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freebsd-dev/lib/libc/gen/elf_utils.c

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On shared object unload, in __cxa_finalize, call and clear all installed atexit and __cxa_atexit handlers that are either installed by unloaded dso, or points to the functions provided by the dso. Use _rtld_addr_phdr to locate segment information from the address of private variable belonging to the dso, supplied by crtstuff.c. Provide utility function __elf_phdr_match_addr to do the match of address against dso executable segment. Call back into libthr from __cxa_finalize using weak __pthread_cxa_finalize symbol to remove any atfork handler which function points into unloaded object. The rtld needs private __pthread_cxa_finalize symbol to not require resolution of the weak undefined symbol at initialization time. This cannot work, since rtld is relocated before sym_zero is set up. Idea by: kan Reviewed by: kan (previous version) MFC after: 3 weeks
2010-08-23 15:38:02 +00:00
/*
* Copyright (c) 2010 Konstantin Belousov <kib@freebsd.org>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $FreeBSD$
*/
Implement __pthread_map_stacks_exec() callback for libc, to change the stack protection to allow execution for single-threaded processes.
2011-01-08 17:13:43 +00:00
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <sys/sysctl.h>
On shared object unload, in __cxa_finalize, call and clear all installed atexit and __cxa_atexit handlers that are either installed by unloaded dso, or points to the functions provided by the dso. Use _rtld_addr_phdr to locate segment information from the address of private variable belonging to the dso, supplied by crtstuff.c. Provide utility function __elf_phdr_match_addr to do the match of address against dso executable segment. Call back into libthr from __cxa_finalize using weak __pthread_cxa_finalize symbol to remove any atfork handler which function points into unloaded object. The rtld needs private __pthread_cxa_finalize symbol to not require resolution of the weak undefined symbol at initialization time. This cannot work, since rtld is relocated before sym_zero is set up. Idea by: kan Reviewed by: kan (previous version) MFC after: 3 weeks
2010-08-23 15:38:02 +00:00
#include <link.h>
Implement __pthread_map_stacks_exec() callback for libc, to change the stack protection to allow execution for single-threaded processes.
2011-01-08 17:13:43 +00:00
#include <stddef.h>
If libthr.so is dlopened without RTLD_GLOBAL flag, the libthr symbols do not participate in the global symbols namespace, but rtld locks are still replaced and functions are interposed. In particular, __pthread_map_stacks_exec is resolved to the libc version. If a library is loaded later, which requires adjustment of the stack protection mode, rtld calls into libc __pthread_map_stacks_exec due to the symbols scope. The libc version might recurse into binder and recursively acquire rtld bind lock, causing the hang. Make libc __pthread_map_stacks_exec() interposed, which synchronizes rtld locks and version of the stack exec hook when libthr loaded, regardless of the symbol scope control or symbol resolution order. The __pthread_map_stacks_exec() symbol is removed from the private version in libthr since libc symbol now operates correctly in presence of libthr. Reported and tested by: markj Sponsored by: The FreeBSD Foundation MFC after: 2 weeks
2016-02-08 19:24:13 +00:00
#include "libc_private.h"
On shared object unload, in __cxa_finalize, call and clear all installed atexit and __cxa_atexit handlers that are either installed by unloaded dso, or points to the functions provided by the dso. Use _rtld_addr_phdr to locate segment information from the address of private variable belonging to the dso, supplied by crtstuff.c. Provide utility function __elf_phdr_match_addr to do the match of address against dso executable segment. Call back into libthr from __cxa_finalize using weak __pthread_cxa_finalize symbol to remove any atfork handler which function points into unloaded object. The rtld needs private __pthread_cxa_finalize symbol to not require resolution of the weak undefined symbol at initialization time. This cannot work, since rtld is relocated before sym_zero is set up. Idea by: kan Reviewed by: kan (previous version) MFC after: 3 weeks
2010-08-23 15:38:02 +00:00
Remove names from some prototypes
