mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-12 22:56:48 +07:00
432c6bacbd
In some cases the kernel needs to execute an instruction from the delay slot of an emulated branch instruction. These cases include: - Emulated floating point branch instructions (bc1[ft]l?) for systems which don't include an FPU, or upon which the kernel is run with the "nofpu" parameter. - MIPSr6 systems running binaries targeting older revisions of the architecture, which may include branch instructions whose encodings are no longer valid in MIPSr6. Executing instructions from such delay slots is done by writing the instruction to memory followed by a trap, as part of an "emuframe", and executing it. This avoids the requirement of an emulator for the entire MIPS instruction set. Prior to this patch such emuframes are written to the user stack and executed from there. This patch moves FP branch delay emuframes off of the user stack and into a per-mm page. Allocating a page per-mm leaves userland with access to only what it had access to previously, and compared to other solutions is relatively simple. When a thread requires a delay slot emulation, it is allocated a frame. A thread may only have one frame allocated at any one time, since it may only ever be executing one instruction at any one time. In order to ensure that we can free up allocated frame later, its index is recorded in struct thread_struct. In the typical case, after executing the delay slot instruction we'll execute a break instruction with the BRK_MEMU code. This traps back to the kernel & leads to a call to do_dsemulret which frees the allocated frame & moves the user PC back to the instruction that would have executed following the emulated branch. In some cases the delay slot instruction may be invalid, such as a branch, or may trigger an exception. In these cases the BRK_MEMU break instruction will not be hit. In order to ensure that frames are freed this patch introduces dsemul_thread_cleanup() and calls it to free any allocated frame upon thread exit. If the instruction generated an exception & leads to a signal being delivered to the thread, or indeed if a signal simply happens to be delivered to the thread whilst it is executing from the struct emuframe, then we need to take care to exit the frame appropriately. This is done by either rolling back the user PC to the branch or advancing it to the continuation PC prior to signal delivery, using dsemul_thread_rollback(). If this were not done then a sigreturn would return to the struct emuframe, and if that frame had meanwhile been used in response to an emulated branch instruction within the signal handler then we would execute the wrong user code. Whilst a user could theoretically place something like a compact branch to self in a delay slot and cause their thread to become stuck in an infinite loop with the frame never being deallocated, this would: - Only affect the users single process. - Be architecturally invalid since there would be a branch in the delay slot, which is forbidden. - Be extremely unlikely to happen by mistake, and provide a program with no more ability to harm the system than a simple infinite loop would. If a thread requires a delay slot emulation & no frame is available to it (ie. the process has enough other threads that all frames are currently in use) then the thread joins a waitqueue. It will sleep until a frame is freed by another thread in the process. Since we now know whether a thread has an allocated frame due to our tracking of its index, the cookie field of struct emuframe is removed as we can be more certain whether we have a valid frame. Since a thread may only ever have a single frame at any given time, the epc field of struct emuframe is also removed & the PC to continue from is instead stored in struct thread_struct. Together these changes simplify & shrink struct emuframe somewhat, allowing twice as many frames to fit into the page allocated for them. The primary benefit of this patch is that we are now free to mark the user stack non-executable where that is possible. Signed-off-by: Paul Burton <paul.burton@imgtec.com> Cc: Leonid Yegoshin <leonid.yegoshin@imgtec.com> Cc: Maciej Rozycki <maciej.rozycki@imgtec.com> Cc: Faraz Shahbazker <faraz.shahbazker@imgtec.com> Cc: Raghu Gandham <raghu.gandham@imgtec.com> Cc: Matthew Fortune <matthew.fortune@imgtec.com> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/13764/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
669 lines
16 KiB
C
669 lines
16 KiB
C
/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 1994 - 1999, 2000 by Ralf Baechle and others.
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* Copyright (C) 2005, 2006 by Ralf Baechle (ralf@linux-mips.org)
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* Copyright (C) 1999, 2000 Silicon Graphics, Inc.
