On 2013-07-26 Petr Salinger <petr.salin...@seznam.cz> wrote:
> Hi.
> it does work. Try i.e.
> ~$ LD_SHOW_AUXV=1 /bin/true
[...]
> The AT_* constant are standardized only partially,
> FreeBSD kernel knows these:
> /* Values for a_type. */
> #define AT_NULL 0 /* Terminates the vector. */
> #define AT_IGNORE 1 /* Ignored entry. */
> #define AT_EXECFD 2 /* File descriptor of program to load. */
> #define AT_PHDR 3 /* Program header of program already loaded.
> */
> #define AT_PHENT 4 /* Size of each program header entry. */
> #define AT_PHNUM 5 /* Number of program header entries. */
> #define AT_PAGESZ 6 /* Page size in bytes. */
> #define AT_BASE 7 /* Interpreter's base address. */
> #define AT_FLAGS 8 /* Flags (unused for i386). */
> #define AT_ENTRY 9 /* Where interpreter should transfer control.
> */
> #define AT_NOTELF 10 /* Program is not ELF ?? */
> #define AT_UID 11 /* Real uid. */
> #define AT_EUID 12 /* Effective uid. */
> #define AT_GID 13 /* Real gid. */
> #define AT_EGID 14 /* Effective gid. */
> #define AT_EXECPATH 15 /* Path to the executable. */
> #define AT_CANARY 16 /* Canary for SSP. */
> #define AT_CANARYLEN 17 /* Length of the canary. */
> #define AT_OSRELDATE 18 /* OSRELDATE. */
> #define AT_NCPUS 19 /* Number of CPUs. */
> #define AT_PAGESIZES 20 /* Pagesizes. */
> #define AT_PAGESIZESLEN 21 /* Number of pagesizes. */
> #define AT_TIMEKEEP 22 /* Pointer to timehands. */
> #define AT_STACKPROT 23 /* Initial stack protection. */
> #define AT_COUNT 24 /* Count of defined aux entry types. */
[...]
Hello Petr,
I hope I understanding you correctly, please tell if I do not. ;-)
> The number 23 is AT_STACKPROT, and value 7 is correct one.
> The {e,}{u,g}id values are not passed from kernel (see above)
> and therefore "On success, getauxval() returns the value
> corresponding to type. If type is not found, 0 is returned."
That means: AT_UID/et.al. are defined in the header, the kernel knows
about them, but they are not usable though getauxval().
> Unfortunately, glibc so far does not allow
> to override AT_* constant lists by a sysdeps bits.
That is where the actual bug is, i.e. the headers are at odds with
the kernel?
(sid_kfreebsd-i386-dchroot)ametzler@fischer:~$ printf '#include
<sys/auxv.h>\nat_secure is AT_SECURE\nat_stackprot is AT_STACKPROT\n' | gcc -E
- | tail -n2
at_secure is 23
at_stackprot is AT_STACKPROT
> What is your use case for getauxval() ?
p11-kit 0.18.5 uses getauxval (AT_SECURE) to detect SUID or SGID
execution.
<http://cgit.freedesktop.org/p11-glue/p11-kit/commit/?h=stable&id=d9808323cb288540c93f0a74b825714cab3c96eb>
It checks at configure time for the function with
AC_CHECK_FUNCS([getauxval], but not whether AT_SECURE works. If
getauxval is missing a replacement will be used. The fact that
getauxval(AT_SECURE) does not throw a compiler error on freebsd (as
in: error: 'AT_SECURE' undeclared) makes writing a configure test
unnecessarily complicated.
cu Andreas
--
`What a good friend you are to him, Dr. Maturin. His other friends are
so grateful to you.'
`I sew his ears on from time to time, sure'
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