V2 [PATCH] ELF: Don't check relocations in non-loaded, non-alloced sections
H.J. Lu
hjl.tools@gmail.com
Wed Jun 3 16:48:36 GMT 2020
On Tue, Jun 02, 2020 at 06:29:16PM -0700, H.J. Lu wrote:
> On Tue, Jun 2, 2020 at 5:06 PM Fangrui Song <i@maskray.me> wrote:
> >
> > I haven't really read the patch, but just wanted to express a point.
> > It is sometimes useful to check relocations even for a non-SHF_ALLOC
> > section. For example, a PC relative relocation type does not make
> > sense from a non-SHF_ALLOC section referencing a SHF_ALLOC section.
> >
> > Conceptually, even if a non-SHF_ALLOC is loaded as part of the memory
> > image, the distance between it and a SHF_ALLOC section may not be a
> > constant, so the linker cannot reasonably resolve the relocation.
> >
>
> Since non-SHF_ALLOC sections have no impact on run-time behavior,
> ld.so ignores dynamic relocations on non-SHF_ALLOC section. In
> checking phase, relocations on non-SHF_ALLOC section shouldn't
> alter other relocatitons against the same symbol. When resolving
> such relocations, linker should ignore any relocation errors for such
> relocations.
>
>
Linker shouldn't ignore any relocation errors for such relocations. But
linker should resolve them to 0:
https://sourceware.org/bugzilla/show_bug.cgi?id=26080
Here is the updated patch. OK for master?
Thanks.
H.J.
---
>From 0e27705c41db5200c248403c9b50f17c5533dd04 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Tue, 2 Jun 2020 06:53:34 -0700
Subject: [PATCH] ELF: Don't check relocations in non-loaded, non-alloced
sections
Don't do anything special with non-loaded, non-alloced sections.
In particular, any relocs in such sections should not affect GOT
and PLT reference counting (ie. we don't allow them to create GOT
or PLT entries), there's no possibility or desire to optimize TLS
relocs, and there's not much point in propagating relocs to shared
libs that the dynamic linker won't relocate. Resolve relocation
in debug section against symbol defined in shared library to 0.
bfd/
PR ld/26080
* elf-m10300.c (mn10300_elf_relocate_section): Resolve relocation
in debug section against symbol defined in shared library to 0.
* elf32-i386.c (elf_i386_check_relocs): Remove SEC_ALLOC check.
* elf32-lm32.c (lm32_elf_check_relocs): Likewise.
* elf32-m32r.c (m32r_elf_check_relocs): Likewise.
* elf32-nds32.c (nds32_elf_check_relocs): Likewise.
* elf32-nios2.c (nios2_elf32_check_relocs): Likewise.
* elf32-or1k.c (or1k_elf_check_relocs): Likewise.
* elf32-ppc.c (ppc_elf_check_relocs): Likewise.
* elf32-sh.c (sh_elf_check_relocs): Likewise.
* elf32-xtensa.c (elf_xtensa_check_relocs): Likewise.
* elf64-alpha.c (elf64_alpha_check_relocs): Likewise.
* elf64-ppc.c (ppc64_elf_check_relocs): Likewise.
* elf64-x86-64.c (elf_x86_64_check_relocs): Likewise.
* elf32-vax.c (elf_vax_check_relocs): Set non_got_ref for non-GOT
reference.
(elf_vax_adjust_dynamic_symbol): Generate a copy reloc only if
there is non-GOT reference.
* elflink.c (_bfd_elf_link_check_relocs): Skip non-loaded,
non-alloced sections.
ld/
PR ld/26080
* testsuite/ld-elf/comm-data.exp: Remove copy_reloc.
* testsuite/ld-elf/comm-data2r.rd: Removed.
* testsuite/ld-elf/comm-data2r.sd: Likewise.
* testsuite/ld-elf/comm-data2r.xd: Likewise.
---
bfd/elf-m10300.c | 6 +++---
bfd/elf32-i386.c | 9 ---------
bfd/elf32-lm32.c | 9 ---------
bfd/elf32-m32r.c | 9 ---------
bfd/elf32-nds32.c | 9 ---------
bfd/elf32-or1k.c | 9 ---------
bfd/elf32-ppc.c | 9 ---------
bfd/elf32-sh.c | 9 ---------
bfd/elf32-vax.c | 10 ++++++++++
bfd/elf32-xtensa.c | 2 +-
bfd/elf64-alpha.c | 9 ---------
bfd/elf64-ppc.c | 9 ---------
bfd/elf64-x86-64.c | 9 ---------
bfd/elflink.c | 12 ++++++++++--
ld/testsuite/ld-elf/comm-data.exp | 15 +++------------
ld/testsuite/ld-elf/comm-data2r.rd | 3 ---
ld/testsuite/ld-elf/comm-data2r.sd | 10 ----------
ld/testsuite/ld-elf/comm-data2r.xd | 2 --
18 files changed, 27 insertions(+), 123 deletions(-)
delete mode 100644 ld/testsuite/ld-elf/comm-data2r.rd
delete mode 100644 ld/testsuite/ld-elf/comm-data2r.sd
delete mode 100644 ld/testsuite/ld-elf/comm-data2r.xd
diff --git a/bfd/elf-m10300.c b/bfd/elf-m10300.c
index 696514ab05..5a0bb9f005 100644
--- a/bfd/elf-m10300.c
+++ b/bfd/elf-m10300.c
@@ -2066,12 +2066,12 @@ mn10300_elf_relocate_section (bfd *output_bfd,
&& elf_hash_table (info)->dynamic_sections_created
&& !SYMBOL_REFERENCES_LOCAL (info, hh))
|| (r_type == R_MN10300_32
+ && !SYMBOL_REFERENCES_LOCAL (info, hh)
/* _32 relocs in executables force _COPY relocs,
such that the address of the symbol ends up
being local. */
- && !bfd_link_executable (info)
- && !SYMBOL_REFERENCES_LOCAL (info, hh)
- && ((input_section->flags & SEC_ALLOC) != 0
+ && (((input_section->flags & SEC_ALLOC) != 0
+ && !bfd_link_executable (info))
/* DWARF will emit R_MN10300_32 relocations
in its sections against symbols defined
externally in shared libraries. We can't
diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index 544b931552..f6f669957c 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -1487,15 +1487,6 @@ elf_i386_check_relocs (bfd *abfd,
if (bfd_link_relocatable (info))
return TRUE;
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
htab = elf_x86_hash_table (info, I386_ELF_DATA);
if (htab == NULL)
{
diff --git a/bfd/elf32-lm32.c b/bfd/elf32-lm32.c
index 3c31dd44c8..aba821ffd1 100644
--- a/bfd/elf32-lm32.c
+++ b/bfd/elf32-lm32.c
@@ -1128,15 +1128,6 @@ lm32_elf_check_relocs (bfd *abfd,
if (bfd_link_relocatable (info))
return TRUE;
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
symtab_hdr = &elf_tdata (abfd)->symtab_hdr;
sym_hashes = elf_sym_hashes (abfd);
sym_hashes_end = sym_hashes + symtab_hdr->sh_size/sizeof (Elf32_External_Sym);
diff --git a/bfd/elf32-m32r.c b/bfd/elf32-m32r.c
index 931e138b37..740be93382 100644
--- a/bfd/elf32-m32r.c
+++ b/bfd/elf32-m32r.c
@@ -3424,15 +3424,6 @@ m32r_elf_check_relocs (bfd *abfd,
if (bfd_link_relocatable (info))
return TRUE;
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
sreloc = NULL;
symtab_hdr = &elf_tdata (abfd)->symtab_hdr;
sym_hashes = elf_sym_hashes (abfd);
diff --git a/bfd/elf32-nds32.c b/bfd/elf32-nds32.c
index 01ea277426..1d3a0f7526 100644
--- a/bfd/elf32-nds32.c
+++ b/bfd/elf32-nds32.c
@@ -7055,15 +7055,6 @@ nds32_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
return TRUE;
}
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
symtab_hdr = &elf_tdata (abfd)->symtab_hdr;
sym_hashes = elf_sym_hashes (abfd);
sym_hashes_end =
diff --git a/bfd/elf32-or1k.c b/bfd/elf32-or1k.c
index ac62d630ab..b25f96b42d 100644
--- a/bfd/elf32-or1k.c
+++ b/bfd/elf32-or1k.c
@@ -1880,15 +1880,6 @@ or1k_elf_check_relocs (bfd *abfd,
if (bfd_link_relocatable (info))
return TRUE;
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
symtab_hdr = &elf_tdata (abfd)->symtab_hdr;
sym_hashes = elf_sym_hashes (abfd);
diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index 0cb7f67504..995e1a95e2 100644
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -2888,15 +2888,6 @@ ppc_elf_check_relocs (bfd *abfd,
if (bfd_link_relocatable (info))
return TRUE;
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
#ifdef DEBUG
_bfd_error_handler ("ppc_elf_check_relocs called for section %pA in %pB",
sec, abfd);
diff --git a/bfd/elf32-sh.c b/bfd/elf32-sh.c
index 9ec745be19..dd670466c3 100644
--- a/bfd/elf32-sh.c
+++ b/bfd/elf32-sh.c
@@ -5350,15 +5350,6 @@ sh_elf_check_relocs (bfd *abfd, struct bfd_link_info *info, asection *sec,
if (bfd_link_relocatable (info))
return TRUE;
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
BFD_ASSERT (is_sh_elf (abfd));
symtab_hdr = &elf_symtab_hdr (abfd);
diff --git a/bfd/elf32-vax.c b/bfd/elf32-vax.c
index fa84e0be19..b5c3d8943a 100644
--- a/bfd/elf32-vax.c
+++ b/bfd/elf32-vax.c
@@ -712,6 +712,11 @@ elf_vax_check_relocs (bfd *abfd, struct bfd_link_info *info, asection *sec,
h->plt.refcount++;
}
+ /* Non-GOT reference may need a copy reloc in executable or
+ a dynamic reloc in shared library. */
+ if (h != NULL)
+ h->non_got_ref = 1;
+
/* If we are creating a shared library, we need to copy the
reloc into the shared library. */
if (bfd_link_pic (info)
@@ -929,6 +934,11 @@ elf_vax_adjust_dynamic_symbol (struct bfd_link_info *info,
if (bfd_link_pic (info))
return TRUE;
+ /* If there are no references to this symbol that do not use the
+ GOT relocation, we don't need to generate a copy reloc. */
+ if (!h->non_got_ref)
+ return TRUE;
+
/* We must allocate the symbol in our .dynbss section, which will
become part of the .bss section of the executable. There will be
an entry for this symbol in the .dynsym section. The dynamic
diff --git a/bfd/elf32-xtensa.c b/bfd/elf32-xtensa.c
index 05c4f8430a..9dc815edbb 100644
--- a/bfd/elf32-xtensa.c
+++ b/bfd/elf32-xtensa.c
@@ -1039,7 +1039,7 @@ elf_xtensa_check_relocs (bfd *abfd,
const Elf_Internal_Rela *rel;
const Elf_Internal_Rela *rel_end;
- if (bfd_link_relocatable (info) || (sec->flags & SEC_ALLOC) == 0)
+ if (bfd_link_relocatable (info))
return TRUE;
BFD_ASSERT (is_xtensa_elf (abfd));
diff --git a/bfd/elf64-alpha.c b/bfd/elf64-alpha.c
index 4e4efae0b1..0b31d450dc 100644
--- a/bfd/elf64-alpha.c
+++ b/bfd/elf64-alpha.c
@@ -1782,15 +1782,6 @@ elf64_alpha_check_relocs (bfd *abfd, struct bfd_link_info *info,
if (bfd_link_relocatable (info))
return TRUE;
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
BFD_ASSERT (is_alpha_elf (abfd));
dynobj = elf_hash_table (info)->dynobj;
diff --git a/bfd/elf64-ppc.c b/bfd/elf64-ppc.c
index 5f99d4344b..769afc5aa5 100644
--- a/bfd/elf64-ppc.c
+++ b/bfd/elf64-ppc.c
@@ -4536,15 +4536,6 @@ ppc64_elf_check_relocs (bfd *abfd, struct bfd_link_info *info,
if (bfd_link_relocatable (info))
return TRUE;
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
BFD_ASSERT (is_ppc64_elf (abfd));
htab = ppc_hash_table (info);
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index 183c808346..eada0e53ed 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -1862,15 +1862,6 @@ elf_x86_64_check_relocs (bfd *abfd, struct bfd_link_info *info,
if (bfd_link_relocatable (info))
return TRUE;
- /* Don't do anything special with non-loaded, non-alloced sections.
- In particular, any relocs in such sections should not affect GOT
- and PLT reference counting (ie. we don't allow them to create GOT
- or PLT entries), there's no possibility or desire to optimize TLS
- relocs, and there's not much point in propagating relocs to shared
- libs that the dynamic linker won't relocate. */
- if ((sec->flags & SEC_ALLOC) == 0)
- return TRUE;
-
htab = elf_x86_hash_table (info, X86_64_ELF_DATA);
if (htab == NULL)
{
diff --git a/bfd/elflink.c b/bfd/elflink.c
index ce6282a9dc..7e86adec5b 100644
--- a/bfd/elflink.c
+++ b/bfd/elflink.c
@@ -3956,8 +3956,16 @@ _bfd_elf_link_check_relocs (bfd *abfd, struct bfd_link_info *info)
Elf_Internal_Rela *internal_relocs;
bfd_boolean ok;
- /* Don't check relocations in excluded sections. */
- if ((o->flags & SEC_RELOC) == 0
+ /* Don't check relocations in excluded sections. Don't do
+ anything special with non-loaded, non-alloced sections.
