fbt_arm.c   [plain text]

/*
 * Copyright (c) 2007 Apple Inc. All rights reserved.
 */
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/* #pragma ident	"@(#)fbt.c	1.15	05/09/19 SMI" */

#ifdef KERNEL
#ifndef _KERNEL
#define _KERNEL			/* Solaris vs. Darwin */
#endif
#endif

#define MACH__POSIX_C_SOURCE_PRIVATE 1	/* pulls in suitable savearea from
					 * mach/ppc/thread_status.h */
#include <kern/thread.h>
#include <mach/thread_status.h>
#include <arm/proc_reg.h>
#include <arm/caches_internal.h>

#include <mach-o/loader.h>
#include <mach-o/nlist.h>
#include <libkern/kernel_mach_header.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/conf.h>
#include <sys/fcntl.h>
#include <miscfs/devfs/devfs.h>

#include <sys/dtrace.h>
#include <sys/dtrace_impl.h>
#include <sys/fbt.h>

#include <sys/dtrace_glue.h>

#define DTRACE_INVOP_PUSH_FRAME 11

#define DTRACE_INVOP_NOP_SKIP		4
#define DTRACE_INVOP_ADD_FP_SP_SKIP	4

#define DTRACE_INVOP_POP_PC_SKIP 2

/*
 * stp	fp, lr, [sp, #val]
 * stp	fp, lr, [sp, #val]!
 */
#define FBT_IS_ARM64_FRAME_PUSH(x)	\
	(((x) & 0xffc07fff) == 0xa9007bfd || ((x) & 0xffc07fff) == 0xa9807bfd)

/*
 * stp	Xt1, Xt2, [sp, #val]
 * stp	Xt1, Xt2, [sp, #val]!
 */
#define FBT_IS_ARM64_PUSH(x)		\
	(((x) & 0xffc003e0) == 0xa90003e0 || ((x) & 0xffc003e0) == 0xa98003e0)

/*
 * ldp	fp, lr, [sp,  #val]
 * ldp	fp, lr, [sp], #val
 */
#define FBT_IS_ARM64_FRAME_POP(x)	\
	(((x) & 0xffc07fff) == 0xa9407bfd || ((x) & 0xffc07fff) == 0xa8c07bfd)

#define FBT_IS_ARM64_ADD_FP_SP(x)	(((x) & 0xffc003ff) == 0x910003fd)	/* add fp, sp, #val  (add fp, sp, #0 == mov fp, sp) */
#define FBT_IS_ARM64_RET(x)		((x) == 0xd65f03c0) 			/* ret */


#define FBT_B_MASK 			0xff000000
#define FBT_B_IMM_MASK			0x00ffffff
#define FBT_B_INSTR			0x14000000

#define FBT_IS_ARM64_B_INSTR(x)		((x & FBT_B_MASK) == FBT_B_INSTR)
#define FBT_GET_ARM64_B_IMM(x)		((x & FBT_B_IMM_MASK) << 2)

#define	FBT_PATCHVAL			0xe7eeee7e
#define FBT_AFRAMES_ENTRY		7
#define FBT_AFRAMES_RETURN		7

#define	FBT_ENTRY	"entry"
#define	FBT_RETURN	"return"
#define	FBT_ADDR2NDX(addr)	((((uintptr_t)(addr)) >> 4) & fbt_probetab_mask)

extern dtrace_provider_id_t	fbt_id;
extern fbt_probe_t		 **fbt_probetab;
extern int      		fbt_probetab_mask;

kern_return_t fbt_perfCallback(int, struct arm_saved_state *, __unused int, __unused int);

int
fbt_invop(uintptr_t addr, uintptr_t * stack, uintptr_t rval)
{
	fbt_probe_t    *fbt = fbt_probetab[FBT_ADDR2NDX(addr)];

	for (; fbt != NULL; fbt = fbt->fbtp_hashnext) {
		if ((uintptr_t) fbt->fbtp_patchpoint == addr) {
			if (0 == CPU->cpu_dtrace_invop_underway) {
				CPU->cpu_dtrace_invop_underway = 1;	/* Race not possible on
									 * this per-cpu state */

				if (fbt->fbtp_roffset == 0) {
					/*
					 * Stack looks like this:
					 *	
					 *	[Higher addresses]
					 *	
					 *	Frame of caller
					 *	Extra args for callee
					 *	------------------------ 
					 *	Frame from traced function: <previous sp (e.g. 0x1000), return address>
					 *	------------------------
					 *	arm_context_t
					 *	------------------------
					 *	Frame from trap handler:  <previous sp (e.g. 0x1000) , traced PC >
					 *				The traced function never got to mov fp, sp,
					 *				so there is no frame in the backtrace pointing 
					 *				to the frame on the stack containing the LR in the
					 *				caller.
					 *	------------------------
					 *	     |
					 *	     |
					 *	     |  stack grows this way
					 *	     |
					 *	     |
					 *	     v
					 *	[Lower addresses]
					 */

					arm_saved_state_t *regs = (arm_saved_state_t *)(&((arm_context_t *)stack)->ss);

