| /* GNU/Linux on ARM target support. |
| |
| Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 |
| Free Software Foundation, Inc. |
| |
| This file is part of GDB. |
| |
| This program is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with this program; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin Street, Fifth Floor, |
| Boston, MA 02110-1301, USA. */ |
| |
| #include "defs.h" |
| #include "target.h" |
| #include "value.h" |
| #include "gdbtypes.h" |
| #include "floatformat.h" |
| #include "gdbcore.h" |
| #include "frame.h" |
| #include "regcache.h" |
| #include "doublest.h" |
| #include "solib-svr4.h" |
| #include "osabi.h" |
| #include "trad-frame.h" |
| #include "tramp-frame.h" |
| |
| #include "arm-tdep.h" |
| #include "glibc-tdep.h" |
| |
| #include "gdb_string.h" |
| |
| /* Under ARM GNU/Linux the traditional way of performing a breakpoint |
| is to execute a particular software interrupt, rather than use a |
| particular undefined instruction to provoke a trap. Upon exection |
| of the software interrupt the kernel stops the inferior with a |
| SIGTRAP, and wakes the debugger. */ |
| |
| static const char arm_linux_arm_le_breakpoint[] = { 0x01, 0x00, 0x9f, 0xef }; |
| |
| static const char arm_linux_arm_be_breakpoint[] = { 0xef, 0x9f, 0x00, 0x01 }; |
| |
| /* However, the EABI syscall interface (new in Nov. 2005) does not look at |
| the operand of the swi if old-ABI compatibility is disabled. Therefore, |
| use an undefined instruction instead. This is supported as of kernel |
| version 2.5.70 (May 2003), so should be a safe assumption for EABI |
| binaries. */ |
| |
| static const char eabi_linux_arm_le_breakpoint[] = { 0xf0, 0x01, 0xf0, 0xe7 }; |
| |
| static const char eabi_linux_arm_be_breakpoint[] = { 0xe7, 0xf0, 0x01, 0xf0 }; |
| |
| /* All the kernels which support Thumb support using a specific undefined |
| instruction for the Thumb breakpoint. */ |
| |
| static const char arm_linux_thumb_be_breakpoint[] = {0xde, 0x01}; |
| |
| static const char arm_linux_thumb_le_breakpoint[] = {0x01, 0xde}; |
| |
| /* Description of the longjmp buffer. */ |
| #define ARM_LINUX_JB_ELEMENT_SIZE INT_REGISTER_SIZE |
| #define ARM_LINUX_JB_PC 21 |
| |
| /* Extract from an array REGBUF containing the (raw) register state |
| a function return value of type TYPE, and copy that, in virtual format, |
| into VALBUF. */ |
| /* FIXME rearnsha/2002-02-23: This function shouldn't be necessary. |
| The ARM generic one should be able to handle the model used by |
| linux and the low-level formatting of the registers should be |
| hidden behind the regcache abstraction. */ |
| static void |
| arm_linux_extract_return_value (struct type *type, |
| gdb_byte regbuf[], |
| gdb_byte *valbuf) |
| { |
| /* ScottB: This needs to be looked at to handle the different |
| floating point emulators on ARM GNU/Linux. Right now the code |
| assumes that fetch inferior registers does the right thing for |
| GDB. I suspect this won't handle NWFPE registers correctly, nor |
| will the default ARM version (arm_extract_return_value()). */ |
| |
| int regnum = ((TYPE_CODE_FLT == TYPE_CODE (type)) |
| ? ARM_F0_REGNUM : ARM_A1_REGNUM); |
| memcpy (valbuf, ®buf[DEPRECATED_REGISTER_BYTE (regnum)], TYPE_LENGTH (type)); |
| } |
| |
| /* |
| Dynamic Linking on ARM GNU/Linux |
| -------------------------------- |
| |
| Note: PLT = procedure linkage table |
| GOT = global offset table |
| |
| As much as possible, ELF dynamic linking defers the resolution of |
| jump/call addresses until the last minute. The technique used is |
| inspired by the i386 ELF design, and is based on the following |
| constraints. |
| |
| 1) The calling technique should not force a change in the assembly |
| code produced for apps; it MAY cause changes in the way assembly |
| code is produced for position independent code (i.e. shared |
| libraries). |
| |
| 2) The technique must be such that all executable areas must not be |
| modified; and any modified areas must not be executed. |
| |
| To do this, there are three steps involved in a typical jump: |
| |
| 1) in the code |
| 2) through the PLT |
| 3) using a pointer from the GOT |
| |
| When the executable or library is first loaded, each GOT entry is |
| initialized to point to the code which implements dynamic name |
