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/*
* Copyright (c) 2002 Andi Kleen <ak@suse.de>
* Copyright (c) 2002 Michal Ludvig <mludvig@suse.cz>
* Copyright (c) 2002 Roland McGrath <roland@redhat.com>
* Copyright (c) 2008-2013 Denys Vlasenko <vda.linux@googlemail.com>
* Copyright (c) 2012 H.J. Lu <hongjiu.lu@intel.com>
* Copyright (c) 2010-2015 Dmitry V. Levin <ldv@altlinux.org>
* Copyright (c) 2015-2018 The strace developers.
* All rights reserved.
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*/
/* Return codes: 1 - ok, 0 - ignore, other - error. */
static int
arch_get_scno(struct tcb *tcp)
{
kernel_ulong_t scno = 0;
unsigned int currpers;
#ifndef __X32_SYSCALL_BIT
# define __X32_SYSCALL_BIT 0x40000000
#endif
/*
* GETREGSET of NT_PRSTATUS tells us regset size,
* which unambiguously detects i386.
*
* Linux kernel distinguishes x86-64 and x32 processes
* solely by looking at __X32_SYSCALL_BIT:
* arch/x86/include/asm/compat.h::is_x32_task():
* if (task_pt_regs(current)->orig_ax & __X32_SYSCALL_BIT)
* return true;
*/
if (x86_io.iov_len == sizeof(i386_regs)) {
scno = i386_regs.orig_eax;
currpers = 1;
} else {
scno = x86_64_regs.orig_rax;
currpers = 0;
if (scno & __X32_SYSCALL_BIT) {
/*
* Syscall number -1 requires special treatment:
* it might be a side effect of SECCOMP_RET_ERRNO
* filtering that sets orig_rax to -1
* in some versions of linux kernel.
* If that is the case, then
* __X32_SYSCALL_BIT logic does not apply.
*/
if ((long long) x86_64_regs.orig_rax != -1) {
currpers = 2;
} else {
# ifdef X32
currpers = 2;
# endif
}
}
}
#ifdef X32
/*
* If we are built for a x32 system, then personality 0 is x32
* (not x86_64), and stracing of x86_64 apps is not supported.
* Stracing of i386 apps is still supported.
*/
if (currpers == 0) {
error_msg("syscall_%" PRI_klu "(...) in unsupported "
"64-bit mode of process PID=%d", scno, tcp->pid);
return 0;
}
currpers &= ~2; /* map 2,1 to 0,1 */
#endif /* X32 */
update_personality(tcp, currpers);
tcp->scno = scno;
return 1;
}
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