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authorZack Weinberg <zackw@panix.com>2018-04-03 18:26:44 -0400
committerZack Weinberg <zackw@panix.com>2018-06-12 09:53:04 -0400
commit329ea513b451ae8322aa7a24ed84da13992af2dd (patch)
tree64568fae803a1dbe3ccdf6897a708ff7fd8b4949 /elf
parent0221ce2a90be2d40fc90f0b5dcec77a1ec013f53 (diff)
downloadglibc-329ea513b451ae8322aa7a24ed84da13992af2dd.tar.gz
Avoid cancellable I/O primitives in ld.so.
Neither the <dlfcn.h> entry points, nor lazy symbol resolution, nor initial shared library load-up, are cancellation points, so ld.so should exclusively use I/O primitives that are not cancellable. We currently achieve this by having the cancellation hooks compile as no-ops when IS_IN(rtld); this patch changes to using exclusively _nocancel primitives in the source code instead, which makes the intent clearer and significantly reduces the amount of code compiled under IS_IN(rtld) as well as IS_IN(libc) -- in particular, elf/Makefile no longer thinks we require a copy of unwind.c in rtld-libc.a. (The older mechanism is preserved as a backstop.) The bulk of the change is splitting up the files that define the _nocancel I/O functions, so they don't also define the variants that *are* cancellation points; after which, the existing logic for picking out the bits of libc that need to be recompiled as part of ld.so Just Works. I did this for all of the _nocancel functions, not just the ones used by ld.so, for consistency. fcntl was a little tricky because it's only a cancellation point for certain opcodes (F_SETLKW(64), which can block), and the existing __fcntl_nocancel wasn't applying the FCNTL_ADJUST_CMD hook, which strikes me as asking for trouble, especially as the only nontrivial definition of FCNTL_ADJUST_CMD (for powerpc64) changes F_*LK* opcodes. To fix this, fcntl_common moves to fcntl_nocancel.c along with __fcntl_nocancel, and changes its name to the extern (but hidden) symbol __fcntl_nocancel_adjusted, so that regular fcntl can continue calling it. __fcntl_nocancel now applies FCNTL_ADJUST_CMD; so that both both fcntl.c and fcntl_nocancel.c can see it, the only nontrivial definition moves from sysdeps/u/s/l/powerpc/powerpc64/fcntl.c to .../powerpc64/sysdep.h and becomes entirely a macro, instead of a macro that calls an inline function. The nptl version of libpthread also changes a little, because its "compat-routines" formerly included files that defined all the _nocancel functions it uses; instead of continuing to duplicate them, I exported the relevant ones from libc.so as GLIBC_PRIVATE. Since the Linux fcntl.c calls a function defined by fcntl_nocancel.c, it can no longer be used from libpthread.so; instead, introduce a custom forwarder, pt-fcntl.c, and export __libc_fcntl from libc.so as GLIBC_PRIVATE. The nios2-linux ABI doesn't include a copy of vfork() in libpthread, and it was handling that by manipulating libpthread-routines in .../linux/nios2/Makefile; it is cleaner to do what other such ports do, and have a pt-vfork.S that defines no symbols. Right now, it appears that Hurd does not implement _nocancel I/O, so sysdeps/generic/not-cancel.h will forward everything back to the regular functions. This changed the names of some of the functions that sysdeps/mach/hurd/dl-sysdep.c needs to interpose. * elf/dl-load.c, elf/dl-misc.c, elf/dl-profile.c, elf/rtld.c * sysdeps/unix/sysv/linux/dl-sysdep.c Include not-cancel.h. Use __close_nocancel instead of __close, __open64_nocancel instead of __open, __read_nocancel instead of __libc_read, and __write_nocancel instead of __libc_write. * csu/check_fds.c (check_one_fd) * sysdeps/posix/fdopendir.c (__fdopendir) * sysdeps/posix/opendir.c (__alloc_dir): Use __fcntl_nocancel instead of __fcntl and/or __libc_fcntl. * sysdeps/unix/sysv/linux/pthread_setname.c (pthread_setname_np) * sysdeps/unix/sysv/linux/pthread_getname.c (pthread_getname_np) * sysdeps/unix/sysv/linux/i386/smp.h (is_smp_system): Use __open64_nocancel instead of __open_nocancel. * sysdeps/unix/sysv/linux/not-cancel.h: Move all of the hidden_proto declarations to the end and issue them if either IS_IN(libc) or IS_IN(rtld). * sysdeps/unix/sysv/linux/Makefile [subdir=io] (sysdep_routines): Add close_nocancel, fcntl_nocancel, nanosleep_nocancel, open_nocancel, open64_nocancel, openat_nocancel, pause_nocancel, read_nocancel, waitpid_nocancel, write_nocancel. * io/Versions [GLIBC_PRIVATE]: Add __libc_fcntl, __fcntl_nocancel, __open64_nocancel, __write_nocancel. * posix/Versions: Add __nanosleep_nocancel, __pause_nocancel. * nptl/pt-fcntl.c: New file. * nptl/Makefile (pthread-compat-wrappers): Remove fcntl. (libpthread-routines): Add pt-fcntl. * include/fcntl.h (__fcntl_nocancel_adjusted): New function. (__libc_fcntl): Remove attribute_hidden. * sysdeps/unix/sysv/linux/fcntl.c (__libc_fcntl): Call __fcntl_nocancel_adjusted, not fcntl_common. (__fcntl_nocancel): Move to new file fcntl_nocancel.c. (fcntl_common): Rename to __fcntl_nocancel_adjusted; also move to fcntl_nocancel.c. * sysdeps/unix/sysv/linux/fcntl_nocancel.c: New file. * sysdeps/unix/sysv/linux/powerpc/powerpc64/fcntl.c: Remove file. * sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h: Define FCNTL_ADJUST_CMD here, as a self-contained macro. * sysdeps/unix/sysv/linux/close.c: Move __close_nocancel to... * sysdeps/unix/sysv/linux/close_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/nanosleep.c: Move __nanosleep_nocancel to... * sysdeps/unix/sysv/linux/nanosleep_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/open.c: Move __open_nocancel to... * sysdeps/unix/sysv/linux/open_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/open64.c: Move __open64_nocancel to... * sysdeps/unix/sysv/linux/open64_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/openat.c: Move __openat_nocancel to... * sysdeps/unix/sysv/linux/openat_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/openat64.c: Move __openat64_nocancel to... * sysdeps/unix/sysv/linux/openat64_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/pause.c: Move __pause_nocancel to... * sysdeps/unix/sysv/linux/pause_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/read.c: Move __read_nocancel to... * sysdeps/unix/sysv/linux/read_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/waitpid.c: Move __waitpid_nocancel to... * sysdeps/unix/sysv/linux/waitpid_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/write.c: Move __write_nocancel to... * sysdeps/unix/sysv/linux/write_nocancel.c: ...this new file. * sysdeps/unix/sysv/linux/nios2/Makefile: Don't override libpthread-routines. * sysdeps/unix/sysv/linux/nios2/pt-vfork.S: New file which defines nothing. * sysdeps/mach/hurd/dl-sysdep.c: Define __read instead of __libc_read, and __write instead of __libc_write. Define __open64 in addition to __open.
Diffstat (limited to 'elf')
-rw-r--r--elf/dl-load.c35
-rw-r--r--elf/dl-misc.c6
-rw-r--r--elf/dl-profile.c14
-rw-r--r--elf/rtld.c3
4 files changed, 30 insertions, 28 deletions
diff --git a/elf/dl-load.c b/elf/dl-load.c
index 431236920f..c52d011efd 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -44,7 +44,7 @@
#include <dl-unmap-segments.h>
#include <dl-machine-reject-phdr.h>
#include <dl-sysdep-open.h>
-
+#include <not-cancel.h>
#include <endian.h>
#if BYTE_ORDER == BIG_ENDIAN
@@ -776,7 +776,7 @@ lose (int code, int fd, const char *name, char *realname, struct link_map *l,
{
/* The file might already be closed. */
if (fd != -1)
- (void) __close (fd);
+ (void) __close_nocancel (fd);
if (l != NULL && l->l_origin != (char *) -1l)
free ((char *) l->l_origin);
free (l);
@@ -835,7 +835,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
{
/* The object is already loaded.
