source: mainline/uspace/lib/libc/arch/ia32/src/fibril.S@ 8476a8d

#
# Copyright (c) 2001-2004 Jakub Jermar
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# - Redistributions of source code must retain the above copyright
#   notice, this list of conditions and the following disclaimer.
# - Redistributions in binary form must reproduce the above copyright
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# - The name of the author may not be used to endorse or promote products
#   derived from this software without specific prior written permission.
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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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#include <kernel/arch/context_offset.h>

.text

.global context_save
.global context_restore


## Save current CPU context
#
# Save CPU context to the context_t variable
# pointed by the 1st argument. Returns 1 in EAX.
#
context_save:
        movl 0(%esp),%eax       # the caller's return %eip
        movl 4(%esp),%edx       # address of the context variable to save context to

                # save registers to the context structure
        CONTEXT_SAVE_ARCH_CORE %edx %eax

        # Save TLS
        movl %gs:0, %eax
        movl %eax, OFFSET_TLS(%edx)     # tls -> ctx->tls
        
        xorl %eax,%eax          # context_save returns 1
        incl %eax
        ret


## Restore saved CPU context
#
# Restore CPU context from context_t variable
# pointed by the 1st argument. Returns 0 in EAX.
#
context_restore:
        movl 4(%esp),%eax       # address of the context variable to restore context from

                # restore registers from the context structure
        CONTEXT_RESTORE_ARCH_CORE %eax %edx

        movl %edx,0(%esp)       # ctx->pc -> saver's return %eip

        # Set thread local storage
        pushl %edx
        movl OFFSET_TLS(%eax), %edx   # Set arg1 to TLS addr
        movl $1, %eax         # Syscall SYS_TLS_SET
        int $0x30
        popl %edx
        
        xorl %eax,%eax          # context_restore returns 0
        ret