[PATCH v4 2/2] Add TARGET_ASM_EMIT_GNU_PROPERTY_NOTE
H.J. Lu
hjl.tools@gmail.com
Thu Sep 23 02:02:07 GMT 2021
Generate the marker for -fno-direct-extern-access to indicate that the
object file uses GOT to access all external symbols. Access to protected
symbols in the resulting shared library is treated as local, which requires
canonical function pointers and cannot be used with copy relocation.
This marker can be used in the following ways:
1. Linker can decide the best way to resolve a relocation against a
protected symbol before seeing all relocations against the symbol.
2. Dynamic linker can decide if it is an error to have a copy relocation
in executable against the protected symbol in a shared library by checking
if the shared library is built with -fno-direct-extern-access.
* configure.ac (HAVE_LD_INDIRECT_EXTERN_ACCESS_SUPPORT): New.
Define to 1 if linker supports
GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS.
* output.h (emit_gnu_property): New.
(emit_gnu_property_note): Likewise.
* target.def (emit_gnu_property_note): Add a argetm.asm_out hook.
* toplev.c (compile_file): Call emit_gnu_property_note before
file_end.
* varasm.c (emit_gnu_property): New.
(emit_gnu_property_note): Likewise.
* config.in: Regenerated.
* configure: Likewise.
* doc/tm.texi: Likewise.
* config/i386/gnu-property.c (emit_gnu_property): Removed.
(TARGET_ASM_EMIT_GNU_PROPERTY_NOTE): New.
* doc/tm.texi.in: Add TARGET_ASM_EMIT_GNU_PROPERTY_NOTE.
---
gcc/config.in | 7 +++++
gcc/config/i386/gnu-property.c | 31 ----------------------
gcc/config/i386/i386.c | 2 ++
gcc/configure | 27 +++++++++++++++++++
gcc/configure.ac | 23 +++++++++++++++++
gcc/doc/tm.texi | 5 ++++
gcc/doc/tm.texi.in | 2 ++
gcc/output.h | 2 ++
gcc/target.def | 8 ++++++
gcc/toplev.c | 3 +++
gcc/varasm.c | 47 ++++++++++++++++++++++++++++++++++
11 files changed, 126 insertions(+), 31 deletions(-)
diff --git a/gcc/config.in b/gcc/config.in
index 61cafe4f6c0..8a756aa3541 100644
--- a/gcc/config.in
+++ b/gcc/config.in
@@ -1690,6 +1690,13 @@
#endif
+/* Define to 1 if your linker supports
+ GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS. */
+#ifndef USED_FOR_TARGET
+#undef HAVE_LD_INDIRECT_EXTERN_ACCESS_SUPPORT
+#endif
+
+
/* Define if your PowerPC64 linker supports a large TOC. */
#ifndef USED_FOR_TARGET
#undef HAVE_LD_LARGE_TOC
diff --git a/gcc/config/i386/gnu-property.c b/gcc/config/i386/gnu-property.c
index 4ba04403002..9fe8d00132e 100644
--- a/gcc/config/i386/gnu-property.c
+++ b/gcc/config/i386/gnu-property.c
@@ -24,37 +24,6 @@ along with GCC; see the file COPYING3. If not see
#include "output.h"
#include "linux-common.h"
-static void
-emit_gnu_property (unsigned int type, unsigned int data)
-{
- int p2align = ptr_mode == SImode ? 2 : 3;
-
- switch_to_section (get_section (".note.gnu.property",
- SECTION_NOTYPE, NULL));
-
- ASM_OUTPUT_ALIGN (asm_out_file, p2align);
- /* name length. */
- fprintf (asm_out_file, ASM_LONG "1f - 0f\n");
- /* data length. */
- fprintf (asm_out_file, ASM_LONG "4f - 1f\n");
- /* note type: NT_GNU_PROPERTY_TYPE_0. */
- fprintf (asm_out_file, ASM_LONG "5\n");
- fprintf (asm_out_file, "0:\n");
- /* vendor name: "GNU". */
- fprintf (asm_out_file, STRING_ASM_OP "\"GNU\"\n");
- fprintf (asm_out_file, "1:\n");
- ASM_OUTPUT_ALIGN (asm_out_file, p2align);
- /* pr_type. */
- fprintf (asm_out_file, ASM_LONG "0x%x\n", type);
- /* pr_datasz. */
- fprintf (asm_out_file, ASM_LONG "3f - 2f\n");
- fprintf (asm_out_file, "2:\n");
- fprintf (asm_out_file, ASM_LONG "0x%x\n", data);
- fprintf (asm_out_file, "3:\n");
- ASM_OUTPUT_ALIGN (asm_out_file, p2align);
- fprintf (asm_out_file, "4:\n");
-}
-
void
file_end_indicate_exec_stack_and_gnu_property (void)
{
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 9ca1ef512a4..3b678c4d5b6 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -24569,6 +24569,8 @@ ix86_libgcc_floating_mode_supported_p
#if !TARGET_MACHO && !TARGET_DLLIMPORT_DECL_ATTRIBUTES
# undef TARGET_ASM_RELOC_RW_MASK
# define TARGET_ASM_RELOC_RW_MASK ix86_reloc_rw_mask
+# undef TARGET_ASM_EMIT_GNU_PROPERTY_NOTE
+# define TARGET_ASM_EMIT_GNU_PROPERTY_NOTE emit_gnu_property_note
#endif
static bool ix86_libc_has_fast_function (int fcode ATTRIBUTE_UNUSED)
diff --git a/gcc/configure b/gcc/configure
index b3de17009b8..13fe041b0b6 100755
--- a/gcc/configure
+++ b/gcc/configure
@@ -32172,6 +32172,33 @@ fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ld_bndplt_support" >&5
$as_echo "$ld_bndplt_support" >&6; }
+# Check if linker supports GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS.
+ld_indirect_extern_access=0
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking linker with GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS" >&5
+$as_echo_n "checking linker with GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS... " >&6; }
+if test x"$ld_is_gold" = xno; then
+ # GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS supported was added to
+ # GNU linker for binutils 2.38 on 2021-07-09.
+ if test $in_tree_ld = yes ; then
+ if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 38 -o "$gcc_cv_gld_major_version" -gt 2; then
+ ld_indirect_extern_access=1
+ fi
+ elif echo "$ld_ver" | grep GNU > /dev/null; then
+ if test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -ge 37 -a "$ld_vers_patch" -ge 50 -a 0"$ld_date" -gt 20210709; then
+ ld_indirect_extern_access=1
+ elif test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -ge 38 -o "$ld_vers_major" -gt 2; then
+ ld_indirect_extern_access=1
+ fi
+ fi
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_LD_INDIRECT_EXTERN_ACCESS_SUPPORT $ld_indirect_extern_access
+_ACEOF
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ld_indirect_extern_access" >&5
+$as_echo "$ld_indirect_extern_access" >&6; }
+
# Check linker supports '--push-state'/'--pop-state'
ld_pushpopstate_support=no
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking linker --push-state/--pop-state options" >&5
diff --git a/gcc/configure.ac b/gcc/configure.ac
index 7d3aab47030..d707ea85d5c 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -7526,6 +7526,29 @@ if test x"$ld_bndplt_support" = xyes; then
fi
AC_MSG_RESULT($ld_bndplt_support)
+# Check if linker supports GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS.
+ld_indirect_extern_access=0
+AC_MSG_CHECKING(linker with GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS)
+if test x"$ld_is_gold" = xno; then
+ # GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS supported was added to
+ # GNU linker for binutils 2.38 on 2021-07-09.
+ if test $in_tree_ld = yes ; then
+ if test "$gcc_cv_gld_major_version" -eq 2 -a "$gcc_cv_gld_minor_version" -ge 38 -o "$gcc_cv_gld_major_version" -gt 2; then
+ ld_indirect_extern_access=1
+ fi
+ elif echo "$ld_ver" | grep GNU > /dev/null; then
+ if test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -ge 37 -a "$ld_vers_patch" -ge 50 -a 0"$ld_date" -gt 20210709; then
+ ld_indirect_extern_access=1
+ elif test "$ld_vers_major" -eq 2 -a "$ld_vers_minor" -ge 38 -o "$ld_vers_major" -gt 2; then
+ ld_indirect_extern_access=1
+ fi
+ fi
+fi
+AC_DEFINE_UNQUOTED(HAVE_LD_INDIRECT_EXTERN_ACCESS_SUPPORT,
+ $ld_indirect_extern_access,
+ [Define to 1 if your linker supports GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS.])
+AC_MSG_RESULT($ld_indirect_extern_access)
+
# Check linker supports '--push-state'/'--pop-state'
ld_pushpopstate_support=no
AC_MSG_CHECKING(linker --push-state/--pop-state options)
diff --git a/gcc/doc/tm.texi b/gcc/doc/tm.texi
index 902402d7503..3f65dc8387c 100644
--- a/gcc/doc/tm.texi
+++ b/gcc/doc/tm.texi
@@ -8095,6 +8095,11 @@ Output to @code{asm_out_file} any text which the assembler expects
to find at the end of a file. The default is to output nothing.
@end deftypefn
+@deftypefn {Target Hook} void TARGET_ASM_EMIT_GNU_PROPERTY_NOTE (void)
+Output a GNU property note to @code{asm_out_file}. The default is to
+output nothing.
+@end deftypefn
+
@deftypefun void file_end_indicate_exec_stack ()
Some systems use a common convention, the @samp{.note.GNU-stack}
special section, to indicate whether or not an object file relies on
diff --git a/gcc/doc/tm.texi.in b/gcc/doc/tm.texi.in
index 86352dc9bd2..5e48a29e55e 100644
--- a/gcc/doc/tm.texi.in
+++ b/gcc/doc/tm.texi.in
@@ -5057,6 +5057,8 @@ This describes the overall framework of an assembly file.