+ In particular, any relocs in such sections should not
+ affect GOT and PLT reference counting (ie. we don't
+ allow them to create GOT or PLT entries), there's no
+ possibility or desire to optimize TLS relocs, and
+ there's not much point in propagating relocs to shared
+ libs that the dynamic linker won't relocate. */
+ if ((o->flags & SEC_ALLOC) == 0
+ || (o->flags & SEC_RELOC) == 0
|| (o->flags & SEC_EXCLUDE) != 0
|| o->reloc_count == 0
|| ((info->strip == strip_all || info->strip == strip_debugger)
diff --git a/ld/testsuite/ld-elf/comm-data.exp b/ld/testsuite/ld-elf/comm-data.exp
index a53a77123c..c735fe244c 100644
--- a/ld/testsuite/ld-elf/comm-data.exp
+++ b/ld/testsuite/ld-elf/comm-data.exp
@@ -79,12 +79,6 @@ setup_xfail "bfin-*-*"
setup_xfail "arm*-*-*" "ld/13802"
-# List targets here that keep copy relocs rather than eliminating
-# them where possible in favour to dynamic relocs in the relevant
-# loadable sections; see also the "-z nocopyreloc" command-line
-# option and the ELIMINATE_COPY_RELOCS macro some backends use.
-set copy_reloc [expr [istarget mn10300-*-*] || [istarget vax-*-*]]
-
# Verify that a common symbol has been converted to an undefined
# reference to the global symbol of the same name defined above
# and that the debug reference has been dropped.
@@ -95,12 +89,9 @@ run_ld_link_tests [list \
"$AFLAGS" \
{ comm-data2.s } \
[list \
- [list readelf -s \
- [expr { $copy_reloc ? "comm-data2r.sd" : "comm-data2.sd"}]] \
- [list readelf -r \
- [expr { $copy_reloc ? "comm-data2r.rd" : "comm-data2.rd"}]] \
- [list readelf "-x .debug_foo" \
- [expr { $copy_reloc ? "comm-data2r.xd" : "comm-data2.xd"}]]] \
+ [list readelf -s comm-data2.sd] \
+ [list readelf -r comm-data2.rd] \
+ [list readelf "-x .debug_foo" comm-data2.xd]] \
"comm-data" \
] \
[list \
diff --git a/ld/testsuite/ld-elf/comm-data2r.rd b/ld/testsuite/ld-elf/comm-data2r.rd
deleted file mode 100644
index 64c0396d26..0000000000
--- a/ld/testsuite/ld-elf/comm-data2r.rd
+++ /dev/null
@@ -1,3 +0,0 @@
-Relocation section '\.rela\.dyn' at offset 0x[0-9a-f]+ contains 1 entry:
- +Offset +Info +Type +Sym\.Value +Sym\. Name \+ Addend
-0*12340000 +[0-9a-f]+ +R_.*_COPY +0*12340000 +foo \+ 0
diff --git a/ld/testsuite/ld-elf/comm-data2r.sd b/ld/testsuite/ld-elf/comm-data2r.sd
deleted file mode 100644
index 685b0befd1..0000000000
--- a/ld/testsuite/ld-elf/comm-data2r.sd
+++ /dev/null
@@ -1,10 +0,0 @@
-Symbol table '\.dynsym' contains [0-9]+ entries:
- +Num: +Value +Size +Type +Bind +Vis +Ndx +Name
-#...
- +[0-9]+: +0*12340000 +4 +OBJECT +GLOBAL +DEFAULT +[0-9]+ +foo
-#...
-Symbol table '\.symtab' contains [0-9]+ entries:
- +Num: +Value +Size +Type +Bind +Vis +Ndx +Name
-#...
- +[0-9]+: +0*12340000 +4 +OBJECT +GLOBAL +DEFAULT +[0-9]+ +foo
-#pass
diff --git a/ld/testsuite/ld-elf/comm-data2r.xd b/ld/testsuite/ld-elf/comm-data2r.xd
deleted file mode 100644
index 58f6f2a88f..0000000000
--- a/ld/testsuite/ld-elf/comm-data2r.xd
+++ /dev/null
@@ -1,2 +0,0 @@
-Hex dump of section '\.debug_foo':
- +0x0*76540000 (?:12340000 00000000|00003412 00000000|00000000 00003412) 00000000 00000000 .*
--
2.26.2
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