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* Copyright (C) 2004 Thiemo Seufer
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* Copyright (C) 2013 Imagination Technologies Ltd.
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*/
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#include <linux/errno.h>
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#include <linux/sched.h>
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#include <linux/tick.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/stddef.h>
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#include <linux/unistd.h>
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#include <linux/export.h>
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#include <linux/ptrace.h>
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#include <linux/mman.h>
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#include <linux/personality.h>
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#include <linux/sys.h>
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#include <linux/init.h>
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#include <linux/completion.h>
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#include <linux/kallsyms.h>
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#include <linux/random.h>
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#include <linux/prctl.h>
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#include <asm/asm.h>
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#include <asm/bootinfo.h>
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#include <asm/cpu.h>
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#include <asm/dsemul.h>
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#include <asm/dsp.h>
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#include <asm/fpu.h>
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#include <asm/msa.h>
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#include <asm/pgtable.h>
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#include <asm/mipsregs.h>
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#include <asm/processor.h>
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#include <asm/reg.h>
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#include <asm/uaccess.h>
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#include <asm/io.h>
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#include <asm/elf.h>
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#include <asm/isadep.h>
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#include <asm/inst.h>
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#include <asm/stacktrace.h>
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#include <asm/irq_regs.h>
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#ifdef CONFIG_HOTPLUG_CPU
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void arch_cpu_idle_dead(void)
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{
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/* What the heck is this check doing ? */
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if (!cpumask_test_cpu(smp_processor_id(), &cpu_callin_map))
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play_dead();
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}
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#endif
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asmlinkage void ret_from_fork(void);
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asmlinkage void ret_from_kernel_thread(void);
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void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
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{
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unsigned long status;
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/* New thread loses kernel privileges. */
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status = regs->cp0_status & ~(ST0_CU0|ST0_CU1|ST0_FR|KU_MASK);
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status |= KU_USER;
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regs->cp0_status = status;
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lose_fpu(0);
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clear_thread_flag(TIF_MSA_CTX_LIVE);
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clear_used_math();
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atomic_set(¤t->thread.bd_emu_frame, BD_EMUFRAME_NONE);
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init_dsp();
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regs->cp0_epc = pc;
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regs->regs[29] = sp;
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}
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void exit_thread(struct task_struct *tsk)
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{
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/*
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* User threads may have allocated a delay slot emulation frame.
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* If so, clean up that allocation.
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*/
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if (!(current->flags & PF_KTHREAD))
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dsemul_thread_cleanup(tsk);
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}
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int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
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{
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/*
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* Save any process state which is live in hardware registers to the
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* parent context prior to duplication. This prevents the new child
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* state becoming stale if the parent is preempted before copy_thread()
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* gets a chance to save the parent's live hardware registers to the
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* child context.
