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score: Clarify TLS support

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This commit is contained in:
Sebastian Huber
2014-04-17 07:57:09 +02:00
parent 10e613ba52
commit 320faf8e68
6 changed files with 26 additions and 7 deletions
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21
doc/cpu_supplement/general.t
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@@ -319,7 +319,26 @@ operations of the default CPU specific fatal error handler.
In order to support thread-local storage (TLS) the CPU port must implement the
facilities mandated by the application binary interface (ABI) of the CPU
architecture. The CPU port must initialize the TLS area in the
@code{_CPU_Context_Initialize} function.
@code{_CPU_Context_Initialize()} function. There are support functions available
via @code{#include <rtems/score/tls.h>} which implement Variants I and II
according to Ulrich Drepper, @cite{ELF Handling For Thread-Local Storage}.
@table @code
@item _TLS_TCB_at_area_begin_initialize()
Uses Variant I, TLS offsets emitted by linker takes the TCB into account. For
a reference implementation see @file{cpukit/score/cpu/arm/cpu.c}.
@item _TLS_TCB_before_TLS_block_initialize()
Uses Variant I, TLS offsets emitted by linker neglects the TCB. For a
reference implementation see
@file{c/src/lib/libcpu/powerpc/new-exceptions/cpu.c}.
@item _TLS_TCB_after_TLS_block_initialize()
Uses Variant II. For a reference implementation see
@file{cpukit/score/cpu/sparc/cpu.c}.
@end table
The board support package (BSP) must provide the following sections and symbols
in its linker command file: