Date: Sat, 21 Jun 2014 22:16:44 -0700 From: John-Mark Gurney <jmg@funkthat.com> To: Andrew Turner <andrew@fubar.geek.nz> Cc: arm@FreeBSD.org Subject: Re: AVILA getting close! Message-ID: <20140622051644.GT31367@funkthat.com> In-Reply-To: <20140621170129.76e62c27@bender.Home> References: <20140618225808.GG31367@funkthat.com> <20140620151023.GZ31367@funkthat.com> <20140620200827.1c33c7da@bender.Home> <20140621010804.GD31367@funkthat.com> <20140621070827.GJ31367@funkthat.com> <20140621170129.76e62c27@bender.Home>
next in thread | previous in thread | raw e-mail | index | archive | help
Andrew Turner wrote this message on Sat, Jun 21, 2014 at 17:01 +0100:
> On Sat, 21 Jun 2014 00:08:28 -0700
> John-Mark Gurney <jmg@funkthat.com> wrote:
> > I've looked at the assembly for donelist_init for both the working
> > and non-working case, and besides an extra store in the good version,
> > which I think is just because of the unoptimized code, things look
> > the same to me...
> I suspect it's more likely the working version is not making
> assumptions on the stack alignment, where the broken one is.
So, is there a way you can fix up the rtld tramp in
rtld-elf/arm/rtld_start.S so that the stack can be traced through?
Right now, when I'm in the plt code, I can get the userland stack,
but once I end up in _rtld_bind_start, I can't get a trace back
past the got which is making this next to imposible to debug..
(gdb) stepi
0x200774d4 in .plt () from /lib/libc.so.7
2: $pc = 0x200774d4
1: $sp = 0xbffff24c
(gdb) bt
#0 0x200774d4 in .plt () from /lib/libc.so.7
#1 0x20171804 in getenv (name=0x20184a98 "MALLOC_CONF")
at /usr/src.avila/lib/libc/stdlib/getenv.c:144
#2 0x200f23b0 in malloc_init_hard () at jemalloc_jemalloc.c:464
#3 0x200f34d8 in jemalloc_constructor () at jemalloc_jemalloc.c:296
#4 0x2001dee0 in objlist_call_init (list=<value optimized out>,
lockstate=0xbffffb40) at /usr/src.avila/libexec/rtld-elf/rtld.c:2385
#5 0x200212b8 in $a () at /usr/src.avila/libexec/rtld-elf/rtld.c:640
#6 0x200212b8 in $a () at /usr/src.avila/libexec/rtld-elf/rtld.c:640
(gdb) stepi
_rtld_bind_start () at /usr/src.avila/libexec/rtld-elf/arm/rtld_start.S:80
80 stmdb sp!,{r0-r4,sl,fp}
2: $pc = 0x20018f84
1: $sp = 0xbffff24c
Current language: auto; currently asm
(gdb) bt
#0 _rtld_bind_start () at /usr/src.avila/libexec/rtld-elf/arm/rtld_start.S:80
#1 0x2019e0c0 in .got () from /lib/libc.so.7
#2 0x2019e0c0 in .got () from /lib/libc.so.7
Poof, now I have no clue where I am anymore... :( Or at least
provide an option (enabled by -DDEBUG) to provide it..
Well, I did manage to work this out.. and I feel a little stupid since
I saw this name and thought it a bit weird.. I believe that gcc is
is not making sure that the stack is aligned when calling
__aeabi_read_tp... I believe that gcc does not think that it is a
full function, but it does go through relocation... If you look at the
disassembly of the sob function in newsyslog, you'll see that it will
leave the stack unaligned off the bat:
9f58: e92d4030 push {r4, r5, lr}
and setting a breakpoint there confirms this:
(gdb) c
Continuing.
Breakpoint 8, sob (
p=0xbfffef20 "/var/log/all.log\t\t\t600 7\t *\t@T00 J\n")
at /usr/src.avila/usr.sbin/newsyslog/newsyslog.c:2400
2400 while (p && *p && isspace(*p))
2: $pc = 0x9f5c
1: $sp = 0xbfffeeec
So, gcc is generating broken code... Can you please fix this?
Thanks.
--
John-Mark Gurney Voice: +1 415 225 5579
"All that I will do, has been done, All that I have, has not."
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20140622051644.GT31367>