Re: [PATCH v5 5/5] powerpc/inst: Optimise copy_inst_from_kernel_nofault()
From: Christophe Leroy
Date: Tue Nov 30 2021 - 00:58:32 EST
Le 29/11/2021 à 23:55, kernel test robot a écrit :
Hi Christophe,
I love your patch! Perhaps something to improve:
[auto build test WARNING on powerpc/next]
[also build test WARNING on v5.16-rc3 next-20211129]
[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/Christophe-Leroy/powerpc-inst-Refactor-___get_user_instr/20211130-015346
base: https://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux.git next
config: powerpc-randconfig-r023-20211129 (https://download.01.org/0day-ci/archive/20211130/202111300652.0yDBNvyJ-lkp@xxxxxxxxx/config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project df08b2fe8b35cb63dfb3b49738a3494b9b4e6f8e)
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://github.com/0day-ci/linux/commit/fb7bff30cc0efc7e4df1b48bb69de1f325eee826
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Christophe-Leroy/powerpc-inst-Refactor-___get_user_instr/20211130-015346
git checkout fb7bff30cc0efc7e4df1b48bb69de1f325eee826
# save the config file to linux build tree
mkdir build_dir
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=powerpc prepare
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>
All warnings (new ones prefixed by >>):
In file included from arch/powerpc/kernel/asm-offsets.c:71:
In file included from arch/powerpc/kernel/../xmon/xmon_bpts.h:7:
arch/powerpc/include/asm/inst.h:165:20: warning: variable 'val' is uninitialized when used here [-Wuninitialized]
*inst = ppc_inst(val);
^~~
arch/powerpc/include/asm/inst.h:53:22: note: expanded from macro 'ppc_inst'
#define ppc_inst(x) (x)
^
arch/powerpc/include/asm/inst.h:155:18: note: initialize the variable 'val' to silence this warning
unsigned int val, suffix;
^
= 0
I can't understand what's wrong here.
We have
__get_kernel_nofault(&val, src, u32, Efault);
if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
__get_kernel_nofault(&suffix, src + 1, u32, Efault);
*inst = ppc_inst_prefix(val, suffix);
} else {
*inst = ppc_inst(val);
}
With
#define __get_kernel_nofault(dst, src, type, err_label) \
__get_user_size_goto(*((type *)(dst)), \
(__force type __user *)(src), sizeof(type), err_label)
And
#define __get_user_size_goto(x, ptr, size, label) \
do { \
BUILD_BUG_ON(size > sizeof(x)); \
switch (size) { \
case 1: __get_user_asm_goto(x, (u8 __user *)ptr, label, "lbz"); break; \
case 2: __get_user_asm_goto(x, (u16 __user *)ptr, label, "lhz"); break; \
case 4: __get_user_asm_goto(x, (u32 __user *)ptr, label, "lwz"); break; \
case 8: __get_user_asm2_goto(x, (u64 __user *)ptr, label); break; \
default: x = 0; BUILD_BUG(); \
} \
} while (0)
And
#define __get_user_asm_goto(x, addr, label, op) \
asm_volatile_goto( \
"1: "op"%U1%X1 %0, %1 # get_user\n" \
EX_TABLE(1b, %l2) \
: "=r" (x) \
: "m<>" (*addr) \
: \
: label)
I see no possibility, no alternative path where val wouldn't be set. The
asm clearly has *addr as an output param so it is always set.
1 warning generated.
<stdin>:1559:2: warning: syscall futex_waitv not implemented [-W#warnings]
#warning syscall futex_waitv not implemented
^
1 warning generated.
arch/powerpc/kernel/vdso32/gettimeofday.S:72:8: error: unsupported directive '.stabs'
.stabs "_restgpr_31_x:F-1",36,0,0,_restgpr_31_x; .globl _restgpr_31_x; _restgpr_31_x:
^
arch/powerpc/kernel/vdso32/gettimeofday.S:73:8: error: unsupported directive '.stabs'
.stabs "_rest32gpr_31_x:F-1",36,0,0,_rest32gpr_31_x; .globl _rest32gpr_31_x; _rest32gpr_31_x:
How should we fix that ? Will clang support .stabs in the future ?
^
make[2]: *** [arch/powerpc/kernel/vdso32/Makefile:55: arch/powerpc/kernel/vdso32/gettimeofday.o] Error 1
make[2]: Target 'include/generated/vdso32-offsets.h' not remade because of errors.
make[1]: *** [arch/powerpc/Makefile:421: vdso_prepare] Error 2
make[1]: Target 'prepare' not remade because of errors.
make: *** [Makefile:219: __sub-make] Error 2
make: Target 'prepare' not remade because of errors.
vim +/val +165 arch/powerpc/include/asm/inst.h
152
153 static inline int copy_inst_from_kernel_nofault(ppc_inst_t *inst, u32 *src)
154 {
155 unsigned int val, suffix;
156
157 if (unlikely(!is_kernel_addr((unsigned long)src)))
158 return -ERANGE;
159
160 __get_kernel_nofault(&val, src, u32, Efault);
161 if (IS_ENABLED(CONFIG_PPC64) && get_op(val) == OP_PREFIX) {
162 __get_kernel_nofault(&suffix, src + 1, u32, Efault);
163 *inst = ppc_inst_prefix(val, suffix);
164 } else {
> 165 *inst = ppc_inst(val);
166 }
167 return 0;
168 Efault:
169 return -EFAULT;
170 }
171
---
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