Allow RW/ZI sections to be used

* Instruct the linker to place any RW/ZI data sections in the last ~16MB
of the memory map, starting from &ff000000 (with the current toolchain,
giving it a fixed base address is much easier than giving it a variable
base address)
* The RW/ZI section is mapped as completely inaccessible to user mode
* The initial content of the RW section is copied over shortly after MMU
startup (in Continue_after_HALInit)
* Since link's -bin option produces a file containing a copy of the
(zero-initialised) ZI section, the kernel binary is now produced from a
"binary with AIF header" AIF with the help of the new 'kstrip' tool.
kstrip extracts just the RO and RW sections, ensuring the ROM doesn't
contain a redundant block of zeros for the ZI section.

This should make it easier to use C code & arbitrary libraries within
the kernel, providing they're compiled with suitable settings (e.g.
non-module, no FP, no stack checking, like HALs typically use)

.gitignore

@@ -5,3 +5,4 @@
 /o/
 /rm/
 /s/TokHelpSrc
+kstrip

Makefile

@@ -88,11 +88,11 @@ inst_dirs:
 install: ${EXPORTS} inst_dirs
 	@${ECHO} ${COMPONENT}: header files installed
 
-${KERNEL_MODULE}: ${ROM_OBJECTS} ${DIRS}
+${KERNEL_MODULE}: ${ROM_OBJECTS} ${DIRS} ${LIBS} kstrip
 	${MKDIR} bin
 	SetEval KernelBase "4" + STR ( 227858432 + ( HALSize LEFT ( LEN HALSize - 1 ) ) * 1024 )
-	Do ${LD} -bin -base <KernelBase> -o $@ ${ROM_OBJECTS}
-	Do ${LD} -aif -base <KernelBase> -bin -d -o ${KERNEL_MODULE}_aif ${ROM_OBJECTS}
+	Do ${LD} -aif -base <KernelBase> -RW-base 0xff000000 -bin -d -o ${KERNEL_MODULE}_aif ${ROM_OBJECTS} ${LIBS}
+	Do kstrip ${KERNEL_MODULE}_aif ${KERNEL_MODULE}
 	${TOGPA} -s ${KERNEL_MODULE}_aif ${KERNEL_MODULE}_gpa
 
 GetAll.o: ${TOKHELPSRC}
@@ -210,5 +210,9 @@ Global.h.VIDCList: hdr.VIDCList
 clean::
 	${XWIPE} Global ${WFLAGS}
 	${XWIPE} bin    ${WFLAGS}
+	${RM} kstrip
+
+kstrip: kstrip.c
+	${MAKE} -f kstrip/mk COMPONENT=kstrip THROWBACK=${THROWBACK}
 
 # Dynamic dependencies:

MkClean,fd7

@@ -15,3 +15,4 @@
 Dir <Obey$Dir>
 amu_machine clean
 stripdepnd
+stripdepnd kstrip/mk

