svn commit: r273266 - in head: lib/libkvm sys/compat/freebsd32 sys/kern sys/sys

[Dimitry Andric]

It is indeed used to calculate an address offset, but as it is already
checked against NOCPU, it should be good:

gnu/usr.bin/gdb/kgdb/kthr.c:                    kt->cpu = td.td_oncpu;
gnu/usr.bin/gdb/kgdb/trgt_i386.c:       if (kt == NULL || kt->cpu == NOCPU)
gnu/usr.bin/gdb/kgdb/trgt_i386.c:       addr += (kt->cpu * NGDT + GPROC0_SEL) * sizeof(sd);

Maybe the test could be strengthened to check that kt->cpu >= 0, but it
might be overkill.

-Dimitry

> On 11 Nov 2014, at 00:17, Adrian Chadd <adrian at FreeBSD.org> wrote:
> 
> just double-check that the cpu id isn't used to size anything; I've
> seen it used as an offset into stuff, and NOCPU would've been entry
> 255 in the array, not -1.
> 
> Ian pointed this out to me recently and I've only just started digging into it.
> 
> 
> 
> -adrian
> 
> 
> On 10 November 2014 12:35, John Baldwin <jhb at freebsd.org> wrote:
>> On Monday, November 10, 2014 09:13:08 PM Dimitry Andric wrote:
>>> I noted something similar for kgdb, when compiled with gcc:
>>> 
>>> cc1: warnings being treated as errors
>>> /usr/src/gnu/usr.bin/gdb/kgdb/trgt_i386.c: In function
>>> 'kgdb_trgt_fetch_tss': /usr/src/gnu/usr.bin/gdb/kgdb/trgt_i386.c:142:
>>> warning: comparison is always false due to limited range of data type
>>> 
>>> In gnu/usr.bin/gdb/kgdb/kgdb.h, there is:
>>> 
>>> struct kthr {
>>>        struct kthr     *next;
>>>        uintptr_t       paddr;
>>>        uintptr_t       kaddr;
>>>        uintptr_t       kstack;
>>>        uintptr_t       pcb;
>>>        int             tid;
>>>        int             pid;
>>>        u_char          cpu;
>>> };
>>> 
>>> The cpu field is assigned from td.td_oncpu (which is an int) in
>>> kgdb_thr_add_procs(), so I think it should be safe to change it to an
>>> int too:
>>> 
>>> Index: gnu/usr.bin/gdb/kgdb/kgdb.h
>>> ===================================================================
>>> --- gnu/usr.bin/gdb/kgdb/kgdb.h (revision 274350)
>>> +++ gnu/usr.bin/gdb/kgdb/kgdb.h (working copy)
>>> @@ -41,7 +41,7 @@
>>>        uintptr_t       pcb;
>>>        int             tid;
>>>        int             pid;
>>> -       u_char          cpu;
>>> +       int             cpu;
>>> };
>>> 
>>> extern struct kthr *curkthr;
>> 
>> Yes, please commit.
>> 
>> --
>> John Baldwin

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