source: mainline/uspace/lib/c/arch/ia32/src/fibril.S@ 32573ff

#
# 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.
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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 <abi/asmtool.h>
#include <libarch/fibril_context.h>

.text

## Save current CPU context
#
# Save CPU context to the context_t variable
# pointed by the 1st argument. Returns 1 in EAX.
#
FUNCTION_BEGIN(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
        movl %esp, CONTEXT_OFFSET_SP(%edx)      # %esp -> ctx->sp
        movl %eax, CONTEXT_OFFSET_PC(%edx)      # %eip -> ctx->pc
        movl %ebx, CONTEXT_OFFSET_EBX(%edx)     # %ebx -> ctx->ebx
        movl %esi, CONTEXT_OFFSET_ESI(%edx)     # %esi -> ctx->esi
        movl %edi, CONTEXT_OFFSET_EDI(%edx)     # %edi -> ctx->edi
        movl %ebp, CONTEXT_OFFSET_EBP(%edx)     # %ebp -> ctx->ebp
        
        # save TLS
        movl %gs:0, %eax
        movl %eax, CONTEXT_OFFSET_TLS(%edx)     # tls -> ctx->tls
        
        xorl %eax, %eax         # context_save returns 1
        incl %eax
        ret
FUNCTION_END(context_save)

## Restore saved CPU context
#
# Restore CPU context from context_t variable
# pointed by the 1st argument. Returns 0 in EAX.
#
FUNCTION_BEGIN(context_restore)
        movl 4(%esp), %eax  # address of the context variable to restore context from
        
        # restore registers from the context structure
        movl CONTEXT_OFFSET_SP(%eax),%esp       # ctx->sp -> %esp
        movl CONTEXT_OFFSET_PC(%eax),%edx       # ctx->pc -> \pc
        movl CONTEXT_OFFSET_EBX(%eax),%ebx      # ctx->ebx -> %ebx
        movl CONTEXT_OFFSET_ESI(%eax),%esi      # ctx->esi -> %esi
        movl CONTEXT_OFFSET_EDI(%eax),%edi      # ctx->edi -> %edi
        movl CONTEXT_OFFSET_EBP(%eax),%ebp      # ctx->ebp -> %ebp
        
        movl %edx, 0(%esp)  # ctx->pc -> saver's return %eip
        
        # set thread local storage
        movl CONTEXT_OFFSET_TLS(%eax), %edx     # Set arg1 to TLS addr
        movl %edx, %gs:0
        
        xorl %eax, %eax         # context_restore returns 0
        ret
FUNCTION_END(context_restore)