arch/alpha/kernel/ptrace.c

// SPDX-License-Identifier: GPL-2.0
/* ptrace.c */
/* By Ross Biro 1/23/92 */
/* edited by Linus Torvalds */
/* mangled further by Bob Manson (manson@santafe.edu) */
/* more mutilation by David Mosberger (davidm@azstarnet.com) */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/security.h>
#include <linux/signal.h>
#include <linux/audit.h>
#include <linux/seccomp.h>
#include <asm/syscall.h>

#include <linux/uaccess.h>
#include <asm/fpu.h>

#include "proto.h"
#include <linux/uio.h>
#include <linux/regset.h>

#define DEBUG	DBG_MEM
#undef DEBUG

#ifndef NT_FPREGSET
#define NT_FPREGSET NT_PRFPREG
#endif

#ifdef DEBUG
enum {
	DBG_MEM		= (1<<0),
	DBG_BPT		= (1<<1),
	DBG_MEM_ALL	= (1<<2)
};
#define DBG(fac,args)	{if ((fac) & DEBUG) printk args;}
#else
#define DBG(fac,args)
#endif

#define BREAKINST	0x00000080	/* call_pal bpt */

/*
 * does not yet catch signals sent when the child dies.
 * in exit.c or in signal.c.
 */

/*
 * Processes always block with the following stack-layout:
 *
 *  +================================+ <---- task + 2*PAGE_SIZE
 *  | PALcode saved frame (ps, pc,   | ^
 *  | gp, a0, a1, a2)		     | |
 *  +================================+ | struct pt_regs
 *  |	        		     | |
 *  | frame generated by SAVE_ALL    | |
 *  |	        		     | v
 *  +================================+
 *  |	        		     | ^
 *  | frame saved by do_switch_stack | | struct switch_stack
 *  |	        		     | v
 *  +================================+
 */

/* 
 * The following table maps a register index into the stack offset at
 * which the register is saved.  Register indices are 0-31 for integer
 * regs, 32-63 for fp regs, and 64 for the pc.  Notice that sp and
 * zero have no stack-slot and need to be treated specially (see
 * get_reg/put_reg below).
 */
enum {
	REG_R0 = 0, REG_F0 = 32, REG_FPCR = 63, REG_PC = 64
};

#define PT_REG(reg) \
  (PAGE_SIZE*2 - sizeof(struct pt_regs) + offsetof(struct pt_regs, reg))

#define SW_REG(reg) \
 (PAGE_SIZE*2 - sizeof(struct pt_regs) - sizeof(struct switch_stack) \
  + offsetof(struct switch_stack, reg))

#define FP_REG(reg) (offsetof(struct thread_info, reg))

static int regoff[] = {
	PT_REG(	   r0), PT_REG(	   r1), PT_REG(	   r2), PT_REG(	  r3),
	PT_REG(	   r4), PT_REG(	   r5), PT_REG(	   r6), PT_REG(	  r7),
	PT_REG(	   r8), SW_REG(	   r9), SW_REG(	  r10), SW_REG(	 r11),
	SW_REG(	  r12), SW_REG(	  r13), SW_REG(	  r14), SW_REG(	 r15),
	PT_REG(	  r16), PT_REG(	  r17), PT_REG(	  r18), PT_REG(	 r19),
	PT_REG(	  r20), PT_REG(	  r21), PT_REG(	  r22), PT_REG(	 r23),
	PT_REG(	  r24), PT_REG(	  r25), PT_REG(	  r26), PT_REG(	 r27),
	PT_REG(	  r28), PT_REG(	   gp),		   -1,		   -1,
	FP_REG(fp[ 0]), FP_REG(fp[ 1]), FP_REG(fp[ 2]), FP_REG(fp[ 3]),
	FP_REG(fp[ 4]), FP_REG(fp[ 5]), FP_REG(fp[ 6]), FP_REG(fp[ 7]),
	FP_REG(fp[ 8]), FP_REG(fp[ 9]), FP_REG(fp[10]), FP_REG(fp[11]),
	FP_REG(fp[12]), FP_REG(fp[13]), FP_REG(fp[14]), FP_REG(fp[15]),
	FP_REG(fp[16]), FP_REG(fp[17]), FP_REG(fp[18]), FP_REG(fp[19]),
	FP_REG(fp[20]), FP_REG(fp[21]), FP_REG(fp[22]), FP_REG(fp[23]),
	FP_REG(fp[24]), FP_REG(fp[25]), FP_REG(fp[26]), FP_REG(fp[27]),
	FP_REG(fp[28]), FP_REG(fp[29]), FP_REG(fp[30]), FP_REG(fp[31]),
	PT_REG(	   pc)
};

static unsigned long zero;

