From: Chris Hanson <org/chris-hanson/cph>
Date: Thu, 5 Oct 1995 03:34:50 +0000 (+0000)
Subject: Implement changes needed for Linux ELF binary format.  This format,
X-Git-Tag: 20090517-FFI~5917
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=f234224a6c837d80cd502d5d9ea94c964866c5c0;p=mit-scheme.git

Implement changes needed for Linux ELF binary format.  This format,
unlike the older a.out format, translates the data segment to begin at
0x08000000, and additionally changes the calling conventions so that
returned structures are allocated by the caller and passed in as
pointers.  We fix the first problem by extending the win32s segment
register manipulation to also be used with Linux ELF.  The second
problem is fixed by extending the OS/2 assembly-language patches to
also cover Linux ELF.
---

diff --git a/v7/src/microcode/cmpauxmd/i386.m4 b/v7/src/microcode/cmpauxmd/i386.m4
index 94fd6e8af..3adcb5e0f 100644
--- a/v7/src/microcode/cmpauxmd/i386.m4
+++ b/v7/src/microcode/cmpauxmd/i386.m4
@@ -1,6 +1,6 @@
 ### -*-Midas-*-
 ###
-###	$Id: i386.m4,v 1.37 1995/10/01 07:19:42 cph Exp $
+###	$Id: i386.m4,v 1.38 1995/10/05 03:32:24 cph Exp $
 ###
 ###	Copyright (c) 1992-95 Massachusetts Institute of Technology
 ###
@@ -116,10 +116,18 @@ ifdef(`DOS',
       `define(IFNDOS,`')',
       `define(IFNDOS,`$1')')
 
+ifdef(`WINNT',
+      `define(IF_WINNT,`$1')',
+      `define(IF_WINNT,`')')
+
 ifdef(`OS2',
       `define(IFOS2,`$1')',
       `define(IFOS2,`')')
 
+ifdef(`LINUX_ELF',
+      `define(IF_LINUX_ELF,`$1')',
+      `define(IF_LINUX_ELF,`')')
+
 ifdef(`DISABLE_387',
       `define(IF387,`')',
       `define(IF387,`$1')')
@@ -138,9 +146,8 @@ ifdef(`DOS',
       `define(use_external_code,`	extrn _$1:near')',
       `define(use_external_code,`')')
 
-ifdef(`OS2',
-      `define(`SUPPRESS_LEADING_UNDERSCORE',1)',
-      `')
+IFOS2(`define(`SUPPRESS_LEADING_UNDERSCORE',1)')
+IF_LINUX_ELF(`define(`SUPPRESS_LEADING_UNDERSCORE',1)')
 
 ifdef(`SUPPRESS_LEADING_UNDERSCORE',
       `define(external_data_reference,`$1')',
@@ -158,7 +165,7 @@ ifdef(`DOS',
 
 ifdef(`DOS',
       `define(define_data,`	public _$1')',
-      `define(define_data,`	.globl external_code_reference($1)')')
+      `define(define_data,`	.globl external_data_reference($1)')')
 
 define(define_c_label,
 `define_code($1)
@@ -305,17 +312,20 @@ use_external_data(Free)
 use_external_data(Ext_Stack_Pointer)
 use_external_data(utility_table)
 
-ifdef(`WINNT',
-`	extrn _RegistersPtr:dword',
-`ifdef(`DOS',
-`use_external_data(Registers)',
-`define_data(Regstart)
+ifdef(`WINNT',`
+	extrn _RegistersPtr:dword
+',`ifdef(`DOS',`
+use_external_data(Registers)
+',`
+define_data(Regstart)
 allocate_space(Regstart,128)
+
 define_data(Registers)
-allocate_space(Registers,eval(REGBLOCK_SIZE_IN_OBJECTS*4))')')
+allocate_space(Registers,eval(REGBLOCK_SIZE_IN_OBJECTS*4))
+')
+')
 
-ifdef(`WINNT',
-`	extrn _winnt_address_delta:dword')
+IF_WINNT(`	extrn _winnt_address_delta:dword')
 
 define_data(i387_presence)
 allocate_longword(i387_presence)
@@ -326,27 +336,53 @@ allocate_longword(C_Stack_Pointer)
 define_data(C_Frame_Pointer)
 allocate_longword(C_Frame_Pointer)
 
