Re: [Crash-utility] [PATCH RFC 02/14] memory: do not compare unsigned expression with negative value
----- Original Message -----
Signed-off-by: Oleksandr Natalenko <oleksandr(a)redhat.com>
---
memory.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/memory.c b/memory.c
index 9926199..abf3982 100644
--- a/memory.c
+++ b/memory.c
@@ -14467,7 +14467,7 @@ display_with_pre_and_post(void *bufptr, ulonglong
addr, struct searchinfo *si)
}
amount = ctx * t;
- addr_d = addr - amount < 0 ? 0 : addr - amount;
+ addr_d = (long)addr - amount < 0 ? 0 : addr - amount;
display_memory(addr_d, ctx, flag, memtype, NULL);
--
I didn't write this code, but I do take the responsibility for accepting the patch.
The code above is used by the "search" command, where if it finds an instance of
the
specified searched-for value, it will not only display the memory location where it
exists,
but also the context around it. The context is a "-x <count>" argument
value passed to
the "search" command, which is multiplied by the word size specified. I'm
not sure
what the originator of this code meant by the "addr - amount < 0"
qualification,
because any kernel virtual address (other than s390x) would be perceived as a negative
number when preceded by "(long)". So if your patch is applied, it would always
be < 0,
set addr_d to 0, which gets ignored by display_memory(), and therefore it would never
show the context preceding the found entity as intended.
So again, you have found a coding irregularity, but your patch breaks what works just
fine.
Probably it should just set addr_d = addr - amount, but that's what the code
effectively
does now (by mistake), so I'm just going to leave this alone.
Dave