2015-09-20 20:21:49 +00:00
int __elf_phdr_match_addr(struct dl_phdr_info *, void *);
Add declarations to eliminate -Wmissing-prototypes warnings
2015-09-20 03:58:27 +00:00
void __pthread_map_stacks_exec(void);
On shared object unload, in __cxa_finalize, call and clear all installed atexit and __cxa_atexit handlers that are either installed by unloaded dso, or points to the functions provided by the dso. Use _rtld_addr_phdr to locate segment information from the address of private variable belonging to the dso, supplied by crtstuff.c. Provide utility function __elf_phdr_match_addr to do the match of address against dso executable segment. Call back into libthr from __cxa_finalize using weak __pthread_cxa_finalize symbol to remove any atfork handler which function points into unloaded object. The rtld needs private __pthread_cxa_finalize symbol to not require resolution of the weak undefined symbol at initialization time. This cannot work, since rtld is relocated before sym_zero is set up. Idea by: kan Reviewed by: kan (previous version) MFC after: 3 weeks
2010-08-23 15:38:02 +00:00
int
__elf_phdr_match_addr(struct dl_phdr_info *phdr_info, void *addr)
{
const Elf_Phdr *ph;
int i;
for (i = 0; i < phdr_info->dlpi_phnum; i++) {
ph = &phdr_info->dlpi_phdr[i];
if (ph->p_type != PT_LOAD || (ph->p_flags & PF_X) == 0)
continue;
if (phdr_info->dlpi_addr + ph->p_vaddr <= (uintptr_t)addr &&
(uintptr_t)addr + sizeof(addr) < phdr_info->dlpi_addr +
ph->p_vaddr + ph->p_memsz)
break;
}
return (i != phdr_info->dlpi_phnum);
}
Implement __pthread_map_stacks_exec() callback for libc, to change the stack protection to allow execution for single-threaded processes.
2011-01-08 17:13:43 +00:00
void
If libthr.so is dlopened without RTLD_GLOBAL flag, the libthr symbols do not participate in the global symbols namespace, but rtld locks are still replaced and functions are interposed. In particular, __pthread_map_stacks_exec is resolved to the libc version. If a library is loaded later, which requires adjustment of the stack protection mode, rtld calls into libc __pthread_map_stacks_exec due to the symbols scope. The libc version might recurse into binder and recursively acquire rtld bind lock, causing the hang. Make libc __pthread_map_stacks_exec() interposed, which synchronizes rtld locks and version of the stack exec hook when libthr loaded, regardless of the symbol scope control or symbol resolution order. The __pthread_map_stacks_exec() symbol is removed from the private version in libthr since libc symbol now operates correctly in presence of libthr. Reported and tested by: markj Sponsored by: The FreeBSD Foundation MFC after: 2 weeks
2016-02-08 19:24:13 +00:00
__libc_map_stacks_exec(void)
Implement __pthread_map_stacks_exec() callback for libc, to change the stack protection to allow execution for single-threaded processes.
2011-01-08 17:13:43 +00:00
{
int mib[2];
struct rlimit rlim;
u_long usrstack;
size_t len;
mib[0] = CTL_KERN;
mib[1] = KERN_USRSTACK;
len = sizeof(usrstack);
if (sysctl(mib, sizeof(mib) / sizeof(mib[0]), &usrstack, &len, NULL, 0)
== -1)
return;
if (getrlimit(RLIMIT_STACK, &rlim) == -1)
return;
mprotect((void *)(uintptr_t)(usrstack - rlim.rlim_cur),
rlim.rlim_cur, _rtld_get_stack_prot());
}
If libthr.so is dlopened without RTLD_GLOBAL flag, the libthr symbols do not participate in the global symbols namespace, but rtld locks are still replaced and functions are interposed. In particular, __pthread_map_stacks_exec is resolved to the libc version. If a library is loaded later, which requires adjustment of the stack protection mode, rtld calls into libc __pthread_map_stacks_exec due to the symbols scope. The libc version might recurse into binder and recursively acquire rtld bind lock, causing the hang. Make libc __pthread_map_stacks_exec() interposed, which synchronizes rtld locks and version of the stack exec hook when libthr loaded, regardless of the symbol scope control or symbol resolution order. The __pthread_map_stacks_exec() symbol is removed from the private version in libthr since libc symbol now operates correctly in presence of libthr. Reported and tested by: markj Sponsored by: The FreeBSD Foundation MFC after: 2 weeks
2016-02-08 19:24:13 +00:00
#pragma weak __pthread_map_stacks_exec
void
__pthread_map_stacks_exec(void)
{
((void (*)(void))__libc_interposing[INTERPOS_map_stacks_exec])();
}
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