[Fixes BZ #14308, #12994, #13651]
AF_UNSPEC results in sending two queries in parallel, one for the A
record and the other for the AAAA record. If one of these is a
referral, then the query fails, which is wrong. It should return at
least the one successful response.
The fix has two parts. The first part makes the referral fall back to
the SERVFAIL path, which results in using the successful response.
There is a bug in that path however, due to which the second part is
necessary. The bug here is that if the first response is a failure
and the second succeeds, __libc_res_nsearch does not detect that and
assumes a failure. The case where the first response is a success and
the second fails, works correctly.
This condition is produced by buggy routers, so here's a crude
interposable library that can simulate such a condition. The library
overrides the recvfrom syscall and modifies the header of the packet
received to reproduce this scenario. It has two key variables:
mod_packet and first_error.
The mod_packet variable when set to 0, results in odd packets being
modified to be a referral. When set to 1, even packets are modified
to be a referral.
The first_error causes the first response to be a failure so that a
domain-appended search is performed to test the second part of the
__libc_nsearch fix.
The driver for this fix is a simple getaddrinfo program that does an
AF_UNSPEC query. I have omitted this since it should be easy to
implement.
I have tested this on x86_64.
The interceptor library source:
/* Override recvfrom and modify the header of the first DNS response to make it
a referral and reproduce bz #845218. We have to resort to this ugly hack
because we cannot make bind return the buggy response of a referral for the
AAAA record and an authoritative response for the A record. */
#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdbool.h>
#include <endian.h>
#include <dlfcn.h>
#include <stdlib.h>
/* Lifted from resolv/arpa/nameser_compat.h. */
typedef struct {
unsigned id :16; /*%< query identification number */
#if BYTE_ORDER == BIG_ENDIAN
/* fields in third byte */
unsigned qr: 1; /*%< response flag */
unsigned opcode: 4; /*%< purpose of message */
unsigned aa: 1; /*%< authoritive answer */
unsigned tc: 1; /*%< truncated message */
unsigned rd: 1; /*%< recursion desired */
/* fields
* in
* fourth
* byte
* */
unsigned ra: 1; /*%< recursion available */
unsigned unused :1; /*%< unused bits (MBZ as of 4.9.3a3) */
unsigned ad: 1; /*%< authentic data from named */
unsigned cd: 1; /*%< checking disabled by resolver */
unsigned rcode :4; /*%< response code */
#endif
#if BYTE_ORDER == LITTLE_ENDIAN || BYTE_ORDER == PDP_ENDIAN
/* fields
* in
* third
* byte
* */
unsigned rd :1; /*%< recursion desired */
unsigned tc :1; /*%< truncated message */
unsigned aa :1; /*%< authoritive answer */
unsigned opcode :4; /*%< purpose of message */
unsigned qr :1; /*%< response flag */
/* fields
* in
* fourth
* byte
* */
unsigned rcode :4; /*%< response code */
unsigned cd: 1; /*%< checking disabled by resolver */
unsigned ad: 1; /*%< authentic data from named */
unsigned unused :1; /*%< unused bits (MBZ as of 4.9.3a3) */
unsigned ra :1; /*%< recursion available */
#endif
/* remaining
* bytes
* */
unsigned qdcount :16; /*%< number of question entries */
unsigned ancount :16; /*%< number of answer entries */
unsigned nscount :16; /*%< number of authority entries */
unsigned arcount :16; /*%< number of resource entries */
} HEADER;
static int done = 0;
/* Packets to modify. 0 for the odd packets and 1 for even packets. */
static const int mod_packet = 0;
/* Set to true if the first request should result in an error, resulting in a
search query. */
static bool first_error = true;
static ssize_t (*real_recvfrom) (int sockfd, void *buf, size_t len, int flags,
struct sockaddr *src_addr, socklen_t *addrlen);
void
__attribute__ ((constructor))
init (void)
{
real_recvfrom = dlsym (RTLD_NEXT, "recvfrom");
if (real_recvfrom == NULL)
{
printf ("Failed to get reference to recvfrom: %s\n", dlerror ());
