerpc/kernel/signal_32.c Michael Neuling 2008-07-02 298 #ifdef CONFIG_VSX > ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 299 /* > ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 300 * Copy VSR 0-31 upper half from thread_struct to local > ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 301 * buffer, then write that to userspace. Also set MSR_VSX in > ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 302 * the saved MSR value to indicate that frame->mc_vregs > ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 303 * contains valid data > ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 304 */ > 16c29d180becc5 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-10-23 305 if (current->thread.used_vsr && ctx_has_vsx_region) { > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 306 unsafe_copy_vsx_to_user(&frame->mc_vsregs, current, failed); > ce48b2100785e5 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 307 msr |= MSR_VSX; > ec67ad82814bee arch/powerpc/kernel/signal_32.c Michael Neuling 2013-11-25 308 } > c6e6771b87d4e3 arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 309 #endif /* CONFIG_VSX */ > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 310 #ifdef CONFIG_SPE > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 311 /* save spe registers */ > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 312 if (current->thread.used_spe) { > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 313 unsafe_copy_to_user(&frame->mc_vregs, current->thread.evr, > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 314 ELF_NEVRREG * sizeof(u32), failed); > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 315 /* set MSR_SPE in the saved MSR value to indicate that > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 316 frame->mc_vregs contains valid data */ > 9e7511861c4f8d arch/powerpc/kernel/signal_32.c Michael Neuling 2008-06-25 317 msr |= MSR_SPE; > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 318 } > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 319 /* else assert((regs->msr & MSR_SPE) == 0) */ > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 320 > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 321 /* We always copy to/from spefscr */ > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 322 unsafe_put_user(current->thread.spefscr, > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 323 (u32 __user *)&frame->mc_vregs + ELF_NEVRREG, failed); > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 324 #endif /* CONFIG_SPE */ > 81e7009ea46c95 arch/powerpc/kernel/signal_32.c Stephen Rothwell 2005-10-18 325 > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 326 unsafe_put_user(msr, &frame->mc_gregs[PT_MSR], failed); > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 327 > 1d25f11fdbcc53 arch/powerpc/kernel/signal_32.c Michael Neuling 2013-06-09 328 /* We need to write 0 the MSR top 32 bits in the tm frame so that we > 1d25f11fdbcc53 arch/powerpc/kernel/signal_32.c Michael Neuling 2013-06-09 329 * can check it on the restore to see if TM is active > 1d25f11fdbcc53 arch/powerpc/kernel/signal_32.c Michael Neuling 2013-06-09 330 */ > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 331 if (tm_frame) > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 332 unsafe_put_user(0, &tm_frame->mc_gregs[PT_MSR], failed); > 1d25f11fdbcc53 arch/powerpc/kernel/signal_32.c Michael Neuling 2013-06-09 333 > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 334 return 0; > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 335 > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 336 failed: > ef75e73182949a arch/powerpc/kernel/signal_32.c Christophe Leroy 2020-08-18 337 return 1; > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 338 } > ^1da177e4c3f41 arch/ppc64/kernel/signal32.c Linus Torvalds 2005-04-16 339 > > :::::: The code at line 297 was first introduced by commit > :::::: ec67ad82814bee92251fd963bf01c7a173856555 powerpc/signals: Improved mark VSX not saved with small contexts fix > > :::::: TO: Michael Neuling <mikey@neuling.org> > :::::: CC: Benjamin Herrenschmidt <benh@kernel.crashing.org> > > --- > 0-DAY CI Kernel Test Service, Intel Corporation > https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org >
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