c/kstrip

+/*
+ * Copyright (c) 2021, RISC OS Open Ltd
+ * 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
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of RISC OS Open Ltd nor the names of its contributors
+ *       may be used to endorse or promote products derived from this software
+ *       without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static FILE *out = NULL;
+static const char *deleteme = NULL;
+
+static void cleanup(void)
+{
+	if (out)
+	{
+		fclose(out);
+		out = NULL;
+	}
+	if (deleteme)
+	{
+		remove(deleteme);
+	}
+}
+
+static void must_read(void *buf,size_t size,FILE *f)
+{
+	size_t amt = fread(buf,1,size,f);
+	if (amt != size)
+	{
+		fprintf(stderr,"Failed reading input\n");
+		exit(1);
+	}
+}
+
+static void must_write(void *buf,size_t size,FILE *f)
+{
+	size_t amt = fwrite(buf,1,size,f);
+	if (amt != size)
+	{
+		fprintf(stderr,"Failed writing output\n");
+		exit(1);
+	}
+}
+
+#define W(X) (header[X] + (header[X+1]<<8) + (header[X+2]<<16) + (header[X+3]<<24))
+
+/* Load an AIF and extract just the RO and RW segments */
+
+int main(int argc,char **argv)
+{
+	if (argc != 3)
+	{
+		fprintf(stderr,"Usage: kstrip <in> <out>\n");
+		exit(1);
+	}
+	FILE *in = fopen(argv[1],"rb");
+	out = fopen(argv[2],"wb");
+	if (out)
+	{
+		deleteme = argv[2];
+		atexit(cleanup);
+	}
+	if (!in || !out)
+	{
+		fprintf(stderr,"Failed to open input/output\n");
+		exit(1);
+	}
+	uint8_t header[128];
+	must_read(header,128,in);
+	uint32_t ro_size = W(0x14);
+	uint32_t rw_size = W(0x18);
+	printf("RO size %8x\n",ro_size);
+	printf("RW size %8x\n",rw_size);
+	uint32_t total = ro_size + rw_size;
+	printf("Total   %8x\n",total);
+	void *buf = malloc(total);
+	if (!buf)
+	{
+		fprintf(stderr,"Failed to get memory\n");
+		exit(1);
+	}
+	must_read(buf,total,in);
+	must_write(buf,total,out);
+	deleteme = NULL;
+	fclose(in);
+	fclose(out);
+	free(buf);
+	return 0;
+}

hdr/KernelWS

@@ -325,6 +325,7 @@ WorkspaceLimit      # 0
 ROM                 * &FC000000
 ROMatTop         SETL {TRUE}
         ASSERT ROM >= WorkspaceLimit
+RWBase              * &FF000000 ; ~16MB of RW data space available to C code
 
 
 IRQSTK              * IRQStackAddress + IRQStackSize

kstrip.mk

+# Copyright (c) 2021, RISC OS Open Ltd
+# 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
+#       notice, this list of conditions and the following disclaimer in the
+#       documentation and/or other materials provided with the distribution.
+#     * Neither the name of RISC OS Open Ltd nor the names of its contributors
+#       may be used to endorse or promote products derived from this software
+#       without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# Makefile for kstrip
+
+include CApp
+include HostTools
+
+# Dynamic dependencies:

s/ChangeDyn

@@ -155,6 +155,7 @@ ABTStack             DefAreaFlags None, PageFlags_Unavailable
 UNDStack             DefAreaFlags None, PageFlags_Unavailable
 Kbuffs               DefAreaFlags Read, PageFlags_Unavailable
 DebuggerSpace        DefAreaFlags Read, PageFlags_Unavailable
+RWArea               DefAreaFlags None, PageFlags_Unavailable
 
   [ DA_Batman
 ChangeDyn_Batcall    * -3               ; special DA number to select Batman usage of OS_ChangeDynamicArea

s/GetAll

@@ -176,7 +176,10 @@ EndOfAMB
         ! 0, "AMB section size = &" :CC: :STR: (EndOfAMB - StartOfAMB)
 
         AREA    zzzzzz, DATA, READONLY
-EndOfKernel
+EndOfKernelRO
+
+        AREA    zzzzzzz, DATA
+EndOfKernelRW
         DCD     0
 
         END

s/HAL

@@ -1537,6 +1537,17 @@ ROMDecompAlign_$pt * 20
         LDR     a3, =(KbuffsSize + &FFF) :AND: &FFFFF000  ;(round to 4k)
         BL      Init_MapInRAM_Clear_$pt
 