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*/
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preempt_disable();
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if (is_msa_enabled())
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save_msa(current);
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else if (is_fpu_owner())
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_save_fp(current);
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save_dsp(current);
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preempt_enable();
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*dst = *src;
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return 0;
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}
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/*
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* Copy architecture-specific thread state
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*/
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int copy_thread(unsigned long clone_flags, unsigned long usp,
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unsigned long kthread_arg, struct task_struct *p)
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{
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struct thread_info *ti = task_thread_info(p);
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struct pt_regs *childregs, *regs = current_pt_regs();
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unsigned long childksp;
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p->set_child_tid = p->clear_child_tid = NULL;
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childksp = (unsigned long)task_stack_page(p) + THREAD_SIZE - 32;
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/* set up new TSS. */
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childregs = (struct pt_regs *) childksp - 1;
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/* Put the stack after the struct pt_regs. */
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childksp = (unsigned long) childregs;
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p->thread.cp0_status = read_c0_status() & ~(ST0_CU2|ST0_CU1);
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if (unlikely(p->flags & PF_KTHREAD)) {
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/* kernel thread */
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unsigned long status = p->thread.cp0_status;
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memset(childregs, 0, sizeof(struct pt_regs));
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ti->addr_limit = KERNEL_DS;
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p->thread.reg16 = usp; /* fn */
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p->thread.reg17 = kthread_arg;
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p->thread.reg29 = childksp;
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p->thread.reg31 = (unsigned long) ret_from_kernel_thread;
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#if defined(CONFIG_CPU_R3000) || defined(CONFIG_CPU_TX39XX)
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status = (status & ~(ST0_KUP | ST0_IEP | ST0_IEC)) |
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((status & (ST0_KUC | ST0_IEC)) << 2);
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#else
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status |= ST0_EXL;
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#endif
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childregs->cp0_status = status;
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return 0;
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}
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/* user thread */
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*childregs = *regs;
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childregs->regs[7] = 0; /* Clear error flag */
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childregs->regs[2] = 0; /* Child gets zero as return value */
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if (usp)
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childregs->regs[29] = usp;
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ti->addr_limit = USER_DS;
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p->thread.reg29 = (unsigned long) childregs;
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p->thread.reg31 = (unsigned long) ret_from_fork;
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/*
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* New tasks lose permission to use the fpu. This accelerates context
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* switching for most programs since they don't use the fpu.
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*/
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childregs->cp0_status &= ~(ST0_CU2|ST0_CU1);
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clear_tsk_thread_flag(p, TIF_USEDFPU);
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clear_tsk_thread_flag(p, TIF_USEDMSA);
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clear_tsk_thread_flag(p, TIF_MSA_CTX_LIVE);
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#ifdef CONFIG_MIPS_MT_FPAFF
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clear_tsk_thread_flag(p, TIF_FPUBOUND);
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#endif /* CONFIG_MIPS_MT_FPAFF */
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atomic_set(&p->thread.bd_emu_frame, BD_EMUFRAME_NONE);
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if (clone_flags & CLONE_SETTLS)
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ti->tp_value = regs->regs[7];
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return 0;
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}
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#ifdef CONFIG_CC_STACKPROTECTOR
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#include <linux/stackprotector.h>
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unsigned long __stack_chk_guard __read_mostly;
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EXPORT_SYMBOL(__stack_chk_guard);
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#endif
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struct mips_frame_info {
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void *func;
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unsigned long func_size;
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int frame_size;
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int pc_offset;
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};
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#define J_TARGET(pc,target) \
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(((unsigned long)(pc) & 0xf0000000) | ((target) << 2))
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static inline int is_ra_save_ins(union mips_instruction *ip)
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{
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#ifdef CONFIG_CPU_MICROMIPS
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union mips_instruction mmi;
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/*
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* swsp ra,offset
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* swm16 reglist,offset(sp)
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* swm32 reglist,offset(sp)
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* sw32 ra,offset(sp)
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* jradiussp - NOT SUPPORTED
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*
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* microMIPS is way more fun...
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*/
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if (mm_insn_16bit(ip->halfword[0])) {
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mmi.word = (ip->halfword[0] << 16);
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return (mmi.mm16_r5_format.opcode == mm_swsp16_op &&
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mmi.mm16_r5_format.rt == 31) ||
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(mmi.mm16_m_format.opcode == mm_pool16c_op &&
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mmi.mm16_m_format.func == mm_swm16_op);
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}
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else {
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mmi.halfword[0] = ip->halfword[1];
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mmi.halfword[1] = ip->halfword[0];
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return (mmi.mm_m_format.opcode == mm_pool32b_op &&
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mmi.mm_m_format.rd > 9 &&
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mmi.mm_m_format.base == 29 &&
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mmi.mm_m_format.func == mm_swm32_func) ||
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(mmi.i_format.opcode == mm_sw32_op &&
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mmi.i_format.rs == 29 &&
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mmi.i_format.rt == 31);
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}
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#else
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/* sw / sd $ra, offset($sp) */
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return (ip->i_format.opcode == sw_op || ip->i_format.opcode == sd_op) &&
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ip->i_format.rs == 29 &&
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ip->i_format.rt == 31;
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#endif
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}
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static inline int is_jump_ins(union mips_instruction *ip)
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{
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#ifdef CONFIG_CPU_MICROMIPS
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/*
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* jr16,jrc,jalr16,jalr16
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* jal
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* jalr/jr,jalr.hb/jr.hb,jalrs,jalrs.hb
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* jraddiusp - NOT SUPPORTED
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*
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* microMIPS is kind of more fun...
