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binutils-gdb/gdb/regcache.h
Pedro Alves 20aa2c606e Extend JIT-reader test and fix GDB problems that exposes 
The jit-reader.exp test isn't really exercising the jit-reader's
unwinder API at all.  This commit address that, and then fixes GDB
problems exposed.

- The custom JIT reader provided for the jit-reader.exp testcase
  always rejects the jitted function's frame...

  This is because the custom JIT reader in the testcase never ever
  sets state->code_begin/end, so the bounds check in
  gdb.base/jitreader.c:unwind_frame:

   if (this_ip >= state->code_end || this_ip < state->code_begin)
     return GDB_FAIL;

  tends to fail, unless you're "lucky" (because it references
  uninitialized data).

  The result is that GDB is always actually using a built-in unwinder
  for the jitted function.

- The provided unwinder doesn't do anything that GDB's built-in
  unwinder can't do.

  IOW, we can't really tell whether the JIT reader's unwinder is
  working or not.

  I fixed that by making the jitted function mangle its own stack
  pointer with a xor, and then teaching the jit unwinder to demangle
  it back (another xor).  So now "backtrace" with GDB's built-in
  unwinder fails while with the jit unwinder, it succeeds.

- GDB crashes after unloading the JIT reader, and flushing frames...

  I made the testcase use the "flushregs" command after unloading the
  JIT reader, to force the JIT frames to be flushed.  However, that
  crashes GDB...

  When reinit_frame_cache tears down a frame's cache, it calls its
  unwinder's dealloc_cache method, which for JIT frames ends up in
  jit.c:jit_dealloc_cache.  This function calls each of the frame's
  gdb_reg_value's "free" pointer:

   for (i = 0; i < gdbarch_num_regs (frame_arch); i++)
     if (priv_data->registers[i] && priv_data->registers[i]->free)
       priv_data->registers[i]->free (priv_data->registers[i]);

  and the problem is these gdb_reg_value instances have been returned
  by the JIT reader that has been already unloaded, and their "free"
  function pointers likely point to functions in the DSO that has
  already been unloaded...

  A fix for that could be to call reinit_frame_cache in
  jit_reader_unload_command _before_ unloading the jit reader DSO so
  that the jit reader is given a chance to clean up the gdb_reg_values
  before it is unloaded.  However, the fix for the point below makes
  this unnecessary, because it stops jit.c from keeping around
  gdb_reg_values in the first place.

- However, it still makes sense to clear the frame cache when loading
  or unloading a JIT unwinder.

  This makes testing a JIT unwinder a bit simpler.

- Not only the frame cache actually -- gdb is not unloading the
  jit-registered objfiles when the JIT reader is unloaded, and not
  loading the already-registered descriptors when a JIT reader is
  loaded.

  The new test exercises unloading the jit reader, loading it back
  again, and then making sure the JIT reader's unwinder works again.
  Without the unload/re-load of already-read descriptors, the newly
  loaded JIT would have no idea where the new function is, because
  it's stored at symbol read time.

- I added a couple "info frame" calls to the test, and that
  crashes GDB...

  The problem is that jit_frame_prev_register assumes it'll only be
  called for raw registers, so when it gets a pseudo register number,
  the "priv->registers[reg]" access is really an out-of-bounds access.

  To fix that, I made jit_frame_prev_register use
  gdbarch_pseudo_register_read_value for reading the pseudo-registers.
  However, that works with a regcache and we don't have one.  To fix
  that, I made the JIT unwinder store a regcache in its cache instead
  of an array of gdb_reg_value pointers.

gdb/ChangeLog:
2016-07-01  Pedro Alves  <palves@redhat.com>
	    Tom Tromey  <tom@tromey.com>

	* jit.c (jit_reader_load_command): Call reinit_frame_cache and
	jit_inferior_created_hook.
	(jit_reader_unload_command): Call reinit_frame_cache and
	jit_inferior_exit_hook.
	* jit.c (struct jit_unwind_private) <registers>: Delete field.
	<regcache>: New field.
	(jit_unwind_reg_set_impl): Set the register's value in the
	regcache.  Free the passed-in gdb_reg_value.
	(jit_dealloc_cache): Adjust to free the regcache.
	(jit_frame_sniffer): Allocate a regcache instead of an array of
	gdb_reg_value pointers.
	(jit_frame_this_id): Adjust.
	(jit_frame_prev_register): Read raw registers off of the regcache
	instead of from the gdb_reg_value pointer array.  Use
	gdbarch_pseudo_register_read_value to read pseudo registers.
	* regcache.c (regcache_raw_set_cached_value): New function,
	factored out from ...
	(regcache_raw_write): ... here.
	* regcache.h (regcache_raw_set_cached_value): Declare.