+; Allocate the RW/ZI data segment
+        IMPORT  |Image$$RW$$Base|
+        LDR     a1, =|Image$$RW$$Base|
+        LDR     a2, =AreaFlags_RWArea
+        IMPORT  |Image$$ZI$$Limit|
+        LDR     a3, =|Image$$ZI$$Limit|+&FFF
+        SUB     a3, a3, a1
+        BIC     a3, a3, #&FF
+        BIC     a3, a3, #&F00
+        BL      Init_MapInRAM_Clear_$pt
+
  [ HiProcVecs
         ; Map in DebuggerSpace
         LDR     a1, =DebuggerSpace

s/Kernel

@@ -320,7 +320,7 @@ RISCOS_Header
         DCD     (RISCOS_Entries_End - RISCOS_Entries) / 4
         DCD     OSROM_ImageSize*1024 - OSROM_HALSize
         DCD     0
-        DCD     EndOfKernel - KernelBaseA
+        DCD     (EndOfKernelRW-RWBase)+EndOfKernelRO - KernelBaseA
         ASSERT  (. - RISCOS_Header) = OSHdr_size
 
 RISCOS_Entries

s/MemInfo

@@ -1212,7 +1212,8 @@ ReleasePhysAddr
 ;                               14=DebuggerSpace
 ;                               15=Scratch space
 ;                               16=Compatibility page
-;                       16-31   reserved (set to 0)
+;                               17=RW data section
+;                       18-31   reserved (set to 0)
 ;
 ;       Out:    r1 = base of area
 ;               r2 = address space allocated for area (whole number of pages)
@@ -1248,6 +1249,7 @@ MAI_TableStart
         B       MAI_DebuggerSpace
         B       MAI_ScratchSpace
         B       MAI_CompatibilityPage
+        B       MAI_RWData
 MAI_TableEnd
 
 70
@@ -1399,6 +1401,15 @@ MAI_CompatibilityPage
       ]
         EXIT
 
+MAI_RWData
+        LDR     r1, =|Image$$RW$$Base|
+        LDR     r2, =|Image$$ZI$$Limit|+&FFF
+        SUB     r2, r2, r1
+        BIC     r2, r2, #&FF
+        BIC     r2, r2, #&F00
+        MOV     r3, r2
+        EXIT
+
 ;----------------------------------------------------------------------------------------
 ;
 ;        In:    r0 = flags
@@ -2503,6 +2514,13 @@ CheckMemoryAccess ROUT
         LDR     r4, =OSROM_ImageSize*1024
         LDR     r5, =CMA_ROM
         BL      CMA_AddRange
+        ASSERT  RWBase > ROM
+        LDR     r3, =RWBase
+        LDR     r4, =|Image$$ZI$$Limit|+&FFF-RWBase
+        BIC     r4, r4, #&FF
+        BIC     r4, r4, #&F00
+        LDR     r5, =CMA_RWArea
+        BL      CMA_AddRange
         ; Finally, high processor vectors/relocated zero page
         ASSERT  ProcVecs = ZeroPage
       [ ZeroPage > 0

s/NewReset

@@ -103,6 +103,19 @@ CONT_Break
 ; Entry point from HALInit
 
 Continue_after_HALInit
+; Initialise the RW data segment
+        IMPORT  |Image$$RW$$Base|
+        IMPORT  |Image$$RO$$Limit|
+        IMPORT  |Image$$ZI$$Base|
+        LDR     R0, =|Image$$RW$$Base|
+        LDR     R1, =|Image$$RO$$Limit|
+        LDR     R2, =|Image$$ZI$$Base|
+31
+        CMP     R0, R2
+        LDRNE   R3, [R1], #4
+        STRNE   R3, [R0], #4
+        BNE     %BT31
+
 
 ; OK, there is quite a bit of code poking below, to various addresses. We'll
 ; defer IMB consideration till the poking's done, then do a full IMB (full

s/Utility

@@ -18,7 +18,7 @@
 ; Arthur Utility commands
 
 SysModules_Info ROUT     ; start of ROM modules chain
-        &       EndOfKernel-SysModules_Info
+        &       (EndOfKernelRW-RWBase)+EndOfKernelRO-SysModules_Info
 
 UtilityMod
 Module_BaseAddr