Paul Mundt writes:

The current behavior of the powerpc boot1_arch.h seems somewhat broken.
Currently room is made on the stack pointer for the link register, but the link
register is never actually pushed onto it. glibc bears the following comments:

    /* Call _dl_start with one parameter pointing at argc */
            mr      r3,r1
    /* (we have to frob the stack pointer a bit to allow room for
       _dl_start to save the link register).  */

followed by the -16 add to r1. Despite the fact that r1 is modified, the link
register is never actually pushed onto r1, thus the adjustment is completely
superfluous.

There's two possible fixes for this, either saving the link register in the way
that glibc does, or getting rid of the r1 adjustment. As I'm not sure if saving
the link register will actually break the _dl_boot2 callin, both options will
probably want to be played with.

The following bit of inline assembly in the attached patch builds cleanly for
me with gcc 3.3 on darwin, but I'm not able to test it any further beyond that.

1 files changed, 3 insertions, 1 deletions

diff --git a/ldso/ldso/powerpc/dl-startup.h b/ldso/ldso/powerpc/dl-startup.h
index 615db6926..2f54ed9d9 100644
--- a/ldso/ldso/powerpc/dl-startup.h
+++ b/ldso/ldso/powerpc/dl-startup.h
@@ -9,8 +9,10 @@ asm("" \
 "	.text\n"			\
 "	.globl	_dl_boot\n"		\
 "_dl_boot:\n"				\
-"	mr	3,1\n"			\
+"	mr	3,1\n"		\
+"	li	4,0\n"			\
 "	addi	1,1,-16\n"		\
+"	stw	4,0(1)\n"		\
 "	bl      _dl_boot2\n"		\
 ".previous\n"				\
 );