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*/
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union mips_instruction mmi;
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mmi.word = (ip->halfword[0] << 16);
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if ((mmi.mm16_r5_format.opcode == mm_pool16c_op &&
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(mmi.mm16_r5_format.rt & mm_jr16_op) == mm_jr16_op) ||
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ip->j_format.opcode == mm_jal32_op)
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return 1;
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if (ip->r_format.opcode != mm_pool32a_op ||
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ip->r_format.func != mm_pool32axf_op)
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return 0;
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return ((ip->u_format.uimmediate >> 6) & mm_jalr_op) == mm_jalr_op;
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#else
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if (ip->j_format.opcode == j_op)
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return 1;
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if (ip->j_format.opcode == jal_op)
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return 1;
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if (ip->r_format.opcode != spec_op)
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return 0;
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return ip->r_format.func == jalr_op || ip->r_format.func == jr_op;
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#endif
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}
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static inline int is_sp_move_ins(union mips_instruction *ip)
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{
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#ifdef CONFIG_CPU_MICROMIPS
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/*
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* addiusp -imm
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* addius5 sp,-imm
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* addiu32 sp,sp,-imm
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* jradiussp - NOT SUPPORTED
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*
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* microMIPS is not more fun...
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*/
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if (mm_insn_16bit(ip->halfword[0])) {
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union mips_instruction mmi;
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mmi.word = (ip->halfword[0] << 16);
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return (mmi.mm16_r3_format.opcode == mm_pool16d_op &&
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mmi.mm16_r3_format.simmediate && mm_addiusp_func) ||
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(mmi.mm16_r5_format.opcode == mm_pool16d_op &&
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mmi.mm16_r5_format.rt == 29);
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}
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return ip->mm_i_format.opcode == mm_addiu32_op &&
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ip->mm_i_format.rt == 29 && ip->mm_i_format.rs == 29;
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#else
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/* addiu/daddiu sp,sp,-imm */
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if (ip->i_format.rs != 29 || ip->i_format.rt != 29)
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return 0;
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if (ip->i_format.opcode == addiu_op || ip->i_format.opcode == daddiu_op)
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return 1;
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#endif
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return 0;
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}
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static int get_frame_info(struct mips_frame_info *info)
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{
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#ifdef CONFIG_CPU_MICROMIPS
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union mips_instruction *ip = (void *) (((char *) info->func) - 1);
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#else
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union mips_instruction *ip = info->func;
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#endif
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unsigned max_insns = info->func_size / sizeof(union mips_instruction);
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unsigned i;
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info->pc_offset = -1;
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info->frame_size = 0;
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if (!ip)
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goto err;
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if (max_insns == 0)
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max_insns = 128U; /* unknown function size */
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max_insns = min(128U, max_insns);
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for (i = 0; i < max_insns; i++, ip++) {
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if (is_jump_ins(ip))
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break;
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if (!info->frame_size) {
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if (is_sp_move_ins(ip))
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{
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#ifdef CONFIG_CPU_MICROMIPS
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if (mm_insn_16bit(ip->halfword[0]))
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{
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unsigned short tmp;
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if (ip->halfword[0] & mm_addiusp_func)
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{
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tmp = (((ip->halfword[0] >> 1) & 0x1ff) << 2);