-ifdef(`WINNT',`define_data(Scheme_Transfer_Address)
-allocate_longword(Scheme_Transfer_Address)')
+IF_WINNT(`define(HACK_SEGMENT_REGS,1)')
+IF_LINUX_ELF(`define(HACK_SEGMENT_REGS,1)')
 
-ifdef(`WINNT',`define_data(Scheme_Code_Segment_Selector)
+ifdef(`HACK_SEGMENT_REGS',`
+
+define_data(Scheme_Transfer_Address)
+allocate_longword(Scheme_Transfer_Address)
+
+define_data(Scheme_Code_Segment_Selector)
 allocate_word(Scheme_Code_Segment_Selector)
+
 define_data(Scheme_Data_Segment_Selector)
 allocate_word(Scheme_Data_Segment_Selector)
+
 define_data(Scheme_Stack_Segment_Selector)
 allocate_word(Scheme_Stack_Segment_Selector)
+
 define_data(C_Code_Segment_Selector)
 allocate_word(C_Code_Segment_Selector)
+
 define_data(C_Data_Segment_Selector)
 allocate_word(C_Data_Segment_Selector)
+
 define_data(C_Extra_Segment_Selector)
 allocate_word(C_Extra_Segment_Selector)
+
 define_data(C_Stack_Segment_Selector)
-allocate_word(C_Stack_Segment_Selector)',
-`IFDOS(`define_data(C_Stack_Segment_Selector)
 allocate_word(C_Stack_Segment_Selector)
+
+IF_WINNT(`define(RETF,`db	0cbh')')
+IF_LINUX_ELF(`define(RETF,`.byte	0xcb')')
+
+IF_WINNT(`define(SEGMENT_DELTA,`EDR(winnt_address_delta)')')
+IF_LINUX_ELF(`define(SEGMENT_DELTA,`IMM(0x08000000)')')
+
+',`IFDOS(`
+
+define_data(C_Stack_Segment_Selector)
+allocate_word(C_Stack_Segment_Selector)
+
 define_data(Scheme_Stack_Segment_Selector)
-allocate_word(Scheme_Stack_Segment_Selector)')')
+allocate_word(Scheme_Stack_Segment_Selector)
+
+')')
+
+IFOS2(`define(USE_STRUCS,1)')
+IF_LINUX_ELF(`define(USE_STRUCS,1)')
 
 DECLARE_CODE_SEGMENT()
 declare_alignment(2)
@@ -356,32 +392,40 @@ define_c_label(i386_interface_initialize)
 	OP(mov,l)	TW(REG(esp),REG(ebp))
 
 							# Initialize selectors
-ifdef(`WINNT',
-`	lea	eax,cross_segment_transfer_point
-	mov	_Scheme_Transfer_Address,eax
-	mov	_C_Extra_Segment_Selector,es		; This assumes it is constant
-
-	mov	_C_Code_Segment_Selector,cs
-	mov	ax,_Scheme_Code_Segment_Selector
-	cmp	ax,0
-	jne	skip_code_assignment
-	mov	_Scheme_Code_Segment_Selector,cs
+ifdef(`HACK_SEGMENT_REGS',`
+	OP(lea,l)	TW(ABS(cross_segment_transfer_point),REG(eax))
+	OP(mov,l)	TW(REG(eax),EDR(Scheme_Transfer_Address))
+	OP(mov,w)	TW(REG(es),EDR(C_Extra_Segment_Selector)) # This assumes it is constant
+
+	OP(mov,w)	TW(REG(cs),EDR(C_Code_Segment_Selector))
+	OP(mov,w)	TW(EDR(Scheme_Code_Segment_Selector),REG(ax))
+	OP(cmp,w)	TW(IMM(0),REG(ax))
+	jne		skip_code_assignment
+	OP(mov,w)	TW(REG(cs),EDR(Scheme_Code_Segment_Selector))
 skip_code_assignment:
 
