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db_search_symbol: prevent pollution from bogus symbols

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The kernel will never map the first page, so any symbols in that
range cannot refer to addresses.  Some third-party assembly files
define internal constants which appear in their symbol table.
Avoiding the lookup for those symbols avoids replacing small offsets
with those symbols during disassembly.

Reported by:	Anton Rang <rang%acm.org>
Reviewed by:	Anton Rang <rang%acm.org>, markj
MFC after:	2 weeks
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D26895
This commit is contained in:
Eric van Gyzen 2020-10-26 16:42:53 +00:00
parent c90590dd92
commit 8310609fdd
1 changed files with 14 additions and 1 deletions
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15
sys/ddb/db_sym.c
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@ -371,8 +371,21 @@ db_search_symbol(db_addr_t val, db_strategy_t strategy, db_expr_t *offp)
unsigned int diff;
size_t newdiff;
int i;
c_db_sym_t ret = C_DB_SYM_NULL, sym;
c_db_sym_t ret, sym;
/*
* The kernel will never map the first page, so any symbols in that
* range cannot refer to addresses. Some third-party assembly files
* define internal constants which appear in their symbol table.
* Avoiding the lookup for those symbols avoids replacing small offsets
* with those symbols during disassembly.
*/
if (val < PAGE_SIZE) {
*offp = 0;
return (C_DB_SYM_NULL);
}
ret = C_DB_SYM_NULL;
newdiff = diff = val;
for (i = 0; i < db_nsymtab; i++) {
sym = X_db_search_symbol(&db_symtabs[i], val, strategy, &newdiff);