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

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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
This commit is contained in:
Russ Cox 2008-12-04 13:49:45 -08:00
parent 1a19cb8ec0
commit cfb9425460
2 changed files with 39 additions and 5 deletions
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43
src/cmd/6l/asm.c
View File

@ -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 */

1
src/cmd/6l/l.h
View File

@ -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);