[PATCH] ELF/LD: Avoid producing hidden and internal dynamic symbols
Maciej W. Rozycki
macro@imgtec.com
Mon Apr 4 16:49:00 GMT 2016
Always turn hidden and internal symbols which have a dynamic index into
local ones. This is required by the the ELF gABI[1]:
"A hidden symbol contained in a relocatable object must be either
removed or converted to STB_LOCAL binding by the link-editor when the
relocatable object is included in an executable file or shared object."
"An internal symbol contained in a relocatable object must be either
removed or converted to STB_LOCAL binding by the link-editor when the
relocatable object is included in an executable file or shared object."
The ELF linker usually respects this requirement, however in the case
where a dynamic symbol has been preallocated due to a reference of the
default export class aka visibility from the object being linked, and
then merged with a hidden or internal symbol definition from within the
same object, then the original export class is carried over to the
output dynamic symbol table, because while merging the generic ELF
linker only converts affected dynamic symbols to local when they are
defined or referenced by the object being linked and a dynamic object
involved in the link both at a time.
The dynamic symbol produced confuses then the dynamic loader at the run
time -- the hidden or internal export class is ignored and the symbol
follows preemption rules as with the default export class.
In the MIPS target it happens when `mips_elf_record_global_got_symbol'
creates a dynamic symbol when a call relocation is encountered.
Additionally if the undefined symbol referred by such a relocation does
specify the intended export class, then a local dynamic symbol is
created instead, which is harmless and allowed, but useless. Normally
no local dynamic symbols are created, except for a single dummy one at
the beginning.
Correct the problem by removing the extra check for a dynamic symbol
being defined or referenced by the object being linked and a dynamic
object involved in the link both at a time. The test cases included
cover the internal and hidden symbol cases, as well as a protected
symbol for a reference, the handling of which is unchanged by this fix.
Both cases described above are covered, that is where an internal or
hidden dynamic symbol is produced and where a local one is.
NB this change affects CRIS results where some symbols in the static
table produced in a final link are now converted from STV_HIDDEN to
STB_LOCAL. This happens whenever the `elf_backend_hide_symbol' handler
is called, so the affected symbols must have been chosen for entering
into the dynamic symbol table, except in these test cases no such symbol
table is produced. In fully linked binaries the static symbol table is
only used for debugging though, so such a change is fine.
References:
[1] "System V Application Binary Interface - DRAFT - 24 April 2001",
The Santa Cruz Operation, Inc., "Symbol Table",
<http://www.sco.com/developers/gabi/2001-04-24/ch4.symtab.html>
2016-04-04 Maciej W. Rozycki <macro@imgtec.com>
bfd/
PR ld/19908
* elflink.c (elf_link_add_object_symbols): Always turn hidden
and internal symbols which have a dynamic index into local
ones.
ld/testsuite/
PR ld/19908
* ld-cris/tls-e-20.d: Adjust for hidden symbol handling fix.
* ld-cris/tls-e-20a.d: Likewise.
* ld-cris/tls-e-21.d: Likewise.
* ld-cris/tls-e-23.d: Likewise.
* ld-cris/tls-e-80.d: Likewise.
* ld-cris/tls-gd-3h.d: Likewise.
* ld-cris/tls-leie-19.d: Likewise.
* ld-mips-elf/export-class-ref-lib.sd: New test.
* ld-mips-elf/export-hidden-ref.sd: New test.
* ld-mips-elf/export-internal-ref.sd: New test.
* ld-mips-elf/export-protected-ref.sd: New test.
* ld-mips-elf/export-class-ref-f0.s: New test source.
* ld-mips-elf/export-class-ref-f1.s: New test source.
* ld-mips-elf/export-class-ref-f2.s: New test source.
* ld-mips-elf/mips-elf.exp: Run the new tests.
---
OK to apply?