Just bump its reference count and return it. */
- __close (fd);
+ __close_nocancel (fd);
/* If the name is not in the list of names for this object add
it. */
@@ -863,7 +863,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
/* No need to bump the refcount of the real object, ld.so will
never be unloaded. */
- __close (fd);
+ __close_nocancel (fd);
/* Add the map for the mirrored object to the object list. */
_dl_add_to_namespace_list (l, nsid);
@@ -877,7 +877,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
/* We are not supposed to load the object unless it is already
loaded. So return now. */
free (realname);
- __close (fd);
+ __close_nocancel (fd);
return NULL;
}
@@ -896,7 +896,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
if (_dl_zerofd == -1)
{
free (realname);
- __close (fd);
+ __close_nocancel (fd);
_dl_signal_error (errno, NULL, NULL,
N_("cannot open zero fill device"));
}
@@ -962,7 +962,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
{
phdr = alloca (maplength);
__lseek (fd, header->e_phoff, SEEK_SET);
- if ((size_t) __libc_read (fd, (void *) phdr, maplength) != maplength)
+ if ((size_t) __read_nocancel (fd, (void *) phdr, maplength) != maplength)
{
errstring = N_("cannot read file data");
goto call_lose_errno;
@@ -1232,7 +1232,7 @@ cannot enable executable stack as shared object requires");
l->l_tls_initimage = (char *) l->l_tls_initimage + l->l_addr;
/* We are done mapping in the file. We no longer need the descriptor. */
- if (__glibc_unlikely (__close (fd) != 0))
+ if (__glibc_unlikely (__close_nocancel (fd) != 0))
{
errstring = N_("cannot close file descriptor");
goto call_lose_errno;
@@ -1447,7 +1447,7 @@ open_verify (const char *name, int fd,
{
/* An audit library changed what we're supposed to open,
so FD no longer matches it. */
- __close (fd);
+ __close_nocancel (fd);
fd = -1;
}
}
@@ -1455,7 +1455,7 @@ open_verify (const char *name, int fd,
if (fd == -1)
/* Open the file. We always open files read-only. */
- fd = __open (name, O_RDONLY | O_CLOEXEC);
+ fd = __open64_nocancel (name, O_RDONLY | O_CLOEXEC);
if (fd != -1)
{
@@ -1474,8 +1474,8 @@ open_verify (const char *name, int fd,
/* Read in the header. */
do
{
- ssize_t retlen = __libc_read (fd, fbp->buf + fbp->len,
- sizeof (fbp->buf) - fbp->len);
+ ssize_t retlen = __read_nocancel (fd, fbp->buf + fbp->len,
+ sizeof (fbp->buf) - fbp->len);
if (retlen <= 0)
break;
fbp->len += retlen;
@@ -1598,7 +1598,8 @@ open_verify (const char *name, int fd,
{
phdr = alloca (maplength);
__lseek (fd, ehdr->e_phoff, SEEK_SET);
- if ((size_t) __libc_read (fd, (void *) phdr, maplength) != maplength)
+ if ((size_t) __read_nocancel (fd, (void *) phdr, maplength)
+ != maplength)
{
read_error:
errval = errno;
@@ -1648,7 +1649,7 @@ open_verify (const char *name, int fd,
abi_note = abi_note_malloced;
}
__lseek (fd, ph->p_offset, SEEK_SET);
- if (__libc_read (fd, (void *) abi_note, size) != size)
+ if (__read_nocancel (fd, (void *) abi_note, size) != size)
{
free (abi_note_malloced);
goto read_error;
@@ -1680,7 +1681,7 @@ open_verify (const char *name, int fd,
|| (GLRO(dl_osversion) && GLRO(dl_osversion) < osversion))
{
close_and_out:
- __close (fd);
+ __close_nocancel (fd);
__set_errno (ENOENT);
fd = -1;
}
@@ -1797,7 +1798,7 @@ open_path (const char *name, size_t namelen, int mode,
/* The shared object cannot be tested for being SUID
