"ps -e" without procfs(5)

[Kostik Belousov]

On Sat, Nov 05, 2011 at 10:37:46PM +0200, Mikolaj Golub wrote:
> 
> On Sat, 5 Nov 2011 21:45:53 +0200 Kostik Belousov wrote:
> 
>  KB> On Sat, Nov 05, 2011 at 08:59:21PM +0200, Mikolaj Golub wrote:
>  >> 
>  >> 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);
>  KB> No, the natural alignment of the structure is the alignment of the most
>  KB> demanding member. So it is 4 bytes on 32bit, and 8 bytes on 64.
> 
>  >> 
>  >> 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);
>  KB> I suggest to use #if __ELF_WORD_SIZE == 32 or 64.
> 
> Thanks. The updated patch:
> 
> http://people.freebsd.org/~trociny/env.sys.3.patch

Oops, I missed this in the previous review. You cannot use fubyte in
proc_read_mem(). fubyte reads a byte from the address space of the current
process. The fix is easy, use proc_rwmem for 1 byte.

I do not think that fall back to single byte read is warranted for
proc_read_mem calls e.g. for ps_strings. Add a flag to indicate whether
the proc_read_mem should fall back to byte read ?

I would prefer using sizeof(uint64_t) and sizeof(uint32_t) instead of 8
and 4 constants in the align checks.

Might be, add PROC_ASSERT_HELD() to get_ps_string() ?

procfs patch looks good.
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