Maciej
binutils-bfd-elf-add-symbol-dynindx-export-class.diff
Index: binutils/bfd/elflink.c
===================================================================
--- binutils.orig/bfd/elflink.c 2016-04-04 02:11:17.482717336 +0100
+++ binutils/bfd/elflink.c 2016-04-04 02:55:57.179886886 +0100
@@ -4569,7 +4569,7 @@ elf_link_add_object_symbols (bfd *abfd,
goto error_free_vers;
}
}
- else if (dynsym && h->dynindx != -1)
+ else if (h->dynindx != -1)
/* If the symbol already has a dynamic index, but
visibility says it should not be visible, turn it into
a local symbol. */
Index: binutils/ld/testsuite/ld-cris/tls-e-20.d
===================================================================
--- binutils.orig/ld/testsuite/ld-cris/tls-e-20.d 2016-04-04 02:11:17.491806432 +0100
+++ binutils/ld/testsuite/ld-cris/tls-e-20.d 2016-04-04 02:18:21.995389532 +0100
@@ -35,8 +35,8 @@ Idx Name Size VMA LM
0+80094 l d \.text 0+ \.text
0+820b0 l d \.tdata 0+ \.tdata
0+820bc l d \.got 0+ \.got
+0+ l \.tdata 0+4 x
0+820bc l O \.got 0+ _GLOBAL_OFFSET_TABLE_
-0+ g \.tdata 0+4 \.hidden x
0+80098 g F \.text 0+6 tlsdsofn2
0+8 g \.tdata 0+4 \.hidden x2
0+80094 g \.text 0+ _start
Index: binutils/ld/testsuite/ld-cris/tls-e-20a.d
===================================================================
--- binutils.orig/ld/testsuite/ld-cris/tls-e-20a.d 2016-04-04 02:11:17.497841393 +0100
+++ binutils/ld/testsuite/ld-cris/tls-e-20a.d 2016-04-04 02:18:22.009797212 +0100
@@ -43,8 +43,8 @@ Idx Name Size VMA LM
0+ l df \*ABS\* 0+ .*
0+ l \.tdata 0+80 tls128
0+ l df \*ABS\* 0+ .*
+0+80 l \.tdata 0+4 x
0+82168 l O \.got 0+ _GLOBAL_OFFSET_TABLE_
-0+80 g \.tdata 0+4 \.hidden x
0+800c4 g F \.text 0+6 tlsdsofn2
0+821b4 g O \.data 0+4 got7var5
0+88 g \.tdata 0+4 \.hidden x2
Index: binutils/ld/testsuite/ld-cris/tls-e-21.d
===================================================================
--- binutils.orig/ld/testsuite/ld-cris/tls-e-21.d 2016-04-04 02:11:17.508056408 +0100
+++ binutils/ld/testsuite/ld-cris/tls-e-21.d 2016-04-04 02:18:22.026221376 +0100
@@ -19,7 +19,7 @@
#...
SYMBOL TABLE:
#...
-0+80 g \.tdata 0+4 \.hidden x
+0+80 l \.tdata 0+4 x
#...
Contents of section \.text:
#...
Index: binutils/ld/testsuite/ld-cris/tls-e-23.d
===================================================================
--- binutils.orig/ld/testsuite/ld-cris/tls-e-23.d 2016-04-04 02:11:17.519228229 +0100
+++ binutils/ld/testsuite/ld-cris/tls-e-23.d 2016-04-04 02:18:22.048799946 +0100
@@ -19,7 +19,7 @@
#...
SYMBOL TABLE:
#...
-0+80 g \.tdata 0+4 \.hidden x
+0+80 l \.tdata 0+4 x
#...
Contents of section \.text:
#...
Index: binutils/ld/testsuite/ld-cris/tls-e-80.d
===================================================================
--- binutils.orig/ld/testsuite/ld-cris/tls-e-80.d 2016-04-04 02:11:17.523346614 +0100
+++ binutils/ld/testsuite/ld-cris/tls-e-80.d 2016-04-04 02:18:22.065386640 +0100
@@ -42,8 +42,8 @@ Idx Name Size VMA LM
0+820c0 l d \.tdata 0+ \.tdata
0+820d0 l d \.tbss 0+ \.tbss
0+820d0 l d \.got 0+ \.got
+0+ l \.tdata 0+4 x
0+820d0 l O \.got 0+ _GLOBAL_OFFSET_TABLE_
-0+ g \.tdata 0+4 \.hidden x
0+800a0 g F \.text 0+6 tlsdsofn2
0+800a8 g F \.text 0+6 tlsfn12
0+c g \.tdata 0+4 \.hidden x2
Index: binutils/ld/testsuite/ld-cris/tls-gd-3h.d
===================================================================
--- binutils.orig/ld/testsuite/ld-cris/tls-gd-3h.d 2016-04-04 02:11:17.530413598 +0100
+++ binutils/ld/testsuite/ld-cris/tls-gd-3h.d 2016-04-04 02:18:22.077650334 +0100
@@ -19,7 +19,7 @@
#...
