e6e335bf3a
The original syscall only used to return errno to indicate if cmpxchg succeeded. It was not returning the "previous" value which typical cmpxchg callers are interested in to build their slowpaths or retry loops. Given user preemption in syscall return path etc, it is not wise to check this in userspace afterwards, but should be what kernel actually observed in the syscall. So change the syscall interface to always return the previous value and additionally set Z flag to indicate whether operation succeeded or not (just like ARM implementation when they used to have this syscall) The flag approach avoids having to put_user errno which is nice given the use case for this syscall cares mostly about the "previous" value. Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
246 lines
6.2 KiB
C
246 lines
6.2 KiB
C
/*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* Amit Bhor, Kanika Nema: Codito Technologies 2004
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*/
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#include <linux/errno.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/fs.h>
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#include <linux/unistd.h>
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#include <linux/ptrace.h>
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#include <linux/slab.h>
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#include <linux/syscalls.h>
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#include <linux/elf.h>
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#include <linux/tick.h>
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SYSCALL_DEFINE1(arc_settls, void *, user_tls_data_ptr)
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{
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task_thread_info(current)->thr_ptr = (unsigned int)user_tls_data_ptr;
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return 0;
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}
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/*
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* We return the user space TLS data ptr as sys-call return code
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* Ideally it should be copy to user.
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* However we can cheat by the fact that some sys-calls do return
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* absurdly high values
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* Since the tls dat aptr is not going to be in range of 0xFFFF_xxxx
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* it won't be considered a sys-call error
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* and it will be loads better than copy-to-user, which is a definite
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* D-TLB Miss
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*/
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SYSCALL_DEFINE0(arc_gettls)
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{
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return task_thread_info(current)->thr_ptr;
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}
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SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
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{
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struct pt_regs *regs = current_pt_regs();
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int uval = -EFAULT;
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/*
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* This is only for old cores lacking LLOCK/SCOND, which by defintion
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* can't possibly be SMP. Thus doesn't need to be SMP safe.
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* And this also helps reduce the overhead for serializing in
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* the UP case
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*/
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WARN_ON_ONCE(IS_ENABLED(CONFIG_SMP));
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/* Z indicates to userspace if operation succeded */
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regs->status32 &= ~STATUS_Z_MASK;
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if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
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return -EFAULT;
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preempt_disable();
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if (__get_user(uval, uaddr))
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goto done;
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if (uval == expected) {
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if (!__put_user(new, uaddr))
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regs->status32 |= STATUS_Z_MASK;
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}
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done:
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preempt_enable();
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return uval;
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}
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void arch_cpu_idle(void)
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{
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/* sleep, but enable all interrupts before committing */
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__asm__ __volatile__(
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"sleep %0 \n"
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:
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:"I"(ISA_SLEEP_ARG)); /* can't be "r" has to be embedded const */
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}
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asmlinkage void ret_from_fork(void);
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/*
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* Copy architecture-specific thread state
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*
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* Layout of Child kernel mode stack as setup at the end of this function is
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*
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* | ... |
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* | ... |
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* | unused |
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* | |
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* ------------------
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* | r25 | <==== top of Stack (thread.ksp)
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* ~ ~
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* | --to-- | (CALLEE Regs of kernel mode)
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* | r13 |
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* ------------------
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* | fp |
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* | blink | @ret_from_fork
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* ------------------
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* | |
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* ~ ~
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* ~ ~
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* | |
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* ------------------
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* | r12 |
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* ~ ~
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* | --to-- | (scratch Regs of user mode)
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* | r0 |
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* ------------------
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* | SP |
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* | orig_r0 |
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* | event/ECR |
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* | user_r25 |
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* ------------------ <===== END of PAGE
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*/
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int copy_thread(unsigned long clone_flags,
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unsigned long usp, unsigned long kthread_arg,
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struct task_struct *p)
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{
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struct pt_regs *c_regs; /* child's pt_regs */
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unsigned long *childksp; /* to unwind out of __switch_to() */
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struct callee_regs *c_callee; /* child's callee regs */
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struct callee_regs *parent_callee; /* paren't callee */
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struct pt_regs *regs = current_pt_regs();
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/* Mark the specific anchors to begin with (see pic above) */
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c_regs = task_pt_regs(p);
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childksp = (unsigned long *)c_regs - 2; /* 2 words for FP/BLINK */
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c_callee = ((struct callee_regs *)childksp) - 1;
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/*
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* __switch_to() uses thread.ksp to start unwinding stack
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* For kernel threads we don't need to create callee regs, the
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* stack layout nevertheless needs to remain the same.
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* Also, since __switch_to anyways unwinds callee regs, we use
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* this to populate kernel thread entry-pt/args into callee regs,
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* so that ret_from_kernel_thread() becomes simpler.
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*/
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p->thread.ksp = (unsigned long)c_callee; /* THREAD_KSP */
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/* __switch_to expects FP(0), BLINK(return addr) at top */
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childksp[0] = 0; /* fp */
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childksp[1] = (unsigned long)ret_from_fork; /* blink */
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if (unlikely(p->flags & PF_KTHREAD)) {
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memset(c_regs, 0, sizeof(struct pt_regs));
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c_callee->r13 = kthread_arg;
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c_callee->r14 = usp; /* function */
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return 0;
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}
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/*--------- User Task Only --------------*/
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/* __switch_to expects FP(0), BLINK(return addr) at top of stack */
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childksp[0] = 0; /* for POP fp */
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childksp[1] = (unsigned long)ret_from_fork; /* for POP blink */
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/* Copy parents pt regs on child's kernel mode stack */
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*c_regs = *regs;
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if (usp)
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c_regs->sp = usp;
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c_regs->r0 = 0; /* fork returns 0 in child */
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parent_callee = ((struct callee_regs *)regs) - 1;
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*c_callee = *parent_callee;
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if (unlikely(clone_flags & CLONE_SETTLS)) {
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/*
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* set task's userland tls data ptr from 4th arg
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* clone C-lib call is difft from clone sys-call
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*/
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task_thread_info(p)->thr_ptr = regs->r3;
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} else {
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/* Normal fork case: set parent's TLS ptr in child */
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task_thread_info(p)->thr_ptr =
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task_thread_info(current)->thr_ptr;
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}
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return 0;
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}
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/*
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* Do necessary setup to start up a new user task
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*/
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void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long usp)
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{
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regs->sp = usp;
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regs->ret = pc;
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/*
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* [U]ser Mode bit set
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* [L] ZOL loop inhibited to begin with - cleared by a LP insn
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* Interrupts enabled
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*/
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regs->status32 = STATUS_U_MASK | STATUS_L_MASK | ISA_INIT_STATUS_BITS;
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/* bogus seed values for debugging */
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regs->lp_start = 0x10;
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regs->lp_end = 0x80;
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}
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/*
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* Some archs flush debug and FPU info here
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*/
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void flush_thread(void)
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{
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}
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int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
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{
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return 0;
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}
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int elf_check_arch(const struct elf32_hdr *x)
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{
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unsigned int eflags;
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if (x->e_machine != EM_ARC_INUSE) {
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pr_err("ELF not built for %s ISA\n",
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is_isa_arcompact() ? "ARCompact":"ARCv2");
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return 0;
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}
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eflags = x->e_flags;
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if ((eflags & EF_ARC_OSABI_MSK) != EF_ARC_OSABI_CURRENT) {
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pr_err("ABI mismatch - you need newer toolchain\n");
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force_sigsegv(SIGSEGV, current);
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return 0;
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}
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return 1;
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}
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EXPORT_SYMBOL(elf_check_arch);
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