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Fix linux personality syscall wrapper
The personality system call, starting with linux kernel commit v2.6.29-6609-g11d06b2a1e5658f448a308aa3beb97bacd64a940, always successfully changes the personality if requested. The syscall wrapper, however, still can return an error in the following cases: - the value returned by the system call looks like an error due to architecture limitations of 32-bit kernels; - a personality greater than 0xffffffff is passed to the system call, and the 64-bit kernel does not have commit v2.6.35-rc1-372-g485d527686850d68a0e9006dd9904f19f122485e that would truncate this value to unsigned int; - on sparc64, the value returned by the system call looks like an error due to sparc64 kernel sign extension bug. The solution is three-fold: - move generic syscalls.list personality entry to generic 64-bit syscalls.list file; - for each 32-bit architecture that use negated errno semantics, add a NOERRNO personality entry to their syscalls.list file; - for sparc64 and 32-bit architectures that use dedicated registers to flag syscall errors, add a wrapper around personality syscall; if the system call return value is flagged as an error, this wrapper returns the negated "would be errno" value, otherwise it returns the system call return value; on sparc64, it also truncates the personality argument to unsigned int before passing it to the kernel. [BZ #19408] * sysdeps/unix/sysv/linux/personality.c: New file. * sysdeps/unix/sysv/linux/sparc/sparc64/personality.c: Likewise. * sysdeps/unix/sysv/linux/tst-personality.c: Likewise. * sysdeps/unix/sysv/linux/Makefile [$(subdir) == misc] (sysdep_routines): Add personality. (tests): Add tst-personality. * sysdeps/unix/sysv/linux/syscalls.list (personality): Move ... * sysdeps/unix/sysv/linux/wordsize-64/syscalls.list: ... here. * sysdeps/unix/sysv/linux/arm/syscalls.list (personality): New entry. * sysdeps/unix/sysv/linux/hppa/syscalls.list (personality): Likewise. * sysdeps/unix/sysv/linux/i386/syscalls.list (personality): Likewise. * sysdeps/unix/sysv/linux/m68k/syscalls.list (personality): Likewise. * sysdeps/unix/sysv/linux/microblaze/syscalls.list (personality): Likewise. * sysdeps/unix/sysv/linux/mips/mips64/n32/syscalls.list (personality): Likewise. * sysdeps/unix/sysv/linux/s390/s390-32/syscalls.list (personality): Likewise. * sysdeps/unix/sysv/linux/sh/syscalls.list (personality): Likewise. * sysdeps/unix/sysv/linux/x86_64/x32/syscalls.list (personality): Likewise.
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Dmitry V. Levin
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Dec 31, 2015
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Original file line number | Diff line number | Diff line change |
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@@ -0,0 +1,49 @@ | ||
/* Copyright (C) 2015 Free Software Foundation, Inc. | ||
This file is part of the GNU C Library. | ||
The GNU C Library is free software; you can redistribute it and/or | ||
modify it under the terms of the GNU Lesser General Public | ||
License as published by the Free Software Foundation; either | ||
version 2.1 of the License, or (at your option) any later version. | ||
The GNU C Library is distributed in the hope that it will be useful, | ||
but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
Lesser General Public License for more details. | ||
You should have received a copy of the GNU Lesser General Public | ||
License along with the GNU C Library; if not, see | ||
<http://www.gnu.org/licenses/>. */ | ||
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#include <sys/personality.h> | ||
#include <sysdep.h> | ||
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extern __typeof (personality) __personality; | ||
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int | ||
__personality (unsigned long persona) | ||
{ | ||
#ifdef PERSONALITY_TRUNCATE_ARGUMENT | ||
/* Starting with kernel commit v2.6.21-3117-g97dc32c, the type of | ||
task_struct->pesonality is "unsigned int". | ||
Starting with kernel commit v2.6.35-rc1-372-g485d527, the personality | ||
syscall accepts "unsigned int" instead of "long unsigned int". | ||
Inbetween, a personality argument that does not fit into "unsigned int" | ||
would result to system call returning -EINVAL. | ||
We explicitly truncate the personality argument to "unsigned int" | ||
to eliminate the uncertainty. */ | ||
persona = (unsigned int) persona; | ||
#endif | ||
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INTERNAL_SYSCALL_DECL (err); | ||
long ret = INTERNAL_SYSCALL (personality, err, 1, persona); | ||
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/* Starting with kernel commit v2.6.29-6609-g11d06b2, the personality syscall | ||
never fails. However, 32-bit kernels might flag valid values as errors, so | ||
we need to reverse the error setting. We can't use the raw result as some | ||
arches split the return/error values. */ | ||
if (__glibc_unlikely (INTERNAL_SYSCALL_ERROR_P (ret, err))) | ||
ret = -INTERNAL_SYSCALL_ERRNO (ret, err); | ||
return ret; | ||
} | ||
weak_alias (__personality, personality) |
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Original file line number | Diff line number | Diff line change |
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/* Work around sign extension bug in the kernel. */ | ||
#define PERSONALITY_TRUNCATE_ARGUMENT | ||
#include <sysdeps/unix/sysv/linux/personality.c> |
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Original file line number | Diff line number | Diff line change |
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/* BZ #19408 linux personality syscall wrapper test. | ||
Copyright (C) 2015 Free Software Foundation, Inc. | ||
This file is part of the GNU C Library. | ||
The GNU C Library is free software; you can redistribute it and/or | ||
modify it under the terms of the GNU Lesser General Public | ||
License as published by the Free Software Foundation; either | ||
version 2.1 of the License, or (at your option) any later version. | ||
The GNU C Library is distributed in the hope that it will be useful, | ||
but WITHOUT ANY WARRANTY; without even the implied warranty of | ||
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | ||
Lesser General Public License for more details. | ||
You should have received a copy of the GNU Lesser General Public | ||
License along with the GNU C Library; if not, see | ||
<http://www.gnu.org/licenses/>. */ | ||
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#include <errno.h> | ||
#include <sys/personality.h> | ||
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static int | ||
do_test (void) | ||
{ | ||
int rc = 0; | ||
unsigned int test_persona = -EINVAL; | ||
unsigned int saved_persona; | ||
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errno = 0xdefaced; | ||
saved_persona = personality (0xffffffff); | ||
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if (personality (test_persona) != saved_persona || | ||
personality (0xffffffff) == -1 || | ||
personality (PER_LINUX) == -1 || | ||
personality (0xffffffff) != PER_LINUX || | ||
0xdefaced != errno) | ||
rc = 1; | ||
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(void) personality (saved_persona); | ||
return rc; | ||
} | ||
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#define TEST_FUNCTION do_test () | ||
#include "../test-skeleton.c" |
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