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Date:   Fri, 25 Dec 2020 18:50:33 +0800
From:   kernel test robot <lkp@...el.com>
To:     Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...capital.net>,
        Masami Hiramatsu <mhiramat@...nel.org>
Cc:     kbuild-all@...ts.01.org, clang-built-linux@...glegroups.com,
        X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 11/19] x86/sev-es: Convert to insn_decode()

Hi Borislav,

I love your patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v5.10 next-20201223]
[cannot apply to tip/perf/core tip/x86/core luto/next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Borislav-Petkov/x86-insn-Add-an-insn_decode-API/20201224-014846
base:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 614cb5894306cfa2c7d9b6168182876ff5948735
config: x86_64-randconfig-a016-20201223 (attached as .config)
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project cee1e7d14f4628d6174b33640d502bff3b54ae45)
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 x86_64 cross compiling tool for clang build
        # apt-get install binutils-x86-64-linux-gnu
        # https://github.com/0day-ci/linux/commit/9cc93591504c88c42ab10903fc69062fc1461ed0
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Borislav-Petkov/x86-insn-Add-an-insn_decode-API/20201224-014846
        git checkout 9cc93591504c88c42ab10903fc69062fc1461ed0
        # save the attached .config to linux build tree
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@...el.com>

All warnings (new ones prefixed by >>):

>> arch/x86/kernel/sev-es.c:258:7: warning: variable 'ret' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
                   if (!insn_decode_regs(&ctxt->insn, ctxt->regs, buffer, res))
                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/x86/kernel/sev-es.c:272:6: note: uninitialized use occurs here
           if (ret < 0)
               ^~~
   arch/x86/kernel/sev-es.c:258:3: note: remove the 'if' if its condition is always true
                   if (!insn_decode_regs(&ctxt->insn, ctxt->regs, buffer, res))
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   arch/x86/kernel/sev-es.c:247:14: note: initialize the variable 'ret' to silence this warning
           int res, ret;
                       ^
                        = 0
   1 warning generated.


vim +258 arch/x86/kernel/sev-es.c

f980f9c31a923e9 Joerg Roedel    2020-09-07  243  
f980f9c31a923e9 Joerg Roedel    2020-09-07  244  static enum es_result vc_decode_insn(struct es_em_ctxt *ctxt)
f980f9c31a923e9 Joerg Roedel    2020-09-07  245  {
f980f9c31a923e9 Joerg Roedel    2020-09-07  246  	char buffer[MAX_INSN_SIZE];
9cc93591504c88c Borislav Petkov 2020-12-23  247  	int res, ret;
f980f9c31a923e9 Joerg Roedel    2020-09-07  248  
5e3427a7bc432ed Joerg Roedel    2020-09-07  249  	if (user_mode(ctxt->regs)) {
5e3427a7bc432ed Joerg Roedel    2020-09-07  250  		res = insn_fetch_from_user(ctxt->regs, buffer);
5e3427a7bc432ed Joerg Roedel    2020-09-07  251  		if (!res) {
5e3427a7bc432ed Joerg Roedel    2020-09-07  252  			ctxt->fi.vector     = X86_TRAP_PF;
5e3427a7bc432ed Joerg Roedel    2020-09-07  253  			ctxt->fi.error_code = X86_PF_INSTR | X86_PF_USER;
5e3427a7bc432ed Joerg Roedel    2020-09-07  254  			ctxt->fi.cr2        = ctxt->regs->ip;
5e3427a7bc432ed Joerg Roedel    2020-09-07  255  			return ES_EXCEPTION;
5e3427a7bc432ed Joerg Roedel    2020-09-07  256  		}
5e3427a7bc432ed Joerg Roedel    2020-09-07  257  
63d702bf108e3ad Borislav Petkov 2020-12-23 @258  		if (!insn_decode_regs(&ctxt->insn, ctxt->regs, buffer, res))
5e3427a7bc432ed Joerg Roedel    2020-09-07  259  			return ES_DECODE_FAILED;
5e3427a7bc432ed Joerg Roedel    2020-09-07  260  	} else {
f980f9c31a923e9 Joerg Roedel    2020-09-07  261  		res = vc_fetch_insn_kernel(ctxt, buffer);
5e3427a7bc432ed Joerg Roedel    2020-09-07  262  		if (res) {
f980f9c31a923e9 Joerg Roedel    2020-09-07  263  			ctxt->fi.vector     = X86_TRAP_PF;
5e3427a7bc432ed Joerg Roedel    2020-09-07  264  			ctxt->fi.error_code = X86_PF_INSTR;
f980f9c31a923e9 Joerg Roedel    2020-09-07  265  			ctxt->fi.cr2        = ctxt->regs->ip;
f980f9c31a923e9 Joerg Roedel    2020-09-07  266  			return ES_EXCEPTION;
f980f9c31a923e9 Joerg Roedel    2020-09-07  267  		}
f980f9c31a923e9 Joerg Roedel    2020-09-07  268  
9cc93591504c88c Borislav Petkov 2020-12-23  269  		ret = insn_decode(&ctxt->insn, buffer, MAX_INSN_SIZE - res, INSN_MODE_64);
5e3427a7bc432ed Joerg Roedel    2020-09-07  270  	}
f980f9c31a923e9 Joerg Roedel    2020-09-07  271  
9cc93591504c88c Borislav Petkov 2020-12-23  272  	if (ret < 0)
9cc93591504c88c Borislav Petkov 2020-12-23  273  		return ES_DECODE_FAILED;
9cc93591504c88c Borislav Petkov 2020-12-23  274  	else
9cc93591504c88c Borislav Petkov 2020-12-23  275  		return ES_OK;
f980f9c31a923e9 Joerg Roedel    2020-09-07  276  }
f980f9c31a923e9 Joerg Roedel    2020-09-07  277  

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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