Refactor; Update comments

1 files changed, 110 insertions, 105 deletions

diff --git a/bxgen.c b/bxgen.c
index 6987216..c123f70 100755
--- a/bxgen.c
+++ b/bxgen.c
@@ -720,8 +720,12 @@ void unit_set_entry_point(Pool *pool, i64 unit, i64 entry_point_proc) {
 void unit_write(Pool *pool, i64 unit, u16 target, i64 io_out, void *io_user_data) {
   //  Docs
   //
-  //  AR  https://man.freebsd.org/cgi/man.cgi?query=ar&sektion=5
-  //  ELF https://man7.org/linux/man-pages/man5/elf.5.html
+  //  AR         https://man.freebsd.org/cgi/man.cgi?query=ar&sektion=5
+  //  ELF        https://man7.org/linux/man-pages/man5/elf.5.html
+  //
+  //  LLVM impl  https://github.com/llvm/llvm-project/blob/main/lld/ELF/Driver.cpp#L2822
+  //             https://github.com/llvm/llvm-project/blob/main/lld/ELF/Writer.cpp#L304
+  //             https://github.com/llvm/llvm-project/blob/main/lld/ELF/OutputSections.cpp#L469
   //
 
   assert(pool != NULL && pool->entities != NULL);
@@ -739,6 +743,90 @@ void unit_write(Pool *pool, i64 unit, u16 target, i64 io_out, void *io_user_data
   u8  elf_abi_ver = 0;  // ABI version
   u16 elf_machine = 62; // x86_64
 
+  #define WRITE(x, n)     io_write( io_out, n,                              x,                    io_user_data )
+  #define WRITE_V(...)    io_write( io_out, sizeof((u8[]) {__VA_ARGS__}),  (u8[])  {__VA_ARGS__}, io_user_data )
+  #define WRITE_DUP(x, n) io_write( io_out, n,                             (u8[n]) {         0 }, io_user_data )
+  #define WRITE_2(x)      io_write( io_out, 2,                            &(u16)   {         x }, io_user_data )
+  #define WRITE_4(x)      io_write( io_out, 4,                            &(u32)   {         x }, io_user_data )
+  #define WRITE_8(x)      io_write( io_out, 8,                            &(u64)   {         x }, io_user_data )
+
+  u16 ehs   = 64;
+  u16 shs   = 0;
+  u16 phs   = 56;
+  u64 align = 8;
+
+  u8 code[16] = {
+    0xb8,             // mov rax
+    0x3c, 0, 0, 0,    // 60            // exit
+    0x48, 0x31, 0xff, // xor rdx, rdx  // rdx = 0
+    0x0f, 0x05,       // syscall
+  };
+
+  u64 code_offset  = ehs + phs;
+  u64 code_size    = sizeof code;
+  u64 entry_offset = 0;
+
+  u64 base_address = 0x400000; // x86_64 base address
+  u64 code_address = base_address + code_offset;
+  u64 entry        = code_address + entry_offset;
+
+  assert((code_offset % align) == 0);
+  assert((code_size % align) == 0);
+
+  //  ELF header
+  //
+
+  WRITE_V( 0x7f, 'E', 'L', 'F' ); // magic
+
+  WRITE_V( elf_class   );
+  WRITE_V( elf_data    );
+  WRITE_V( elf_ver     );
+  WRITE_V( elf_abi     );
+  WRITE_V( elf_abi_ver );
+
+  WRITE_DUP(0, 7); // padding
+
+  WRITE_2(           2 ); // executable
+  WRITE_2( elf_machine );
+  WRITE_4(           1 ); // current version
+  WRITE_8( entry       ); // entry point address
+  WRITE_8( ehs         ); // program header offset
+  WRITE_8(           0 ); // section header offset
+  WRITE_4(           0 ); // flags
+  WRITE_2( ehs         ); // ELF header size
+  WRITE_2( phs         ); // program header size
+  WRITE_2(           1 ); // program header count
+  WRITE_2( shs         ); // section header size
+  WRITE_2(           0 ); // section header count
+  WRITE_2(           0 ); // string table section header index
+
+  //  Program header
+  //
+
+  WRITE_4(            1 ); // type   (PT_LOAD)
+  WRITE_4(            5 ); // flags  (PF_X | PF_R)
+  WRITE_8( code_offset  ); // offset
+  WRITE_8( code_address ); // vaddr
+  WRITE_8( code_address ); // paddr
+  WRITE_8( code_size    ); // filesz
+  WRITE_8( code_size    ); // memsz
+  WRITE_8(            8 ); // align
+
+  //  Code
+  //
+
+  for (i64 i = code_offset - ehs - phs; i > 0; --i)
+    WRITE_V( 0 );
+
+  WRITE( code, code_size );
+
+  #undef WRITE_V
+  #undef WRITE_DUP
+  #undef WRITE_32
+  #undef WRITE_64
+
+  #undef WRITE
+
   //  Read dependencies
   //
   {
@@ -1065,25 +1153,23 @@ void unit_write(Pool *pool, i64 unit, u16 target, i64 io_out, void *io_user_data
               current_offset = prev_offset;
             }
 
