source: mainline/uspace/lib/c/arch/amd64/src/fibril.S@ 84a1a54

Last change on this file since 84a1a54 was 1a5eca4, checked in by Jakub Jermar <jakub@…>, 10 years ago

amd64: Make TLS settable from uspace

The TLS document[1] mandates that %fs[0] is the thread pointer on amd64.
That is good as it allows userspace-only TLS management for fibrils:
fibril_save/restore() simply manipulate the thread pointer in %fs:0 and
don't need to ask the kernel to modify %fs's base. The kernel treats
%fs:0 as another preserved register and preserves it across context
switches. GCC gets in the way a little bit because it by default assumes
that TLS is accessible from negative %fs offsets (which would
necessitate a kernel-assisted solution). Fortunately, there is a GCC
option to suppress this assumption.

  • Introduce the concept of virtual registers, with VREG_TP (thread pointer) being the first of them
  • Preserve VREG_TP in context_save/restore()
  • Stop using sys_tls_set() in favour of using %fs:0 as the thread pointer
  • Make GCC generate code that always goes through %gs:0 to access TLS
  • Introduce kseg: a per-CPU area accessible from GS_KERNEL that holds the kernel stack, kernel FS base and a scratch space for syscall and int handlers to use

[1] Drepper, U.: ELF Handling For Thread-Local Storage
  • Property mode set to 100644
File size: 2.8 KB
RevLine 
[29a9f62]1#
[df4ed85]2# Copyright (c) 2001-2004 Jakub Jermar
[29a9f62]3# All rights reserved.
4#
5# Redistribution and use in source and binary forms, with or without
6# modification, are permitted provided that the following conditions
7# are met:
8#
9# - Redistributions of source code must retain the above copyright
10# notice, this list of conditions and the following disclaimer.
11# - Redistributions in binary form must reproduce the above copyright
12# notice, this list of conditions and the following disclaimer in the
13# documentation and/or other materials provided with the distribution.
14# - The name of the author may not be used to endorse or promote products
15# derived from this software without specific prior written permission.
16#
17# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27#
28
[3b0f1b9a]29#include <abi/asmtool.h>
[4dc7a84]30#include <libarch/fibril_context.h>
[29a9f62]31
[3b0f1b9a]32.text
33
[29a9f62]34## Save current CPU context
35#
36# Save CPU context to context_t variable
37# pointed by the 1st argument. Returns 1 in EAX.
38#
[3b0f1b9a]39FUNCTION_BEGIN(context_save)
[29a9f62]40 movq (%rsp), %rdx # the caller's return %eip
[1dbfe98]41
[4dc7a84]42 # in %rdi is passed 1st argument
43 movq %rdx, CONTEXT_OFFSET_PC(%rdi)
44 movq %rsp, CONTEXT_OFFSET_SP(%rdi)
45
46 movq %rbx, CONTEXT_OFFSET_RBX(%rdi)
47 movq %rbp, CONTEXT_OFFSET_RBP(%rdi)
48 movq %r12, CONTEXT_OFFSET_R12(%rdi)
49 movq %r13, CONTEXT_OFFSET_R13(%rdi)
50 movq %r14, CONTEXT_OFFSET_R14(%rdi)
51 movq %r15, CONTEXT_OFFSET_R15(%rdi)
[29a9f62]52
53 movq %fs:0, %rax
[4dc7a84]54 movq %rax, CONTEXT_OFFSET_TLS(%rdi)
[e4c8e751]55
[4dc7a84]56 xorl %eax, %eax # context_save returns 1
[e80329d6]57 incl %eax
[29a9f62]58 ret
[3b0f1b9a]59FUNCTION_END(context_save)
[29a9f62]60
61## Restore current CPU context
62#
63# Restore CPU context from context_t variable
64# pointed by the 1st argument. Returns 0 in EAX.
65#
[3b0f1b9a]66FUNCTION_BEGIN(context_restore)
[4dc7a84]67 movq CONTEXT_OFFSET_R15(%rdi), %r15
68 movq CONTEXT_OFFSET_R14(%rdi), %r14
69 movq CONTEXT_OFFSET_R13(%rdi), %r13
70 movq CONTEXT_OFFSET_R12(%rdi), %r12
71 movq CONTEXT_OFFSET_RBP(%rdi), %rbp
72 movq CONTEXT_OFFSET_RBX(%rdi), %rbx
73
74 movq CONTEXT_OFFSET_SP(%rdi), %rsp # ctx->sp -> %rsp
75
76 movq CONTEXT_OFFSET_PC(%rdi), %rdx
[29a9f62]77
78 movq %rdx,(%rsp)
[e4c8e751]79
[1a5eca4]80 movq CONTEXT_OFFSET_TLS(%rdi), %rdi
81 movq %rdi, %fs:0
[e4c8e751]82
[4dc7a84]83 xorl %eax, %eax # context_restore returns 0
[29a9f62]84 ret
[3b0f1b9a]85FUNCTION_END(context_restore)
[4dc7a84]86
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