gdb/testsuite/ChangeLog:
2016-07-01  Pedro Alves  <palves@redhat.com>

	* gdb.base/jit-reader.exp (info_registers_current_frame): New
	procedure.
	(jit_reader_test): Test the jit reader's unwinder.
	* gdb.base/jithost.c (jit_function_00_code): New global.
	(main): Use memcpy to fill in the mmapped code, instead of poking
	bytes manually here.
	* gdb.base/jitreader.c (enum register_mapping) <AMD64_RBP>: New
	value.
	(read_debug_info): Save the function's range.
	(read_sp): New function.
	(unwind_frame): Use it.  Also unwind RBP.
	(get_frame_id): Use read_sp.
	(gdb_init_reader): Use calloc instead of malloc.
	* lib/gdb.exp (get_hexadecimal_valueof): Add optional 'test'
	parameter.  Use gdb_test_multiple.
2016-07-01 11:56:39 +01:00

226 lines
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/* Cache and manage the values of registers for GDB, the GNU debugger.
Copyright (C) 1986-2016 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 3 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, see <http://www.gnu.org/licenses/>. */
#ifndef REGCACHE_H
#define REGCACHE_H
#include "common-regcache.h"
struct regcache;
struct regset;
struct gdbarch;
struct address_space;
extern struct regcache *get_current_regcache (void);
extern struct regcache *get_thread_regcache (ptid_t ptid);
extern struct regcache *get_thread_arch_regcache (ptid_t, struct gdbarch *);
extern struct regcache *get_thread_arch_aspace_regcache (ptid_t,
struct gdbarch *,
struct address_space *);
void regcache_xfree (struct regcache *regcache);
struct cleanup *make_cleanup_regcache_xfree (struct regcache *regcache);
struct regcache *regcache_xmalloc (struct gdbarch *gdbarch,
struct address_space *aspace);
/* Return REGCACHE's architecture. */
extern struct gdbarch *get_regcache_arch (const struct regcache *regcache);
/* Return REGCACHE's address space. */
extern struct address_space *get_regcache_aspace (const struct regcache *);
enum register_status regcache_register_status (const struct regcache *regcache,
int regnum);
/* Transfer a raw register [0..NUM_REGS) between core-gdb and the
regcache. The read variants return the status of the register. */
enum register_status regcache_raw_read (struct regcache *regcache,
int rawnum, gdb_byte *buf);
void regcache_raw_write (struct regcache *regcache, int rawnum,
const gdb_byte *buf);
extern enum register_status
regcache_raw_read_signed (struct regcache *regcache,
int regnum, LONGEST *val);
extern void regcache_raw_write_signed (struct regcache *regcache,
int regnum, LONGEST val);
extern void regcache_raw_write_unsigned (struct regcache *regcache,
int regnum, ULONGEST val);
/* Set a raw register's value in the regcache's buffer. Unlike
regcache_raw_write, this is not write-through. The intention is
allowing to change the buffer contents of a read-only regcache
allocated with regcache_xmalloc. */
extern void regcache_raw_set_cached_value
(struct regcache *regcache, int regnum, const gdb_byte *buf);
/* Partial transfer of raw registers. These perform read, modify,
write style operations. The read variant returns the status of the
register. */
extern enum register_status
regcache_raw_read_part (struct regcache *regcache, int regnum,
int offset, int len, gdb_byte *buf);
void regcache_raw_write_part (struct regcache *regcache, int regnum,
int offset, int len, const gdb_byte *buf);
void regcache_invalidate (struct regcache *regcache, int regnum);
/* Transfer of pseudo-registers. The read variants return a register
status, as an indication of when a ``cooked'' register was
constructed from valid, invalid or unavailable ``raw''
registers. */
/* Transfer a cooked register [0..NUM_REGS+NUM_PSEUDO_REGS). */
enum register_status regcache_cooked_read (struct regcache *regcache,
int rawnum, gdb_byte *buf);
void regcache_cooked_write (struct regcache *regcache, int rawnum,
const gdb_byte *buf);
/* Read register REGNUM from REGCACHE and return a new value. This
will call mark_value_bytes_unavailable as appropriate. */
struct value *regcache_cooked_read_value (struct regcache *regcache,
int regnum);