-	mov	_C_Data_Segment_Selector,ds
-	mov	ax,_Scheme_Data_Segment_Selector
-	cmp	ax,0
-	jne	skip_data_assignment
-	mov	_Scheme_Data_Segment_Selector,ds
-skip_data_assignment:')
+	OP(mov,w)	TW(REG(ds),EDR(C_Data_Segment_Selector))
+	OP(mov,w)	TW(EDR(Scheme_Data_Segment_Selector),REG(ax))
+	OP(cmp,w)	TW(IMM(0),REG(ax))
+	jne		skip_data_assignment
+	OP(mov,w)	TW(REG(ds),EDR(Scheme_Data_Segment_Selector))
+skip_data_assignment:
 
-IFDOS(`	OP(mov,w)	TW(REG(ss),EDR(C_Stack_Segment_Selector))
+	OP(mov,w)	TW(REG(ss),EDR(C_Stack_Segment_Selector))
 	OP(mov,w)	TW(EDR(Scheme_Stack_Segment_Selector),REG(ax))
 	OP(cmp,w)	TW(IMM(0),REG(ax))
 	jne		skip_stack_assignment
 	OP(mov,w)	TW(REG(ds),EDR(Scheme_Stack_Segment_Selector))
-skip_stack_assignment:')
-
+skip_stack_assignment:
+',`IFDOS(`
+	OP(mov,w)	TW(REG(ss),EDR(C_Stack_Segment_Selector))
+	OP(mov,w)	TW(EDR(Scheme_Stack_Segment_Selector),REG(ax))
+	OP(cmp,w)	TW(IMM(0),REG(ax))
+	jne		skip_stack_assignment
+	OP(mov,w)	TW(REG(ds),EDR(Scheme_Stack_Segment_Selector))
+skip_stack_assignment:
+')
+')
 	OP(xor,l)	TW(REG(eax),REG(eax))		# No 387 available
 
 # Unfortunately, the `movl cr0,ecx' instruction is privileged.
@@ -408,7 +452,8 @@ IF387(`
 	      `OP(or,w)	TW(IMM(HEX(0220)),WOF(-2,REG(ebp)))')
 	fldcw	WOF(-2,REG(ebp))
 
-i386_initialize_no_fp:')
+i386_initialize_no_fp:
+')
 	OP(mov,l)	TW(REG(eax),EDR(i387_presence))
 	leave
 	ret
@@ -427,10 +472,11 @@ define_c_label(C_to_interface)
 							# Register block = %esi
 							# Scheme offset in NT
 
-	ifdef(`WINNT',
-	`mov	esi,dword ptr _RegistersPtr
-	sub	esi,_winnt_address_delta',	
-	`OP(lea,l)	TW(ABS(EDR(Registers)),regs)')
+ifdef(`WINNT',
+`	OP(mov,l)	TW(ABS(EDR(RegistersPtr)),regs)',
+`	OP(lea,l)	TW(ABS(EDR(Registers)),regs)')
+ifdef(`HACK_SEGMENT_REGS',
+`	OP(sub,l)	TW(SEGMENT_DELTA,regs)')
 	jmp	external_code_reference(interface_to_scheme)
 
 define_c_label(asm_trampoline_to_interface)
@@ -446,38 +492,44 @@ define_debugging_label(scheme_to_interface_call)
 
 define_c_label(asm_scheme_to_interface)
 define_debugging_label(scheme_to_interface)
-ifdef(`WINNT',
-`	push	dword ptr 36[esi]			; 4th utility arg
-	push	eax					; Save utility index
+ifdef(`HACK_SEGMENT_REGS',
+`	OP(push,l)	LOF(36,regs)			# 4th utility arg
+	OP(push,l)	REG(eax)			# Save utility index
 
-	mov	ax,es					; C ds
-	mov	ds,ax
+	OP(mov,w)	TW(REG(es),REG(ax))		# C ds
+	OP(mov,w)	TW(REG(ax),REG(ds))
 
-	mov	ax,_C_Extra_Segment_Selector		; C es
-	mov	es,ax
-	add	edi,_winnt_address_delta		; Map Free to C data space
-	mov	_Free,edi
+	OP(mov,w)	TW(EDR(C_Extra_Segment_Selector),REG(ax)) # C es
+	OP(mov,w)	TW(REG(ax),REG(es))
 
-	mov	eax,esp					; Map SP to C data space
-	add	eax,_winnt_address_delta
-	mov	_Ext_Stack_Pointer,eax
+# Map Free to C data space
+	OP(add,l)	TW(SEGMENT_DELTA,rfree)
+	OP(mov,l)	TW(rfree,EDR(Free))
 
