Messages in this thread | | | Date | Tue, 12 Feb 2008 14:34:51 -0500 | From | "Frank Ch. Eigler" <> | Subject | Re: [git pull] kgdb-light -v10 |
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Hi -
On Tue, Feb 12, 2008 at 10:20:10AM -0800, Andrew Morton wrote: > [...] Bear in mind that one of the things you do with kgdb is to > modify kernel memory [...]
Just for completeness, keep in mind that one can already do these sorts of things on a batch basis using systemtap:
> int foo; > ... > if (foo == 1) > special_stuff(); > ... > > to trigger a particular behaviour at a particular time. [...]
If "foo" is a global within a particular compliation unit, any old function in that CU can be probed to set/get the global. (Setting incoming function parameters works too.)
# cat delayed-set.stp # set a systemtap script variable based on a /proc control file probe procfs("activate").write { setit = $value } global setit # check the systemtap global in order to set the kernel global probe kernel.function("foo_checking_fn") { if (setit=="1") { setit = ""; $foo = 1 } } # stap -g -m ds delayed-set.stp & # echo 1 > /proc/systemtap/ds/activate
> OT: another thing you can do with kgdb is error-path testing: > foo = kmalloc(...) > BP-> if (!foo) > recover(); > put a breakpoint on the !foo test and set foo to zero by hand.
# cat setit2.stp probe kernel.statement("*@dir/function.c:222") { /*if (desired)*/ $foo = 0 } # stap -g setit2.stp &
- FChE
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