/* Read a register as a signed/unsigned quantity. */
extern enum register_status
regcache_cooked_read_signed (struct regcache *regcache,
int regnum, LONGEST *val);
extern enum register_status
regcache_cooked_read_unsigned (struct regcache *regcache,
int regnum, ULONGEST *val);
extern void regcache_cooked_write_signed (struct regcache *regcache,
int regnum, LONGEST val);
extern void regcache_cooked_write_unsigned (struct regcache *regcache,
int regnum, ULONGEST val);
/* Partial transfer of a cooked register. These perform read, modify,
write style operations. */
enum register_status regcache_cooked_read_part (struct regcache *regcache,
int regnum, int offset,
int len, gdb_byte *buf);
void regcache_cooked_write_part (struct regcache *regcache, int regnum,
int offset, int len, const gdb_byte *buf);
/* Special routines to read/write the PC. */
/* For regcache_read_pc see common/common-regcache.h. */
extern void regcache_write_pc (struct regcache *regcache, CORE_ADDR pc);
/* Transfer a raw register [0..NUM_REGS) between the regcache and the
target. These functions are called by the target in response to a
target_fetch_registers() or target_store_registers(). */
extern void regcache_raw_supply (struct regcache *regcache,
int regnum, const void *buf);
extern void regcache_raw_collect (const struct regcache *regcache,
int regnum, void *buf);
/* Mapping between register numbers and offsets in a buffer, for use
in the '*regset' functions below. In an array of
'regcache_map_entry' each element is interpreted like follows:
- If 'regno' is a register number: Map register 'regno' to the
current offset (starting with 0) and increase the current offset
by 'size' (or the register's size, if 'size' is zero). Repeat
this with consecutive register numbers up to 'regno+count-1'.
- If 'regno' is REGCACHE_MAP_SKIP: Add 'count*size' to the current
offset.
- If count=0: End of the map. */
struct regcache_map_entry
{
int count;
int regno;
int size;
};
/* Special value for the 'regno' field in the struct above. */
enum
{
REGCACHE_MAP_SKIP = -1,
};
/* Transfer a set of registers (as described by REGSET) between
REGCACHE and BUF. If REGNUM == -1, transfer all registers
belonging to the regset, otherwise just the register numbered
REGNUM. The REGSET's 'regmap' field must point to an array of
'struct regcache_map_entry'.
These functions are suitable for the 'regset_supply' and
'regset_collect' fields in a regset structure. */
extern void regcache_supply_regset (const struct regset *regset,
struct regcache *regcache,
int regnum, const void *buf,
size_t size);
extern void regcache_collect_regset (const struct regset *regset,
const struct regcache *regcache,
int regnum, void *buf, size_t size);
/* The type of a register. This function is slightly more efficient
then its gdbarch vector counterpart since it returns a precomputed
value stored in a table. */
extern struct type *register_type (struct gdbarch *gdbarch, int regnum);
/* Return the size of register REGNUM. All registers should have only
one size. */
extern int register_size (struct gdbarch *gdbarch, int regnum);
/* Save/restore a register cache. The set of registers saved /
restored into the DST regcache determined by the save_reggroup /
restore_reggroup respectively. COOKED_READ returns zero iff the
register's value can't be returned. */
typedef enum register_status (regcache_cooked_read_ftype) (void *src,
int regnum,
gdb_byte *buf);
extern void regcache_save (struct regcache *dst,
regcache_cooked_read_ftype *cooked_read,
void *cooked_read_context);
/* Copy/duplicate the contents of a register cache. By default, the
operation is pass-through. Writes to DST and reads from SRC will
go through to the target. See also regcache_cpy_no_passthrough.
regcache_cpy can not have overlapping SRC and DST buffers. */
extern struct regcache *regcache_dup (struct regcache *regcache);
extern void regcache_cpy (struct regcache *dest, struct regcache *src);
extern void registers_changed (void);
extern void registers_changed_ptid (ptid_t);
#endif /* REGCACHE_H */
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