-	mov	ss,_C_Stack_Segment_Selector		; Switch stack segment
-	mov	esp,_C_Stack_Pointer
-	mov	ebp,_C_Frame_Pointer
+# Map SP to C data space
+	OP(mov,l)	TW(REG(esp),REG(eax))
+	OP(add,l)	TW(SEGMENT_DELTA,REG(eax))
+	OP(mov,l)	TW(REG(eax),EDR(Ext_Stack_Pointer))
 
-	xor	eax,eax
-	mov	ax,_C_Code_Segment_Selector
-	push	eax
-	push	_Scheme_Transfer_Address
-	db	0cbh					; retf
+# Switch stack segment
+	OP(mov,w)	TW(EDR(C_Stack_Segment_Selector),REG(ss))
+	OP(mov,l)	TW(EDR(C_Stack_Pointer),REG(esp))
+	OP(mov,l)	TW(EDR(C_Frame_Pointer),REG(ebp))
 
-cross_segment_transfer_point:
+	OP(xor,l)	TW(REG(eax),REG(eax))
+	OP(mov,w)	TW(EDR(C_Code_Segment_Selector),REG(ax))
+	OP(push,l)	REG(eax)
+	OP(push,l)	EDR(Scheme_Transfer_Address)
+	RETF
 
-	mov	eax,_Ext_Stack_Pointer
-	push	dword ptr 4[eax]			; 4th utility arg
-	add	_Ext_Stack_Pointer,8
-	mov	eax, dword ptr [eax]			; utility index
+cross_segment_transfer_point:
+ifdef(`USE_STRUCS',`
+	OP(sub,l)	TW(IMM(8),REG(esp))	# alloc space for struct return
+')
+	OP(mov,l)	TW(EDR(Ext_Stack_Pointer),REG(eax))
+	OP(push,l)	LOF(4,REG(eax))			# 4th utility arg
+	OP(add,l)	TW(IMM(8),EDR(Ext_Stack_Pointer))
+	OP(mov,l)	TW(IND(REG(eax)),REG(eax))	# utility index
 ',
 
 `	OP(mov,l)	TW(REG(esp),EDR(Ext_Stack_Pointer))
@@ -488,7 +540,8 @@ IFDOS(`	OP(mov,w)	TW(EDR(C_Stack_Segment_Selector),REG(ss))')	# Swap stack segme
 	OP(mov,l)	TW(EDR(C_Stack_Pointer),REG(esp))
 	OP(mov,l)	TW(EDR(C_Frame_Pointer),REG(ebp))
 
-IFOS2(`	OP(sub,l)	TW(IMM(8),REG(esp))	# alloc space for struct return
+ifdef(`USE_STRUCS',`
+	OP(sub,l)	TW(IMM(8),REG(esp))	# alloc space for struct return
 ')
 	OP(push,l)	LOF(REGBLOCK_UTILITY_ARG4(),regs) # Utility args
 ')
@@ -496,7 +549,8 @@ IFOS2(`	OP(sub,l)	TW(IMM(8),REG(esp))	# alloc space for struct return
 	OP(push,l)	REG(edx)
 	OP(push,l)	REG(ecx)
 
-IFOS2(`	OP(mov,l)	TW(REG(esp),REG(ecx))	# push pointer to struct return
+ifdef(`USE_STRUCS',`
+	OP(mov,l)	TW(REG(esp),REG(ecx))	# push pointer to struct return
 	OP(add,l)	TW(IMM(16),REG(ecx))
 	OP(push,l)	REG(ecx)
 ')
@@ -504,22 +558,26 @@ IFOS2(`	OP(mov,l)	TW(REG(esp),REG(ecx))	# push pointer to struct return
 	OP(xor,l)	TW(REG(ecx),REG(ecx))
 	OP(mov,b)	TW(REG(al),REG(cl))
 	OP(mov,l)	TW(SDX(EDR(utility_table),REG(ecx),4),REG(eax))
-	call	IJMP(REG(eax))
+	call		IJMP(REG(eax))
 
 define_debugging_label(scheme_to_interface_return)
-IFOS2(`	OP(add,l)	TW(IMM(4),REG(esp))	# pop pointer to struct return
+ifdef(`USE_STRUCS',`
+	OP(add,l)	TW(IMM(4),REG(esp))	# pop pointer to struct return
 ')
 	OP(add,l)	TW(IMM(16),REG(esp))		# Pop utility args
 