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info->frame_size = -(signed short)(tmp | ((tmp & 0x100) ? 0xfe00 : 0));
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} else {
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tmp = (ip->halfword[0] >> 1);
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info->frame_size = -(signed short)(tmp & 0xf);
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}
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ip = (void *) &ip->halfword[1];
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ip--;
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} else
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#endif
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info->frame_size = - ip->i_format.simmediate;
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}
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continue;
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}
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if (info->pc_offset == -1 && is_ra_save_ins(ip)) {
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info->pc_offset =
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ip->i_format.simmediate / sizeof(long);
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break;
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}
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}
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if (info->frame_size && info->pc_offset >= 0) /* nested */
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return 0;
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if (info->pc_offset < 0) /* leaf */
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return 1;
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/* prologue seems bogus... */
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err:
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return -1;
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}
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static struct mips_frame_info schedule_mfi __read_mostly;
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#ifdef CONFIG_KALLSYMS
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static unsigned long get___schedule_addr(void)
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{
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return kallsyms_lookup_name("__schedule");
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}
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#else
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static unsigned long get___schedule_addr(void)
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{
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union mips_instruction *ip = (void *)schedule;
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int max_insns = 8;
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int i;
|
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for (i = 0; i < max_insns; i++, ip++) {
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if (ip->j_format.opcode == j_op)
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return J_TARGET(ip, ip->j_format.target);
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}
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return 0;
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}
|
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#endif
|
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|
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static int __init frame_info_init(void)
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{
|
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unsigned long size = 0;
|
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#ifdef CONFIG_KALLSYMS
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unsigned long ofs;
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#endif
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unsigned long addr;
|
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|
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addr = get___schedule_addr();
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if (!addr)
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addr = (unsigned long)schedule;
|
|
|
|
#ifdef CONFIG_KALLSYMS
|
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kallsyms_lookup_size_offset(addr, &size, &ofs);
|
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#endif
|
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schedule_mfi.func = (void *)addr;
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schedule_mfi.func_size = size;
|
|
|
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get_frame_info(&schedule_mfi);
|
|
|
|
/*
|
|
* Without schedule() frame info, result given by
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|
* thread_saved_pc() and get_wchan() are not reliable.
|
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*/
|
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if (schedule_mfi.pc_offset < 0)
|
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printk("Can't analyze schedule() prologue at %p\n", schedule);
|
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|
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return 0;
|
|
}
|
|
|
|
arch_initcall(frame_info_init);
|
|
|
|
/*
|
|
* Return saved PC of a blocked thread.
|
|
*/
|
|
unsigned long thread_saved_pc(struct task_struct *tsk)
|
|
{
|
|
struct thread_struct *t = &tsk->thread;
|
|
|
|
/* New born processes are a special case */
|
|
if (t->reg31 == (unsigned long) ret_from_fork)
|
|
return t->reg31;
|
|
if (schedule_mfi.pc_offset < 0)
|
|
return 0;
|
|
return ((unsigned long *)t->reg29)[schedule_mfi.pc_offset];
|
|
}
|
|
|
|
|
|
#ifdef CONFIG_KALLSYMS
|
|
/* generic stack unwinding function */
|
|
unsigned long notrace unwind_stack_by_address(unsigned long stack_page,
|
|
unsigned long *sp,
|
|
unsigned long pc,
|
|
unsigned long *ra)
|
|
{
|
|
struct mips_frame_info info;
|
|
unsigned long size, ofs;
|
|
int leaf;
|
|
extern void ret_from_irq(void);
|
|
extern void ret_from_exception(void);
|
|
|
|
if (!stack_page)
|
|
return 0;
|
|
|
|
/*
|
|
* If we reached the bottom of interrupt context,
|
|
* return saved pc in pt_regs.