/*
 * Get address of register REGNO in task TASK.
 */
static unsigned long *
get_reg_addr(struct task_struct * task, unsigned long regno)
{
	unsigned long *addr;

	if (regno == 30) {
		addr = &task_thread_info(task)->pcb.usp;
	} else if (regno == 65) {
		addr = &task_thread_info(task)->pcb.unique;
	} else if (regno == 31 || regno > 65) {
		zero = 0;
		addr = &zero;
	} else {
		addr = task_stack_page(task) + regoff[regno];
	}
	return addr;
}

/*
 * Get contents of register REGNO in task TASK.
 */
static unsigned long
get_reg(struct task_struct * task, unsigned long regno)
{
	/* Special hack for fpcr -- combine hardware and software bits.  */
	if (regno == 63) {
		unsigned long fpcr = *get_reg_addr(task, regno);
		unsigned long swcr
		  = task_thread_info(task)->ieee_state & IEEE_SW_MASK;
		swcr = swcr_update_status(swcr, fpcr);
		return fpcr | swcr;
	}
	return *get_reg_addr(task, regno);
}

static void alpha_elf_fpregs_get(struct task_struct *target,
			 elf_fpreg_t *fpregs)  /* points to ELF_NFPREG entries */
{
	memcpy(fpregs, task_thread_info(target)->fp, sizeof(elf_fpregset_t));
}

static void alpha_elf_fpregs_set(struct task_struct *target,
			 const elf_fpreg_t *fpregs,
			 size_t nwords)
{
	size_t n = min_t(size_t, nwords, ELF_NFPREG);

	memcpy(task_thread_info(target)->fp, fpregs, n * sizeof(elf_fpreg_t));
}

static void alpha_elf_gregs_set(struct task_struct *child,
			const elf_greg_t *src,
			size_t nwords)
{
	struct pt_regs *pt = task_pt_regs(child);
	struct thread_info *ti = task_thread_info(child);
	struct switch_stack *sw = ((struct switch_stack *)pt) - 1;

	/* GPRs r0..r8 live in pt_regs */
	if (nwords > 0)
		pt->r0 = src[0];
	if (nwords > 1)
		pt->r1 = src[1];
	if (nwords > 2)
		pt->r2 = src[2];
	if (nwords > 3)
		pt->r3 = src[3];
	if (nwords > 4)
		pt->r4 = src[4];
	if (nwords > 5)
		pt->r5 = src[5];
	if (nwords > 6)
		pt->r6 = src[6];
	if (nwords > 7)
		pt->r7 = src[7];
	if (nwords > 8)
		pt->r8 = src[8];

	/* r9..r15 live in switch_stack */
	if (nwords > 9)
		sw->r9 = src[9];
	if (nwords > 10)
		sw->r10 = src[10];
	if (nwords > 11)
		sw->r11 = src[11];
	if (nwords > 12)
		sw->r12 = src[12];
	if (nwords > 13)
		sw->r13 = src[13];
	if (nwords > 14)
		sw->r14 = src[14];
	if (nwords > 15)
		sw->r15 = src[15];

	/* r16..r28 live in pt_regs */
	if (nwords > 16)
		pt->r16 = src[16];
	if (nwords > 17)
		pt->r17 = src[17];
	if (nwords > 18)
		pt->r18 = src[18];
	if (nwords > 19)
		pt->r19 = src[19];
	if (nwords > 20)
		pt->r20 = src[20];
	if (nwords > 21)
		pt->r21 = src[21];
	if (nwords > 22)
		pt->r22 = src[22];
	if (nwords > 23)
		pt->r23 = src[23];
	if (nwords > 24)
		pt->r24 = src[24];
	if (nwords > 25)
		pt->r25 = src[25];
	if (nwords > 26)
		pt->r26 = src[26];
	if (nwords > 27)
		pt->r27 = src[27];
	if (nwords > 28)
		pt->r28 = src[28];