-	ifdef(`WINNT',
-	`',
-`IFDOS(`OP(mov,l)	TW(LOF(4,REG(eax)),REG(edx))
-	OP(mov,l)	TW(IND(REG(eax)),REG(eax))')')
-
-IFOS2(`	OP(pop,l)	REG(eax)	# Pop struct return into registers
-	OP(pop,l)	REG(edx)')
+ifdef(`WINNT',`',`
+IFDOS(`
+	OP(mov,l)	TW(LOF(4,REG(eax)),REG(edx))
+	OP(mov,l)	TW(IND(REG(eax)),REG(eax))
+')
+')
 
-	jmp	IJMP(REG(eax))				# Invoke handler
+ifdef(`USE_STRUCS',`
+	OP(pop,l)	REG(eax)	# Pop struct return into registers
+	OP(pop,l)	REG(edx)
+')
+	jmp		IJMP(REG(eax))			# Invoke handler
 
 define_c_label(interface_to_scheme)
 IF387(`
@@ -533,59 +591,56 @@ IF387(`
 	ffree	ST(5)
 	ffree	ST(6)
 	ffree	ST(7)
-interface_to_scheme_proceed:')
-ifdef(`WINNT',
-`	mov	edi,_Free				; Free pointer = %edi
-	sub	edi,_winnt_address_delta		; as a scheme offset
-
-	mov	ebp,67108863				; pointer mask #x03ffffff
-
-	mov	eax,_Ext_Stack_Pointer			; Switch stacks
-	sub	eax,_winnt_address_delta
-	mov	ss,_Scheme_Stack_Segment_Selector
-	mov	esp,eax
-				
-	sub	edx,_winnt_address_delta		; Entry point to new space
-	xor	ecx,ecx					; Setup cross-segment jump
-	mov	cx,_Scheme_Code_Segment_Selector
-
-	mov	ax,ds					; Store C ds in es,
-	mov	es,ax					;  unused by Scheme.
-	mov	ax,_Scheme_Data_Segment_Selector	; Switch data segments
-	mov	ds,ax
-							
-	push	ecx
-	push	edx
-
-	mov	eax,dword ptr 8[esi]			; Value/dynamic link
-	mov	ecx,eax					; Preserve if used
-	and	ecx,ebp					; Restore potential
-							;  dynamic link
-	mov	dword ptr 16[esi],ecx
-	db	0cbh					; retf
+interface_to_scheme_proceed:
+')
+ifdef(`HACK_SEGMENT_REGS',
+`	OP(mov,l)	TW(EDR(Free),rfree)
+	OP(sub,l)	TW(SEGMENT_DELTA,rfree)
+	OP(mov,l)	TW(IMM(ADDRESS_MASK),rmask)
+
+	OP(mov,l)	TW(EDR(Ext_Stack_Pointer),REG(eax)) # Switch stacks
+	OP(sub,l)	TW(SEGMENT_DELTA,REG(eax))
+	OP(mov,w)	TW(EDR(Scheme_Stack_Segment_Selector),REG(ss))
+	OP(mov,l)	TW(REG(eax),REG(esp))
+
+	OP(sub,l)	TW(SEGMENT_DELTA,REG(edx))	# Entry point to new space
+	OP(xor,l)	TW(REG(ecx),REG(ecx))		# Setup cross-segment jump
+	OP(mov,w)	TW(EDR(Scheme_Code_Segment_Selector),REG(ecx))
+
+	OP(mov,w)	TW(REG(ds),REG(ax))		# Store C ds in es,
+	OP(mov,w)	TW(REG(ax),REG(es))		#  unused by Scheme.
+	OP(mov,w)	TW(EDR(Scheme_Data_Segment_Selector),REG(ax)) # Switch data segments
+	OP(mov,w)	TW(REG(ax),REG(ds))
+
+	OP(push,l)	REG(ecx)
+	OP(push,l)	REG(edx)
+
+	OP(mov,l)	TW(LOF(REGBLOCK_VAL(),regs),REG(eax)) # Value/dynamic link
+	OP(mov,l)	TW(REG(eax),REG(ecx))		# Preserve if used
+	OP(and,l)	TW(rmask,REG(ecx))		# Restore potential dynamic link
+	OP(mov,l)	TW(REG(ecx),LOF(REGBLOCK_DLINK(),regs))
+	RETF						# Perform cross-segment jump
 ',
 `	OP(mov,l)	TW(EDR(Free),rfree)		# Free pointer = %edi
-							# Value/dynamic link
-	OP(mov,l)	TW(LOF(REGBLOCK_VAL(),regs),REG(eax))
+	OP(mov,l)	TW(LOF(REGBLOCK_VAL(),regs),REG(eax)) # Value/dynamic link
 	OP(mov,l)	TW(IMM(ADDRESS_MASK),rmask)	# = %ebp
 
