honggyukim
commented
5 years ago typedef struct {
Elf32_Sword d_tag;
union {
Elf32_Word d_val;
Elf32_Addr d_ptr;
Elf32_Off d_off;
} d_un;
} Elf32_Dyn;DT_PLTGOT (d_tag)
- The
d_ptrfield of this entry gives the address of the first byte in the Procedure Linkage Table (.PLT in the Section called Procedure Linkage Table).
DT_JMPREL (d_tag)
- This entry is associated with a table of relocation entries for the PLT. For zSeries this entry is mandatory both for executable and shared object files. Moreover, the relocation table's entries must have a one-to-one correspondence with the PLT. The table of
DT_JMPRELrelocation entries is wholly contained within theDT_RELAreferenced table. See the Section called Procedure Linkage Table for more information.
http://refspecs.linuxfoundation.org/ELF/zSeries/lzsabi0_zSeries/x2251.html
The symbol refers to the start of the .got section. Two words in the GOT are reserved:
The word at _GLOBAL_OFFSET_TABLE_[0] is set by the linkage editor to hold the address of the dynamic structure, referenced with the symbol _DYNAMIC. This allows a program, such as the dynamic linker, to find its own dynamic structure without having yet processed its relocation entries. This is especially important for the dynamic linker, because it must initialize itself without relying on other programs to relocate its memory image.
The word at _GLOBAL_OFFSET_TABLE_[1] is reserved for future use.
The Global Offset Table resides in the ELF .got section.
https://docs.oracle.com/cd/E19683-01/817-3677/chapter6-42444/index.html
Dynamic Section
If an object file participates in dynamic linking, its program header table will have an element of type PT_DYNAMIC. This segment contains the .dynamic section. A special symbol, _DYNAMIC, labels the section, which contains an array of the following structures, defined in sys/link.h:
typedef struct {
Elf32_Sword d_tag;
union {
Elf32_Word d_val;
Elf32_Addr d_ptr;
Elf32_Off d_off;
} d_un;
} Elf32_Dyn;
typedef struct {
Elf64_Xword d_tag;
union {
Elf64_Xword d_val;
Elf64_Addr d_ptr;
} d_un;
} Elf64_Dyn;For each object with this type, d_tag controls the interpretation of d_un.
d_val
- These objects represent integer values with various interpretations.
d_ptr
- These objects represent program virtual addresses. A file's virtual addresses might not match the memory virtual addresses during execution. When interpreting addresses contained in the dynamic structure, the runtime linker computes actual addresses, based on the original file value and the memory "base address". For consistency, files do not contain relocation entries to correct addresses in the dynamic structure.
3d4ea6b plthook: Trace dynamic (PLT) symbols too 04e7dd2 Implement plthook on ARM fc664ce fixup for ARM plthook 2f2baf2 Access _GLOBAL_OFFSETTABLE through DT_PLTGOT info cae6af7 Use mprotect() before updating GOT d532a65 Find dynamic symbols to skip on __monstartup() 30cf417 Prevent recursion on plthook 16a31e2 Add support for library symbols c3c8f72 Save resolved addresses of dynamic symbols 1437299 Speed up PLT hooking on x86_64 d8c6a4f Speed up PLT hooking on ARM 53b370f Handle fork() call in child
fee3062 mcount: Create libmcount directory 37d8201 mcount: Build dynsym idxlist for setjmp/longjmp 9635a1a mcount: Add basic support for setjmp/longjmp b13df20 filter: Add '@plt' filter for PLT functions f6fe591 mcount: Fix PLT record after filtering 124653d mcount: Protect resolved PLT addresses using mutex 244ce79 mcount: Fix PLT recursion with filter * c5c2f79 mcount: Protect recursion from malloc() 80319b9 mcount: Ignore mcount() after it finished 9bf99b3 mcount: Flush rstack on special functions 8479be5 mcount: Pass mcount_regs to plthook_entry also
1a54771 mcount: Split PLT-hooking code into separate file 76899f8 mcount: Introduce struct mcount_thread_data 450becc mcount: Move plthook related data to mcount_thread_data 7e7ac2e mcount: Use map load address to adjust symbol offset 9b57d31 mcount: Pass offset to the PLT hook function 5b79331 mcount: Skip PLT hooking when no PLT reloc entries found b7fdfbc mcount: Fix return value of PLT functions 3912dfa mcount: Cleanup the plthook_exit() * 78db558 mcount: Prevent recursive call in mtd_dtor() * 8eb2330 mcount: Fix recursion during fork() 87a0ee7 mcount: Hook dlopen() to trace functions in the dynamic library * 6e3f577 mcount: Move raw access of mtd under unlikely 582ad22 mcount: Move recursion check out of mcount_should_stop() * 3814d4f mcount: Check recursion in mcount_prepare() eb47108 mcount: Use binary search for special PLT functions ** 9479ec2 mcount: Separate PLTGOT overwrite * 3ec95cf mcount: Do not hook PLT of mcount() * 66ac84a mcount: Fix a bug when longjmp() called twice 263ba58 mcount: Hook dlopen() early * ad5869b mcount: Return saved address from plthook_entry() ** 3e0c35b mcount: Introduce setup_pltgot() * 9392847 mcount: Basic support for bind-now binaries
mcount: Introduce mcount_arch_plthook_addr() * 5f2e7d6 mcount: Introduce mcount_arch_plthook_addr() * 6ef9641 mcount: Eliminate plthook_guard ffbfd59 mcount: Don't restore parent ip in rstacks on longjmp() * 2b2403e symbol: Fix SYMTAB_FL_ADJ_OFFSET usage in plthook 7f94a7e plthook: Skip binary has no PLTGOT address ** ef7137f plthook: Introduce struct plthook_data ** 14c9ac3 plthook: Setup module id for BIND-NOW binaries 50f43df plthook: Pass 'pd' to mcount_arch_plthook_addr()
** 3594de2 plthook: Support nested libcall tracing f1f0b28 plthook: Handle special dynsym index per pd * bd4a1a7 plthook: Restore already resolved PLT entries * 4d39415 plthook: Save and use PLT0 address on ARM 1d10f0c plthook: Set resolver address only once
8d90229 symbol: Load and save all module symbols fc41d32 plthook: Make x86's mcount_arch_plthook_addr() as default ** 8503de4 plthook: Resolve address of pthread_exit() 5c8c4ee plthook: Handle recursion in plthook_entry() c6fde0e plthook: Handle corrupted rstack after vfork() 2cb0901 plthook: Check PT_GNU_RELRO 5604ae5 plthook: Pre-resolve address of special functions 3f20adf plthook: Fix infinite loop in execl() on ARM b7230be plthook: Do not call dlsym() in the init routine 0c18764 plthook: Allow architecture to hook no-PLT libcall 5d81130 plthook: Remove mcount_arch_undo_bindnow() * 961518c Revert "Handle mcount/plthook_return() return 0" * 0ba73d0 mcount: Add ARCH_CAN_RESTORE_PLTHOOK logic