|
|
*/
|
|
if (pc == (unsigned long)ret_from_irq ||
|
|
pc == (unsigned long)ret_from_exception) {
|
|
struct pt_regs *regs;
|
|
if (*sp >= stack_page &&
|
|
*sp + sizeof(*regs) <= stack_page + THREAD_SIZE - 32) {
|
|
regs = (struct pt_regs *)*sp;
|
|
pc = regs->cp0_epc;
|
|
if (!user_mode(regs) && __kernel_text_address(pc)) {
|
|
*sp = regs->regs[29];
|
|
*ra = regs->regs[31];
|
|
return pc;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
if (!kallsyms_lookup_size_offset(pc, &size, &ofs))
|
|
return 0;
|
|
/*
|
|
* Return ra if an exception occurred at the first instruction
|
|
*/
|
|
if (unlikely(ofs == 0)) {
|
|
pc = *ra;
|
|
*ra = 0;
|
|
return pc;
|
|
}
|
|
|
|
info.func = (void *)(pc - ofs);
|
|
info.func_size = ofs; /* analyze from start to ofs */
|
|
leaf = get_frame_info(&info);
|
|
if (leaf < 0)
|
|
return 0;
|
|
|
|
if (*sp < stack_page ||
|
|
*sp + info.frame_size > stack_page + THREAD_SIZE - 32)
|
|
return 0;
|
|
|
|
if (leaf)
|
|
/*
|
|
* For some extreme cases, get_frame_info() can
|
|
* consider wrongly a nested function as a leaf
|
|
* one. In that cases avoid to return always the
|
|
* same value.
|
|
*/
|
|
pc = pc != *ra ? *ra : 0;
|
|
else
|
|
pc = ((unsigned long *)(*sp))[info.pc_offset];
|
|
|
|
*sp += info.frame_size;
|
|
*ra = 0;
|
|
return __kernel_text_address(pc) ? pc : 0;
|
|
}
|
|
EXPORT_SYMBOL(unwind_stack_by_address);
|
|
|
|
/* used by show_backtrace() */
|
|
unsigned long unwind_stack(struct task_struct *task, unsigned long *sp,
|
|
unsigned long pc, unsigned long *ra)
|
|
{
|
|
unsigned long stack_page = (unsigned long)task_stack_page(task);
|
|
return unwind_stack_by_address(stack_page, sp, pc, ra);
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* get_wchan - a maintenance nightmare^W^Wpain in the ass ...
|
|
*/
|
|
unsigned long get_wchan(struct task_struct *task)
|
|
{
|
|
unsigned long pc = 0;
|
|
#ifdef CONFIG_KALLSYMS
|
|
unsigned long sp;
|
|
unsigned long ra = 0;
|
|
#endif
|
|
|
|
if (!task || task == current || task->state == TASK_RUNNING)
|
|
goto out;
|
|
if (!task_stack_page(task))
|
|
goto out;
|
|
|
|
pc = thread_saved_pc(task);
|
|
|
|
#ifdef CONFIG_KALLSYMS
|
|
sp = task->thread.reg29 + schedule_mfi.frame_size;
|
|
|
|
while (in_sched_functions(pc))
|
|
pc = unwind_stack(task, &sp, pc, &ra);
|
|
#endif
|
|
|
|
out:
|
|
return pc;
|
|
}
|
|
|
|
/*
|
|
* Don't forget that the stack pointer must be aligned on a 8 bytes
|
|
* boundary for 32-bits ABI and 16 bytes for 64-bits ABI.
