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[PATCH] x86: Treat relocation against IFUNC symbol as FUNC

From: "H.J. Lu" <hjl dot tools at gmail dot com>
To: binutils at sourceware dot org
Date: Wed, 7 Mar 2018 05:36:45 -0800
Subject: [PATCH] x86: Treat relocation against IFUNC symbol as FUNC
Authentication-results: sourceware.org; auth=none

When resolving a relocation against IFUNC symbol in a SHT_NOTE section
without SHF_ALLOC, we treat it as relocation against FUNC symbol since
it needs the address of IFUNC symbol, not the address returned by IFUNC
function.

Any comments?

H.J.
---
bfd/

	PR ld/22929
	* elf32-i386.c (elf_i386_relocate_section): Treat relocation
	against IFUNC symbol in SHT_NOTE section without SHF_ALLOC as
	relocation against FUNC symbol.
	* elf64-x86-64.c (elf_x86_64_relocate_section): Likewise.

ld/

	PR ld/22929
	* testsuite/ld-i386/i386.exp: Run PR ld/22929 test.
	* testsuite/ld-x86-64/x86-64.exp: Likewise.
	* testsuite/ld-i386/pr22929.d: New file.
	* testsuite/ld-i386/pr22929.s: Likewise.
	* testsuite/ld-x86-64/pr22929.d: Likewise.
	* testsuite/ld-x86-64/pr22929.s: Likewise.
---
 bfd/elf32-i386.c                  |  5 +++++
 bfd/elf64-x86-64.c                |  5 +++++
 ld/testsuite/ld-i386/i386.exp     |  1 +
 ld/testsuite/ld-i386/pr22929.d    | 11 +++++++++++
 ld/testsuite/ld-i386/pr22929.s    | 21 +++++++++++++++++++++
 ld/testsuite/ld-x86-64/pr22929.d  | 11 +++++++++++
 ld/testsuite/ld-x86-64/pr22929.s  | 21 +++++++++++++++++++++
 ld/testsuite/ld-x86-64/x86-64.exp |  1 +
 8 files changed, 76 insertions(+)
 create mode 100644 ld/testsuite/ld-i386/pr22929.d
 create mode 100644 ld/testsuite/ld-i386/pr22929.s
 create mode 100644 ld/testsuite/ld-x86-64/pr22929.d
 create mode 100644 ld/testsuite/ld-x86-64/pr22929.s

diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c
index 61a14097b0..557084647c 100644
--- a/bfd/elf32-i386.c
+++ b/bfd/elf32-i386.c
@@ -2221,6 +2221,10 @@ elf_i386_relocate_section (bfd *output_bfd,
 
 	  if ((input_section->flags & SEC_ALLOC) == 0)
 	    {
+	      /* If this is a SHT_NOTE section without SHF_ALLOC, treat
+	         STT_GNU_IFUNC symbol as STT_FUNC.  */
+	      if (elf_section_type (input_section) == SHT_NOTE)
+		goto skip_ifunc;
 	      /* Dynamic relocs are not propagated for SEC_DEBUGGING
 		 sections because such sections are not SEC_ALLOC and
 		 thus ld.so will not process them.  */
@@ -2440,6 +2444,7 @@ do_ifunc_pointer:
 	    }
 	}
 
+skip_ifunc:
       resolved_to_zero = (eh != NULL
 			  && UNDEFINED_WEAK_RESOLVED_TO_ZERO (info, eh));
 
diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c
index 7016964ace..a964316e44 100644
--- a/bfd/elf64-x86-64.c
+++ b/bfd/elf64-x86-64.c
@@ -2503,6 +2503,10 @@ elf_x86_64_relocate_section (bfd *output_bfd,
 
 	  if ((input_section->flags & SEC_ALLOC) == 0)
 	    {
+	      /* If this is a SHT_NOTE section without SHF_ALLOC, treat
+	         STT_GNU_IFUNC symbol as STT_FUNC.  */
+	      if (elf_section_type (input_section) == SHT_NOTE)
+		goto skip_ifunc;
 	      /* Dynamic relocs are not propagated for SEC_DEBUGGING
 		 sections because such sections are not SEC_ALLOC and
 		 thus ld.so will not process them.  */
@@ -2726,6 +2730,7 @@ do_ifunc_pointer:
 	    }
 	}
 
