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Delegate to target_ops->beneath for TARGET_OBJECT_RAW_MEMORY

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GDB on x86_64-linux is unable to disassemble on core-file target.

$ ./gdb ./testsuite/gdb.base/corefile
(gdb) core-file ./testsuite/gdb.base/corefile.core
(gdb) disassemble main
Dump of assembler code for function main:
   0x0000000000400976 <+0>:	Cannot access memory at address 0x400976

However, it works if we turn code-cache off.

(gdb) set code-cache off
(gdb) disassemble main,+4
Dump of assembler code from 0x400976 to 0x40097a:
   0x0000000000400976 <main+0>:	push   %rbp
   0x0000000000400977 <main+1>:	mov    %rsp,%rbp
End of assembler dump.

When code-cache is off, GDB will iterate target_ops from top to bottom
and call to_xfer_partial.  When current_target is "core", it will call
to_xfer_partial of target "exec", which reads the contents for
disassemble.  However, dcache uses TARGET_OBJECT_RAW_MEMORY to read,
but target_xfer_partial doesn't delegate requests to beneath for
TARGET_OBJECT_RAW_MEMORY.

This patch factors out the iteration from top to bottom to a new
function, raw_memory_xfer_partial, and use it for
TARGET_OBJECT_RAW_MEMORY.

Regression tested on x86_64-linux.

gdb:

2013-11-29  Yao Qi  <yao@codesourcery.com>
	    Pedro Alves  <palves@redhat.com>

	* dcache.c (dcache_read_line): Use current_target.beneath
	instead of &current_target.
	* target.c (memory_xfer_partial_1): Factor code out to ...
	(raw_memory_xfer_partial): ... it.  New function.
	(target_xfer_partial): Call raw_memory_xfer_partial if OBJECT
	is TARGET_OBJECT_RAW_MEMORY.
This commit is contained in:
Yao Qi 2013-11-27 18:01:05 +08:00
parent 5425b0d80b
commit 9f7132948d
3 changed files with 49 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
gdb/ChangeLog
View File

@ -1,3 +1,13 @@
2013-11-29 Yao Qi <yao@codesourcery.com>
Pedro Alves <palves@redhat.com>
* dcache.c (dcache_read_line): Use current_target.beneath
instead of &current_target.
* target.c (memory_xfer_partial_1): Factor code out to ...
(raw_memory_xfer_partial): ... it. New function.
(target_xfer_partial): Call raw_memory_xfer_partial if OBJECT
is TARGET_OBJECT_RAW_MEMORY.
2013-11-28 Doug Evans <xdje42@gmail.com>
* breakpoint.h (gdbpy_breakpoint_object): Renamed from

4
gdb/dcache.c
View File

@ -336,8 +336,8 @@ dcache_read_line (DCACHE *dcache, struct dcache_block *db)
len -= reg_len;
continue;
}
res = target_read (&current_target, TARGET_OBJECT_RAW_MEMORY,
res = target_read (current_target.beneath, TARGET_OBJECT_RAW_MEMORY,
NULL, myaddr, memaddr, reg_len);
if (res < reg_len)
return 0;

67
gdb/target.c
View File

@ -1398,6 +1398,35 @@ memory_xfer_live_readonly_partial (struct target_ops *ops,
return 0;
}
/* Read memory from more than one valid target. A core file, for
instance, could have some of memory but delegate other bits to
the target below it. So, we must manually try all targets. */
static LONGEST
raw_memory_xfer_partial (struct target_ops *ops, void *readbuf,
const void *writebuf, ULONGEST memaddr, LONGEST len)
{
LONGEST res;
do
{
res = ops->to_xfer_partial (ops, TARGET_OBJECT_MEMORY, NULL,
readbuf, writebuf, memaddr, len);
if (res > 0)
break;
/* We want to continue past core files to executables, but not
past a running target's memory. */
if (ops->to_has_all_memory (ops))
break;
ops = ops->beneath;
}
while (ops != NULL);
return res;
}
/* Perform a partial memory transfer.
For docs see target.h, to_xfer_partial. */
@ -1571,26 +1600,8 @@ memory_xfer_partial_1 (struct target_ops *ops, enum target_object object,
to_xfer_partial is enough; if it doesn't recognize an object
it will call the to_xfer_partial of the next target down.
But for memory this won't do. Memory is the only target
object which can be read from more than one valid target.
A core file, for instance, could have some of memory but
delegate other bits to the target below it. So, we must
manually try all targets. */
do
{
res = ops->to_xfer_partial (ops, TARGET_OBJECT_MEMORY, NULL,
readbuf, writebuf, memaddr, reg_len);
if (res > 0)
break;
/* We want to continue past core files to executables, but not
past a running target's memory. */
if (ops->to_has_all_memory (ops))
break;
ops = ops->beneath;
}
while (ops != NULL);
object which can be read from more than one valid target. */
res = raw_memory_xfer_partial (ops, readbuf, writebuf, memaddr, reg_len);
/* Make sure the cache gets updated no matter what - if we are writing
to the stack. Even if this write is not tagged as such, we still need
@ -1702,18 +1713,14 @@ target_xfer_partial (struct target_ops *ops,
|| object == TARGET_OBJECT_CODE_MEMORY)
retval = memory_xfer_partial (ops, object, readbuf,
writebuf, offset, len);
else
else if (object == TARGET_OBJECT_RAW_MEMORY)
{
enum target_object raw_object = object;
/* If this is a raw memory transfer, request the normal
memory object from other layers. */
if (raw_object == TARGET_OBJECT_RAW_MEMORY)
raw_object = TARGET_OBJECT_MEMORY;
retval = ops->to_xfer_partial (ops, raw_object, annex, readbuf,
writebuf, offset, len);
/* Request the normal memory object from other layers. */
retval = raw_memory_xfer_partial (ops, readbuf, writebuf, offset, len);
}
else
retval = ops->to_xfer_partial (ops, object, annex, readbuf,
writebuf, offset, len);
if (targetdebug)
{