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Release Notes for DTrace 2.0.0 1.7
Seventh errata of the standalone userspace implementation.
This is a pre-release with limited functionality.
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Argumsnts passed for SDT probes can now be retrieved using the arg0 through arg9 builtin variables.
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A -xbpflog option has been added to request the BPF verifier log to be generated and displayed regardles sf the outcome of trying to load BPF programs. The option can also be set with a D option pragma.
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The strjoin() subroutine has been implemented.
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The substr() subroutine has been implemented.
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Trampoline generation has been corrected to ensure that the correct probe context is set during code generation.
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The type alignment handling code used to determine the alilgnment size for a given datatype was treating enums as integers, which is incorrect. Proper alignment determination is now done, avoiding libctf-related failures.
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The handling of ERROR probe invocations within the BEGIN probe execution has been fixed.
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The size of string data in the trace output buffer has been corrected to acocunt for the 2-byte length prefix and the terminating NUL byte.
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The data size for value copy operations has been corrected. It was determined solely on the data size of the source data, even if the destination was smaller. It now uses the lesser of the two sizes.
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Provider implemenations now use standard functions to clear oe copy the CPU register state at the time a probe fires.
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New macros set_upper_bound() and set_lower_bound() are available for use in C-to-BPF source code. They are used to provide hints about value and range boundaries for the BPF verifier.
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Precopiled BPF code can now use the STRSZ BPF symbol to represent the maximum string size.
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The precompiled dt_memcpy() function has been replaced with a call to the bpf_probe_read() BPF helper function.
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Support has been added for the compilation of BPF assembler source files (.S) into object files (.o). This feature makes uses of the GCC BPF cross compiler.
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The generic scratch memory area is now accessible through a pointer to its base address. This pointer can be found in dctx->mem. The stack trace implementation has been updated to make use of this area. This scratch memory area is also used to provide temporary string space to be used in string manipulation functions.
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The length prefix for strings has been changed from a variable-length integer to a 2-byte fixed width integer. This was made necessay due to BPF verifier limitations. This is an interim solution while a more permanent reworking of the string handling code is dveloped.