Messages in this thread | | | Date | Tue, 29 Nov 2016 01:27:11 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCH 2/4] x86/dumpstack: remove kernel text addresses from stack dump |
| |
On Mon, Nov 28, 2016 at 02:49:58PM -0600, Josh Poimboeuf wrote: > On Fri, Nov 25, 2016 at 03:26:04PM +0300, Kirill A. Shutemov wrote: > > On Tue, Oct 25, 2016 at 09:51:12AM -0500, Josh Poimboeuf wrote: > > > Printing kernel text addresses in stack dumps is of questionable value, > > > especially now that address randomization is becoming common. > > > > > > It can be a security issue because it leaks kernel addresses. It also > > > affects the usefulness of the stack dump. Linus says: > > > > > > "I actually spend time cleaning up commit messages in logs, because > > > useless data that isn't actually information (random hex numbers) is > > > actively detrimental. > > > > > > It makes commit logs less legible. > > > > > > It also makes it harder to parse dumps. > > > > > > It's not useful. That makes it actively bad. > > > > > > I probably look at more oops reports than most people. I have not > > > found the hex numbers useful for the last five years, because they are > > > just randomized crap. > > > > > > The stack content thing just makes code scroll off the screen etc, for > > > example." > > > > > > The only real downside to removing these addresses is that they can be > > > used to disambiguate duplicate symbol names. However such cases are > > > rare, and the context of the stack dump should be enough to be able to > > > figure it out. > > > > > > There's now a 'faddr2line' script which can be used to convert a > > > function address to a file name and line: > > > > > > $ ./scripts/faddr2line ~/k/vmlinux write_sysrq_trigger+0x51/0x60 > > > write_sysrq_trigger+0x51/0x60: > > > write_sysrq_trigger at drivers/tty/sysrq.c:1098 > > > > > > Or gdb can be used: > > > > > > $ echo "list *write_sysrq_trigger+0x51" |gdb ~/k/vmlinux |grep "is in" > > > (gdb) 0xffffffff815b5d83 is in driver_probe_device (/home/jpoimboe/git/linux/drivers/base/dd.c:378). > > > > > > (But note that when there are duplicate symbol names, gdb will only show > > > the first symbol it finds. faddr2line is recommended over gdb because > > > it handles duplicates and it also does function size checking.) > > > > The commit breaks scripts/decode_stacktrace.sh. > > > > Not sure if it's possible to fix it only on decode_stacktrace.sh side: we > > seems don't have a way to clearly distinguish stack trace line of any > > other. > > How about this bash regex? Seems to work for me with no false > positives. > > [[ $line =~ [^+\ ]+\+0x[0-9a-f]+/0x[0-9a-f]+ ]]
Seems works fine to me. Thanks.
Feel free to use my tested-by.
-- Kirill A. Shutemov
| |