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b5fa0f7f88
Anton says: In commit 4db7327194db ("powerpc: Add option to use jump
label for cpu_has_feature()") and commit c12e6f24d413 ("powerpc: Add
option to use jump label for mmu_has_feature()") we added:
BUILD_BUG_ON(!__builtin_constant_p(feature))
to cpu_has_feature() and mmu_has_feature() in order to catch usage
issues (such as cpu_has_feature(cpu_has_feature(X), which has happened
once in the past). Unfortunately LLVM isn't smart enough to resolve
this, and it errors out.
I work around it in my clang/LLVM builds of the kernel, but I have just
discovered that it causes a lot of issues for the bcc (eBPF) trace tool
(which uses LLVM).
For now just #ifdef it away for clang builds.
Fixes: 4db7327194db ("powerpc: Add option to use jump label for cpu_has_feature()")
Fixes: c12e6f24d413 ("powerpc: Add option to use jump label for mmu_has_feature()")
Cc: stable@vger.kernel.org # v4.8+
Reported-by: Anton Blanchard <anton@samba.org>
Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
56 lines
1.2 KiB
C
56 lines
1.2 KiB
C
#ifndef __ASM_POWERPC_CPUFEATURES_H
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#define __ASM_POWERPC_CPUFEATURES_H
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#ifndef __ASSEMBLY__
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#include <linux/bug.h>
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#include <asm/cputable.h>
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static inline bool early_cpu_has_feature(unsigned long feature)
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{
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return !!((CPU_FTRS_ALWAYS & feature) ||
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(CPU_FTRS_POSSIBLE & cur_cpu_spec->cpu_features & feature));
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}
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#ifdef CONFIG_JUMP_LABEL_FEATURE_CHECKS
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#include <linux/jump_label.h>
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#define NUM_CPU_FTR_KEYS BITS_PER_LONG
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extern struct static_key_true cpu_feature_keys[NUM_CPU_FTR_KEYS];
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static __always_inline bool cpu_has_feature(unsigned long feature)
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{
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int i;
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#ifndef __clang__ /* clang can't cope with this */
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BUILD_BUG_ON(!__builtin_constant_p(feature));
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#endif
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#ifdef CONFIG_JUMP_LABEL_FEATURE_CHECK_DEBUG
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if (!static_key_initialized) {
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printk("Warning! cpu_has_feature() used prior to jump label init!\n");
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dump_stack();
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return early_cpu_has_feature(feature);
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}
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#endif
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if (CPU_FTRS_ALWAYS & feature)
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return true;
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if (!(CPU_FTRS_POSSIBLE & feature))
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return false;
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i = __builtin_ctzl(feature);
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return static_branch_likely(&cpu_feature_keys[i]);
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}
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#else
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static inline bool cpu_has_feature(unsigned long feature)
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{
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return early_cpu_has_feature(feature);
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}
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#endif
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_POWERPC_CPUFEATURE_H */
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