Blame SOURCES/ltrace-0.7.91-x86_64-irelative.patch

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@@ -, +, @@ 
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 relocation
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- In general they are.  But IRELATIVE relocations are sorted to come
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  last, and PLT entries are not sorted accordingly.
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---
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 sysdeps/linux-gnu/x86/arch.h |   11 +++++
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 sysdeps/linux-gnu/x86/plt.c  |  101 +++++++++++++++++++++++++++++++++++++++++-
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 2 files changed, 111 insertions(+), 1 deletions(-)
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--- a/sysdeps/linux-gnu/x86/arch.h	
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+++ a/sysdeps/linux-gnu/x86/arch.h	
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@@ -19,6 +19,10 @@ 
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  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
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  * 02110-1301 USA
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  */
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+#ifndef LTRACE_X86_ARCH_H
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+#define LTRACE_X86_ARCH_H
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+
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+#include "vect.h"
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 #define BREAKPOINT_VALUE {0xcc}
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 #define BREAKPOINT_LENGTH 1
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@@ -30,9 +34,16 @@ 
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 #define ARCH_HAVE_ADD_PLT_ENTRY
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+#define ARCH_HAVE_LTELF_DATA
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+struct arch_ltelf_data {
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+	struct vect plt_map;
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+};
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+
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 #ifdef __x86_64__
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 #define LT_ELFCLASS	ELFCLASS64
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 #define LT_ELF_MACHINE	EM_X86_64
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 #endif
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 #define LT_ELFCLASS2	ELFCLASS32
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 #define LT_ELF_MACHINE2	EM_386
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+
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+#endif /* LTRACE_X86_ARCH_H */
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--- a/sysdeps/linux-gnu/x86/plt.c	
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+++ a/sysdeps/linux-gnu/x86/plt.c	
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@@ -27,10 +27,19 @@ 
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 #include "library.h"
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 #include "trace.h"
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+static GElf_Addr
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+x86_plt_offset(uint32_t i)
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+{
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+	/* Skip the first PLT entry, which contains a stub to call the
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+	 * resolver.  */
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+	return (i + 1) * 16;
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+}
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+
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 GElf_Addr
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 arch_plt_sym_val(struct ltelf *lte, size_t ndx, GElf_Rela *rela)
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 {
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-	return lte->plt_addr + (ndx + 1) * 16;
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+	uint32_t i = *VECT_ELEMENT(&lte->arch.plt_map, uint32_t, ndx);
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+	return x86_plt_offset(i) + lte->plt_addr;
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 }
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 void *
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@@ -62,3 +71,93 @@ arch_elf_add_plt_entry(struct process *proc, struct ltelf *lte,
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 	return PLT_DEFAULT;
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 }
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+
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+int
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+arch_elf_init(struct ltelf *lte, struct library *lib)
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+{
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+	VECT_INIT(&lte->arch.plt_map, unsigned int);
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+
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+	/* IRELATIVE slots may make the whole situation a fair deal
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+	 * more complex.  On x86{,_64}, the PLT slots are not
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+	 * presented in the order of the corresponding relocations,
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+	 * but in the order it which these symbols are in the symbol
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+	 * table.  That's static symbol table, which may be stripped
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+	 * off, not dynsym--that doesn't contain IFUNC symbols at all.
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+	 * So we have to decode each PLT entry to figure out what
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+	 * entry it corresponds to.  We need to interpret the PLT
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+	 * table to figure this out.
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+	 *
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+	 * On i386, the PLT entry format is as follows:
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+	 *
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+	 *	8048300:   ff 25 0c a0 04 08       jmp    *0x804a00c
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+	 *	8048306:   68 20 00 00 00          push   $0x20
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+	 *	804830b:   e9 e0 ff ff ff          jmp    80482f0 <_init+0x30>
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+	 *
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+	 * For PIE binaries it is the following:
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+	 *
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+	 *	    410:   ff a3 10 00 00 00       jmp    *0x10(%ebx)
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+	 *	    416:   68 00 00 00 00          push   $0x0
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+	 *	    41b:   e9 d0 ff ff ff          jmp    3f0 <_init+0x30>
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+	 *
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+	 * On x86_64, it is:
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+	 *
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+	 *	 400420:   ff 25 f2 0b 20 00       jmpq   *0x200bf2(%rip)        # 601018 <_GLOBAL_OFFSET_TABLE_+0x18>
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+	 *	 400426:   68 00 00 00 00          pushq  $0x0
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+	 *	 40042b:   e9 e0 ff ff ff          jmpq   400410 <_init+0x18>
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+	 *
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+         * On i386, the argument to push is an offset of relocation to
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+	 * use.  The first PLT slot has an offset of 0x0, the second
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+	 * 0x8, etc.  On x86_64, it's directly the index that we are
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+	 * looking for.
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+	 */
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+
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+	/* Here we scan the PLT table and initialize a map of
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+	 * relocation->slot number in lte->arch.plt_map.  */
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+
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+	size_t i;
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+	for (i = 0; i < vect_size(&lte->plt_relocs); ++i) {
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+
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+		GElf_Addr offset = x86_plt_offset(i);
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+		uint32_t reloc_arg = 0;
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+
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+		uint8_t byte;
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+		if (elf_read_next_u8(lte->plt_data, &offset, &byte) < 0
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+		    || byte != 0xff
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+		    || elf_read_next_u8(lte->plt_data, &offset, &byte) < 0
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+		    || (byte != 0xa3 && byte != 0x25))
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+			goto next;
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+
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+		/* Skip immediate argument in the instruction.  */
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+		offset += 4;
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+
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+		if (elf_read_next_u8(lte->plt_data, &offset, &byte) < 0
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+		    || byte != 0x68
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+		    || elf_read_next_u32(lte->plt_data,
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+					 &offset, &reloc_arg) < 0) {
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+			reloc_arg = 0;
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+			goto next;
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+		}
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+
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+		if (lte->ehdr.e_machine == EM_386) {
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+			if (reloc_arg % 8 != 0) {
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+				reloc_arg = 0;
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+				goto next;
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+			}
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+			reloc_arg /= 8;
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+		}
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+
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+	next:
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+		if (VECT_PUSHBACK(&lte->arch.plt_map, &reloc_arg) < 0) {
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+			arch_elf_destroy(lte);
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+			return -1;
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+		}
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+	}
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+
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+	return 0;
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+}
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+
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+void
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+arch_elf_destroy(struct ltelf *lte)
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+{
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+	VECT_DESTROY(&lte->arch.plt_map, uint32_t, NULL, NULL);
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+}
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--