ck_pr: fix ptr output operand widths on x86 and x86_64 #175
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Operations on a variable of type "ptr" specify that the output operand can be a memory address. Most such operations specify that the output operand is of type char, so it has width 1. Convert these to uint64_t on x86_64 and uint32_t on x86. No functional change intended. With clang 12.0.1 there is no difference in the generated code before and after this change. The compiler needs to know the true width of the destination operand in some cases. In particular, when compiling with LLVM's MemorySanitizer enabled, the generated code updates shadow state to mark variables as initialized (or not) at byte granularity. When instrumenting inline assembly, the compiler uses the width of the output operand(s) to figure out how many bytes of shadow state to update. When the output operand is cast to char, the runtime would only update one byte of shadow state even though the store modified eight bytes of memory. This led to false positives when enabling MSAN in the FreeBSD kernel.
markjdb
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This does not appear to change generated code with the default toolchain. However, KMSAN makes use of output operand specifications to instrument inline asm, and with incorrect specifications we get false positives in code that uses the CK_(S)LIST macros. This was submitted upstream: concurrencykit/ck#175 The commit applies the same change locally to make KMSAN usable until something equivalent is merged upstream. MFC after: 1 week Sponsored by: The FreeBSD Foundation
freebsd-git
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Aug 11, 2021
This does not appear to change generated code with the default toolchain. However, KMSAN makes use of output operand specifications to instrument inline asm, and with incorrect specifications we get false positives in code that uses the CK_(S)LIST macros. This was submitted upstream: concurrencykit/ck#175 The commit applies the same change locally to make KMSAN usable until something equivalent is merged upstream. MFC after: 1 week Sponsored by: The FreeBSD Foundation
kev009
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Aug 11, 2021
agrajag9
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Aug 13, 2021
This does not appear to change generated code with the default toolchain. However, KMSAN makes use of output operand specifications to instrument inline asm, and with incorrect specifications we get false positives in code that uses the CK_(S)LIST macros. This was submitted upstream: concurrencykit/ck#175 The commit applies the same change locally to make KMSAN usable until something equivalent is merged upstream. MFC after: 1 week Sponsored by: The FreeBSD Foundation
bsdjhb
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Dec 23, 2021
This does not appear to change generated code with the default toolchain. However, KMSAN makes use of output operand specifications to instrument inline asm, and with incorrect specifications we get false positives in code that uses the CK_(S)LIST macros. This was submitted upstream: concurrencykit/ck#175 The commit applies the same change locally to make KMSAN usable until something equivalent is merged upstream. MFC after: 1 week Sponsored by: The FreeBSD Foundation
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Operations on a variable of type "ptr" specify that the output operand
can be a memory address. Most such operations specify that the output
operand is of type char, so it has width 1. Convert these to uint64_t
on x86_64 and uint32_t on x86.
No functional change intended. With clang 12.0.1 there is no difference
in the generated code before and after this change.
The compiler needs to know the true width of the destination operand in
some cases. In particular, when compiling with LLVM's MemorySanitizer
enabled, the generated code updates shadow state to mark variables as
initialized (or not) at byte granularity. When instrumenting inline
assembly, the compiler uses the width of the output operand(s) to figure
out how many bytes of shadow state to update. When the output operand
is cast to char, the runtime would only update one byte of shadow state
even though the store modified eight bytes of memory. This led to false
positives when enabling MSAN in the FreeBSD kernel.