'Oleksandr Natalenko' via OSS Drivers writes:
> Hi.
>
> Obligatory disclaimer: building the kernel with -O3 is a non-standard
> thing done via this patch [1], but I've asked people in #kernelnewbies,
> and it was suggested that the issue should be still investigated.
>
> So, with v5.1 kernel release I cannot build the kernel with -O3 anymore.
> It fails as shown below:
I guess it's because constant prop. Could you try the following change to
__emit_shift?
drivers/net/ethernet/netronome/nfp/bpf/jit.c
__emit_shift:331
- if (sc == SHF_SC_L_SHF)
+ if (sc == SHF_SC_L_SHF && shift)
shift = 32 - shift;
emit_shf_indir is passing "0" as shift to __emit_shift which will
eventually be turned into 32 and it was OK because we truncate to 5-bit,
but before truncation, it will overflow the shift mask.
Regards,
Jiong
>
> ===
> CC drivers/net/ethernet/netronome/nfp/bpf/jit.o
> In file included from ./include/asm-generic/bug.h:5,
> from ./arch/x86/include/asm/bug.h:83,
> from ./include/linux/bug.h:5,
> from drivers/net/ethernet/netronome/nfp/bpf/jit.c:6:
> In function ‘__emit_shf’,
> inlined from ‘emit_shf.constprop’ at
> drivers/net/ethernet/netronome/nfp/bpf/jit.c:364:2,
> inlined from ‘shl_reg64_lt32_low’ at
> drivers/net/ethernet/netronome/nfp/bpf/jit.c:379:2,
> inlined from ‘shl_reg’ at
> drivers/net/ethernet/netronome/nfp/bpf/jit.c:2506:2:
> ./include/linux/compiler.h:344:38: error: call to
> ‘__compiletime_assert_341’ declared with attribute error: BUILD_BUG_ON
> failed: (((0x001f0000000ULL) + (1ULL <<
> (__builtin_ffsll(0x001f0000000ULL) - 1))) & (((0x001f0000000ULL) + (1ULL
> << (__builtin_ffsll(0x001f0000000ULL) - 1))) - 1)) != 0
> _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
> ^
> ./include/linux/compiler.h:325:4: note: in definition of macro
> ‘__compiletime_assert’
> prefix ## suffix(); \
> ^~~~~~
> ./include/linux/compiler.h:344:2: note: in expansion of macro
> ‘_compiletime_assert’
> _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
> ^~~~~~~~~~~~~~~~~~~
> ./include/linux/build_bug.h:39:37: note: in expansion of macro
> ‘compiletime_assert’
> #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> ^~~~~~~~~~~~~~~~~~
> ./include/linux/bitfield.h:57:3: note: in expansion of macro
> ‘BUILD_BUG_ON_MSG’
> BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \
> ^~~~~~~~~~~~~~~~
> ./include/linux/bitfield.h:89:3: note: in expansion of macro
> ‘__BF_FIELD_CHECK’
> __BF_FIELD_CHECK(_mask, 0ULL, _val, "FIELD_PREP: "); \
> ^~~~~~~~~~~~~~~~
> drivers/net/ethernet/netronome/nfp/bpf/jit.c:341:3: note: in expansion
> of macro ‘FIELD_PREP’
> FIELD_PREP(OP_SHF_SHIFT, shift) |
> ^~~~~~~~~~
> make[1]: *** [scripts/Makefile.build:276:
> drivers/net/ethernet/netronome/nfp/bpf/jit.o] Error 1
> make: *** [Makefile:1726: drivers/net/ethernet/netronome/nfp/bpf/jit.o]
> Error 2
> ===
>
> Needless to say, with -O2 this file is built just fine. My compiler is:
>
> ===
> $ gcc --version
> gcc (GCC) 8.3.0
> Copyright (C) 2018 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions. There is
> NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
> PURPOSE.
> ===
>
> I had no issues with -O3 before, so, maybe, this deserves a peek.
>
> I'm open to testing patches and providing more info if needed.
>
> Thanks.
>
> [1]
> https://gitlab.com/post-factum/pf-kernel/commit/7fef93015ff1776d08119ef3d057a9e9433954a9
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