elf: switch to HPA segelf scheme [closes #172][skip CI]

fdpp/clang.mak

@@ -2,7 +2,7 @@
 # CLANG.MAK - kernel copiler options for clang
 #
 
-LLD ?= $(shell which ld.lld 2>/dev/null)
+LLD ?= ~/src/binutils-segelf/ld/ld-new
 CCACHE ?= $(shell which ccache 2>/dev/null)
 CC = $(CCACHE) clang++
 CLANG_VER := $(shell $(CC) -v 2>&1 | head -n 1 | \
@@ -26,7 +26,7 @@ else
 $(warning lld not installed)
 CROSS_LD ?= ld
 endif
-NASM ?= nasm
+NASM ?= ~/src/nasm/nasm
 PKG_CONFIG ?= pkg-config
 
 TARGETOPT = -std=c++11 -c -fno-threadsafe-statics -fpic

fdpp/elf.c

@@ -36,26 +36,41 @@ struct elfstate {
     Elf *elf;
     Elf_Scn *symtab_scn;
     GElf_Shdr symtab_shdr;
+    Elf_Scn *rel_scn;
+    GElf_Shdr rel_shdr;
     uint32_t load_offs;
 };
 
-static void elf_dl(char *addr, uint16_t seg)
+static void elf_dl(struct elfstate *state, uint16_t seg)
 {
-    const int reloc_tab[] = {
-        #include "rel.h"
-    };
-    size_t i;
-#define _countof(array) (sizeof(array) / sizeof(array[0]))
-
-    for (i = 0; i < _countof(reloc_tab); i++)
-        memcpy(&addr[reloc_tab[i]-1], &seg, sizeof(seg));
+    Elf_Data *data;
+    int count, i;
+
+    data = elf_getdata(state->rel_scn, NULL);
+    count = state->rel_shdr.sh_size / state->rel_shdr.sh_entsize;
+
+    for (i = 0; i < count; i++) {
+        uint16_t *val;
+        GElf_Rel rel;
+        gelf_getrel(data, i, &rel);
+        if (ELF32_R_TYPE(rel.r_info) != 48 || ELF32_R_SYM(rel.r_info) != 0) {
+            fprintf(stderr, "unsupported reloc %lx %li off=%lx\n",
+                ELF32_R_TYPE(rel.r_info),
+                ELF32_R_SYM(rel.r_info), rel.r_offset);
+            return;
+        }
+        val = (uint16_t *)(state->addr + state->load_offs + rel.r_offset);
+        *val += seg;
+    }
 }
 
 void *elf_open(const char *name)
 {
     Elf         *elf;
     Elf_Scn     *scn = NULL;
     GElf_Shdr   shdr;
+    Elf_Scn     *rel_scn = NULL;
+    GElf_Shdr   rel_shdr;
     GElf_Phdr   phdr;
     int         fd;
     int         i;
@@ -110,12 +125,24 @@ void *elf_open(const char *name)
         goto err;
     }
 
+    while ((rel_scn = elf_nextscn(elf, rel_scn)) != NULL) {
+        gelf_getshdr(rel_scn, &rel_shdr);
+        if (rel_shdr.sh_type == SHT_REL)
+            break;
+    }
+    if (!rel_scn) {
+        fprintf(stderr, "elf: not found SHT_REL\n");
+        goto err;
+    }
+
     ret = (struct elfstate *)malloc(sizeof(*ret));
     ret->addr = addr;
     ret->mapsize = mapsize;
     ret->elf = elf;
     ret->symtab_scn = scn;
     ret->symtab_shdr = shdr;
+    ret->rel_scn = rel_scn;
+    ret->rel_shdr = rel_shdr;
     ret->load_offs = load_offs;
     return ret;
 
@@ -130,7 +157,7 @@ void elf_reloc(void *arg, uint16_t seg)
 {
     struct elfstate *state = (struct elfstate *)arg;
 
-    elf_dl(state->addr, seg);
+    elf_dl(state, seg);
 }
 
 void elf_close(void *arg)

fdpp/kernel.ld

@@ -2,11 +2,9 @@
 
 /* these GROUPs play the same role as GROUPS (segments) in OMF */
 /* TINY model, all segments are equal */
-PGROUP = DOS_PSP;
-LGROUP = DOS_PSP;
-DGROUP = DOS_PSP;
-TGROUP = DOS_PSP;
-IGROUP = DOS_PSP;
+_LGROUP = 0;
+_DGROUP = 0;
+_IGROUP = 0;
 
 SECTIONS
   {

fdpp/makefile

@@ -59,8 +59,6 @@ ALL = $(FDPPLIB) $(FDPPDEVL) $(TARGET).elf $(TARGET).map $(GEN_EXT)
 
 all: $(ALL)
 
-elf.o: rel.h
-
 # New makes have a way to avoid parallel invocation with the use of &:
 # On old make you would write "%.elf %.map :" which is a bit silly
 # given the names are fixed. Also $(TARGET).% won't work that way at all:
@@ -73,20 +71,10 @@ $(TARGET).elf $(TARGET).map &: $(DEPS_OF_ELF)
 else
 %.elf %.map : $(DEPS_OF_ELF)
 endif
-	$(CROSS_LD) -melf_i386 -static -Map=$(TARGET).map -o $@ \
-		$(^:%.ld=-T%.ld) --defsym=DOS_PSP=0x60
-	chmod -x $@
-
-$(TARGET).elf.tmp: $(srcdir)/kernel.ld $(OBJS) $(PPOBJS) $(DOBJS)
-	$(CROSS_LD) -melf_i386 -static -o $@ \
-		$(^:%.ld=-T%.ld) --defsym=DOS_PSP=0
+	$(CROSS_LD) -melf_i386 -static -pie -Map=$(TARGET).map -o $@ \
+		$(^:%.ld=-T%.ld)
 	chmod -x $@
 
-rel.h: $(TARGET).elf $(TARGET).elf.tmp
-	cmp -l $^ | grep "140   0" | sed 's/^ *//' | cut -d " " -f 1 | \
-		sed 's/$$/,/' > $@
-
-
 clean:
 	+cd parsers && $(MAKE) srcdir=$(abspath $(srcdir))/parsers clean
 	-$(RM) .tstamp *.map $(TARGET).elf *.inc \
@@ -117,7 +105,7 @@ PLPHDRS = farobj.hpp farptr.hpp dispatch.hpp ctors.hpp
 _PPHDRS = $(PLPHDRS) dosobj.h farhlp.hpp thunks_priv.h smalloc.h \
     farhlp_sta.h
 PPHDRS = $(addprefix $(srcdir)/,$(_PPHDRS))
-GEN_HEADERS = thunk_calls.h thunk_asms.h rel.h
+GEN_HEADERS = thunk_calls.h thunk_asms.h
 GEN_HEADERS_FD = glob_asmdefs.h
 GEN_ASMS = plt.asm cdata.asm
 # dont change file order in GEN_TMP as it matches the gen script

kernel/segs.inc

@@ -66,12 +66,12 @@ group   I_GROUP         ID_B ID ID_E IC IDATA IB_B IB IB_E
 
 BITS 16
 ; groups are defined in the linker script kernel.ld
-extern PGROUP
-extern DGROUP
-extern LGROUP
-extern TGROUP
-extern IGROUP
-extern I_GROUP
+extern _DGROUP
+extern _LGROUP
+extern _IGROUP
+%define DGROUP seg _DGROUP
+%define LGROUP seg _LGROUP
+%define IGROUP seg _IGROUP
 %define class(x)
 %define stack
 %define INITSTACKSIZE 512