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Re: [committed, PATCH] PR ld/19031: R_386_PC32 does not imply a call

From: "H.J. Lu" <hongjiu dot lu at intel dot com>
To: binutils at sourceware dot org
Date: Thu, 1 Oct 2015 10:52:44 -0700
Subject: Re: [committed, PATCH] PR ld/19031: R_386_PC32 does not imply a call
Authentication-results: sourceware.org; auth=none
References: <20150930154647 dot GA28775 at intel dot com>
Reply-to: "H.J. Lu" <hjl dot tools at gmail dot com>

On Wed, Sep 30, 2015 at 08:46:47AM -0700, H.J. Lu wrote:
> Since something like ".long foo - ." may be used as pointer, we make
> sure that PLT is used if foo is a function defined in a shared library.
> 
> bfd/
> 
> 	PR ld/19031
> 	* elf32-i386.c (elf_i386_check_relocs): Set
> 	pointer_equality_needed for R_386_PC32 reloc in non-code
> 	sections.
> 
> ld/testsuite/
> 
> 	PR ld/19031
> 	* ld-i386/i386.exp: Run PR ld/19031 test.
> 	* ld/testsuite/ld-i386/pr19031.out: New file.
> 	* ld/testsuite/ld-i386/pr19031a.c: Likewise.
> 	* ld/testsuite/ld-i386/pr19031b.S: Likewise.
> 	* ld/testsuite/ld-i386/pr19031c.c: Likewise.

I checked in this patch for the x86-64 case.


H.J.
---
Since something like ".long foo - ." may be used as pointer, we make
sure that PLT is used if foo is a function defined in a shared library.

bfd/

	PR ld/19031
	* elf64-x86-64.c (elf_x86_64_check_relocs): Set
	pointer_equality_needed for R_X86_64_PC32 reloc in non-code
	sections.

ld/testsuite/

	PR ld/19031
	* ld-x86-64/x86-64.exp: Run PR ld/19031 test.
	* ld-x86-64/pr19031.out: New file.
	* ld-x86-64/pr19031a.c: Likewise.
	* ld-x86-64/pr19031b.S: Likewise.
	* ld-x86-64/pr19031c.c: Likewise.
---
 bfd/ChangeLog                      |  7 +++++++
 bfd/elf64-x86-64.c                 | 13 ++++++++++---
 ld/testsuite/ChangeLog             | 17 +++++++++++++----
 ld/testsuite/ld-x86-64/pr19031.out |  1 +
 ld/testsuite/ld-x86-64/pr19031a.c  |  4 ++++
 ld/testsuite/ld-x86-64/pr19031b.S  | 18 ++++++++++++++++++
 ld/testsuite/ld-x86-64/pr19031c.c  | 14 ++++++++++++++
 ld/testsuite/ld-x86-64/x86-64.exp  | 16 ++++++++++++++++
 8 files changed, 83 insertions(+), 7 deletions(-)
 create mode 100644 ld/testsuite/ld-x86-64/pr19031.out
 create mode 100644 ld/testsuite/ld-x86-64/pr19031a.c
 create mode 100644 ld/testsuite/ld-x86-64/pr19031b.S
 create mode 100644 ld/testsuite/ld-x86-64/pr19031c.c

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 55cfa53..c4312c8 100644
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -1,3 +1,10 @@
+2015-10-01  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/19031
+	* elf64-x86-64.c (elf_x86_64_check_relocs): Set
+	pointer_equality_needed for R_X86_64_PC32 reloc in non-code
+	sections.
+
 2015-10-01  Renlin Li  <renlin.li@arm.com>
 
 	* elfnn-aarch64.c (elfNN_aarch64_output_plt_map): Remove.
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index cbb8cfb..29639d8 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -1961,9 +1961,16 @@ pointer:
 	      /* We may need a .plt entry if the function this reloc
 		 refers to is in a shared lib.  */
 	      h->plt.refcount += 1;
-	      if (r_type != R_X86_64_PC32
-		  && r_type != R_X86_64_PC32_BND
-		  && r_type != R_X86_64_PC64)
+	      if (r_type == R_X86_64_PC32)
+		{
+		  /* Since something like ".long foo - ." may be used
+		     as pointer, make sure that PLT is used if foo is
+		     a function defined in a shared library.  */
+		  if ((sec->flags & SEC_CODE) == 0)
+		    h->pointer_equality_needed = 1;
+		}
+	      else if (r_type != R_X86_64_PC32_BND
+		       && r_type != R_X86_64_PC64)
 		{
 		  h->pointer_equality_needed = 1;
 		  /* At run-time, R_X86_64_64 can be resolved for both
diff --git a/ld/testsuite/ChangeLog b/ld/testsuite/ChangeLog
index fdf4b3c..41be8cd 100644
--- a/ld/testsuite/ChangeLog
+++ b/ld/testsuite/ChangeLog
@@ -1,3 +1,12 @@
+2015-10-01  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/19031
+	* ld-x86-64/x86-64.exp: Run PR ld/19031 test.
+	* ld-x86-64/pr19031.out: New file.
+	* ld-x86-64/pr19031a.c: Likewise.
+	* ld-x86-64/pr19031b.S: Likewise.
+	* ld-x86-64/pr19031c.c: Likewise.
+
 2015-10-01  Renlin Li  <renlin.li@arm.com>
 