or this bit is not set. In this case we must not
use this object. */
- __close (fd);
+ __close_nocancel (fd);
fd = -1;
/* We simply ignore the file, signal this by setting
the error value which would have been set by `open'. */
@@ -1818,7 +1819,7 @@ open_path (const char *name, size_t namelen, int mode,
{
/* No memory for the name, we certainly won't be able
to load and link it. */
- __close (fd);
+ __close_nocancel (fd);
return -1;
}
}
diff --git a/elf/dl-misc.c b/elf/dl-misc.c
index b7174994cd..2eb81eeb02 100644
--- a/elf/dl-misc.c
+++ b/elf/dl-misc.c
@@ -33,7 +33,7 @@
#include <sysdep.h>
#include <_itoa.h>
#include <dl-writev.h>
-
+#include <not-cancel.h>
/* Read the whole contents of FILE into new mmap'd space with given
protections. *SIZEP gets the size of the file. On error MAP_FAILED
@@ -44,7 +44,7 @@ _dl_sysdep_read_whole_file (const char *file, size_t *sizep, int prot)
{
void *result = MAP_FAILED;
struct stat64 st;
- int fd = __open (file, O_RDONLY | O_CLOEXEC);
+ int fd = __open64_nocancel (file, O_RDONLY | O_CLOEXEC);
if (fd >= 0)
{
if (__fxstat64 (_STAT_VER, fd, &st) >= 0)
@@ -65,7 +65,7 @@ _dl_sysdep_read_whole_file (const char *file, size_t *sizep, int prot)
#endif
, fd, 0);
}
- __close (fd);
+ __close_nocancel (fd);
}
return result;
}
diff --git a/elf/dl-profile.c b/elf/dl-profile.c
index 7f15352123..bac3718c11 100644
--- a/elf/dl-profile.c
+++ b/elf/dl-profile.c
@@ -35,6 +35,7 @@
#include <sys/param.h>
#include <sys/stat.h>
#include <atomic.h>
+#include <not-cancel.h>
/* The LD_PROFILE feature has to be implemented different to the
normal profiling using the gmon/ functions. The problem is that an
@@ -324,7 +325,7 @@ _dl_start_profile (void)
*cp++ = '/';
__stpcpy (__stpcpy (cp, GLRO(dl_profile)), ".profile");
- fd = __open (filename, O_RDWR | O_CREAT | O_NOFOLLOW, DEFFILEMODE);
+ fd = __open64_nocancel (filename, O_RDWR|O_CREAT|O_NOFOLLOW, DEFFILEMODE);
if (fd == -1)
{
char buf[400];
@@ -335,7 +336,7 @@ _dl_start_profile (void)
print_error:
errnum = errno;
if (fd != -1)
- __close (fd);
+ __close_nocancel (fd);
_dl_error_printf (errstr, filename,
__strerror_r (errnum, buf, sizeof buf));
return;
@@ -364,15 +365,14 @@ _dl_start_profile (void)
goto print_error;
}
- if (TEMP_FAILURE_RETRY (__libc_write (fd, buf, (expected_size
- & (GLRO(dl_pagesize)
- - 1))))
+ if (TEMP_FAILURE_RETRY
+ (__write_nocancel (fd, buf, (expected_size & (GLRO(dl_pagesize) - 1))))
< 0)
goto cannot_create;
}
else if (st.st_size != expected_size)
{
- __close (fd);
+ __close_nocancel (fd);
wrong_format:
if (addr != NULL)
@@ -392,7 +392,7 @@ _dl_start_profile (void)
}
/* We don't need the file descriptor anymore. */
- __close (fd);
+ __close_nocancel (fd);
/* Pointer to data after the header. */
hist = (char *) (addr + 1);
diff --git a/elf/rtld.c b/elf/rtld.c
index e7681ebb1f..8c732adb68 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -41,6 +41,7 @@
#include <tls.h>
#include <stap-probe.h>
#include <stackinfo.h>
+#include <not-cancel.h>
#include <assert.h>
@@ -2673,7 +2674,7 @@ process_envvars (enum mode *modep)
*--startp = '.';
startp = memcpy (startp - name_len, debug_output, name_len);
- GLRO(dl_debug_fd) = __open (startp, flags, DEFFILEMODE);
+ GLRO(dl_debug_fd) = __open64_nocancel (startp, flags, DEFFILEMODE);
if (GLRO(dl_debug_fd) == -1)
/* We use standard output if opening the file failed. */
GLRO(dl_debug_fd) = STDOUT_FILENO;