20aa2c606e
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.
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| include | ||
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| ld | ||
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| sim | ||
| texinfo | ||
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| COPYING | ||
| COPYING.LIB | ||
| COPYING.LIBGLOSS | ||
| COPYING.NEWLIB | ||
| COPYING3 | ||
| COPYING3.LIB | ||
| ChangeLog | ||
| MAINTAINERS | ||
| Makefile.def | ||
| Makefile.in | ||
| Makefile.tpl | ||
| README | ||
| README-maintainer-mode | ||
| compile | ||
| config-ml.in | ||
| config.guess | ||
| config.rpath | ||
| config.sub | ||
| configure | ||
| configure.ac | ||
| depcomp | ||
| djunpack.bat | ||
| install-sh | ||
| libtool.m4 | ||
| ltgcc.m4 | ||
| ltmain.sh | ||
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| missing | ||
| mkdep | ||
| mkinstalldirs | ||
| move-if-change | ||
| setup.com | ||
| src-release.sh | ||
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