Date: Sat, 05 Nov 2011 20:59:21 +0200 From: Mikolaj Golub <trociny@freebsd.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-hackers@freebsd.org, Robert Watson <rwatson@freebsd.org> Subject: Re: "ps -e" without procfs(5) Message-ID: <86ehxmjsza.fsf@kopusha.home.net> In-Reply-To: <20111105154443.GB50300@deviant.kiev.zoral.com.ua> (Kostik Belousov's message of "Sat, 5 Nov 2011 17:44:43 %2B0200") References: <86y5wkeuw9.fsf@kopusha.home.net> <20111016171005.GB50300@deviant.kiev.zoral.com.ua> <86aa8qozyx.fsf@kopusha.home.net> <20111025082451.GO50300@deviant.kiev.zoral.com.ua> <86aa8k2im0.fsf@kopusha.home.net> <20111031094948.GB50300@deviant.kiev.zoral.com.ua> <86vcr21agm.fsf@kopusha.home.net> <20111105135801.GT50300@deviant.kiev.zoral.com.ua> <86ehxmpogp.fsf@kopusha.home.net> <20111105154443.GB50300@deviant.kiev.zoral.com.ua>
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On Sat, 5 Nov 2011 17:44:43 +0200 Kostik Belousov wrote:
>> KB> I think that the aux vector must be naturally aligned. You can return
>> KB> ENOEXEC early if vptr is not aligned.
>>
>> Not sure I see what you mean. vptr for auxv is calculated just couple lines
>> above, and I check the result here, in the part common for all vector types.
KB> You do not check for the alignment. Am I wrong ?
I see now. If natural alignment means "addr % sizeof(aux) == 0" then the aux
vectors are not naturally aligned. After adding this check:
if (vptr % sizeof(aux) != 0)
return (ENOEXEC);
I started to observe many ENOEXEC errors. Adding printf showed that the
vectors are half size aligned.
On i386:
get_proc_vector(pid = getty[3442], type = 2): vptr (2143284876) % sizeof(aux) (8) = 4)
On amd64:
get_proc_vector(pid = getty[2425], type = 2): vptr (140737488346568) % sizeof(aux) (16) = 8)
Looking at exec_copyout_strings() from kern_exec.c, how destp is calculated, I
think they are sizeof(char *) aligned.
Do you think it is worth adding the check for sizeof(char *) alignment?
if (vptr % (sizeof(char *) != 0)
return (ENOEXEC);
--
Mikolaj Golub
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