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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