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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