NPTL - Revision history

Cltang: /* ELF Definitions */

2011-12-19T11:13:52Z

‎ELF Definitions

Joseph Myers: Revert spam.

2010-02-18T21:38:56Z

Revert spam.

Joseph Myers: /* Design Choices */ Correct description to detail TLS variant that was actually used.

2007-11-22T15:07:00Z

‎Design Choices: Correct description to detail TLS variant that was actually used.

Drow: /* Status */

2007-10-03T13:05:39Z

‎Status

Drow: /* Authors */

2007-10-03T13:05:04Z

‎Authors

Joseph Myers: Note debug info change in history.

2007-10-03T00:28:23Z

Note debug info change in history.

Joseph Myers: Describe use of relocations for debug info - see http://www.codesourcery.com/archives/mips-tls/msg00051.html

2007-10-03T00:26:52Z

Describe use of relocations for debug info - see http://www.codesourcery.com/archives/mips-tls/msg00051.html

Joseph Myers: Describe changes to relocations made in the course of inclusion in GNU binutils - see http://sourceware.org/ml/binutils/2005-02/msg00108.html and thread.

2007-10-03T00:12:32Z

Describe changes to relocations made in the course of inclusion in GNU binutils - see http://sourceware.org/ml/binutils/2005-02/msg00108.html and thread.

Show changes

Joseph Myers: Fix typos.

2007-10-02T23:50:37Z

Fix typos.

Joseph Myers: Update to mention $3 fast-path decision from 2005 - see http://www.codesourcery.com/archives/mips-tls/msg00050.html and http://gcc.gnu.org/ml/gcc-patches/2005-03/msg00925.html

2007-10-02T23:49:19Z

Update to mention $3 fast-path decision from 2005 - see http://www.codesourcery.com/archives/mips-tls/msg00050.html and http://gcc.gnu.org/ml/gcc-patches/2005-03/msg00925.html

@@ Line 308: / Line 308: @@
      #define R_MIPS_TLS_TPREL_HI16       49
      #define R_MIPS_TLS_TPREL_LO16       50
 == History ==

@@ Line 9: / Line 9: @@
 relocations that must be generated by the assembler, and the processing
 that must be performed by the linker.
-−
-−
 == Design Choices ==

@@ Line 15: / Line 15: @@
 * There are no available hardware registers to designate as the thread register.
 Therefore, kernel magic will be used to make the thread pointer available to userspace. The mechanism for obtaining the thread pointer will be encapsulated in the <code>__tls_get_addr</code> function.  For the Initial Exec and Local Exec models, a <code>rdhwr</code> instruction will be used, and this will be emulated by the kernel as necessary.
-* Use TLS Variant II (in which the TLS data areas precede the TCB in memory).
+* Use TLS Variant I (in which the TLS data areas follow the TCB in memory).
-As noted in Drepper's paper, this design permits the compiler to generate efficient code for the case that the main executable accesses TLS variables from the executable itself.
+* The thread pointer is offset by 0x7000 from the start of the TLS data areas for modules loaded at startup, and the DTP for a module is offset by 0x8000 from the start of the TLS data area for that module.  The use of these offsets, taken from Power, makes more data accessible with signed 16-bit offsets.
 * The <code>__tls_get_addr</code> function has the prototype:

@@ Line 1: / Line 1: @@
 == Status ==
-Currently NPTL for Linux/MIPS is work in progress.  Ulrich Drepper's [http://people.redhat.com/drepper/nptl-design.pdf NPTL Design Document] contains some information on the NTPL design including implementation details on other architectures. One prerequirement for NPTL is TLS, as documented in [http://people.redhat.com/drepper/tls.pdf Thread Local Storage].
+NPTL for Linux/MIPS is functionally complete.  Ulrich Drepper's [http://people.redhat.com/drepper/nptl-design.pdf NPTL Design Document] contains some information on the NTPL design including implementation details on other architectures. One prerequirement for NPTL is TLS, as documented in [http://people.redhat.com/drepper/tls.pdf Thread Local Storage].
 == Overview ==

@@ Line 320: / Line 320: @@
 == Authors ==
-* Mark Mitchell (mark@codesourcery.com), CodeSourcery, LLC
+* Mark Mitchell (mark@codesourcery.com), CodeSourcery
-* Daniel Jacobowitz (dan@debian.org), CodeSourcery, LLC
+* Daniel Jacobowitz (dan@codesourcery.com), CodeSourcery

← Older revision		Revision as of 00:26, 3 October 2007
Line 277:		Line 277:

	Here, <code>lw</code> may be replaced with any other load/store instruction, as for Code Sequence III in the Local Dynamic model.		Here, <code>lw</code> may be replaced with any other load/store instruction, as for Code Sequence III in the Local Dynamic model.
		+
		+	== Debug Information ==
		+
		+	For DWARF-2 debug information for thread-local variables, a single static relocation for the whole 32-bit or 64-bit TLS offset is needed. The relocations <code>R_MIPS_TLS_DTPREL32</code> and <code>R_MIPS_TLS_DTPREL64</code>, generated by assembler directives <code>.dtprelword</code> and <code>.dtpreldword</code>, are resolved by the static linker to a DTP-relative offset for the given variable. A typical use is of the form
		+
		+	DW_OP_addr
		+	.dtprelword x+0x8000
		+	DW_OP_GNU_push_tls_address

	== Linker Optimizations ==		== Linker Optimizations ==

@@ Line 37: / Line 37: @@
 In what follows, all references to registers other than <code>$2</code> (when it is
-used as the return register), <code>$2</code> (when it is used for the output of <code>rdhwr</code>, <code>$4</code> (when it used as an argument
+used as the return register), <code>$3</code> (when it is used for the output of <code>rdhwr</code>), <code>$4</code> (when it used as an argument
 register), <code>$25</code> (the address of a called function), and <code>$28</code> (the
 global pointer) are arbitrary; the compiler is free to use other

@@ Line 37: / Line 37: @@
 In what follows, all references to registers other than <code>$2</code> (when it is
-used as the return register), <code>$4</code> (when it used as an argument
+used as the return register), <code>$2</code> (when it is used for the output of <code>rdhwr</code>, <code>$4</code> (when it used as an argument
 register), <code>$25</code> (the address of a called function), and <code>$28</code> (the
 global pointer) are arbitrary; the compiler is free to use other
-registers instead.
+registers instead.  <code>$3</code> must be used in the <code>rdhwr</code> instruction for fast-path emulation; using any other register in its place will be much slower.
 Where <code>...</code> appears in a code sequence the compiler may insert zero or
@@ Line 222: / Line 222: @@
 The second code sequence (beginning at address <code>0x0c</code>) demonstrates that the thread register can be reused after it has been loaded.
-The use of registers <code>$2</code> and <code>$3</code> in the above code sequence is arbitrary.  The compiler is free to use alternative registers if convenient.
+The use of register <code>$2</code> in the above code sequence is arbitrary.  The compiler is free to use alternative registers if convenient.
 == Local Exec TLS Model ==
@@ Line 304: / Line 304: @@
 == History ==
 MIPS Technologies has reserved hardware register <tt>$29</tt> for ABI use.  Earlier drafts of this page were using <tt>$5</tt>.
 == Authors ==
 * Mark Mitchell (mark@codesourcery.com), CodeSourcery, LLC
 * Daniel Jacobowitz (dan@debian.org), CodeSourcery, LLC