* 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
* 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
@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
@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}}
(@pxref{PopSection}).
This directive swaps the current section (and subsection) with most recently
-referenced section (and subsection) prior to this one. Multiple
+referenced section/subsection pair prior to this one. Multiple
@code{.previous} directives in a row will flip between two sections (and their
-subsections).
+subsections). For example:
+
+@smallexample
+.section A
+ .subsection 1
+ .word 0x1234
+ .subsection 2
+ .word 0x5678
+.previous
+ .word 0x9abc
+@end smallexample
+
+Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
+section A. Whilst:
+
+@smallexample
+.section A
+.subsection 1
+ # Now in section A subsection 1
+ .word 0x1234
+.section B
+.subsection 0
+ # Now in section B subsection 0
+ .word 0x5678
+.subsection 1
+ # Now in section B subsection 1
+ .word 0x9abc
+.previous
+ # Now in section B subsection 0
+ .word 0xdef0
+@end smallexample
+
+Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
+section B and 0x9abc into subsection 1 of section B.
In terms of the section stack, this directive swaps the current section with
the top section on the section stack.
The syntaxes supported are:
@smallexample
- .type <name> STT_FUNCTION
- .type <name> STT_OBJECT
+ .type <name> STT_<TYPE_IN_UPPER_CASE>
+ .type <name>,#<type>
+ .type <name>,@@<type>
+ .type <name>,%>type>
+ .type <name>,"<type>"
+@end smallexample
- .type <name>,#function
- .type <name>,#object
+The types supported are:
- .type <name>,@@function
- .type <name>,@@object
+@table @gcctabopt
+@item STT_FUNC
+@itemx function
+Mark the symbol as being a function name.
+
+@item STT_OBJECT
+@itemx object
+Mark the symbol as being a data object.
+
+@item STT_TLS
+@itemx tls_object
+Mark the symbol as being a thead-local data object.
+
+@item STT_COMMON
+@itemx common
+Mark the symbol as being a common data object.
+@end table
+
+Note: Some targets support extra types in addition to those listed above.
- .type <name>,%function
- .type <name>,%object
-
- .type <name>,"function"
- .type <name>,"object"
-@end smallexample
@end ifset
@end ifset
@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
projects / deliverable / binutils-gdb.git / blobdiff