-							# Swap stack segments
-IFDOS(`	OP(mov,w)	TW(EDR(Scheme_Stack_Segment_Selector),REG(ss))')
+IFDOS(`	OP(mov,w)	TW(EDR(Scheme_Stack_Segment_Selector),REG(ss))') # Swap stack segments
 
 	OP(mov,l)	TW(EDR(Ext_Stack_Pointer),REG(esp))
 	OP(mov,l)	TW(REG(eax),REG(ecx))		# Preserve if used
-	OP(and,l)	TW(rmask,REG(ecx))		# Restore potential
-							#  dynamic link
+	OP(and,l)	TW(rmask,REG(ecx))		# Restore potential dynamic link
 	OP(mov,l)	TW(REG(ecx),LOF(REGBLOCK_DLINK(),regs))
-	jmp	IJMP(REG(edx))')
+	jmp		IJMP(REG(edx))')
 
-ifdef(`WINNT',
-`	extrn	_WinntExceptionTransferHook:near
+IF_WINNT(`
+	extrn	_WinntExceptionTransferHook:near
 
 	public	_callWinntExceptionTransferHook
 _callWinntExceptionTransferHook:
 	call	_WinntExceptionTransferHook
-	mov	edx,eax')
+	mov	edx,eax
+')
 
 define_c_label(interface_to_C)
 IF387(`
diff --git a/v7/src/microcode/cmpintmd/i386.h b/v7/src/microcode/cmpintmd/i386.h
index e9064a5ed..ebe5e41d2 100644
--- a/v7/src/microcode/cmpintmd/i386.h
+++ b/v7/src/microcode/cmpintmd/i386.h
@@ -1,8 +1,8 @@
 /* -*-C-*-
 
-$Id: i386.h,v 1.25 1994/11/28 04:05:21 cph Exp $
+$Id: i386.h,v 1.26 1995/10/05 03:32:49 cph Exp $
 
-Copyright (c) 1992-94 Massachusetts Institute of Technology
+Copyright (c) 1992-95 Massachusetts Institute of Technology
 
 This material was developed by the Scheme project at the Massachusetts
 Institute of Technology, Department of Electrical Engineering and
@@ -497,13 +497,8 @@ long i386_pc_displacement_relocation = 0;
 
 #define ASM_RESET_HOOK i386_reset_hook
 
-#if !defined(WINNT) || defined(WINNT_RAW_ADDRESSES)
-#  define HOOK_TO_SCHEME_OFFSET(hook) 					\
-  ((unsigned long) (hook))
-#else
-extern unsigned long winnt_address_delta;
-#  define HOOK_TO_SCHEME_OFFSET(hook)					\
-  (((unsigned long) (hook)) - winnt_address_delta)
+#ifndef HOOK_TO_SCHEME_OFFSET
+#define HOOK_TO_SCHEME_OFFSET(hook) ((unsigned long) (hook))
 #endif
 
 #define SETUP_REGISTER(hook) do						\
diff --git a/v7/src/microcode/config.h b/v7/src/microcode/config.h
index b94f32535..197fc564a 100644
--- a/v7/src/microcode/config.h
+++ b/v7/src/microcode/config.h
@@ -1,6 +1,6 @@
 /* -*-C-*-
 
-$Id: config.h,v 9.90 1995/10/04 22:53:58 cph Exp $
+$Id: config.h,v 9.91 1995/10/05 03:32:04 cph Exp $
 
