On all of our platforms, db_expr_t is a signed integer while
db_addr_t is an unsigned integer value. db_search_symbol used variables
of type db_expr_t to hold the current offset of the requested address from
the "best" symbol found so far. This value was initialized to '~0'.
When a new symbol is found from a symbol table, the associated diff for the
new symbol is compared against the existing value as 'if (newdiff < diff)'
to determine if the new symbol had a smaller diff and was thus a closer
match.
On 64-bit MIPS, the '~0' was treated as a negative value (-1). A lookup
that found a perfect match of an address against a symbol returned a diff
of 0. However, in signed comparisons, 0 is not less than -1. As a result,
DDB on 64-bit MIPS never resolved any addresses to symbols. Workaround
this by using casts to force an unsigned comparison.
Probably the diff returned from db_search_symbol() and X_db_search_symbol()
should be changed to a db_addr_t instead of a db_expr_t as it is an
unsigned value (and is an offset of an address, so should fit in the same
size as an address).
Sponsored by: DARPA / AFRL
ecb65f66c6