Date: Sat, 22 Nov 2014 18:18:56 -0800 From: Mark Johnston <markj@FreeBSD.org> To: Rui Paulo <rpaulo@me.com> Cc: Shrikanth Kamath <shrikanth07@gmail.com>, John Baldwin <jhb@freebsd.org>, freebsd-hackers@freebsd.org, avg@freebsd.org, Konstantin Belousov <kostikbel@gmail.com>, freebsd-dtrace@freebsd.org Subject: Re: DTrace: stack() does not print kernel module functions for i386 Message-ID: <20141123021856.GA54708@raichu> In-Reply-To: <AE2A9617-8E59-4F44-9C1F-8344EF5B05C7@me.com> References: <CAEOAkMXnwqC42gZKc0f80cppff077pYGjs5PUPht0DBcyEi8Jw@mail.gmail.com> <20141109093632.GV53947@kib.kiev.ua> <9011F920-3092-4E61-9CDC-68FD9092BB7D@me.com> <201411131336.12334.jhb@freebsd.org> <AE2A9617-8E59-4F44-9C1F-8344EF5B05C7@me.com>
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On Thu, Nov 13, 2014 at 07:49:27PM -0800, Rui Paulo wrote:
> On Nov 13, 2014, at 10:36, John Baldwin <jhb@freebsd.org> wrote:
> > Why have the #ifdef? In theory other platforms besides amd64 could use
> > sys/kern/link_elf_obj.c. It doesn't hurt to just let the code always accept
> > both ET_DYN and ET_REL does it?
>
> No, it doesn't hurt.
The suggested patch doesn't seem quite right; there are other functions
in dt_module.c with the same assignment (i.e.
"is_elf_obj = ehdr.e_type == ET_REL"), but the same modification is not
correct in all cases - fixing it everywhere breaks stack() again - and
"is_elf_obj" seems like the wrong name if DSOs are counted as well.
The root of the problem is that dmp->dm_*_va offsets don't have the kld
load address taken into account on i386, since they're currently set based
only on the ELF section addresses. This is handled by
dmp->dm_reloc_offset for symbols, but that's a separate case.
When is_elf_obj is true, we include the load address when setting the
dmp->dm_*_va fields. I suggest we do that unconditionally, and only set
elements of dmp->dm_sec_offsets if is_elf_obj is true. This fixes the
bug for me on i386. Any opinions?
Thanks,
-Mark
diff --git a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_module.c b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_module.c
index e3905c1..9dd52b5 100644
--- a/cddl/contrib/opensolaris/lib/libdtrace/common/dt_module.c
+++ b/cddl/contrib/opensolaris/lib/libdtrace/common/dt_module.c
@@ -1211,13 +1211,13 @@ dt_module_update(dtrace_hdl_t *dtp, struct kld_file_stat *k_stat)
#if defined(__FreeBSD__)
if (sh.sh_size == 0)
continue;
- if (is_elf_obj && (sh.sh_type == SHT_PROGBITS ||
- sh.sh_type == SHT_NOBITS)) {
+ if (sh.sh_type == SHT_PROGBITS || sh.sh_type == SHT_NOBITS) {
alignmask = sh.sh_addralign - 1;
mapbase += alignmask;
mapbase &= ~alignmask;
sh.sh_addr = mapbase;
- dmp->dm_sec_offsets[elf_ndxscn(sp)] = sh.sh_addr;
+ if (is_elf_obj)
+ dmp->dm_sec_offsets[elf_ndxscn(sp)] = sh.sh_addr;
mapbase += sh.sh_size;
}
#endif
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