	/* gp, usp, pc, unique */
	if (nwords > 29)
		pt->gp = src[29];

	if (nwords > 30) {
		ti->pcb.usp = src[30];
		/*
		 * If someone ever does this to current (rare), keep the
		 * hardware usp consistent.
		 */
		if (child == current)
			wrusp(src[30]);
	}

	if (nwords > 31)
		pt->pc = src[31];

	if (nwords > 32)
		ti->pcb.unique = src[32];

/*
 * PTRACE_SETREGSET can be used at a syscall-entry stop to skip the
 * syscall by setting the syscall number to -1.  The seccomp/ptrace
 * selftests use this to synthesize errno returns.
 *
 * Alpha uses r19/a3 as the error flag, so a skipped syscall with a
 * small positive r0 and a clear r19 must be normalized to an error
 * return.
 */
	if (pt->r1 == (unsigned long)-1 &&
	    pt->r19 == 0 &&
	    pt->r0 > 0 &&
	    pt->r0 < MAX_ERRNO)
		pt->r19 = 1;
}


/*
 * Write contents of register REGNO in task TASK.
 */
static int
put_reg(struct task_struct *task, unsigned long regno, unsigned long data)
{
	struct pt_regs *regs = task_pt_regs(task);

	if (regno == 63) {
		task_thread_info(task)->ieee_state
		  = ((task_thread_info(task)->ieee_state & ~IEEE_SW_MASK)
		     | (data & IEEE_SW_MASK));
		data = (data & FPCR_DYN_MASK) | ieee_swcr_to_fpcr(data);
	}

	*get_reg_addr(task, regno) = data;

	/*
	 * Alpha historically exposes r0/v0 as the syscall number at a
	 * syscall-entry stop.  The generic-entry conversion keeps the
	 * mutable syscall number in regs->r1, so old ptrace users such
	 * as strace that skip a syscall by poking r0 to -1 must also
	 * update the internal shadow syscall number.
	 *
	 * Do not mirror other r0 writes.  strace later pokes r0 to the
	 * injected return value, e.g. 42, while r1 must remain -1.
	 */

	if (regno == 0 && data == (unsigned long)-1) {
		regs->r1 = data;
		regs->r19 = 0;
	}

	return 0;
}

static inline int
read_int(struct task_struct *task, unsigned long addr, int * data)
{
	int copied = access_process_vm(task, addr, data, sizeof(int),
			FOLL_FORCE);
	return (copied == sizeof(int)) ? 0 : -EIO;
}

static inline int
write_int(struct task_struct *task, unsigned long addr, int data)
{
	int copied = access_process_vm(task, addr, &data, sizeof(int),
			FOLL_FORCE | FOLL_WRITE);
	return (copied == sizeof(int)) ? 0 : -EIO;
}

/*
 * Set breakpoint.
 */
int
ptrace_set_bpt(struct task_struct * child)
{
	int displ, i, res, reg_b, nsaved = 0;
	unsigned int insn, op_code;
	unsigned long pc;

	pc  = get_reg(child, REG_PC);
	res = read_int(child, pc, (int *) &insn);
	if (res < 0)
		return res;

	op_code = insn >> 26;
	if (op_code >= 0x30) {
		/*
		 * It's a branch: instead of trying to figure out
		 * whether the branch will be taken or not, we'll put
		 * a breakpoint at either location.  This is simpler,
		 * more reliable, and probably not a whole lot slower
		 * than the alternative approach of emulating the
		 * branch (emulation can be tricky for fp branches).
		 */
		displ = ((s32)(insn << 11)) >> 9;
		task_thread_info(child)->bpt_addr[nsaved++] = pc + 4;
		if (displ)		/* guard against unoptimized code */
			task_thread_info(child)->bpt_addr[nsaved++]
			  = pc + 4 + displ;
		DBG(DBG_BPT, ("execing branch\n"));
	} else if (op_code == 0x1a) {
		reg_b = (insn >> 16) & 0x1f;
		task_thread_info(child)->bpt_addr[nsaved++] = get_reg(child, reg_b);
		DBG(DBG_BPT, ("execing jump\n"));
	} else {
		task_thread_info(child)->bpt_addr[nsaved++] = pc + 4;
		DBG(DBG_BPT, ("execing normal insn\n"));
	}