| resolution and code finding. This is normally a function in the |
| program interpreter (on ARM GNU/Linux this is usually |
| ld-linux.so.2, but it does not have to be). On the first |
| invocation, the function is located and the GOT entry is replaced |
| with the real function address. Subsequent calls go through steps |
| 1, 2 and 3 and end up calling the real code. |
| |
| 1) In the code: |
| |
| b function_call |
| bl function_call |
| |
| This is typical ARM code using the 26 bit relative branch or branch |
| and link instructions. The target of the instruction |
| (function_call is usually the address of the function to be called. |
| In position independent code, the target of the instruction is |
| actually an entry in the PLT when calling functions in a shared |
| library. Note that this call is identical to a normal function |
| call, only the target differs. |
| |
| 2) In the PLT: |
| |
| The PLT is a synthetic area, created by the linker. It exists in |
| both executables and libraries. It is an array of stubs, one per |
| imported function call. It looks like this: |
| |
| PLT[0]: |
| str lr, [sp, #-4]! @push the return address (lr) |
| ldr lr, [pc, #16] @load from 6 words ahead |
| add lr, pc, lr @form an address for GOT[0] |
| ldr pc, [lr, #8]! @jump to the contents of that addr |
| |
| The return address (lr) is pushed on the stack and used for |
| calculations. The load on the second line loads the lr with |
| &GOT[3] - . - 20. The addition on the third leaves: |
| |
| lr = (&GOT[3] - . - 20) + (. + 8) |
| lr = (&GOT[3] - 12) |
| lr = &GOT[0] |
| |
| On the fourth line, the pc and lr are both updated, so that: |
| |
| pc = GOT[2] |
| lr = &GOT[0] + 8 |
| = &GOT[2] |
| |
| NOTE: PLT[0] borrows an offset .word from PLT[1]. This is a little |
| "tight", but allows us to keep all the PLT entries the same size. |
| |
| PLT[n+1]: |
| ldr ip, [pc, #4] @load offset from gotoff |
| add ip, pc, ip @add the offset to the pc |
| ldr pc, [ip] @jump to that address |
| gotoff: .word GOT[n+3] - . |
| |
| The load on the first line, gets an offset from the fourth word of |
| the PLT entry. The add on the second line makes ip = &GOT[n+3], |
| which contains either a pointer to PLT[0] (the fixup trampoline) or |
| a pointer to the actual code. |
| |
| 3) In the GOT: |
| |
| The GOT contains helper pointers for both code (PLT) fixups and |
| data fixups. The first 3 entries of the GOT are special. The next |
| M entries (where M is the number of entries in the PLT) belong to |
| the PLT fixups. The next D (all remaining) entries belong to |
| various data fixups. The actual size of the GOT is 3 + M + D. |
| |
| The GOT is also a synthetic area, created by the linker. It exists |
| in both executables and libraries. When the GOT is first |
| initialized , all the GOT entries relating to PLT fixups are |
| pointing to code back at PLT[0]. |
| |
| The special entries in the GOT are: |
| |
| GOT[0] = linked list pointer used by the dynamic loader |
| GOT[1] = pointer to the reloc table for this module |
| GOT[2] = pointer to the fixup/resolver code |
| |
| The first invocation of function call comes through and uses the |
| fixup/resolver code. On the entry to the fixup/resolver code: |
| |
| ip = &GOT[n+3] |
| lr = &GOT[2] |
| stack[0] = return address (lr) of the function call |
| [r0, r1, r2, r3] are still the arguments to the function call |
| |
| This is enough information for the fixup/resolver code to work |
| with. Before the fixup/resolver code returns, it actually calls |
| the requested function and repairs &GOT[n+3]. */ |
| |
| /* The constants below were determined by examining the following files |
| in the linux kernel sources: |
| |
| arch/arm/kernel/signal.c |
| - see SWI_SYS_SIGRETURN and SWI_SYS_RT_SIGRETURN |
| include/asm-arm/unistd.h |
| - see __NR_sigreturn, __NR_rt_sigreturn, and __NR_SYSCALL_BASE */ |
| |
| #define ARM_LINUX_SIGRETURN_INSTR 0xef900077 |
| #define ARM_LINUX_RT_SIGRETURN_INSTR 0xef9000ad |
| |
| /* For ARM EABI, recognize the pattern that glibc uses... alternatively, |
| we could arrange to do this by function name, but they are not always |
| exported. */ |
| #define ARM_SET_R7_SIGRETURN 0xe3a07077 |
| #define ARM_SET_R7_RT_SIGRETURN 0xe3a070ad |
| #define ARM_EABI_SYSCALL 0xef000000 |
| |
| static void |
