Check memory accesses

Vladimir Prus
2006-11-09T20:36:41Z

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This patch makes gdb, when target memory map is available, optionally reject
all memory accesses outside of regions in memory map. The rationale is that:

1. It's sometimes better to get error that have the write silently do
nothing or read returning garbase.

2. For some targets, accesses to non-existent memory "wedge" them.

Since memory maps are still rare, this behaviour is enabled only by a new
command.

OK?

- Volodya

* memattr.h (enum mem_access_mode): New value
MEM_NONE.
* memattr.c (unknown_mem_attrib): New.
(inaccessible_by_default): New.
(show_inaccessible_by_default): New.
(lookup_mem_region): Check inaccessible_by_default.
(dummy_cmd): New.
(mem_set_cmdlist, mem_show_cmdlist): New.
(_initialize_mem): Register new "set" and "show"
commands.
* target.c (memory_xfer_partial): If memory type
is MEM_NONE, return an error.
Clip to region size when calling to_xfer_partial.
If upper limit of memory range is 0, don't clip
anything.

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Index: memattr.c
===================================================================
RCS file: /cvs/src/src/gdb/memattr.c,v
retrieving revision 1.25
diff -u -r1.25 memattr.c
--- memattr.c 21 Sep 2006 14:00:53 -0000 1.25
+++ memattr.c 9 Nov 2006 20:28:25 -0000
@@ -29,6 +29,7 @@
#include "language.h"
#include "vec.h"
#include "gdb_string.h"
+#include "gdb_locale.h"

const struct mem_attrib default_mem_attrib =
{
@@ -40,6 +41,16 @@
-1 /* Flash blocksize not specified. */
};

+const struct mem_attrib unknown_mem_attrib =
+{
+ MEM_NONE, /* mode */
+ MEM_WIDTH_UNSPECIFIED,
+ 0, /* hwbreak */
+ 0, /* cache */
+ 0, /* verify */
+ -1 /* Flash blocksize not specified. */
+};
+
VEC(mem_region_s) *mem_region_list, *target_mem_region_list;
static int mem_number = 0;

@@ -53,6 +64,25 @@
empty, then the target can't supply memory regions. */
static int target_mem_regions_valid;

+/* If this flag is set, gdb will assume that memory ranges not
+ specified by the memory map have type MEM_NONE, and will
+ emit errors on all accesses to that memory. */
+static int inaccessible_by_default = 0;
+
+static void
+show_inaccessible_by_default (struct ui_file *file, int from_tty,
+ struct cmd_list_element *c,
+ const char *value)
+{
+ if (inaccessible_by_default)
+ fprintf_filtered (file, _("\
+Unknown memory addresses will be treated as inaccessible.\n"));
+ else
+ fprintf_filtered (file, _("\
+Unknown memory addresses will be treated as RAM.\n"));
+}
+
+
/* Predicate function which returns true if LHS should sort before RHS
in a list of memory regions, useful for VEC_lower_bound. */

@@ -215,13 +245,17 @@
lo = 0;
hi = 0;

- /* If we ever want to support a huge list of memory regions, this
+ /* Either find memory range containing ADDRESS, or set LO and HI
+ to the nearest boundaries of an existing memory range.
+
+ If we ever want to support a huge list of memory regions, this
check should be replaced with a binary search (probably using
VEC_lower_bound). */
for (ix = 0; VEC_iterate (mem_region_s, mem_region_list, ix, m); ix++)
{
if (m->enabled_p == 1)
{
+ /* If address is in memory return, return that memory range. */
if (addr >= m->lo && (addr < m->hi || m->hi == 0))
return m;

@@ -243,7 +277,15 @@
was learned above. */
region.lo = lo;
region.hi = hi;
- region.attrib = default_mem_attrib;
+
+ /* When no memory map is defined at all, we always set 'default_mem_attrib',
+ so that we do not make the all memory inaccessible for targets that don't
+ provide a memory map. */
+ if (inaccessible_by_default && !VEC_empty (mem_region_s, mem_region_list))
+ region.attrib = unknown_mem_attrib;
+ else
+ region.attrib = default_mem_attrib;
+
return &region;
}

@@ -674,9 +716,17 @@

dont_repeat ();
}
+
+static void
+dummy_cmd (char *args, int from_tty)
+{
+}
\f
extern initialize_file_ftype _initialize_mem; /* -Wmissing-prototype */

+static struct cmd_list_element *mem_set_cmdlist;
+static struct cmd_list_element *mem_show_cmdlist;
+
void
_initialize_mem (void)
{
@@ -709,4 +759,25 @@

add_info ("mem", mem_info_command,
_("Memory region attributes"));
+
+ add_prefix_cmd ("mem", class_vars, dummy_cmd, _("\
+Memory regions settings"),
+ &mem_set_cmdlist, "set mem ",
+ 0/* allow-unknown */, &setlist);
+ add_prefix_cmd ("mem", class_vars, dummy_cmd, _("\
+Memory regions settings"),
+ &mem_show_cmdlist, "show mem ",
+ 0/* allow-unknown */, &showlist);
+
+ add_setshow_boolean_cmd ("inaccessible-by-default", no_class,
+ &inaccessible_by_default, _("\
+Set handling of unknown memory regions."), _("\
+Show handling of unknown memory regions."), _("\
+If on, and some memory map is defined, debugger will emit errors on\n\
+accesses to memory not defined in the memory map. If off, accesses to all\n\
+memory addresses will be allowed."),
+ NULL,
+ show_inaccessible_by_default,
+ &mem_set_cmdlist,
+ &mem_show_cmdlist);
}
Index: memattr.h
===================================================================
RCS file: /cvs/src/src/gdb/memattr.h,v
retrieving revision 1.7
diff -u -r1.7 memattr.h
--- memattr.h 21 Sep 2006 13:54:02 -0000 1.7
+++ memattr.h 9 Nov 2006 20:28:25 -0000
@@ -26,6 +26,7 @@

enum mem_access_mode
{
+ MEM_NONE, /* Memory that is not physically present. */
MEM_RW, /* read/write */
MEM_RO, /* read only */
MEM_WO, /* write only */
@@ -76,7 +77,10 @@

struct mem_region
{
+ /* Lowest address in the region. */
CORE_ADDR lo;
+ /* Address past the highest address of the region.
+ If 0, upper bound is "infinity". */
CORE_ADDR hi;

/* Item number of this memory region. */
Index: target.c
===================================================================
RCS file: /cvs/src/src/gdb/target.c,v
retrieving revision 1.128
diff -u -r1.128 target.c
--- target.c 17 Oct 2006 21:55:23 -0000 1.128
+++ target.c 9 Nov 2006 20:28:26 -0000
@@ -1015,7 +1015,8 @@

/* Try GDB's internal data cache. */
region = lookup_mem_region (memaddr);
- if (memaddr + len < region->hi)
+ /* region->hi means there's no upper bound. */
+ if (memaddr + len < region->hi || region->hi == 0)
reg_len = len;
else
reg_len = region->hi - memaddr;
@@ -1037,6 +1038,9 @@
if (writebuf != NULL)
error (_("Writing to flash memory forbidden in this context"));
break;
+
+ case MEM_NONE:
+ return -1;
}

if (region->attrib.cache)
@@ -1072,7 +1076,7 @@
do
{
res = ops->to_xfer_partial (ops, TARGET_OBJECT_MEMORY, NULL,
- readbuf, writebuf, memaddr, len);
+ readbuf, writebuf, memaddr, reg_len);
if (res > 0)
return res;