The corner case addressed by this patch can be triggered, e.g., with
this command (`sparse' can be substituted with `test-linearize' in
which case `-ventry' is not required):
$ ./sparse -vv -ventry compat/mmap-blob.c
compat/mmap-blob.c:20:21: error: undefined identifier 'CHUNK'
compat/mmap-blob.c:21:17: error: undefined identifier 'die'
compat/mmap-blob.c:22:20: error: undefined identifier 'NULL'
compat/mmap-blob.c:24:23: error: undefined identifier 'NULL'
compat/mmap-blob.c:30:31: error: undefined identifier 'CHUNK'
compat/mmap-blob.c:31:17: error: undefined identifier 'die'
blob_alloc:
ep 0xb74f700c: blob_alloc
.L0xb74ef00c:
compat/mmap-blob.c:16
<entry-point>
# snop.32 VOID -> 0[size]
# lnop.32 %r1 <- 0[size]
Segmentation fault
The problem here is that no semantical meaning is found for `CHUNK'
identifier (sparse emits an error for this properly) so the respective
symbol is stored as a "missing" (NULL) reference in the resulting
semantical tree, connected with OP_SYMADDR instruction.
With described example, we would normally never have encountered this
as the problematic instruction is inactive -- unless we use
"be double-verbose" (-vv) switch. This makes sparse library output
also such inactive instructions, and when it comes to our OP_SYMADDR,
it does segfault due to NULL pointer dereference.
The underscore convention mimics the usage of other angle-bracketed
labels (namely "<bad_string>" in tokenize.c).
Signed-off-by: Jan Pokorny <pokorny_jan@xxxxxxxxx>
---
linearize.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/linearize.c b/linearize.c
index f2034ce..e29ebe8 100644
--- a/linearize.c
+++ b/linearize.c
@@ -313,6 +313,10 @@ const char *show_instruction(struct instruction *insn)
struct symbol *sym = insn->symbol->sym;
buf += sprintf(buf, "%s <- ", show_pseudo(insn->target));
+ if (!sym) {
+ buf += sprintf(buf, "<missing_symbol>");
+ break;
+ }
if (sym->bb_target) {
buf += sprintf(buf, ".L%p", sym->bb_target);
break;
--
1.7.1
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