SYMBOL TABLE:
#...
-0+80 g \.tdata 0+4 \.hidden x
+0+80 l \.tdata 0+4 x
#...
Contents of section \.text:
#...
Index: binutils/ld/testsuite/ld-cris/tls-leie-19.d
===================================================================
--- binutils.orig/ld/testsuite/ld-cris/tls-leie-19.d 2016-04-04 02:11:17.539511136 +0100
+++ binutils/ld/testsuite/ld-cris/tls-leie-19.d 2016-04-04 02:18:22.087797215 +0100
@@ -26,13 +26,13 @@
CONTENTS.*
SYMBOL TABLE:
#...
-0+88 g .tdata 0+4 x
+0+84 l \.tdata 0+4 x2
#...
-0+84 g \.tdata 0+4 \.hidden x2
+0+80 l \.tdata 0+4 x1
#...
-0+8c g .tdata 0+4 z
+0+88 g .tdata 0+4 x
#...
-0+80 g \.tdata 0+4 \.hidden x1
+0+8c g .tdata 0+4 z
#...
Contents of section \.text:
#...
Index: binutils/ld/testsuite/ld-mips-elf/export-class-ref-f0.s
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils/ld/testsuite/ld-mips-elf/export-class-ref-f0.s 2016-04-04 17:46:54.691435206 +0100
@@ -0,0 +1,37 @@
+ .abicalls
+ .text
+
+ .if refv == 3
+ .protected f1
+ .elseif refv == 2
+ .hidden f1
+ .elseif refv == 1
+ .internal f1
+ .endif
+
+ .globl f0
+ .ent f0
+f0:
+ .frame $sp, 32, $31
+ .mask 0x80000000, -4
+ .fmask 0x00000000, 0
+ .set noreorder
+ .cpload $25
+ .set reorder
+ addiu $sp, $sp, -32
+ sw $31, 28($sp)
+ .cprestore 16
+
+ lw $25, %call16(f1)($28)
+ jalr $25
+ lw $28, 16($sp)
+
+ lw $25, %call16(f2)($28)
+ jalr $25
+ lw $28, 16($sp)
+
+ move $2, $0
+ lw $31, 28($sp)
+ addiu $sp, $sp, 32
+ jr $31
+ .end f0
Index: binutils/ld/testsuite/ld-mips-elf/export-class-ref-f1.s
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils/ld/testsuite/ld-mips-elf/export-class-ref-f1.s 2016-04-04 02:20:33.265839001 +0100
@@ -0,0 +1,18 @@
+ .abicalls
+ .text
+
+ .globl f1
+ .if defv == 3
+ .protected f1
+ .elseif defv == 2
+ .hidden f1
+ .elseif defv == 1
+ .internal f1
+ .endif
+ .ent f1
+f1:
+ .frame $sp, 0, $31
+ .mask 0x00000000, 0
+ .fmask 0x00000000, 0
+ jr $31
+ .end f1
Index: binutils/ld/testsuite/ld-mips-elf/export-class-ref-f2.s
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils/ld/testsuite/ld-mips-elf/export-class-ref-f2.s 2016-04-04 02:18:22.152518507 +0100
@@ -0,0 +1,20 @@
+ .abicalls
+ .text
+
+ .globl f1
+ .ent f1
+f1:
+ .frame $sp, 0, $31
+ .mask 0x00000000, 0
+ .fmask 0x00000000, 0
+ jr $31
+ .end f1
+
+ .globl f2
+ .ent f2
+f2:
+ .frame $sp, 0, $31
+ .mask 0x00000000, 0
+ .fmask 0x00000000, 0
+ jr $31
+ .end f2
Index: binutils/ld/testsuite/ld-mips-elf/export-class-ref-lib.sd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils/ld/testsuite/ld-mips-elf/export-class-ref-lib.sd 2016-04-04 02:18:22.170814493 +0100
@@ -0,0 +1,6 @@
+# Make sure `f1' is present in the dynamic symbol table, e.g.:
+# Num: Value Size Type Bind Vis Ndx Name
+# 6: 000002d0 8 FUNC GLOBAL DEFAULT 7 f1
+#...
