Messages in this thread |  | | Subject | Re: [PATCH 0/2] introduce DUMP_PREFIX_UNHASHED for hex dumps | From | Timur Tabi <> | Date | Tue, 19 Jan 2021 13:55:29 -0600 |
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On 1/19/21 1:45 PM, Kees Cook wrote: > How about this so the base address is hashed once, with the offset added > to it for each line instead of each line having a "new" hash that makes > no sense: > > diff --git a/lib/hexdump.c b/lib/hexdump.c > index 9301578f98e8..20264828752d 100644 > --- a/lib/hexdump.c > +++ b/lib/hexdump.c > @@ -242,12 +242,17 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type, > const void *buf, size_t len, bool ascii) > { > const u8 *ptr = buf; > + const u8 *addr; > int i, linelen, remaining = len; > unsigned char linebuf[32 * 3 + 2 + 32 + 1]; > > if (rowsize != 16 && rowsize != 32) > rowsize = 16; > > + if (prefix_type == DUMP_PREFIX_ADDRESS && > + ptr_to_hashval(ptr, &addr)) > + addr = 0; > + > for (i = 0; i < len; i += rowsize) { > linelen = min(remaining, rowsize); > remaining -= rowsize; > @@ -258,7 +263,7 @@ void print_hex_dump(const char *level, const char *prefix_str, int prefix_type, > switch (prefix_type) { > case DUMP_PREFIX_ADDRESS: > printk("%s%s%p: %s\n", > - level, prefix_str, ptr + i, linebuf); > + level, prefix_str, addr + i, linebuf);
Well, this is better than nothing, but not by much. Again, as long as %px exists for printk(), I just cannot understand any resistance to allowing it in print_hex_dump().
Frankly, I think this patch and my patch should both be added. During debugging, it's very difficult if not impossible to work with hashed addresses. I use print_hex_dump() with an unhashed address all the time, either by applying my patch to my own kernel or just replacing the %p with %px.
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