 	* ld-aarch64/aarch64-elf.exp: Run the new test.
@@ -17,10 +26,10 @@
 
 	PR ld/19031
 	* ld-i386/i386.exp: Run PR ld/19031 test.
-	* ld/testsuite/ld-i386/pr19031.out: New file.
-	* ld/testsuite/ld-i386/pr19031a.c: Likewise.
-	* ld/testsuite/ld-i386/pr19031b.S: Likewise.
-	* ld/testsuite/ld-i386/pr19031c.c: Likewise.
+	* ld-i386/pr19031.out: New file.
+	* ld-i386/pr19031a.c: Likewise.
+	* ld-i386/pr19031b.S: Likewise.
+	* ld-i386/pr19031c.c: Likewise.
 
 2015-09-30  H.J. Lu  <hongjiu.lu@intel.com>
 
diff --git a/ld/testsuite/ld-x86-64/pr19031.out b/ld/testsuite/ld-x86-64/pr19031.out
new file mode 100644
index 0000000..d86bac9
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/pr19031.out
@@ -0,0 +1 @@
+OK
diff --git a/ld/testsuite/ld-x86-64/pr19031a.c b/ld/testsuite/ld-x86-64/pr19031a.c
new file mode 100644
index 0000000..fa34d37
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/pr19031a.c
@@ -0,0 +1,4 @@
+void
+f (void)
+{
+}
diff --git a/ld/testsuite/ld-x86-64/pr19031b.S b/ld/testsuite/ld-x86-64/pr19031b.S
new file mode 100644
index 0000000..ccc9125
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/pr19031b.S
@@ -0,0 +1,18 @@
+	.text
+	.globl g
+	.type g, @function
+g:
+	movq f@GOTPCREL(%rip), %rax
+	retq
+
+	.globl h
+	.type h, @function
+h:
+	leaq zed, %rax
+	movslq zed, %rbx
+	addq %rbx, %rax
+	retq
+
+	.data
+zed:
+        .long f - .
diff --git a/ld/testsuite/ld-x86-64/pr19031c.c b/ld/testsuite/ld-x86-64/pr19031c.c
new file mode 100644
index 0000000..60eccaf
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/pr19031c.c
@@ -0,0 +1,14 @@
+#include <stdio.h>
+
+extern void *h (void);
+extern void *g (void);
+
+int
+main (void)
+{
+
+  if (h () == g ())
+    printf ("OK\n");
+
+  return 0;
+}
diff --git a/ld/testsuite/ld-x86-64/x86-64.exp b/ld/testsuite/ld-x86-64/x86-64.exp
index 5de67ca..69728c2 100644
--- a/ld/testsuite/ld-x86-64/x86-64.exp
+++ b/ld/testsuite/ld-x86-64/x86-64.exp
@@ -503,6 +503,14 @@ if { [isnative] && [which $CC] != 0 } {
 	    {{readelf {-Wrd} pr18900b.rd}} \
 	    "pr18900b" \
 	] \
+	[list \
+	    "Build pr19031.so" \
+	    "-shared" \
+	    "-fPIC" \
+	    { pr19031a.c } \
+	    "" \
+	    "pr19031.so" \
+	] \
     ]
 
     run_ld_link_exec_tests [] [list \
@@ -557,6 +565,14 @@ if { [isnative] && [which $CC] != 0 } {
 	    "pr18900" \
 	    "pr18900.out" \
 	] \
+	[list \
+	    "Run pr19031" \
+	    "tmpdir/pr19031.so" \
+	    "" \
+	    { pr19031b.S pr19031c.c } \
+	    "pr19031" \
+	    "pr19031.out" \
+	] \
     ]
 
     if { [istarget "x86_64-*-linux*"] \
-- 
2.4.3

Follow-Ups:
- Re: [committed, PATCH] PR ld/19031: R_386_PC32 does not imply a call
  - From: Rafael EspÃndola

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