[patch] Cut memory address width
Jan Kratochvil
jan.kratochvil@redhat.com
Thu Sep 28 17:27:00 GMT 2006
Hi,
On Wed, 27 Sep 2006 21:01:11 +0200, Mark Kettenis wrote:
...
> This should almost certainly be handled in value.c:value_as_address().
> You could add an i386-specific integer_to_address(), that would
> truncate the address to 32 bits. But in fact, I can't think of a
> reason why truncating to the size of a pointer shouldn't be the
> default behaviour.
Made the default way, I also do not see the reason to keep larger addresses.
There is some note about `ADDR_BITS_REMOVE' but I believe it is only about the
lowest (0-2 or so) bits and the high bits should not hurt anyone.
On Wed, 27 Sep 2006 21:24:27 +0200, Jim Blandy wrote:
...
> Just as a sanity check: what does 'show architecture' say when you're
> debugging an i386 inferior on gdb/amd64?
as expected:
The target architecture is set automatically (currently i386)
...
> Is there some code there assuming that host == target?
I do not believe so, it is handled everything by `LONGEST' / `unpack_long'.
Regards,
Jan
-------------- next part --------------
2006-09-28 Jan Kratochvil <jan.kratochvil@redhat.com>
* gdb/utils.c (paddress): Disable cutting of the printed addresses
to the target's address bit size; user wants to see everything.
* gdb/value.c (value_as_address_core): Original `value_as_address'.
(value_as_address): New `value_as_address' wrapper - cut memory address
to the target's address bit size, bugreport by John Reiser.
Index: gdb/utils.c
===================================================================
RCS file: /cvs/src/src/gdb/utils.c,v
retrieving revision 1.169
diff -u -p -r1.169 utils.c
--- gdb/utils.c 21 Sep 2006 13:50:51 -0000 1.169
+++ gdb/utils.c 28 Sep 2006 17:06:03 -0000
@@ -2596,6 +2596,14 @@ paddr_nz (CORE_ADDR addr)
const char *
paddress (CORE_ADDR addr)
{
+ /* Do no cut the address as the user should see all the information
+ available. Otherwise 64-bit gdb debugging 32-bit inferior would
+ report for `x/x 0xffffffffffffce70' error
+ `Cannot access memory at 0xffffce70' while the error occured just
+ because of the higher order bits 0xffffffff00000000 there.
+ This specific error no longer occurs as the address is now cut
+ during execution by `value_as_address'. */
+#if 0
/* Truncate address to the size of a target address, avoiding shifts
larger or equal than the width of a CORE_ADDR. The local
variable ADDR_BIT stops the compiler reporting a shift overflow
@@ -2609,6 +2617,8 @@ paddress (CORE_ADDR addr)
if (addr_bit < (sizeof (CORE_ADDR) * HOST_CHAR_BIT))
addr &= ((CORE_ADDR) 1 << addr_bit) - 1;
+#endif
+
return hex_string (addr);
}
Index: gdb/value.c
===================================================================
RCS file: /cvs/src/src/gdb/value.c,v
retrieving revision 1.36
diff -u -p -r1.36 value.c
--- gdb/value.c 31 Mar 2006 10:36:18 -0000 1.36
+++ gdb/value.c 28 Sep 2006 17:06:03 -0000
@@ -950,11 +950,10 @@ value_as_double (struct value *val)
error (_("Invalid floating value found in program."));
return foo;
}
-/* Extract a value as a C pointer. Does not deallocate the value.
- Note that val's type may not actually be a pointer; value_as_long
- handles all the cases. */
-CORE_ADDR
-value_as_address (struct value *val)
+
+/* See `value_as_address' below - core of value to C pointer extraction. */
+static CORE_ADDR
+value_as_address_core (struct value *val)
{
/* Assume a CORE_ADDR can fit in a LONGEST (for now). Not sure
whether we want this to be true eventually. */
@@ -1054,6 +1053,33 @@ value_as_address (struct value *val)
return unpack_long (value_type (val), value_contents (val));
#endif
}
+
+/* Extract a value as a C pointer. Does not deallocate the value.
+ Note that val's type may not actually be a pointer; value_as_long
+ handles all the cases. */
+CORE_ADDR
+value_as_address (struct value *val)
+{
+ CORE_ADDR addr;
+
+ addr = value_as_address_core (val);
+
+ /* Truncate address to the size of a target address, avoiding shifts
+ larger or equal than the width of a CORE_ADDR. The local
+ variable ADDR_BIT stops the compiler reporting a shift overflow
+ when it won't occur. */
+ /* NOTE: This assumes that the significant address information is
+ kept in the least significant bits of ADDR - the upper bits were
+ either zero or sign extended. Should ADDRESS_TO_POINTER() or
+ some ADDRESS_TO_PRINTABLE() be used to do the conversion? */
+
+ int addr_bit = TARGET_ADDR_BIT;
+
+ if (addr_bit < (sizeof (CORE_ADDR) * HOST_CHAR_BIT))
+ addr &= ((CORE_ADDR) 1 << addr_bit) - 1;
+
+ return addr;
+}
/* Unpack raw data (copied from debugee, target byte order) at VALADDR
as a long, or as a double, assuming the raw data is described
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