/* GNU/Linux on ARM target support.
- Copyright 1999, 2000 Free Software Foundation, Inc.
+ Copyright 1999, 2000, 2001 Free Software Foundation, Inc.
This file is part of GDB.
#include "target.h"
#include "value.h"
#include "gdbtypes.h"
+#include "floatformat.h"
+#include "gdbcore.h"
+#include "frame.h"
+#include "regcache.h"
+
+/* For arm_linux_skip_solib_resolver. */
+#include "symtab.h"
+#include "symfile.h"
+#include "objfiles.h"
#ifdef GET_LONGJMP_TARGET
memcpy (valbuf, ®buf[REGISTER_BYTE (regnum)], TYPE_LENGTH (type));
}
+/* Note: ScottB
+
+ This function does not support passing parameters using the FPA
+ variant of the APCS. It passes any floating point arguments in the
+ general registers and/or on the stack.
+
+ FIXME: This and arm_push_arguments should be merged. However this
+ function breaks on a little endian host, big endian target
+ using the COFF file format. ELF is ok.
+
+ ScottB. */
+
+/* Addresses for calling Thumb functions have the bit 0 set.
+ Here are some macros to test, set, or clear bit 0 of addresses. */
+#define IS_THUMB_ADDR(addr) ((addr) & 1)
+#define MAKE_THUMB_ADDR(addr) ((addr) | 1)
+#define UNMAKE_THUMB_ADDR(addr) ((addr) & ~1)
+
+CORE_ADDR
+arm_linux_push_arguments (int nargs, value_ptr * args, CORE_ADDR sp,
+ int struct_return, CORE_ADDR struct_addr)
+{
+ char *fp;
+ int argnum, argreg, nstack_size;
+
+ /* Walk through the list of args and determine how large a temporary
+ stack is required. Need to take care here as structs may be
+ passed on the stack, and we have to to push them. */
+ nstack_size = -4 * REGISTER_SIZE; /* Some arguments go into A1-A4. */
+
+ if (struct_return) /* The struct address goes in A1. */
+ nstack_size += REGISTER_SIZE;
+
+ /* Walk through the arguments and add their size to nstack_size. */
+ for (argnum = 0; argnum < nargs; argnum++)
+ {
+ int len;
+ struct type *arg_type;
+
+ arg_type = check_typedef (VALUE_TYPE (args[argnum]));
+ len = TYPE_LENGTH (arg_type);
+
+ /* ANSI C code passes float arguments as integers, K&R code
+ passes float arguments as doubles. Correct for this here. */
+ if (TYPE_CODE_FLT == TYPE_CODE (arg_type) && REGISTER_SIZE == len)
+ nstack_size += FP_REGISTER_VIRTUAL_SIZE;
+ else
+ nstack_size += len;
+ }
+
+ /* Allocate room on the stack, and initialize our stack frame
+ pointer. */
+ fp = NULL;
+ if (nstack_size > 0)
+ {
+ sp -= nstack_size;
+ fp = (char *) sp;
+ }
+
+ /* Initialize the integer argument register pointer. */
+ argreg = A1_REGNUM;
+
+ /* The struct_return pointer occupies the first parameter passing
+ register. */
+ if (struct_return)
+ write_register (argreg++, struct_addr);
+
+ /* Process arguments from left to right. Store as many as allowed
+ in the parameter passing registers (A1-A4), and save the rest on
+ the temporary stack. */
+ for (argnum = 0; argnum < nargs; argnum++)
+ {
+ int len;
+ char *val;
+ double dbl_arg;
+ CORE_ADDR regval;
+ enum type_code typecode;
+ struct type *arg_type, *target_type;
+
+ arg_type = check_typedef (VALUE_TYPE (args[argnum]));
+ target_type = TYPE_TARGET_TYPE (arg_type);
+ len = TYPE_LENGTH (arg_type);
+ typecode = TYPE_CODE (arg_type);
+ val = (char *) VALUE_CONTENTS (args[argnum]);
+