printf ("Cannot simulate test\n");
abort ();
}
}
/* Modify the second packet that we receive to set the header in a manner as to
reproduce BZ #845218. */
static void
mod_buf (HEADER *h, int port)
{
if (done % 2 == mod_packet || (first_error && done == 1))
{
printf ("(Modifying header)");
if (first_error && done == 1)
h->rcode = 3;
else
h->rcode = 0; /* NOERROR == 0. */
h->ancount = 0;
h->aa = 0;
h->ra = 0;
h->arcount = 0;
}
done++;
}
ssize_t
recvfrom (int sockfd, void *buf, size_t len, int flags,
struct sockaddr *src_addr, socklen_t *addrlen)
{
ssize_t ret = real_recvfrom (sockfd, buf, len, flags, src_addr, addrlen);
int port = htons (((struct sockaddr_in *) src_addr)->sin_port);
struct in_addr addr = ((struct sockaddr_in *) src_addr)->sin_addr;
const char *host = inet_ntoa (addr);
printf ("\n*** From %s:%d: ", host, port);
mod_buf (buf, port);
printf ("returned %zd\n", ret);
return ret;
}
This patch removes the ports/README now that ports is no longer
being used. It also adds a header to all ChangeLogs for all machines
that were moved to the main libc tree. The header indicates that the
ChangeLog is no longer used.
This patch optimizes the FPSCR update on exception and rounding change
functions by just updating its value if new value if different from
current one. It also optimizes fedisableexcept and feenableexcept by
removing an unecessary FPSCR read.
__int128 was added in GCC 4.6 and __int128_t was added before x86-64
was supported. This patch replaces __int128 with __int128_t so that
the installed bits/link.h can be used with older GCC.
* sysdeps/x86/bits/link.h (La_x86_64_regs): Replace __int128
with __int128_t.
(La_x86_64_retval): Likewise.
In the glibc manual we have a "Roadmap to the manual" section at
the end of the "Introduction" chapter.
The introductory text says "Here is an overview of the contents
of the remaining chapters of this manual.", but then proceeds to
list chapters out of order and some chapter are never referenced.
This commit reorders the overview to correctly match the manual
order.
See:
https://sourceware.org/ml/libc-alpha/2014-02/msg00823.html
This patch removes the arch specific powerpc implementation and instead
uses the linux default one. Although the current powerpc implementation
already constains the required memory barriers for correct
initialization, the default implementation shows a better performance on
newer chips.
Calling setcontext from a signal handler can be done safely so
it is sufficient to note that it is not recommended.
Also mention in setcontext documentation that the behaviour of
setcontext when restoring a context created by a call to a signal
handler is unspecified.
2014-04-17 Will Newton <will.newton@linaro.org>
* manual/setjmp.texi (System V contexts): Add note that
calling setcontext on a context created by a call to a
signal handler is undefined. Update text to note that
setcontext from a signal handler is possible but not
recommended.
On aarch64 calling swapcontext clobbers the state of the signal
stack (BZ #16629). Check that the address and size of the signal
stack before and after the call to swapcontext remains the same.
ChangeLog:
2014-04-17 Will Newton <will.newton@linaro.org>
[BZ #16629]
* stdlib/tst-setcontext.c: Include signal.h.
(main): Check that the signal stack before and
after swapcontext is the same.
The current implementation of setcontext uses rt_sigreturn to restore
the contents of registers. This contrasts with the way most other
architectures implement setcontext:
powerpc64, mips, tile:
Call rt_sigreturn if context was created by a call to a signal handler,
otherwise restore in user code.
powerpc32:
Call swapcontext system call and don't call sigreturn or rt_sigreturn.
x86_64, sparc, hppa, sh, ia64, m68k, s390, arm:
Only support restoring "synchronous" contexts, that is contexts
created by getcontext, and restoring in user code and don't call
sigreturn or rt_sigreturn.
alpha:
Call sigreturn (but not rt_sigreturn) in all cases to do the restore.