 Copyright (c) 1987-95 Massachusetts Institute of Technology
 
@@ -459,9 +459,35 @@ extern unsigned long winnt_address_delta;
 
 #define SCHEME_ADDR_TO_ADDR(saddr) (DATUM_TO_ADDRESS (saddr))
 #define ADDR_TO_SCHEME_ADDR(caddr) (ADDRESS_TO_DATUM (caddr))
+#define HOOK_TO_SCHEME_OFFSET(hook) (ADDRESS_TO_DATUM (hook))
 
 #endif /* WINNT && !WINNT_RAW_ADDRESSES */
 
+#if defined(__linux) && defined(__ELF__)
+
+/* Linux ELF adds a data-segment bit which must be translated away.
+   We'll use the same trick as Win32s since the code is there and it
+   maintains binary compatibility.  */
+
+#define _LINUX_ELF 1
+#define LINUX_ELF_DATA_SEGMENT_START 0x08000000
+#define LINUX_ELF_DATA_SEGMENT_LIMIT 0x04000
+
+#define DATUM_TO_ADDRESS(datum)						\
+  ((SCHEME_OBJECT *)							\
+   (((unsigned long) (datum)) + LINUX_ELF_DATA_SEGMENT_START))
+
+#define ADDRESS_TO_DATUM(address)					\
+  ((SCHEME_OBJECT)							\
+   (((unsigned long) (address)) - LINUX_ELF_DATA_SEGMENT_START))
+
+typedef unsigned long SCHEME_ADDR;
+#define SCHEME_ADDR_TO_ADDR(saddr) (DATUM_TO_ADDRESS (saddr))
+#define ADDR_TO_SCHEME_ADDR(caddr) (ADDRESS_TO_DATUM (caddr))
+#define HOOK_TO_SCHEME_OFFSET(hook) (ADDRESS_TO_DATUM (hook))
+
+#endif /* __linux && __ELF__ */
+
 #endif /* i386 */
 
 #ifdef mips
diff --git a/v7/src/microcode/s/linux.h b/v7/src/microcode/s/linux.h
index ba5c8c542..5acc0c126 100644
--- a/v7/src/microcode/s/linux.h
+++ b/v7/src/microcode/s/linux.h
@@ -1,7 +1,7 @@
 /* -*-C-*-
    System file for Linux
 
-$Id: linux.h,v 1.3 1995/10/01 07:19:07 cph Exp $
+$Id: linux.h,v 1.4 1995/10/05 03:34:50 cph Exp $
 
 Copyright (c) 1995 Massachusetts Institute of Technology
 
@@ -41,32 +41,8 @@ MIT in each case. */
 
 #define ALTERNATE_M4 s/ultrix.m4
 
-/* The following change is necessary if ELF binaries are used.
-   Unfortunately, it is insufficient, because the Linux ELF
-   implementation also moves the data segment to 0x08000000, which
-   means that all of the pointer manipulation code must be changed.
-   This is normal for some architectures, e.g. the MIPS and HPPA, but
-   it make the binaries for Linux ELF different for the binaries for
-   all other i386 machines.
-
-   Since I don't currently know any way to adjust the mapping of the
-   data segment, if ELF is in use, I'll just force the switch that
-   causes GCC to generate a.out format instead of ELF.  This is a
-   temporary patch, because one of these days a.out won't be
-   supported, but hopefully by then we'll know how to fix this
-   correctly.  */
-#if 0
 #ifdef __ELF__
-#define M4_SWITCH_SYSTEM -P "define(SUPPRESS_LEADING_UNDERSCORE,1)"
+#define M4_SWITCH_SYSTEM -P "define(LINUX_ELF,1)"
 #else
 #define M4_SWITCH_SYSTEM
 #endif
-#endif
-
-#ifdef __ELF__
-#define C_SWITCH_SYSTEM -b i486-linuxaout
-#define LD_SWITCH_SYSTEM -b i486-linuxaout
-#else
-#define C_SWITCH_SYSTEM
-#define LD_SWITCH_SYSTEM
-#endif
diff --git a/v7/src/microcode/uxtop.c b/v7/src/microcode/uxtop.c
index c1baa53d1..b553230fc 100644
--- a/v7/src/microcode/uxtop.c
+++ b/v7/src/microcode/uxtop.c
@@ -1,8 +1,8 @@
 /* -*-C-*-
 