@hook TARGET_ASM_FILE_END
+@hook TARGET_ASM_EMIT_GNU_PROPERTY_NOTE
+
@deftypefun void file_end_indicate_exec_stack ()
Some systems use a common convention, the @samp{.note.GNU-stack}
special section, to indicate whether or not an object file relies on
diff --git a/gcc/output.h b/gcc/output.h
index 73ca4545f4f..f9cbf7cab37 100644
--- a/gcc/output.h
+++ b/gcc/output.h
@@ -607,6 +607,8 @@ extern void default_asm_declare_constant_name (FILE *, const char *,
extern void default_file_start (void);
extern void file_end_indicate_exec_stack (void);
extern void file_end_indicate_split_stack (void);
+extern void emit_gnu_property (unsigned int, unsigned int);
+extern void emit_gnu_property_note (void);
extern void default_elf_asm_output_external (FILE *file, tree,
const char *);
diff --git a/gcc/target.def b/gcc/target.def
index c5d90cace80..e27c0f7c0f8 100644
--- a/gcc/target.def
+++ b/gcc/target.def
@@ -715,6 +715,14 @@ to find at the end of a file. The default is to output nothing.",
void, (void),
hook_void_void)
+/* Output a GNU property note. */
+DEFHOOK
+(emit_gnu_property_note,
+ "Output a GNU property note to @code{asm_out_file}. The default is to\n\
+output nothing.",
+ void, (void),
+ hook_void_void)
+
/* Output any boilerplate text needed at the beginning of an
LTO output stream. */
DEFHOOK
diff --git a/gcc/toplev.c b/gcc/toplev.c
index 14d1335e79e..38decb1e8eb 100644
--- a/gcc/toplev.c
+++ b/gcc/toplev.c
@@ -586,6 +586,9 @@ compile_file (void)
/* Invoke registered plugin callbacks. */
invoke_plugin_callbacks (PLUGIN_FINISH_UNIT, NULL);
+ /* Output a GNU property note. */
+ targetm.asm_out.emit_gnu_property_note ();
+
/* This must be at the end. Some target ports emit end of file directives
into the assembly file here, and hence we cannot output anything to the
assembly file after this point. */
diff --git a/gcc/varasm.c b/gcc/varasm.c
index 2d261b353bf..aa97ae91d4e 100644
--- a/gcc/varasm.c
+++ b/gcc/varasm.c
@@ -7735,6 +7735,53 @@ default_file_start (void)
}
}
+/* Emit one GNU property of TYPE and DATA. */
+
+void
+emit_gnu_property (unsigned int type, unsigned int data)
+{
+ int p2align = ptr_mode == SImode ? 2 : 3;
+
+ switch_to_section (get_section (".note.gnu.property",
+ SECTION_NOTYPE, NULL));
+
+ ASM_OUTPUT_ALIGN (asm_out_file, p2align);
+ /* name length. */
+ fprintf (asm_out_file, ASM_LONG "1f - 0f\n");
+ /* data length. */
+ fprintf (asm_out_file, ASM_LONG "4f - 1f\n");
+ /* note type: NT_GNU_PROPERTY_TYPE_0. */
+ fprintf (asm_out_file, ASM_LONG "5\n");
+ fprintf (asm_out_file, "0:\n");
+ /* vendor name: "GNU". */
+ fprintf (asm_out_file, STRING_ASM_OP "\"GNU\"\n");
+ fprintf (asm_out_file, "1:\n");
+ ASM_OUTPUT_ALIGN (asm_out_file, p2align);
+ /* pr_type. */
+ fprintf (asm_out_file, ASM_LONG "0x%x\n", type);
+ /* pr_datasz. */
+ fprintf (asm_out_file, ASM_LONG "3f - 2f\n");
+ fprintf (asm_out_file, "2:\n");
+ fprintf (asm_out_file, ASM_LONG "0x%x\n", data);
+ fprintf (asm_out_file, "3:\n");
+ ASM_OUTPUT_ALIGN (asm_out_file, p2align);
+ fprintf (asm_out_file, "4:\n");
+}
+
+/* This is a generic routine for TARGET_ASM_EMIT_GNU_PROPERTY_NOTE to
+ emit a NT_GNU_PROPERTY_TYPE_0 note. This is primarily a GNU extension
+ to ELF but could be used on other targets. */
+
+void
+emit_gnu_property_note (void)
+{
+ if (HAVE_LD_INDIRECT_EXTERN_ACCESS_SUPPORT
+ && !flag_direct_extern_access)
+ /* Emite a GNU_PROPERTY_1_NEEDED note with
+ GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS. */
+ emit_gnu_property (0xb0008000, (1U << 0));
+}
+
/* This is a generic routine suitable for use as TARGET_ASM_FILE_END
which emits a special section directive used to indicate whether or
not this object file needs an executable stack. This is primarily
--
2.31.1
More information about the Gcc-patches
mailing list