// SPDX-License-Identifier: GPL-2.0/* * x86 single-step support code, common to 32-bit and 64-bit. */#include <linux/sched.h>#include <linux/sched/task_stack.h>#include <linux/mm.h>#include <linux/ptrace.h> #include <asm/desc.h>#include <asm/debugreg.h>#include <asm/mmu_context.h> unsigned long convert_ip_to_linear(struct task_struct *child, struct pt_regs *regs){	unsigned long addr, seg; 	addr = regs->ip;	seg = regs->cs;	if (v8086_mode(regs)) {		addr = (addr & 0xffff) + (seg << 4);		return addr;	} #ifdef CONFIG_MODIFY_LDT_SYSCALL	/*	 * We'll assume that the code segments in the GDT	 * are all zero-based. That is largely true: the	 * TLS segments are used for data, and the PNPBIOS	 * and APM bios ones we just ignore here.	 */	if ((seg & SEGMENT_TI_MASK) == SEGMENT_LDT) {		struct desc_struct *desc;		unsigned long base; 		seg >>= 3; 		mutex_lock(&child->mm->context.lock);		if (unlikely(!child->mm->context.ldt ||			     seg >= child->mm->context.ldt->nr_entries))			addr = -1L; /* bogus selector, access would fault */		else {			desc = &child->mm->context.ldt->entries[seg];			base = get_desc_base(desc); 			/* 16-bit code segment? */			if (!desc->d)				addr &= 0xffff;			addr += base;		}		mutex_unlock(&child->mm->context.lock);	}#endif 	return addr;} static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs){	int i, copied;	unsigned char opcode[15];	unsigned long addr = convert_ip_to_linear(child, regs); 	copied = access_process_vm(child, addr, opcode, sizeof(opcode),			FOLL_FORCE);	for (i = 0; i < copied; i++) {		switch (opcode[i]) {		/* popf and iret */		case 0x9d: case 0xcf:			return 1; 			/* CHECKME: 64 65 */ 		/* opcode and address size prefixes */		case 0x66: case 0x67:			continue;		/* irrelevant prefixes (segment overrides and repeats) */		case 0x26: case 0x2e:		case 0x36: case 0x3e:		case 0x64: case 0x65:		case 0xf0: case 0xf2: case 0xf3:			continue; #ifdef CONFIG_X86_64		case 0x40 ... 0x4f:			if (!user_64bit_mode(regs))				/* 32-bit mode: register increment */				return 0;			/* 64-bit mode: REX prefix */			continue;#endif 			/* CHECKME: f2, f3 */ 		/*		 * pushf: NOTE! We should probably not let		 * the user see the TF bit being set. But		 * it's more pain than it's worth to avoid		 * it, and a debugger could emulate this		 * all in user space if it _really_ cares.		 */		case 0x9c:		default:			return 0;		}	}	return 0;} /* * Enable single-stepping.  Return nonzero if user mode is not using TF itself. */static int enable_single_step(struct task_struct *child){	struct pt_regs *regs = task_pt_regs(child);	unsigned long oflags; 	/*	 * If we stepped into a sysenter/syscall insn, it trapped in	 * kernel mode; do_debug() cleared TF and set TIF_SINGLESTEP.	 * If user-mode had set TF itself, then it's still clear from	 * do_debug() and we need to set it again to restore the user	 * state so we don't wrongly set TIF_FORCED_TF below.	 * If enable_single_step() was used last and that is what	 * set TIF_SINGLESTEP, then both TF and TIF_FORCED_TF are	 * already set and our bookkeeping is fine.	 */	if (unlikely(test_tsk_thread_flag(child, TIF_SINGLESTEP)))		regs->flags |= X86_EFLAGS_TF; 	/*	 * Always set TIF_SINGLESTEP.  This will also	 * cause us to set TF when returning to user mode.	 */	set_tsk_thread_flag(child, TIF_SINGLESTEP); 	/*	 * Ensure that a trap is triggered once stepping out of a system	 * call prior to executing any user instruction.	 */	set_task_syscall_work(child, SYSCALL_EXIT_TRAP); 	oflags = regs->flags; 	/* Set TF on the kernel stack.. */	regs->flags |= X86_EFLAGS_TF; 	/*	 * ..but if TF is changed by the instruction we will trace,	 * don't mark it as being "us" that set it, so that we	 * won't clear it by hand later.	 *	 * Note that if we don't actually execute the popf because	 * of a signal arriving right now or suchlike, we will lose	 * track of the fact that it really was "us" that set it.	 */	if (is_setting_trap_flag(child, regs)) {		clear_tsk_thread_flag(child, TIF_FORCED_TF);		return 0;	} 	/*	 * If TF was already set, check whether it was us who set it.	 * If not, we should never attempt a block step.	 */	if (oflags & X86_EFLAGS_TF)		return test_tsk_thread_flag(child, TIF_FORCED_TF); 	set_tsk_thread_flag(child, TIF_FORCED_TF); 	return 1;} void set_task_blockstep(struct task_struct *task, bool on){	unsigned long debugctl; 	/*	 * Ensure irq/preemption can't change debugctl in between.	 * Note also that both TIF_BLOCKSTEP and debugctl should	 * be changed atomically wrt preemption.	 *	 * NOTE: this means that set/clear TIF_BLOCKSTEP is only safe if	 * task is current or it can't be running, otherwise we can race	 * with __switch_to_xtra(). We rely on ptrace_freeze_traced().	 */	local_irq_disable();	debugctl = get_debugctlmsr();	if (on) {		debugctl |= DEBUGCTLMSR_BTF;		set_tsk_thread_flag(task, TIF_BLOCKSTEP);	} else {		debugctl &= ~DEBUGCTLMSR_BTF;		clear_tsk_thread_flag(task, TIF_BLOCKSTEP);	}	if (task == current)		update_debugctlmsr(debugctl);	local_irq_enable();} /* * Enable single or block step. */static void enable_step(struct task_struct *child, bool block){	/*	 * Make sure block stepping (BTF) is not enabled unless it should be.	 * Note that we don't try to worry about any is_setting_trap_flag()	 * instructions after the first when using block stepping.	 * So no one should try to use debugger block stepping in a program	 * that uses user-mode single stepping itself.	 */	if (enable_single_step(child) && block)		set_task_blockstep(child, true);	else if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))		set_task_blockstep(child, false);} void user_enable_single_step(struct task_struct *child){	enable_step(child, 0);} void user_enable_block_step(struct task_struct *child){	enable_step(child, 1);} void user_disable_single_step(struct task_struct *child){	/*	 * Make sure block stepping (BTF) is disabled.	 */	if (test_tsk_thread_flag(child, TIF_BLOCKSTEP))		set_task_blockstep(child, false); 	/* Always clear TIF_SINGLESTEP... */	clear_tsk_thread_flag(child, TIF_SINGLESTEP);	clear_task_syscall_work(child, SYSCALL_EXIT_TRAP); 	/* But touch TF only if it was set by us.. */	if (test_and_clear_tsk_thread_flag(child, TIF_FORCED_TF))		task_pt_regs(child)->flags &= ~X86_EFLAGS_TF;}