-$Id: uxtop.c,v 1.16 1994/12/02 20:38:54 cph Exp $
+$Id: uxtop.c,v 1.17 1995/10/05 03:34:14 cph Exp $
 
-Copyright (c) 1990-94 Massachusetts Institute of Technology
+Copyright (c) 1990-95 Massachusetts Institute of Technology
 
 This material was developed by the Scheme project at the Massachusetts
 Institute of Technology, Department of Electrical Engineering and
@@ -38,6 +38,14 @@ MIT in each case. */
 #include "uxutil.h"
 #include "errors.h"
 #include "option.h"
+#include "config.h"
+#include "extern.h"
+
+#ifdef _LINUX_ELF
+#include <linux/ldt.h>
+#include <linux/unistd.h>
+static void EXFUN (initialize_linux_elf_segments, (void));
+#endif
 
 extern void EXFUN (UX_initialize_channels, (void));
 extern void EXFUN (UX_initialize_ctty, (int interactive));
@@ -109,6 +117,9 @@ DEFUN_VOID (OS_initialize)
 #ifdef _SUNOS
   vadvise (VA_ANOM);		/* Anomolous paging, don't try to guess. */
 #endif
+#ifdef _LINUX_ELF
+  initialize_linux_elf_segments ();
+#endif
 }
 
 void
@@ -420,3 +431,54 @@ OS_syserr_names (unsigned int * length, unsigned char *** names)
   (*length) = ((sizeof (syserr_names_table)) / (sizeof (char *)));
   (*names) = ((unsigned char **) syserr_names_table);
 }
+
+/* Special hacking for Linux ELF memory management.  */
+
+#ifdef _LINUX_ELF
+
+extern unsigned short Scheme_Code_Segment_Selector;
+extern unsigned short Scheme_Data_Segment_Selector;
+extern unsigned short Scheme_Stack_Segment_Selector;
+
+static _syscall3 (int, modify_ldt, int, func, void *, buffer, unsigned long, nbytes)
+
+static void
+DEFUN_VOID (initialize_linux_elf_segments)
+{
+  struct modify_ldt_ldt_s mldt;
+
+  (mldt . entry_number) = 1;
+  (mldt . base_addr) = LINUX_ELF_DATA_SEGMENT_START;
+  (mldt . limit) = LINUX_ELF_DATA_SEGMENT_LIMIT;
+  (mldt . seg_32bit) = 1;
+  (mldt . contents) = MODIFY_LDT_CONTENTS_CODE;
+  (mldt . read_exec_only) = 1;
+  (mldt . limit_in_pages) = 1;
+  (mldt . seg_not_present) = 0;
+  if ((modify_ldt (1, (&mldt), (sizeof (mldt)))) != 0)
+    {
+      outf_fatal ("\n%s: unable to allocate code segment descriptor\n",
+	       scheme_program_name);
+      Microcode_Termination (TERM_EXIT);
+    }
+  Scheme_Code_Segment_Selector = (((mldt . entry_number) << 3) | 0x7);
+    
+  (mldt . entry_number) = 2;
+  (mldt . base_addr) = LINUX_ELF_DATA_SEGMENT_START;
+  (mldt . limit) = LINUX_ELF_DATA_SEGMENT_LIMIT;
+  (mldt . seg_32bit) = 1;
+  (mldt . contents) = MODIFY_LDT_CONTENTS_DATA;
+  (mldt . read_exec_only) = 0;
+  (mldt . limit_in_pages) = 1;
+  (mldt . seg_not_present) = 0;
+  if ((modify_ldt (1, (&mldt), (sizeof (mldt)))) != 0)
+    {
+      outf_fatal ("\n%s: unable to allocate data segment descriptor\n",
+	       scheme_program_name);
+      Microcode_Termination (TERM_EXIT);
+    }
+  Scheme_Data_Segment_Selector = (((mldt . entry_number) << 3) | 0x7);
+  Scheme_Stack_Segment_Selector = Scheme_Data_Segment_Selector;
+}
+
+#endif /* _LINUX_ELF */