|
|
*/
|
|
unsigned long arch_align_stack(unsigned long sp)
|
|
{
|
|
if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
|
|
sp -= get_random_int() & ~PAGE_MASK;
|
|
|
|
return sp & ALMASK;
|
|
}
|
|
|
|
static void arch_dump_stack(void *info)
|
|
{
|
|
struct pt_regs *regs;
|
|
|
|
regs = get_irq_regs();
|
|
|
|
if (regs)
|
|
show_regs(regs);
|
|
|
|
dump_stack();
|
|
}
|
|
|
|
void arch_trigger_all_cpu_backtrace(bool include_self)
|
|
{
|
|
smp_call_function(arch_dump_stack, NULL, 1);
|
|
}
|
|
|
|
int mips_get_process_fp_mode(struct task_struct *task)
|
|
{
|
|
int value = 0;
|
|
|
|
if (!test_tsk_thread_flag(task, TIF_32BIT_FPREGS))
|
|
value |= PR_FP_MODE_FR;
|
|
if (test_tsk_thread_flag(task, TIF_HYBRID_FPREGS))
|
|
value |= PR_FP_MODE_FRE;
|
|
|
|
return value;
|
|
}
|
|
|
|
static void prepare_for_fp_mode_switch(void *info)
|
|
{
|
|
struct mm_struct *mm = info;
|
|
|
|
if (current->mm == mm)
|
|
lose_fpu(1);
|
|
}
|
|
|
|
int mips_set_process_fp_mode(struct task_struct *task, unsigned int value)
|
|
{
|
|
const unsigned int known_bits = PR_FP_MODE_FR | PR_FP_MODE_FRE;
|
|
struct task_struct *t;
|
|
int max_users;
|
|
|
|
/* Check the value is valid */
|
|
if (value & ~known_bits)
|
|
return -EOPNOTSUPP;
|
|
|
|
/* Avoid inadvertently triggering emulation */
|
|
if ((value & PR_FP_MODE_FR) && cpu_has_fpu &&
|
|
!(current_cpu_data.fpu_id & MIPS_FPIR_F64))
|
|
return -EOPNOTSUPP;
|
|
if ((value & PR_FP_MODE_FRE) && cpu_has_fpu && !cpu_has_fre)
|
|
return -EOPNOTSUPP;
|
|
|
|
/* FR = 0 not supported in MIPS R6 */
|
|
if (!(value & PR_FP_MODE_FR) && cpu_has_fpu && cpu_has_mips_r6)
|
|
return -EOPNOTSUPP;
|
|
|
|
/* Proceed with the mode switch */
|
|
preempt_disable();
|
|
|
|
/* Save FP & vector context, then disable FPU & MSA */
|
|
if (task->signal == current->signal)
|
|
lose_fpu(1);
|
|
|
|
/* Prevent any threads from obtaining live FP context */
|
|
atomic_set(&task->mm->context.fp_mode_switching, 1);
|
|
smp_mb__after_atomic();
|
|
|
|
/*
|
|
* If there are multiple online CPUs then force any which are running
|
|
* threads in this process to lose their FPU context, which they can't
|
|
* regain until fp_mode_switching is cleared later.
|
|
*/
|
|
if (num_online_cpus() > 1) {
|
|
/* No need to send an IPI for the local CPU */
|
|
max_users = (task->mm == current->mm) ? 1 : 0;
|
|
|
|
if (atomic_read(¤t->mm->mm_users) > max_users)
|
|
smp_call_function(prepare_for_fp_mode_switch,
|
|
(void *)current->mm, 1);
|
|
}
|
|
|
|
/*
|
|
* There are now no threads of the process with live FP context, so it
|
|
* is safe to proceed with the FP mode switch.
|
|
*/
|
|
for_each_thread(task, t) {
|
|
/* Update desired FP register width */
|
|
if (value & PR_FP_MODE_FR) {
|
|
clear_tsk_thread_flag(t, TIF_32BIT_FPREGS);
|
|
} else {
|
|
set_tsk_thread_flag(t, TIF_32BIT_FPREGS);
|
|
clear_tsk_thread_flag(t, TIF_MSA_CTX_LIVE);
|
|
}
|
|
|
|
/* Update desired FP single layout */
|
|
if (value & PR_FP_MODE_FRE)
|
|
set_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
|
|
else
|
|
clear_tsk_thread_flag(t, TIF_HYBRID_FPREGS);
|
|
}
|
|
|
|
/* Allow threads to use FP again */
|
|
atomic_set(&task->mm->context.fp_mode_switching, 0);
|
|
preempt_enable();
|
|
|
|
return 0;
|
|
}
|