thunks: derive remaining plt bits from elf

This simplifies plt considerably.
Completely removed SetSymTab() and FdppCtrl()!

The intention is to make that infrastructure easily portable
to other projects. Unfortunately, that requires those "other
projects" to switch to elf, too. Which they haven't done just yet...
But I'd rather write yet another custom elf loader, than to port
this silly plt stuff.

fdpp/plt.S

@@ -1,6 +1,6 @@
 /*
  *  FDPP - freedos port to modern C++
- *  Copyright (C) 2018  Stas Sergeev (stsp)
+ *  Copyright (C) 2018-2023  Stas Sergeev (stsp)
  *
  *  This program is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -109,34 +109,11 @@ init_near_wrp:
 
     global plt_init
 plt_init:
-    push bp
-    mov bp, sp
-
     ; copy plt entry
     mov ax, FDPP_BS_SEG
     mov es, ax
     mov ax, [es:FDPP_BS_OFF+FDPP_PLT_OFFSET]
     mov bx, [es:FDPP_BS_OFF+FDPP_PLT_OFFSET+2]
     mov [fdpp_plt], ax
     mov [fdpp_plt + 2], bx
-
-    mov al, 0 ; reserved
-    mov ah, FDPP_KERNEL_VERSION
-    mov bx, 0 ; reserved
-    ; fill in struct fdpp_symtab
-    push word IGROUP
-    push word init_near_wrp           ; near_wrp[1]
-    push word TGROUP
-    push word near_wrp                ; near_wrp[0]
-    ; fdpp_symtab filled
-    mov si, sp
-
-    push ds
-    mov di, DGROUP
-    mov ds, di
-    call far [es:FDPP_BS_OFF+FDPP_PLT_OFFSET+4]
-    pop ds
-
-    mov sp, bp
-    pop bp
     ret

fdpp/thunks.cc

@@ -1,6 +1,6 @@
 /*
  *  FDPP - freedos port to modern C++
- *  Copyright (C) 2018  Stas Sergeev (stsp)
+ *  Copyright (C) 2018-2023  Stas Sergeev (stsp)
  *
  *  This program is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -42,8 +42,8 @@ struct asm_dsc_s {
 struct asm_dsc_s *asm_tab;
 #define asm_tab_len num_cthunks
 static farhlp sym_tab;
-static struct far_s *near_wrp;
 #define num_wrps 2
+static struct far_s near_wrp[num_wrps];
 static int recur_cnt;
 
 enum { ASM_OK, ASM_NORET, ASM_ABORT, PING_ABORT };
@@ -131,10 +131,6 @@ int is_dos_space(const void *ptr)
     return fdpp->is_dos_space(ptr);
 }
 
-struct fdpp_symtab {
-    struct far_s near_wrp[2];
-};
-
 static void do_relocs(UWORD old_seg, uint8_t *start_p, uint8_t *end_p,
         uint16_t delta)
 {
@@ -174,27 +170,9 @@ static void do_relocs(UWORD old_seg, uint8_t *start_p, uint8_t *end_p,
     fdlogprintf("processed %i relocs\n", reloc);
 }
 
-static void FdppSetSymTab(struct fdpp_symtab *symtab)
-{
-    free(near_wrp);
-    near_wrp = (struct far_s *)malloc(sizeof(struct far_s) * num_wrps);
-    memcpy(near_wrp, symtab->near_wrp, sizeof(struct far_s) * num_wrps);
-}
-
 int FdppCtrl(int idx, struct vm86_regs *regs)
 {
-#define DL_SET_SYMTAB 0
-    switch (idx) {
-    case DL_SET_SYMTAB:
-        if (HI_BYTE(regs->eax) != FDPP_KERNEL_VERSION) {
-            fdloudprintf("\nfdpp version mismatch: expected %i, got %i\n",
-                    FDPP_KERNEL_VERSION, HI_BYTE(regs->eax));
-            _fail();
-        }
-        FdppSetSymTab(
-                (struct fdpp_symtab *)so2lin(regs->ss, LO_WORD(regs->esi)));
-        return 0;
-    }
+    // so empty then???
     return -1;
 }
 
@@ -757,6 +735,11 @@ const void *FdppKernelReloc(void *handle, uint16_t seg)
         asm_tab[i].off = off;
     }
 
+    f.off = elf_getsymoff(h->elf, "near_wrp");
+    near_wrp[0] = f;
+    f.off = elf_getsymoff(h->elf, "init_near_wrp");
+    near_wrp[1] = f;
+
     return h->start;
 }