	/* install breakpoints: */
	for (i = 0; i < nsaved; ++i) {
		res = read_int(child, task_thread_info(child)->bpt_addr[i],
			       (int *) &insn);
		if (res < 0)
			return res;
		task_thread_info(child)->bpt_insn[i] = insn;
		DBG(DBG_BPT, ("    -> next_pc=%lx\n",
			      task_thread_info(child)->bpt_addr[i]));
		res = write_int(child, task_thread_info(child)->bpt_addr[i],
				BREAKINST);
		if (res < 0)
			return res;
	}
	task_thread_info(child)->bpt_nsaved = nsaved;
	return 0;
}

/*
 * Ensure no single-step breakpoint is pending.  Returns non-zero
 * value if child was being single-stepped.
 */
int
ptrace_cancel_bpt(struct task_struct * child)
{
	int i, nsaved = task_thread_info(child)->bpt_nsaved;

	task_thread_info(child)->bpt_nsaved = 0;

	if (nsaved > 2) {
		printk("ptrace_cancel_bpt: bogus nsaved: %d!\n", nsaved);
		nsaved = 2;
	}

	for (i = 0; i < nsaved; ++i) {
		write_int(child, task_thread_info(child)->bpt_addr[i],
			  task_thread_info(child)->bpt_insn[i]);
	}
	return (nsaved != 0);
}

void user_enable_single_step(struct task_struct *child)
{
	/* Mark single stepping.  */
	task_thread_info(child)->bpt_nsaved = -1;
}

void user_disable_single_step(struct task_struct *child)
{
	ptrace_cancel_bpt(child);
}

/*
 * Called by kernel/ptrace.c when detaching..
 *
 * Make sure the single step bit is not set.
 */
void ptrace_disable(struct task_struct *child)
{ 
	user_disable_single_step(child);
}

long arch_ptrace(struct task_struct *child, long request,
		 unsigned long addr, unsigned long data)
{
	unsigned long tmp;
	size_t copied;
	long ret;

	switch (request) {
	/* When I and D space are separate, these will need to be fixed.  */
	case PTRACE_PEEKTEXT: /* read word at location addr. */
	case PTRACE_PEEKDATA:
		copied = ptrace_access_vm(child, addr, &tmp, sizeof(tmp),
				FOLL_FORCE);
		ret = -EIO;
		if (copied != sizeof(tmp))
			break;
		
		force_successful_syscall_return();
		ret = tmp;
		break;

	/* Read register number ADDR. */
	case PTRACE_PEEKUSR:
		force_successful_syscall_return();
		ret = get_reg(child, addr);
		DBG(DBG_MEM, ("peek $%lu->%#lx\n", addr, ret));
		break;

	/* When I and D space are separate, this will have to be fixed.  */
	case PTRACE_POKETEXT: /* write the word at location addr. */
	case PTRACE_POKEDATA:
		ret = generic_ptrace_pokedata(child, addr, data);
		break;

	case PTRACE_POKEUSR: /* write the specified register */
		DBG(DBG_MEM, ("poke $%lu<-%#lx\n", addr, data));
		ret = put_reg(child, addr, data);
		break;
	default:
		ret = ptrace_request(child, request, addr, data);
		break;
	}
	return ret;
}

asmlinkage unsigned long syscall_trace_enter(void)
{
	struct pt_regs *regs = current_pt_regs();

	if (test_thread_flag(TIF_SYSCALL_TRACE) &&
		!ptrace_report_syscall_permit_entry(regs)) {
		syscall_set_nr(current, regs, -1);
		if (regs->r19 == 0 && regs->r0 == (unsigned long)-1)
			syscall_set_return_value(current, regs, -ENOSYS, 0);
		return -1UL;
	}

	/*
	 * Do the secure computing after ptrace; failures should be fast.
	 * If this fails, seccomp may already have set up the return value
	 * (e.g. SECCOMP_RET_ERRNO / TRACE).
	 */
	if (!seccomp_permit_syscall()) {
		if (regs->r19 == 0 && regs->r0 == (unsigned long)-1)
			syscall_set_return_value(current, regs, -ENOSYS, 0);
		syscall_set_nr(current, regs, -1);
		return -1UL;
	}

