@@ -, +, @@ 

 relocation

- In general they are.  But IRELATIVE relocations are sorted to come

  last, and PLT entries are not sorted accordingly.

---

 sysdeps/linux-gnu/x86/arch.h |   11 +++++

 sysdeps/linux-gnu/x86/plt.c  |  101 +++++++++++++++++++++++++++++++++++++++++-

 2 files changed, 111 insertions(+), 1 deletions(-)

--- a/sysdeps/linux-gnu/x86/arch.h	

+++ a/sysdeps/linux-gnu/x86/arch.h	

@@ -19,6 +19,10 @@ 

  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA

  * 02110-1301 USA

  */

+#ifndef LTRACE_X86_ARCH_H

+#define LTRACE_X86_ARCH_H

+

+#include "vect.h"

 #define BREAKPOINT_VALUE {0xcc}

 #define BREAKPOINT_LENGTH 1

@@ -30,9 +34,16 @@ 

 #define ARCH_HAVE_ADD_PLT_ENTRY

+#define ARCH_HAVE_LTELF_DATA

+struct arch_ltelf_data {

+	struct vect plt_map;

+};

+

 #ifdef __x86_64__

 #define LT_ELFCLASS	ELFCLASS64

 #define LT_ELF_MACHINE	EM_X86_64

 #endif

 #define LT_ELFCLASS2	ELFCLASS32

 #define LT_ELF_MACHINE2	EM_386

+

+#endif /* LTRACE_X86_ARCH_H */

--- a/sysdeps/linux-gnu/x86/plt.c	

+++ a/sysdeps/linux-gnu/x86/plt.c	

@@ -27,10 +27,19 @@ 

 #include "library.h"

 #include "trace.h"

+static GElf_Addr

+x86_plt_offset(uint32_t i)

+{

+	/* Skip the first PLT entry, which contains a stub to call the

+	 * resolver.  */

+	return (i + 1) * 16;

+}

+

 GElf_Addr

 arch_plt_sym_val(struct ltelf *lte, size_t ndx, GElf_Rela *rela)

 {

-	return lte->plt_addr + (ndx + 1) * 16;

+	uint32_t i = *VECT_ELEMENT(&lte->arch.plt_map, uint32_t, ndx);

+	return x86_plt_offset(i) + lte->plt_addr;

 }

 void *

@@ -62,3 +71,93 @@ arch_elf_add_plt_entry(struct process *proc, struct ltelf *lte,

 	return PLT_DEFAULT;

 }

+

+int

+arch_elf_init(struct ltelf *lte, struct library *lib)

+{

+	VECT_INIT(&lte->arch.plt_map, unsigned int);

+

+	/* IRELATIVE slots may make the whole situation a fair deal

+	 * more complex.  On x86{,_64}, the PLT slots are not

+	 * presented in the order of the corresponding relocations,

+	 * but in the order it which these symbols are in the symbol

+	 * table.  That's static symbol table, which may be stripped

+	 * off, not dynsym--that doesn't contain IFUNC symbols at all.

+	 * So we have to decode each PLT entry to figure out what

+	 * entry it corresponds to.  We need to interpret the PLT

+	 * table to figure this out.

+	 *

+	 * On i386, the PLT entry format is as follows:

+	 *

+	 *	8048300:   ff 25 0c a0 04 08       jmp    *0x804a00c

+	 *	8048306:   68 20 00 00 00          push   $0x20

+	 *	804830b:   e9 e0 ff ff ff          jmp    80482f0 <_init+0x30>

+	 *

+	 * For PIE binaries it is the following:

+	 *

+	 *	    410:   ff a3 10 00 00 00       jmp    *0x10(%ebx)

+	 *	    416:   68 00 00 00 00          push   $0x0

+	 *	    41b:   e9 d0 ff ff ff          jmp    3f0 <_init+0x30>

+	 *

+	 * On x86_64, it is:

+	 *

+	 *	 400420:   ff 25 f2 0b 20 00       jmpq   *0x200bf2(%rip)        # 601018 <_GLOBAL_OFFSET_TABLE_+0x18>

+	 *	 400426:   68 00 00 00 00          pushq  $0x0

+	 *	 40042b:   e9 e0 ff ff ff          jmpq   400410 <_init+0x18>

+	 *

+         * On i386, the argument to push is an offset of relocation to

+	 * use.  The first PLT slot has an offset of 0x0, the second

+	 * 0x8, etc.  On x86_64, it's directly the index that we are

+	 * looking for.

+	 */

+

+	/* Here we scan the PLT table and initialize a map of

+	 * relocation->slot number in lte->arch.plt_map.  */

+

+	size_t i;

+	for (i = 0; i < vect_size(&lte->plt_relocs); ++i) {

+

+		GElf_Addr offset = x86_plt_offset(i);

+		uint32_t reloc_arg = 0;

+

+		uint8_t byte;

+		if (elf_read_next_u8(lte->plt_data, &offset, &byte) < 0

+		    || byte != 0xff

+		    || elf_read_next_u8(lte->plt_data, &offset, &byte) < 0

+		    || (byte != 0xa3 && byte != 0x25))

+			goto next;

+

+		/* Skip immediate argument in the instruction.  */

+		offset += 4;

+

+		if (elf_read_next_u8(lte->plt_data, &offset, &byte) < 0

+		    || byte != 0x68

+		    || elf_read_next_u32(lte->plt_data,

+					 &offset, &reloc_arg) < 0) {

+			reloc_arg = 0;

+			goto next;

+		}

+

+		if (lte->ehdr.e_machine == EM_386) {

+			if (reloc_arg % 8 != 0) {

+				reloc_arg = 0;

+				goto next;

+			}

+			reloc_arg /= 8;

+		}

+

+	next:

+		if (VECT_PUSHBACK(&lte->arch.plt_map, &reloc_arg) < 0) {

+			arch_elf_destroy(lte);

+			return -1;

+		}

+	}

+

+	return 0;

+}

+

+void

+arch_elf_destroy(struct ltelf *lte)

+{

+	VECT_DESTROY(&lte->arch.plt_map, uint32_t, NULL, NULL);

+}

--