+ *[0-9]+: +[0-9a-f]+ +[0-9]+ FUNC +GLOBAL +DEFAULT +[0-9]+ f1
+#pass
Index: binutils/ld/testsuite/ld-mips-elf/export-hidden-ref.sd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils/ld/testsuite/ld-mips-elf/export-hidden-ref.sd 2016-04-04 02:18:22.185140491 +0100
@@ -0,0 +1,7 @@
+# Make sure no hidden symbol is present in the dynamic symbol table, e.g.:
+# Num: Value Size Type Bind Vis Ndx Name
+# 6: 004003f0 8 FUNC GLOBAL HIDDEN 8 f1
+#failif
+#...
+.+ +HIDDEN +.+ +f1
+#pass
Index: binutils/ld/testsuite/ld-mips-elf/export-internal-ref.sd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils/ld/testsuite/ld-mips-elf/export-internal-ref.sd 2016-04-04 02:18:22.196436449 +0100
@@ -0,0 +1,7 @@
+# Make sure no internal symbol is present in the dynamic symbol table, e.g.:
+# Num: Value Size Type Bind Vis Ndx Name
+# 6: 004003f0 8 FUNC GLOBAL INTERNAL 8 f1
+#failif
+#...
+.+ +INTERNAL +.+ +f1
+#pass
Index: binutils/ld/testsuite/ld-mips-elf/export-local-ref.sd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils/ld/testsuite/ld-mips-elf/export-local-ref.sd 2016-04-04 02:18:22.225153971 +0100
@@ -0,0 +1,7 @@
+# Make sure no local symbol is present in the dynamic symbol table, e.g.:
+# Num: Value Size Type Bind Vis Ndx Name
+# 6: 004003f0 8 FUNC LOCAL DEFAULT 8 f1
+#failif
+#...
+.+ +LOCAL +.+ +f1
+#pass
Index: binutils/ld/testsuite/ld-mips-elf/export-protected-ref.sd
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ binutils/ld/testsuite/ld-mips-elf/export-protected-ref.sd 2016-04-04 02:18:22.211966274 +0100
@@ -0,0 +1,6 @@
+# Make sure a protected symbol is present in the dynamic symbol table, e.g.:
+# Num: Value Size Type Bind Vis Ndx Name
+# 6: 004003f0 8 FUNC GLOBAL PROTECTED 8 f1
+#...
+ *[0-9]+: +[0-9a-f]+ +[0-9]+ FUNC +GLOBAL +PROTECTED +[0-9]+ f1
+#pass
Index: binutils/ld/testsuite/ld-mips-elf/mips-elf.exp
===================================================================
--- binutils.orig/ld/testsuite/ld-mips-elf/mips-elf.exp 2016-04-04 02:11:17.572090593 +0100
+++ binutils/ld/testsuite/ld-mips-elf/mips-elf.exp 2016-04-04 17:38:01.625645616 +0100
@@ -899,3 +899,31 @@ if { $linux_gnu } {
n32 -1 1 umips
}
}
+
+# PR ld/19908 export class tests.
+if { $linux_gnu } {
+ run_ld_link_tests [list \
+ [list "Shared library for MIPS export class symbol reference test" \
+ "$abi_ldflags(o32) -shared" "" \
+ "$abi_asflags(o32)" \
+ { export-class-ref-f2.s } \
+ { { readelf --dyn-syms export-class-ref-lib.sd } } \
+ "export-class-ref-lib.so"]]
+ foreach { class flag } { internal 1 hidden 2 protected 3 } {
+ run_ld_link_tests [list \
+ [list "MIPS $class symbol reference test 1" \
+ "$abi_ldflags(o32) -e f0" "tmpdir/export-class-ref-lib.so" \
+ "$abi_asflags(o32) --defsym defv=$flag" \
+ { export-class-ref-f0.s export-class-ref-f1.s } \
+ [list [list readelf --dyn-syms export-$class-ref.sd] \
+ [list readelf --dyn-syms export-local-ref.sd]] \
+ "export-$class-ref"] \
+ [list "MIPS $class symbol reference test 2" \
+ "$abi_ldflags(o32) -e f0" "tmpdir/export-class-ref-lib.so" \
+ "$abi_asflags(o32) --defsym defv=$flag --defsym refv=$flag" \
+ { export-class-ref-f0.s export-class-ref-f1.s } \
+ [list [list readelf --dyn-syms export-$class-ref.sd] \
+ [list readelf --dyn-syms export-local-ref.sd]] \
+ "export-$class-ref"]]
+ }
+}
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