#ifdef CONFIG_AUDITSYSCALL
	audit_syscall_entry(syscall_get_nr(current, regs),
		regs->r16, regs->r17, regs->r18, regs->r19);
#endif
	return syscall_get_nr(current, regs);
}



asmlinkage void
syscall_trace_leave(void)
{
	audit_syscall_exit(current_pt_regs());
	if (test_thread_flag(TIF_SYSCALL_TRACE))
		ptrace_report_syscall_exit(current_pt_regs(), 0);
}

/*
 * Minimal regset support for Alpha.
 *
 * Alpha-specific notes:
 *  - Do NOT use ELF_CORE_COPY_REGS(): it uses current_thread_info(),
 *    which is wrong for non-current tasks.
 *  - dump_elf_task() returns 1 unconditionally in this tree, while
 *    regset_get should return 0 on success. So call dump_elf_thread()
 *    directly and return membuf_write()'s result.
 */

static int alpha_regset_set(struct task_struct *target,
			    const struct user_regset *regset,
			    unsigned int pos, unsigned int count,
			    const void *kbuf,
			    const void __user *ubuf)
{
	elf_gregset_t gregs;
	unsigned int nwords;

	if (pos + count > sizeof(gregs))
		return -EIO;

	/*
	 * Preserve registers outside the written range.
	 */
	dump_elf_thread(gregs, task_pt_regs(target),
			task_thread_info(target));

	if (user_regset_copyin(&pos, &count, &kbuf, &ubuf,
				gregs, 0, sizeof(gregs)))
		return -EFAULT;

	nwords = sizeof(gregs) / sizeof(elf_greg_t);
	alpha_elf_gregs_set(target, gregs, nwords);

	return 0;
}

static int alpha_fpregset_set(struct task_struct *target,
			      const struct user_regset *regset,
			      unsigned int pos, unsigned int count,
			      const void *kbuf,
			      const void __user *ubuf)
{
	elf_fpregset_t fpregs;
	unsigned int nwords;

	if (pos + count > sizeof(fpregs))
		return -EIO;

	alpha_elf_fpregs_get(target, fpregs);

	if (user_regset_copyin(&pos, &count, &kbuf, &ubuf,
				fpregs, 0, sizeof(fpregs)))
		return -EFAULT;

	nwords = sizeof(fpregs) / sizeof(elf_fpreg_t);
	alpha_elf_fpregs_set(target, fpregs, nwords);

	return 0;
}

static int alpha_regset_get(struct task_struct *target,
			    const struct user_regset *regset,
			    struct membuf to)
{
	struct pt_regs *pt = task_pt_regs(target);
	struct thread_info *ti = task_thread_info(target);
	elf_gregset_t gregs;

	dump_elf_thread(gregs, pt, ti);
	return membuf_write(&to, gregs, sizeof(gregs));
}

static int alpha_fpregset_get(struct task_struct *target,
			      const struct user_regset *regset,
			      struct membuf to)
{
	elf_fpregset_t fpregs;

	alpha_elf_fpregs_get(target, fpregs);
	return membuf_write(&to, fpregs, sizeof(fpregs));
}

enum alpha_regset {
	REGSET_GPR,
	REGSET_FPR,
};

static const struct user_regset alpha_user_regsets[] = {
	[REGSET_GPR] = {
		.core_note_type	= NT_PRSTATUS,
		.n		= ELF_NGREG,
		.size		= sizeof(elf_greg_t),
		.align		= sizeof(elf_greg_t),
		.regset_get	= alpha_regset_get,
		.set		= alpha_regset_set,
	},
	[REGSET_FPR] = {
		.core_note_type	= NT_PRFPREG,
		.core_note_name	= "CORE",
		.n		= ELF_NFPREG,
		.size		= sizeof(elf_fpreg_t),
		.align		= sizeof(elf_fpreg_t),
		.regset_get	= alpha_fpregset_get,
		.set		= alpha_fpregset_set,
	},
};

static const struct user_regset_view user_alpha_view = {
	.name		= "alpha",
	.e_machine	= EM_ALPHA,
	.ei_osabi	= ELF_OSABI,
	.regsets	= alpha_user_regsets,
	.n		= ARRAY_SIZE(alpha_user_regsets),
};

const struct user_regset_view *task_user_regset_view(struct task_struct *task)
{
	return &user_alpha_view;
}