+ /* ANSI C code passes float arguments as integers, K&R code
+ passes float arguments as doubles. The .stabs record for
+ for ANSI prototype floating point arguments records the
+ type as FP_INTEGER, while a K&R style (no prototype)
+ .stabs records the type as FP_FLOAT. In this latter case
+ the compiler converts the float arguments to double before
+ calling the function. */
+ if (TYPE_CODE_FLT == typecode && REGISTER_SIZE == len)
+ {
+ /* Float argument in buffer is in host format. Read it and
+ convert to DOUBLEST, and store it in target double. */
+ DOUBLEST dblval;
+
+ len = TARGET_DOUBLE_BIT / TARGET_CHAR_BIT;
+ floatformat_to_doublest (HOST_FLOAT_FORMAT, val, &dblval);
+ store_floating (&dbl_arg, len, dblval);
+ val = (char *) &dbl_arg;
+ }
+
+ /* If the argument is a pointer to a function, and it is a Thumb
+ function, set the low bit of the pointer. */
+ if (TYPE_CODE_PTR == typecode
+ && NULL != target_type
+ && TYPE_CODE_FUNC == TYPE_CODE (target_type))
+ {
+ CORE_ADDR regval = extract_address (val, len);
+ if (arm_pc_is_thumb (regval))
+ store_address (val, len, MAKE_THUMB_ADDR (regval));
+ }
+
+ /* Copy the argument to general registers or the stack in
+ register-sized pieces. Large arguments are split between
+ registers and stack. */
+ while (len > 0)
+ {
+ int partial_len = len < REGISTER_SIZE ? len : REGISTER_SIZE;
+
+ if (argreg <= ARM_LAST_ARG_REGNUM)
+ {
+ /* It's an argument being passed in a general register. */
+ regval = extract_address (val, partial_len);
+ write_register (argreg++, regval);
+ }
+ else
+ {
+ /* Push the arguments onto the stack. */
+ write_memory ((CORE_ADDR) fp, val, REGISTER_SIZE);
+ fp += REGISTER_SIZE;
+ }
+
+ len -= partial_len;
+ val += partial_len;
+ }
+ }
+
+ /* Return adjusted stack pointer. */
+ return sp;
+}
+
+/*
+ Dynamic Linking on ARM 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 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]. */
+
+/* Find the minimal symbol named NAME, and return both the minsym
+ struct and its objfile. This probably ought to be in minsym.c, but
+ everything there is trying to deal with things like C++ and
+ SOFUN_ADDRESS_MAYBE_TURQUOISE, ... Since this is so simple, it may
+ be considered too special-purpose for general consumption. */
+
+static struct minimal_symbol *
+find_minsym_and_objfile (char *name, struct objfile **objfile_p)
+{
+ struct objfile *objfile;
+
+ ALL_OBJFILES (objfile)
+ {
+ struct minimal_symbol *msym;
+
+ ALL_OBJFILE_MSYMBOLS (objfile, msym)
+ {
+ if (SYMBOL_NAME (msym)
+ && STREQ (SYMBOL_NAME (msym), name))
+ {
+ *objfile_p = objfile;
+ return msym;
+ }
+ }
+ }
+
+ return 0;
+}
+
+
+static CORE_ADDR
+skip_hurd_resolver (CORE_ADDR pc)
+{
+ /* The HURD dynamic linker is part of the GNU C library, so many
+ GNU/Linux distributions use it. (All ELF versions, as far as I
+ know.) An unresolved PLT entry points to "_dl_runtime_resolve",
+ which calls "fixup" to patch the PLT, and then passes control to
+ the function.
+
+ We look for the symbol `_dl_runtime_resolve', and find `fixup' in
+ the same objfile. If we are at the entry point of `fixup', then
+ we set a breakpoint at the return address (at the top of the
+ stack), and continue.
