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| -rw-r--r-- | gas/ChangeLog | 6 | ||||
| -rw-r--r-- | gas/doc/as.texinfo | 148 |
2 files changed, 151 insertions, 3 deletions
diff --git a/gas/ChangeLog b/gas/ChangeLog index 26bcf58..688bc94 100644 --- a/gas/ChangeLog +++ b/gas/ChangeLog @@ -1,3 +1,9 @@ +2007-10-12 Daniel Jacobowitz <dan@codesourcery.com> + + * doc/as.texinfo (Object Attributes): New chapter. + (Pseudo Ops): Document .gnu_attribute. + (LNS directives): Correct .loc_mark_labels documentation. + 2007-10-11 Nick Clifton <nickc@redhat.com> * config/obj-elf.c (obj_elf_section): When pushing a section, if diff --git a/gas/doc/as.texinfo b/gas/doc/as.texinfo index ed12baf..64ce6a1 100644 --- a/gas/doc/as.texinfo +++ b/gas/doc/as.texinfo @@ -189,6 +189,9 @@ section entitled ``GNU Free Documentation License''. * Symbols:: Symbols * Expressions:: Expressions * Pseudo Ops:: Assembler Directives +@ifset ELF +* Object Attributes:: Object Attributes +@end ifset * Machine Dependencies:: Machine Dependent Features * Reporting Bugs:: Reporting Bugs * Acknowledgements:: Who Did What @@ -3828,6 +3831,7 @@ Some machine configurations provide additional directives. * Func:: @code{.func} * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}} @ifset ELF +* Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}} * Hidden:: @code{.hidden @var{names}} @end ifset @@ -4254,9 +4258,9 @@ state machine to @var{value}, which must be an unsigned integer. @end table -@section @code{.loc_mark_blocks @var{enable}} -@cindex @code{loc_mark_blocks} directive -The @code{.loc_mark_blocks} directive makes the assembler emit an entry +@section @code{.loc_mark_labels @var{enable}} +@cindex @code{loc_mark_labels} directive +The @code{.loc_mark_labels} directive makes the assembler emit an entry to the @code{.debug_line} line number matrix with the @code{basic_block} register in the state machine set whenever a code label is seen. The @var{enable} argument should be either 1 or 0, to enable or disable @@ -4582,6 +4586,10 @@ partial programs. You may need the HPPA-only @code{.EXPORT} directive as well. @end ifset @ifset ELF +@node Gnu_attribute +@section @code{.gnu_attribute @var{tag},@var{value}} +Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}. + @node Hidden @section @code{.hidden @var{names}} @@ -6393,6 +6401,140 @@ They are included for compatibility with older assemblers. @item .line @end table +@ifset ELF +@node Object Attributes +@chapter Object Attributes +@cindex object attributes + +@command{@value{AS}} assembles source files written for a specific architecture +into object files for that architecture. But not all object files are alike. +Many architectures support incompatible variations. For instance, floating +point arguments might be passed in floating point registers if the object file +requires hardware floating point support---or floating point arguments might be +passed in integer registers if the object file supports processors with no +hardware floating point unit. Or, if two objects are built for different +generations of the same architecture, the combination may require the +newer generation at run-time. + +This information is useful during and after linking. At link time, +@command{@value{LD}} can warn about incompatible object files. After link +time, tools like @command{gdb} can use it to process the linked file +correctly. + +Compatibility information is recorded as a series of object attributes. Each +attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a +string, and indicates who sets the meaning of the tag. The tag is an integer, +and indicates what property the attribute describes. The value may be a string +or an integer, and indicates how the property affects this object. Missing +attributes are the same as attributes with a zero value or empty string value. + +Object attributes were developed as part of the ABI for the ARM Architecture. +The file format is documented in @cite{ELF for the ARM Architecture}. + +@menu +* GNU Object Attributes:: @sc{gnu} Object Attributes +* Defining New Object Attributes:: Defining New Object Attributes +@end menu + +@node GNU Object Attributes +@section @sc{gnu} Object Attributes + +The @code{.gnu_attribute} directive records an object attribute +with vendor @samp{gnu}. + +Except for @samp{Tag_compatibility}, which has both an integer and a string for +its value, @sc{gnu} attributes have a string value if the tag number is odd and +an integer value if the tag number is even. The second bit (@code{@var{tag} & +2} is set for architecture-independent attributes and clear for +architecture-dependent ones. + +@subsection Common @sc{gnu} attributes + +These attributes are valid on all architectures. + +@table @r +@item Tag_compatibility (32) +The compatibility attribute takes an integer flag value and a vendor name. If +the flag value is 0, the file is compatible with other toolchains. If it is 1, +then the file is only compatible with the named toolchain. If it is greater +than 1, the file can only be processed by other toolchains under some private +arrangement indicated by the flag value and the vendor name. +@end table + +@subsection MIPS Attributes + +@table @r +@item Tag_GNU_MIPS_ABI_FP (4) +The floating-point ABI used by this object file. The value will be: + +@itemize @bullet +@item +0 for files not affected by the floating-point ABI. +@item +1 for files using the hardware floating-point with a standard double-precision +FPU. +@item +2 for files using the hardware floating-point ABI with a single-precision FPU. +@item +3 for files using the software floating-point ABI. +@end itemize +@end table + +@subsection PowerPC Attributes + +@table @r +@item Tag_GNU_Power_ABI_FP (4) +The floating-point ABI used by this object file. The value will be: + +@itemize @bullet +@item +0 for files not affected by the floating-point ABI. +@item +1 for files using the hardware floating-point ABI. +@item +2 for files using the software floating-point ABI. +@end itemize + +@item Tag_GNU_Power_ABI_Vector (8) +The vector ABI used by this object file. The value will be: + +@itemize @bullet +@item +0 for files not affected by the vector ABI. +@item +1 for files using general purpose registers to pass vectors. +@item +2 for files using AltiVec registers to pass vectors. +@item +3 for files using SPE registers to pass vectors. +@end itemize +@end table + +@node Defining New Object Attributes +@section Defining New Object Attributes + +If you want to define a new @sc{gnu} object attribute, here are the places you +will need to modify. New attributes should be discussed on the @samp{binutils} +mailing list. + +@itemize @bullet +@item +This manual, which is the official register of attributes. +@item +The header for your architecture @file{include/elf}, to define the tag. +@item +The @file{bfd} support file for your architecture, to merge the attribute +and issue any appropriate link warnings. +@item +Test cases in @file{ld/testsuite} for merging and link warnings. +@item +@file{binutils/readelf.c} to display your attribute. +@item +GCC, if you want the compiler to mark the attribute automatically. +@end itemize + +@end ifset + @ifset GENERIC @node Machine Dependencies @chapter Machine Dependent Features |