emit dynamically linked 6.out on darwin instead of static,

unless given -d flag.

the resulting binary doesn't *use* any dynamic libraries,
it just has a reference to the dynamic linker and an
empty list of needed symbols and libraries.

this is enough to make 6.out binaries that can be run
under dtrace / dtruss.

R=r
DELTA=39  (34 added, 0 deleted, 5 changed)
OCL=20476
CL=20482

diff --git a/src/cmd/6l/asm.c b/src/cmd/6l/asm.c
index 5bb6cc414995eefae627240b2a3e568f20588d2e..fec8fd0e16b12ebe761ba6afddf69f96830b311d 100644 (file)
--- a/src/cmd/6l/asm.c
+++ b/src/cmd/6l/asm.c
@@ -121,7 +121,7 @@ asmb(void)
 {
        Prog *p;
        int32 v, magic;
-       int a, np;
+       int a, nl, np;
        uchar *op1;
        vlong vl, va, fo, w, symo;
        int strtabsize;
@@ -357,10 +357,12 @@ asmb(void)
                lputl((1<<24)|7);               /* cputype - x86/ABI64 */
                lputl(3);                       /* subtype - x86 */
                lputl(2);                       /* file type - mach executable */
-               if (debug['s'])
-                       lputl(4);                       /* number of loads */
-               else
-                       lputl(7);                       /* number of loads */
+               nl = 4;
+               if (!debug['s'])
+                       nl += 3;
+               if (!debug['d'])        // -d = turn off "dynamic loader"
+                       nl += 2;
+               lputl(nl);                      /* number of loads */
                lputl(machheadr()-32);          /* size of loads */
                lputl(1);                       /* flags - no undefines */
                lputl(0);                       /* reserved */
@@ -399,6 +401,7 @@ asmb(void)
                        0,0,0,0,                /* offset align reloc nreloc */
                        1);                     /* flag - zero fill */
 
+               machdylink();
                machstack(va+HEADR);
 
                if (!debug['s']) {
@@ -824,6 +827,32 @@ machsect(char *name, char *seg, vlong addr, vlong size, uint32 off,
        lputl(0);       /* reserved */
 }
 
+// Emit a section requesting the dynamic loader
+// but giving it no work to do (an empty dynamic symbol table).
+// This is enough to make the Apple tracing programs (like dtrace)
+// accept the binary, so that one can run dtruss on a 6.out.
+// The dynamic linker loads at 0x8fe00000, so if we want to
+// be able to build >2GB binaries, we're going to need to move
+// the text segment to 4G like Apple does.
+void
+machdylink(void)
+{
+       int i;
+
+       if(debug['d'])
+               return;
+
+       lputl(11);      /* LC_DYSYMTAB */
+       lputl(80);      /* byte count */
+       for(i=0; i<18; i++)
+               lputl(0);
+
+       lputl(14);      /* LC_LOAD_DYLINKER */
+       lputl(28);      /* byte count */
+       lputl(12);      /* offset to string */
+       strnput("/usr/lib/dyld", 16);
+}
+
 void
 machstack(vlong e)
 {
@@ -855,6 +884,10 @@ machheadr(void)
        a += 20;        /* data sect */
        a += 20;        /* bss sect */
        a += 46;        /* stack sect */
+       if (!debug['d']) {
+               a += 20;        /* dysymtab */
+               a += 7; /* load dylinker */
+       }
        if (!debug['s']) {
                a += 18;        /* symdat seg */
                a += 4; /* symtab seg */

diff --git a/src/cmd/6l/l.h b/src/cmd/6l/l.h
index ce3ff8eaf6ae9792aa5c4654d46bc7cd8dab2ea4..7367bfec2a51ef2369e4e57674d6525683ea821b 100644 (file)
--- a/src/cmd/6l/l.h
+++ b/src/cmd/6l/l.h
@@ -438,6 +438,7 @@ void        machseg(char*, vlong, vlong, vlong, vlong, uint32, uint32, uint32, uint32);
 void   machsymseg(uint32, uint32);
 void   machsect(char*, char*, vlong, vlong, uint32, uint32, uint32, uint32, uint32);
 void   machstack(vlong);
+void   machdylink(void);
 uint32 machheadr(void);
 
 uint32 linuxheadr(void);