various nptl patches

Joakim Tjernlund joakim.tjernlund at transmode.se
Sat Apr 17 09:53:45 UTC 2010


> >
> > Austin Foxley wrote:
> > > On 04/16/2010 07:37 AM, Timo Teräs wrote:
> > >> Ok, second try on getting the libc - libpthread interactions right.
> > >>
> > >>
> > >> This includes the Joakim's patch for protected symbols, with a
> > >> little fix from me.
> > >
> > > I thought the hidden symbol thing would work, because I thought when
> > > you turned on stdio-futexes, everywhere used futexes. I didn't
> > > realize other places were using __pthread* symbols directly...
> >
> > Yeah, that was my impression too. But it turns out to work
> > differently :/
> >
> > > We'll need to patch all the other arch's ldso as well to handle
> > > protected symbols, but I'll apply this for now. If I'm not mistaken,
> > > other archs will be no worse off than they are now in this situation.
> > > Right?
> >
> > Right. It makes things slightly better for other archs too, but
> > in practice it won't work until they support protected symbols too.
>
> Finally looked at the ldso patch and I am not entirely happy with it.
> I think the general structure should be different to make it easier
> to follow the code and port it to other archs. I can probably
> take a stab at it during the weekend but I have no env. to test in
> so I will have to do it blindly.
>
>  Jocke

So this is what I came up with. I do wonder if not linux_resolver
need PROTECTED support too? Have you tested with LAZY relocation too?

 Jocke

>From 315d855288d05d6503ec66320a66f9d29c52246d Mon Sep 17 00:00:00 2001
From: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
Date: Sat, 17 Apr 2010 11:39:24 +0200
Subject: [PATCH 1/2] ldso,i386: Cleanup PROTECTED support.


Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
---
 ldso/ldso/i386/elfinterp.c |   21 +++++++++++----------
 1 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/ldso/ldso/i386/elfinterp.c b/ldso/ldso/i386/elfinterp.c
index 1e3a2b2..7e05c14 100644
--- a/ldso/ldso/i386/elfinterp.c
+++ b/ldso/ldso/i386/elfinterp.c
@@ -175,11 +175,16 @@ _dl_do_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
 	symbol_addr = 0;
 	symname = strtab + symtab[symtab_index].st_name;

-	if (symtab_index &&
-	    (ELF32_ST_VISIBILITY(symtab[symtab_index].st_other)
-	     != STV_PROTECTED)) {
-		symbol_addr = (unsigned long)_dl_find_hash(symname, scope, tpnt,
-							   elf_machine_type_class(reloc_type), &tls_tpnt);
+	if (symtab_index) {
+	    if (ELF32_ST_VISIBILITY(symtab[symtab_index].st_other)
+		!= STV_PROTECTED)
+		    symbol_addr = (unsigned long)_dl_find_hash(symname, scope,
+							       tpnt,
+							       elf_machine_type_class(reloc_type),
+							       &tls_tpnt);
+	    else
+		    symbol_addr = DL_FIND_HASH_VALUE(tpnt, elf_machine_type_class(reloc_type),
+						     &symtab[symtab_index]);

 		/*
 		 * We want to allow undefined references to weak symbols - this
@@ -190,11 +195,7 @@ _dl_do_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
 					&& ELF32_ST_BIND(symtab[symtab_index].st_info) != STB_WEAK))
 			return 1;
 	} else {
-		if (symtab_index)
-			symbol_addr = DL_FIND_HASH_VALUE(tpnt, elf_machine_type_class(reloc_type),
-							 &symtab[symtab_index]);
-		else
-			symbol_addr = symtab[symtab_index].st_value;
+		symbol_addr = symtab[symtab_index].st_value;
 		tls_tpnt = tpnt;
 	}

--
1.6.4.4

>From d4607f34aa60c201c731eac4b7297291d72cdf27 Mon Sep 17 00:00:00 2001
From: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
Date: Sat, 17 Apr 2010 11:47:20 +0200
Subject: [PATCH 2/2] ldso,i386: Remove suspect code.

Make it work as glibc. Possibly one need to add
test for NULL tls_tpnt inside switch{} stmt too(glibc does)

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
---
 ldso/ldso/i386/elfinterp.c |    4 ----
 1 files changed, 0 insertions(+), 4 deletions(-)

diff --git a/ldso/ldso/i386/elfinterp.c b/ldso/ldso/i386/elfinterp.c
index 7e05c14..b04febc 100644
--- a/ldso/ldso/i386/elfinterp.c
+++ b/ldso/ldso/i386/elfinterp.c
@@ -194,11 +194,7 @@ _dl_do_reloc(struct elf_resolve *tpnt, struct dyn_elf *scope,
 		if (unlikely(!symbol_addr && (ELF_ST_TYPE(symtab[symtab_index].st_info) != STT_TLS)
 					&& ELF32_ST_BIND(symtab[symtab_index].st_info) != STB_WEAK))
 			return 1;
-	} else {
-		symbol_addr = symtab[symtab_index].st_value;
-		tls_tpnt = tpnt;
 	}
-

 #if defined (__SUPPORT_LD_DEBUG__)
 	old_val = *reloc_addr;
--
1.6.4.4



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