The text of the setcontext manpage suggests that the requirement to be
able to restore a signal handler created context has been dropped from
SUSv2:
If the context was obtained by a call to a signal handler, then old
standard text says that "program execution continues with the program
instruction following the instruction interrupted by the signal".
However, this sentence was removed in SUSv2, and the present verdict
is "the result is unspecified".
Implementing setcontext by calling rt_sigreturn unconditionally causes
problems when used with sigaltstack as in BZ #16629. On this basis it
seems that aarch64 is broken and that new ports should only support
restoring contexts created with getcontext and do not need to call
rt_sigreturn at all.
This patch re-implements the aarch64 setcontext function to restore
the context in user code in a similar manner to x86_64 and other ports.
ChangeLog:
2014-04-17 Will Newton <will.newton@linaro.org>
[BZ #16629]
* sysdeps/unix/sysv/linux/aarch64/setcontext.S (__setcontext):
Re-implement to restore registers in user code and avoid
rt_sigreturn system call.
Besides fixing the bugzilla, this also fixes corner-cases where the high
and low double differ greatly in magnitude, and handles a denormal
input without resorting to a fp rescale.
[BZ #16740]
[BZ #16619]
* sysdeps/ieee754/ldbl-128ibm/s_frexpl.c (__frexpl): Rewrite.
* math/libm-test.inc (frexp_test_data): Add tests.
Using -lm and -lpthread results in the shared objects in the system
being used to link against. This happened to work for libm because
there haven't been any changes to the libm ABI recently that could
break the existing benchmarks. This doesn't always work for the
pthread benchmarks. The correct way to build against libraries in the
build directory is to have the binaries explicitly depend on them so
that $(+link) can pick them up.
We initialize _r_debug for static binaries to allows debug
agents to treat static binaries a little more like dyanmic
ones. This simplifies the work a debug agent has to do to
access TLS in a static binary via libthread_db.
Tested on x86_64.
See:
https://sourceware.org/ml/libc-alpha/2014-04/msg00183.html
[BZ #16831]
* csu/libc-start.c (LIBC_START_MAIN) [!SHARED]: Call
_dl_debug_initialize.
The SELinux team has indicated to me that glibc's SELinux checks
in nscd are not being carried out as they would expect the API
to be used today. They would like to move away from static header
defines for class and permissions and instead use dynamic checks
at runtime that provide an answer which is dependent on the runtime
status of SELinux i.e. more dynamic.
The following patch is a minimal change that moves us forward in
this direction.
It does the following:
* Stop checking for SELinux headers that define NSCD__SHMEMHOST.
Check only for the presence or absence of the library.
* Don't encode the specific SELinux permission constants into a
table at build time, and instead use the symbolic name for the
permission as expected.
* Lookup the "What do we do if we don't know this permission?"
policy and use that if we find SELinux's policy is older than
the glibc policy e.g. we make a request for a permission that
SELinux doesn't know about.
* Lastly, translate the class and permission and then make
the permission check. This is done every time we lookup
a permission, and this is the expected way to use the API.
SELinux will optimize this for us, and we expect the network
latencies to hide these extra library calls.
Tested on x86, x86-64, and via Fedora Rawhide since November 2013.
See:
https://sourceware.org/ml/libc-alpha/2014-04/msg00179.html
Siddhesh Poyarekar
Carlos O'Donell
Steve Ellcey
Stefan Liebler
Adhemerval Zanella
Carlos O'Donell
Ondřej Bílka
Wilco Dijkstra
H.J. Lu
Ian Bolton
David S. Miller
Yufeng Zhang
Venkataramanan Kumar
Sihai Yao
Will Newton
Wilco
Richard Henderson
Marcus Shawcroft
Igor Zamyatin
Samuel Thibault
Alan Modra