-            printf("%-18s", type >= 1 && type <= 17 ? (c8 const *[]) {
-                     "Program data",
-                     "Symbols",
-                     "String table",
-                     "Rel width addends",
-                     "Dynamic",
-                     "Note",
-                     "Zero",
-                     "Rel",
-                     "",
-                     "",
-                     "",
-                     "",
-                     "",
-                     "",
-                     "",
-                     "",
-                     "Group",
-                   }[type - 1] : "");
+            printf(
+              "%-18s",
+              type >= 1 && type <= 8 ?
+                (c8 const *[]) {
+                  "Program data",
+                  "Symbols",
+                  "String table",
+                  "Rel width addends",
+                  "Dynamic",
+                  "Note",
+                  "No data",
+                  "Rel",
+                }[type - 1] :
+              type == 17 ?
+                  "Group"   :
+                  ""
+            );
 
             if ((flags & 1) == 1)
               printf("  Writable");
@@ -1092,6 +1178,9 @@ void unit_write(Pool *pool, i64 unit, u16 target, i64 io_out, void *io_user_data
             if ((flags & 4) == 4)
               printf("  Executable");
 
+            //  NOTE
+            //  Only alloc sections should be written to the output binary.
+
             printf("\n");
           }
 
@@ -1121,90 +1210,6 @@ void unit_write(Pool *pool, i64 unit, u16 target, i64 io_out, void *io_user_data
       io_close(f, io_user_data);
     }
   }
-
-  #define WRITE(x, n)     io_write( io_out, n,                              x,                    io_user_data )
-  #define WRITE_V(...)    io_write( io_out, sizeof((u8[]) {__VA_ARGS__}),  (u8[])  {__VA_ARGS__}, io_user_data )
-  #define WRITE_DUP(x, n) io_write( io_out, n,                             (u8[n]) {         0 }, io_user_data )
-  #define WRITE_2(x)      io_write( io_out, 2,                            &(u16)   {         x }, io_user_data )
-  #define WRITE_4(x)      io_write( io_out, 4,                            &(u32)   {         x }, io_user_data )
-  #define WRITE_8(x)      io_write( io_out, 8,                            &(u64)   {         x }, io_user_data )
-
-  u16 ehs   = 64;
-  u16 shs   = 0;
-  u16 phs   = 56;
-  u64 align = 8;
-
-  u8 code[16] = {
-    0xb8,             // mov rax
-    0x3c, 0, 0, 0,    // 60            // exit
-    0x48, 0x31, 0xff, // xor rdx, rdx  // rdx = 0
-    0x0f, 0x05,       // syscall
-  };
-
-  u64 code_offset  = ehs + phs;
-  u64 code_size    = sizeof code;
-  u64 entry_offset = 0;
-
-  u64 base_address = 0x400000; // x86_64 base address
-  u64 code_address = base_address + code_offset;
-  u64 entry        = code_address + entry_offset;
-
-  assert((code_offset % align) == 0);
-  assert((code_size % align) == 0);
-
-  //  ELF header
-  //
-
-  WRITE_V( 0x7f, 'E', 'L', 'F' ); // magic
-
-  WRITE_V( elf_class   );
-  WRITE_V( elf_data    );
-  WRITE_V( elf_ver     );
-  WRITE_V( elf_abi     );
-  WRITE_V( elf_abi_ver );
-
-  WRITE_DUP(0, 7); // padding
-
-  WRITE_2(           2 ); // executable
-  WRITE_2( elf_machine );
-  WRITE_4(           1 ); // current version
-  WRITE_8( entry       ); // entry point address
-  WRITE_8( ehs         ); // program header offset
-  WRITE_8(           0 ); // section header offset
-  WRITE_4(           0 ); // flags
-  WRITE_2( ehs         ); // ELF header size
-  WRITE_2( phs         ); // program header size
-  WRITE_2(           1 ); // program header count
-  WRITE_2( shs         ); // section header size
-  WRITE_2(           0 ); // section header count
-  WRITE_2(           0 ); // string table section header index
-
-  //  Program header
-  //
-
-  WRITE_4(            1 ); // type   (PT_LOAD)
-  WRITE_4(            5 ); // flags  (PF_X | PF_R)
-  WRITE_8( code_offset  ); // offset
-  WRITE_8( code_address ); // vaddr
-  WRITE_8( code_address ); // paddr
-  WRITE_8( code_size    ); // filesz
-  WRITE_8( code_size    ); // memsz
-  WRITE_8(            8 ); // align
-
-  //  Code
-  //
-
-  for (i64 i = code_offset - ehs - phs; i > 0; --i)
-    WRITE_V( 0 );
-
-  WRITE( code, code_size );
-
-  #undef WRITE_V
-  #undef WRITE_DUP
-  #undef WRITE_32
-  #undef WRITE_64
-
-  #undef WRITE
 }
 
 i64 io_open_read(i64 name_size, c8 *name, void *user_data) {