2019-10-07 05:22:16 +02:00
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// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2019 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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2022-06-26 08:53:27 +02:00
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//
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// This context switch is smaller than asio's and fits in a single iline
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//
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2019-10-07 05:22:16 +02:00
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#include <ircd/config.h>
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2023-01-18 03:56:51 +01:00
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#include <boost/version.hpp>
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2019-10-07 05:22:16 +02:00
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#if defined(__x86_64__) && defined(__ELF__)
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.file "ctx_x86_64.S"
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.globl jump_fcontext
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2023-01-18 03:56:51 +01:00
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// Sizes of additional items saved on context switch
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.equiv x87_ctrl_sz, 0x04
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.equiv mmx_ctrl_sz, 0x04
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.equiv stack_prot_sz, 0x08
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// Total size of all additional items
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.if BOOST_VERSION >= 108100
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.equiv alloc_sz, x87_ctrl_sz + mmx_ctrl_sz + stack_prot_sz
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.else
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.equiv alloc_sz, x87_ctrl_sz + mmx_ctrl_sz
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.endif
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2019-10-07 05:22:16 +02:00
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.text
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.type jump_fcontext, @function
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.align 16
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// returns struct transfer_t { void *fctx, *data; };
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// param DI = void *to
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// param SI = void *vp
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jump_fcontext:
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push %rbp // store rbp 0x30
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push %rbx // store rbx 0x28
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push %r15 // store r15 0x20
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push %r14 // store r14 0x18
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push %r13 // store r13 0x10
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push %r12 // store r12 0x08
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2023-01-18 03:56:51 +01:00
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subq $alloc_sz, %rsp // additional allocation
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fnstcw 0x04(%rsp) // store x87 control-word
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stmxcsr 0x00(%rsp) // store MMX control- and status-word
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2019-10-07 05:22:16 +02:00
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xchgq %rsp, %rdi // swap stack
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movq %rsi, %rdx // store transfer_t.data (retval)
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movq %rdi, %rax // store transfer_t.fctx (retval)
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2023-01-18 03:56:51 +01:00
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ldmxcsr 0x00(%rsp) // load MMX control- and status-word
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fldcw 0x04(%rsp) // load x87 control-word
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addq $alloc_sz, %rsp // free allocation
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2019-10-07 12:50:24 +02:00
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pop %r12 // load r12 <-- LLd miss
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2019-10-07 05:22:16 +02:00
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pop %r13 // load r13
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pop %r14 // load r14
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pop %r15 // load r15
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pop %rbx // load rbx
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2019-10-07 12:50:24 +02:00
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pop %rbp // load rbp <-- LLd miss
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2019-10-07 05:22:16 +02:00
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retq // enter context
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// mark the size of jump_fcontext
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.size jump_fcontext, .-jump_fcontext
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// Mark that we don't need executable stack.
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.section .note.GNU-stack, "", %progbits
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#endif
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