+
+ It's kind of gross to do all these checks every time we're
+ called, since they don't change once the executable has gotten
+ started. But this is only a temporary hack --- upcoming versions
+ of Linux will provide a portable, efficient interface for
+ debugging programs that use shared libraries. */
+
+ struct objfile *objfile;
+ struct minimal_symbol *resolver
+ = find_minsym_and_objfile ("_dl_runtime_resolve", &objfile);
+
+ if (resolver)
+ {
+ struct minimal_symbol *fixup
+ = lookup_minimal_symbol ("fixup", 0, objfile);
+
+ if (fixup && SYMBOL_VALUE_ADDRESS (fixup) == pc)
+ return (SAVED_PC_AFTER_CALL (get_current_frame ()));
+ }
+
+ return 0;
+}
+
+/* See the comments for SKIP_SOLIB_RESOLVER at the top of infrun.c.
+ This function:
+ 1) decides whether a PLT has sent us into the linker to resolve
+ a function reference, and
+ 2) if so, tells us where to set a temporary breakpoint that will
+ trigger when the dynamic linker is done. */
+
+CORE_ADDR
+arm_linux_skip_solib_resolver (CORE_ADDR pc)
+{
+ CORE_ADDR result;
+
+ /* Plug in functions for other kinds of resolvers here. */
+ result = skip_hurd_resolver (pc);
+
+ if (result)
+ return result;
+
+ return 0;
+}
+
+/* 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
+
+/* arm_linux_in_sigtramp determines if PC points at one of the
+ instructions which cause control to return to the Linux kernel upon
+ return from a signal handler. FUNC_NAME is unused. */
+
+int
+arm_linux_in_sigtramp (CORE_ADDR pc, char *func_name)
+{
+ unsigned long inst;
+
+ inst = read_memory_integer (pc, 4);
+
+ return (inst == ARM_LINUX_SIGRETURN_INSTR
+ || inst == ARM_LINUX_RT_SIGRETURN_INSTR);
+
+}
+
+/* arm_linux_sigcontext_register_address returns the address in the
+ sigcontext of register REGNO given a stack pointer value SP and
+ program counter value PC. The value 0 is returned if PC is not
+ pointing at one of the signal return instructions or if REGNO is
+ not saved in the sigcontext struct. */
+
+CORE_ADDR
+arm_linux_sigcontext_register_address (CORE_ADDR sp, CORE_ADDR pc, int regno)
+{
+ unsigned long inst;
+ CORE_ADDR reg_addr = 0;
+
+ inst = read_memory_integer (pc, 4);
+
+ if (inst == ARM_LINUX_SIGRETURN_INSTR || inst == ARM_LINUX_RT_SIGRETURN_INSTR)
+ {
+ CORE_ADDR sigcontext_addr;
+
+ /* The sigcontext structure is at different places for the two
+ signal return instructions. For ARM_LINUX_SIGRETURN_INSTR,
+ it starts at the SP value. For ARM_LINUX_RT_SIGRETURN_INSTR,
+ it is at SP+8. For the latter instruction, it may also be
+ the case that the address of this structure may be determined
+ by reading the 4 bytes at SP, but I'm not convinced this is
+ reliable.
+
+ In any event, these magic constants (0 and 8) may be
+ determined by examining struct sigframe and struct
+ rt_sigframe in arch/arm/kernel/signal.c in the Linux kernel
+ sources. */
+
+ if (inst == ARM_LINUX_RT_SIGRETURN_INSTR)
+ sigcontext_addr = sp + 8;
+ else /* inst == ARM_LINUX_SIGRETURN_INSTR */
+ sigcontext_addr = sp + 0;
+
+ /* The layout of the sigcontext structure for ARM GNU/Linux is
+ in include/asm-arm/sigcontext.h in the Linux kernel sources.
+
+ There are three 4-byte fields which precede the saved r0
+ field. (This accounts for the 12 in the code below.) The
+ sixteen registers (4 bytes per field) follow in order. The
+ PSR value follows the sixteen registers which accounts for
+ the constant 19 below. */
+
+ if (0 <= regno && regno <= PC_REGNUM)
+ reg_addr = sigcontext_addr + 12 + (4 * regno);
+ else if (regno == PS_REGNUM)
+ reg_addr = sigcontext_addr + 19 * 4;
+ }
+
+ return reg_addr;
+}
+
void
_initialize_arm_linux_tdep (void)
{
projects / deliverable / binutils-gdb.git / blobdiff