| arm_linux_sigtramp_cache (struct frame_info *next_frame, |
| struct trad_frame_cache *this_cache, |
| CORE_ADDR func, int regs_offset) |
| { |
| CORE_ADDR sp = frame_unwind_register_unsigned (next_frame, ARM_SP_REGNUM); |
| CORE_ADDR base = sp + regs_offset; |
| int i; |
| |
| for (i = 0; i < 16; i++) |
| trad_frame_set_reg_addr (this_cache, i, base + i * 4); |
| |
| trad_frame_set_reg_addr (this_cache, ARM_PS_REGNUM, base + 16 * 4); |
| |
| /* The VFP or iWMMXt registers may be saved on the stack, but there's |
| no reliable way to restore them (yet). */ |
| |
| /* Save a frame ID. */ |
| trad_frame_set_id (this_cache, frame_id_build (sp, func)); |
| } |
| |
| static void |
| arm_linux_sigreturn_init (const struct tramp_frame *self, |
| struct frame_info *next_frame, |
| struct trad_frame_cache *this_cache, |
| CORE_ADDR func) |
| { |
| arm_linux_sigtramp_cache (next_frame, this_cache, func, |
| 0x0c /* Offset to registers. */); |
| } |
| |
| static void |
| arm_linux_rt_sigreturn_init (const struct tramp_frame *self, |
| struct frame_info *next_frame, |
| struct trad_frame_cache *this_cache, |
| CORE_ADDR func) |
| { |
| arm_linux_sigtramp_cache (next_frame, this_cache, func, |
| 0x88 /* Offset to ucontext_t. */ |
| + 0x14 /* Offset to sigcontext. */ |
| + 0x0c /* Offset to registers. */); |
| } |
| |
| static struct tramp_frame arm_linux_sigreturn_tramp_frame = { |
| SIGTRAMP_FRAME, |
| 4, |
| { |
| { ARM_LINUX_SIGRETURN_INSTR, -1 }, |
| { TRAMP_SENTINEL_INSN } |
| }, |
| arm_linux_sigreturn_init |
| }; |
| |
| static struct tramp_frame arm_linux_rt_sigreturn_tramp_frame = { |
| SIGTRAMP_FRAME, |
| 4, |
| { |
| { ARM_LINUX_RT_SIGRETURN_INSTR, -1 }, |
| { TRAMP_SENTINEL_INSN } |
| }, |
| arm_linux_rt_sigreturn_init |
| }; |
| |
| static struct tramp_frame arm_eabi_linux_sigreturn_tramp_frame = { |
| SIGTRAMP_FRAME, |
| 4, |
| { |
| { ARM_SET_R7_SIGRETURN, -1 }, |
| { ARM_EABI_SYSCALL, -1 }, |
| { TRAMP_SENTINEL_INSN } |
| }, |
| arm_linux_sigreturn_init |
| }; |
| |
| static struct tramp_frame arm_eabi_linux_rt_sigreturn_tramp_frame = { |
| SIGTRAMP_FRAME, |
| 4, |
| { |
| { ARM_SET_R7_RT_SIGRETURN, -1 }, |
| { ARM_EABI_SYSCALL, -1 }, |
| { TRAMP_SENTINEL_INSN } |
| }, |
| arm_linux_rt_sigreturn_init |
| }; |
| |
| static void |
| arm_linux_init_abi (struct gdbarch_info info, |
| struct gdbarch *gdbarch) |
| { |
| struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); |
| |
| tdep->lowest_pc = 0x8000; |
| if (info.byte_order == BFD_ENDIAN_BIG) |
| { |
| if (tdep->arm_abi == ARM_ABI_AAPCS) |
| tdep->arm_breakpoint = eabi_linux_arm_be_breakpoint; |
| else |
| tdep->arm_breakpoint = arm_linux_arm_be_breakpoint; |
| tdep->thumb_breakpoint = arm_linux_thumb_be_breakpoint; |
| } |
| else |
| { |
| if (tdep->arm_abi == ARM_ABI_AAPCS) |
| tdep->arm_breakpoint = eabi_linux_arm_le_breakpoint; |
| else |
| tdep->arm_breakpoint = arm_linux_arm_le_breakpoint; |
| tdep->thumb_breakpoint = arm_linux_thumb_le_breakpoint; |
| } |
| tdep->arm_breakpoint_size = sizeof (arm_linux_arm_le_breakpoint); |
| tdep->thumb_breakpoint_size = sizeof (arm_linux_thumb_le_breakpoint); |
| |
| if (tdep->fp_model == ARM_FLOAT_AUTO) |
| tdep->fp_model = ARM_FLOAT_FPA; |
| |
| tdep->jb_pc = ARM_LINUX_JB_PC; |
| tdep->jb_elt_size = ARM_LINUX_JB_ELEMENT_SIZE; |
| |
| set_solib_svr4_fetch_link_map_offsets |
| (gdbarch, svr4_ilp32_fetch_link_map_offsets); |
| |
| /* The following override shouldn't be needed. */ |
| set_gdbarch_deprecated_extract_return_value (gdbarch, arm_linux_extract_return_value); |
| |
| /* Shared library handling. */ |
| set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target); |
| set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver); |
| |
| /* Enable TLS support. */ |
| set_gdbarch_fetch_tls_load_module_address (gdbarch, |
| svr4_fetch_objfile_link_map); |
| |
| tramp_frame_prepend_unwinder (gdbarch, |
| &arm_linux_sigreturn_tramp_frame); |
| tramp_frame_prepend_unwinder (gdbarch, |
| &arm_linux_rt_sigreturn_tramp_frame); |
| tramp_frame_prepend_unwinder (gdbarch, |
| &arm_eabi_linux_sigreturn_tramp_frame); |
| tramp_frame_prepend_unwinder (gdbarch, |
| &arm_eabi_linux_rt_sigreturn_tramp_frame); |
| } |
| |
| void |
| _initialize_arm_linux_tdep (void) |
| { |
| gdbarch_register_osabi (bfd_arch_arm, 0, GDB_OSABI_LINUX, |
| arm_linux_init_abi); |
| } |