+skip_ifunc:
       resolved_to_zero = (eh != NULL
 			  && UNDEFINED_WEAK_RESOLVED_TO_ZERO (info, eh));
 
diff --git a/ld/testsuite/ld-i386/i386.exp b/ld/testsuite/ld-i386/i386.exp
index 240850a02c..243c0a57a1 100644
--- a/ld/testsuite/ld-i386/i386.exp
+++ b/ld/testsuite/ld-i386/i386.exp
@@ -459,6 +459,7 @@ run_dump_test "pr22115-1c"
 run_dump_test "pr22115-1d"
 run_dump_test "pr22135"
 run_dump_test "pr22782"
+run_dump_test "pr22929"
 
 if { !([istarget "i?86-*-linux*"]
        || [istarget "i?86-*-gnu*"]
diff --git a/ld/testsuite/ld-i386/pr22929.d b/ld/testsuite/ld-i386/pr22929.d
new file mode 100644
index 0000000000..099880e94d
--- /dev/null
+++ b/ld/testsuite/ld-i386/pr22929.d
@@ -0,0 +1,11 @@
+#as: --32
+#ld: -melf_i386 -shared
+#readelf: -r --wide -s
+
+There are no relocations in this file.
+#...
+Symbol table '.symtab' contains [0-9]+ entries:
+   Num:    Value  Size Type    Bind   Vis      Ndx Name
+#...
+[ \t]+[a-f0-9]+: [a-f0-9]+ +1 IFUNC +GLOBAL DEFAULT +[a-f0-9]+ +foo
+#...
diff --git a/ld/testsuite/ld-i386/pr22929.s b/ld/testsuite/ld-i386/pr22929.s
new file mode 100644
index 0000000000..3fa3dc949c
--- /dev/null
+++ b/ld/testsuite/ld-i386/pr22929.s
@@ -0,0 +1,21 @@
+	.text
+	.globl	foo
+	.type foo, %gnu_indirect_function
+foo:
+	ret
+	.size	foo, .-foo
+	.pushsection .gnu.build.attributes, "", %note
+	.dc.l 6		# size of name
+	.dc.l 16	# descsz = sizeof (addresses)
+	.dc.l 0x101	# type = FUNC
+	.dc.b 0x47, 0x41, 0x2a, 0x2, 0, 0 	# name (numeric: -fstack-protector status)
+	.dc.b 0, 0 	# Padding
+	.dc.a foo
+	.dc.a foo_end	# description (symbol name)
+	.popsection
+
+foo_end:
+	.section	.rodata.cst4,"aM",@progbits,4
+	.align 4
+.LC0:
+	.long	1065353216
diff --git a/ld/testsuite/ld-x86-64/pr22929.d b/ld/testsuite/ld-x86-64/pr22929.d
new file mode 100644
index 0000000000..537b3969e8
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/pr22929.d
@@ -0,0 +1,11 @@
+#as: --64
+#ld: -melf_x86_64 -shared
+#readelf: -r --wide -s
+
+There are no relocations in this file.
+#...
+Symbol table '.symtab' contains [0-9]+ entries:
+   Num:    Value          Size Type    Bind   Vis      Ndx Name
+#...
+[ \t]+[a-f0-9]+: [a-f0-9]+ +1 IFUNC +GLOBAL DEFAULT +[a-f0-9]+ +foo
+#...
diff --git a/ld/testsuite/ld-x86-64/pr22929.s b/ld/testsuite/ld-x86-64/pr22929.s
new file mode 100644
index 0000000000..3fa3dc949c
--- /dev/null
+++ b/ld/testsuite/ld-x86-64/pr22929.s
@@ -0,0 +1,21 @@
+	.text
+	.globl	foo
+	.type foo, %gnu_indirect_function
+foo:
+	ret
+	.size	foo, .-foo
+	.pushsection .gnu.build.attributes, "", %note
+	.dc.l 6		# size of name
+	.dc.l 16	# descsz = sizeof (addresses)
+	.dc.l 0x101	# type = FUNC
+	.dc.b 0x47, 0x41, 0x2a, 0x2, 0, 0 	# name (numeric: -fstack-protector status)
+	.dc.b 0, 0 	# Padding
+	.dc.a foo
+	.dc.a foo_end	# description (symbol name)
+	.popsection
+
+foo_end:
+	.section	.rodata.cst4,"aM",@progbits,4
+	.align 4
+.LC0:
+	.long	1065353216
diff --git a/ld/testsuite/ld-x86-64/x86-64.exp b/ld/testsuite/ld-x86-64/x86-64.exp
index 02aa38a75a..5a06947057 100644
--- a/ld/testsuite/ld-x86-64/x86-64.exp
+++ b/ld/testsuite/ld-x86-64/x86-64.exp
@@ -605,6 +605,7 @@ run_dump_test "pr20253-5a"
 run_dump_test "pr20253-5b"
 run_dump_test "tlsdesc2"
 run_dump_test "pr22048"
+run_dump_test "pr22929"
 
 proc undefined_weak {cflags ldflags} {
     set testname "Undefined weak symbol"
-- 
2.14.3

Follow-Ups:
- Re: [PATCH] x86: Treat relocation against IFUNC symbol as FUNC
  - From: Nick Clifton

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