add dnload import method to 64-bit version (unoptimized atm)

Makefile

@@ -40,7 +40,8 @@ CXXFLAGS += -m$(BITS) $(shell pkg-config --cflags sdl2)
 
 LIBS=-lc
 
-ASFLAGS += -DUSE_INTERP -DALIGN_STACK -DNO_START_ARG #-DUSE_DT_DEBUG
+SMOLFLAGS += -d
+ASFLAGS   += -DUSE_INTERP -DALIGN_STACK -DNO_START_ARG #-DUSE_DT_DEBUG
 
 NASM    ?= nasm
 PYTHON3 ?= python3

smol.py

@@ -30,6 +30,8 @@ def main():
     parser.add_argument('--readelf', default=shutil.which('readelf'), \
         help="which readelf binary to use")
 
+    parser.add_argument('-d', '--dnload', default=False, action='store_true', \
+        help="Use dnload's mechanism of importing functions. Slightly larger, but usually better compressable.")
 #   parser.add_argument('--libsep', default=False, action='store_true', \
 #       help="Separete import symbols per library, instead of looking at every library when resolving a symbol.")
 
@@ -64,7 +66,7 @@ def main():
         symbols.setdefault(library, [])
         symbols[library].append((symbol, reloc))
 
-    output(arch, symbols, args.output)
+    output(arch, symbols, args.dnload, args.output)
 
 if __name__ == '__main__':
     main()

smolemit.py

@@ -51,9 +51,11 @@ def output_x86(libraries, outf):
 # end output_x86
 
 
-def output_amd64(libraries, outf):
+def output_amd64(libraries, dnload, outf):
     outf.write('; vim: set ft=nasm:\n')
     outf.write('bits 64\n')
+    if dnload:
+        outf.write('%define USE_DNLOAD_LOADER\n')
 
     shorts = { l: l.split('.', 1)[0].lower().replace('-', '_') for l in libraries }
 
@@ -108,9 +110,9 @@ global {name}
 # end output_amd64
 
 
-def output(arch, libraries, outf):
+def output(arch, libraries, dnload, outf):
     if arch == 'i386': output_x86(libraries, outf)
-    elif arch == 'x86_64': output_amd64(libraries, outf)
+    elif arch == 'x86_64': output_amd64(libraries, dnload, outf)
     else:
         eprintf("E: cannot emit for arch '" + str(arch) + "'")
         sys.exit(1)

src/elf.inc

@@ -32,3 +32,9 @@
 %define DT_SYMTAB ( 6)
 %define DT_DEBUG  (21)
 
+%define ST_NAME_OFF  ( 0)
+;  ,---- not 16?
+; v
+%define ST_VALUE_OFF ( 8)
+%define SYMTAB_SIZE  (24)
+

src/loader64.asm

@@ -41,8 +41,100 @@ _smol_start:
     mov r12, [r12 + L_NEXT_OFF] ; skip this binary
 ;   mov r12, [r12 + L_NEXT_OFF] ; skip the vdso
         ; the second one isn't needed anymore, see code below (.next_link)
+;%elifdef USE_DNLOAD_LOADER
+;    mov r12, [r12 + L_NEXT_OFF] ; skip this binary
 %endif
 
+%ifdef USE_DNLOAD_LOADER
+   push _symbols
+   push r12
+    pop r11
+    pop rdi
+
+;.loopme: jmp short .loopme ; debugging
+    .next_hash:
+            ;
+        mov r14d, dword [rdi]
+            ; assume it's nonzero
+       push r11
+        pop r12
+
+        .next_link:
+            mov r12, [r12 + L_NEXT_OFF]
+                ; ElfW(Dyn)* dyn(rsi) = r12->l_ld
+            mov rsi, [r12 + L_LD_OFF]
+
+                ; get strtab off
+            .next_dyn:
+              lodsq
+                cmp al, DT_STRTAB
+              lodsq
+                jne short .next_dyn
+
+                ; void* addr(rcx) = r12->l_addr
+                ; const char* strtab(r9) = lookup(rsi,DT_STRTAB), *symtab_end(r8)=r9;
+            mov rcx, [r12 + L_ADDR_OFF]
+            cmp rax, rcx
+            jge short .noreldynaddr
+            add rax, rcx
+        .noreldynaddr:
+           push rax
+           push rax
+            pop r8
+            pop r9
+
+                ; const ElfW(Sym)* symtab(rdx) = lookup(rsi, DT_SYMTAB);
+          lodsq ; SYMTAB d_tag
+          lodsq ; SYMTAB d_un.d_ptr
+            cmp rax, rcx
+            jge short .norelsymaddr
+            add rax, rcx
+        .norelsymaddr:
+           push rax
+            pop rdx
+
+        .next_sym:
+            mov esi, dword [rdx + ST_NAME_OFF]
+            add rsi, r9
+
+           push 33
+           push 5381
+           push 0
+            pop rcx
+            pop rax
+            pop rbx
+        .nexthashiter:
+                ; TODO: optimize register usage so that lodsb can be used
+            mov cl, byte [rsi]
+            inc rsi
+             or cl, cl
+             jz short .breakhash
+
+           push rdx
+            mul ebx
+            pop rdx
+            add eax, ecx
+            jmp short .nexthashiter
+        .breakhash:
+
+            cmp r14d, eax
+             je short .eq
+
+            add rdx, SYMTAB_SIZE
+            cmp rdx, r8
+             jl short .next_sym
+;          int3
+            jmp short .next_link
+
+        .eq:
+            mov rax, [rdx + ST_VALUE_OFF]
+            add rax, [r12 + L_ADDR_OFF]
+          stosq
+            cmp word [rdi], 0
+            jne short .next_hash
+
+; if USE_DNLOAD_LOADER
+%else
        push _smol_start
        push r12
        push -1
@@ -134,6 +226,9 @@ repne scasd ; technically, scasq should be used, but ehhhh
             ; } while (1)
 ;       jmp short .next_hash
 
+; if USE_DNLOAD_LOADER ... else ...
+%endif
+
 .needed_end:
 ;  int3 ; debugging
 ;   xor rbp, rbp ; still 0 from _dl_start_user
@@ -142,8 +237,11 @@ repne scasd ; technically, scasq should be used, but ehhhh
     mov rdi, rsp
 %endif
 %ifdef ALIGN_STACK
+%ifdef USE_DNLOAD_LOADER
+   push rax
+%else
        ; apparently not needed?
-; push rax
+%endif
 %endif
 %ifdef USE_DL_FINI
    xchg rsi, r13 ; _dl_fini

src/rtld.inc

@@ -18,11 +18,13 @@
 
 %define DT_SYMSIZE_SHIFT         4
 
+%define DT_STRTAB                0x5
 %define DT_SYMTAB                0x6
 
 %else
 %define L_ADDR_OFF           (  0)
 %define L_NAME_OFF           (  8)
+%define L_LD_OFF             ( 16)
 %define L_NEXT_OFF           ( 24)
 %define L_INFO_OFF           ( 64)
 %define L_INFO_DT_SYMTAB_OFF (112)