					/* 
					 * cpu_dtrace_caller compensates for fact that the traced function never got to update its fp. 
					 * When walking the stack, when we reach the frame where we extract a PC in the patched 
					 * function, we put the cpu_dtrace_caller in the backtrace instead.  The next frame we extract
					 * will be in the caller's caller, so we output a backtrace starting at the caller and going 
					 * sequentially up the stack.
					 */
					CPU->cpu_dtrace_caller = get_saved_state_lr(regs); 
					dtrace_probe(fbt->fbtp_id, get_saved_state_reg(regs, 0), get_saved_state_reg(regs, 1),
					    get_saved_state_reg(regs, 2), get_saved_state_reg(regs, 3),get_saved_state_reg(regs, 4));
					CPU->cpu_dtrace_caller = 0;
				} else {
					/*
					 * When fbtp_roffset is non-zero, we know we are handling a return probe point.
					 * 
					 *
					 * Stack looks like this, as we've already popped the frame in the traced callee, and
					 * we trap with lr set to the return address in the caller.
					 *	[Higher addresses]
					 *	
					 *	Frame of caller
					 *	Extra args for callee
					 *	------------------------ 
					 *	arm_context_t
					 *	------------------------
					 *	Frame from trap handler:  <sp at time of trap, traced PC >
					 *	------------------------
					 *	     |
					 *	     |
					 *	     |  stack grows this way
					 *	     |
					 *	     |
					 *	     v
					 *	[Lower addresses]
					 */
					arm_saved_state_t *regs = (arm_saved_state_t *)(&((arm_context_t *)stack)->ss);

					CPU->cpu_dtrace_caller = get_saved_state_lr(regs);
					dtrace_probe(fbt->fbtp_id, fbt->fbtp_roffset, rval, 0, 0, 0);
					CPU->cpu_dtrace_caller = 0;
				}
				CPU->cpu_dtrace_invop_underway = 0;
			}
		
			/*
				On other architectures, we return a DTRACE constant to let the callback function
				know what was replaced. On the ARM, since the function prologue/epilogue machine code
				can vary, we need the actual bytes of the instruction, so return the savedval instead.
			*/
			return (fbt->fbtp_savedval);
		}
	}

	return (0);
}

#define IS_USER_TRAP(regs)   (PSR64_IS_USER(get_saved_state_cpsr(regs)))
#define T_INVALID_OPCODE EXC_BAD_INSTRUCTION
#define FBT_EXCEPTION_CODE T_INVALID_OPCODE

kern_return_t
fbt_perfCallback(
		 int trapno,
		 struct arm_saved_state * regs,
		 __unused int unused1,
		 __unused int unused2)
{
	kern_return_t   retval = KERN_FAILURE;

	if (FBT_EXCEPTION_CODE == trapno && !IS_USER_TRAP(regs)) {
		boolean_t oldlevel = 0;
		machine_inst_t emul = 0;
		uint64_t sp, pc, lr, imm;

		oldlevel = ml_set_interrupts_enabled(FALSE);

		__asm__ volatile(
			"Ldtrace_invop_callsite_pre_label:\n"
			".data\n"
			".private_extern _dtrace_invop_callsite_pre\n"
			"_dtrace_invop_callsite_pre:\n"
			"  .quad Ldtrace_invop_callsite_pre_label\n"
			".text\n"
				 );

		emul = dtrace_invop(get_saved_state_pc(regs), (uintptr_t*) regs, get_saved_state_reg(regs,0));

		__asm__ volatile(
			"Ldtrace_invop_callsite_post_label:\n"
			".data\n"
			".private_extern _dtrace_invop_callsite_post\n"
			"_dtrace_invop_callsite_post:\n"
			"  .quad Ldtrace_invop_callsite_post_label\n"
			".text\n"
				 );

		if (emul == DTRACE_INVOP_NOP) {
			/*
			 * Skip over the patched NOP planted by sdt
			 */
			pc = get_saved_state_pc(regs);
			set_saved_state_pc(regs, pc + DTRACE_INVOP_NOP_SKIP);
			retval = KERN_SUCCESS;
		} else if (FBT_IS_ARM64_ADD_FP_SP(emul)) {
			/* retrieve the value to add */
			uint64_t val = (emul >> 10) & 0xfff;
			assert(val < 4096);

			/* retrieve sp */
			sp = get_saved_state_sp(regs);

			/*
			 * emulate the instruction:
			 * 	add 	fp, sp, #val
			 */
			assert(sp < (UINT64_MAX - val));
			set_saved_state_fp(regs, sp + val);

			/* skip over the bytes of the patched instruction */
			pc = get_saved_state_pc(regs);
			set_saved_state_pc(regs, pc + DTRACE_INVOP_ADD_FP_SP_SKIP);

			retval = KERN_SUCCESS;
		} else if (FBT_IS_ARM64_RET(emul)) {
			lr = get_saved_state_lr(regs);
			set_saved_state_pc(regs, lr);
			retval = KERN_SUCCESS;			
		} else if (FBT_IS_ARM64_B_INSTR(emul)) {
			pc = get_saved_state_pc(regs);
			imm = FBT_GET_ARM64_B_IMM(emul);
			set_saved_state_pc(regs, pc + imm);
			retval = KERN_SUCCESS;
		} else if (emul == FBT_PATCHVAL) {
			/* Means we encountered an error but handled it, try same inst again */
			retval = KERN_SUCCESS;
		} else {
			retval = KERN_FAILURE;
		}

		ml_set_interrupts_enabled(oldlevel);
	}

	return retval;
}

void
fbt_provide_probe(struct modctl *ctl, uintptr_t instrLow, uintptr_t instrHigh, char *modname, char* symbolName, machine_inst_t* symbolStart)
{
	unsigned int	j;
        int		doenable = 0;
	dtrace_id_t	thisid;

	fbt_probe_t	*newfbt, *retfbt, *entryfbt;
	machine_inst_t *instr, *pushinstr = NULL, *limit, theInstr;
	int             foundPushLR, savedRegs;
	
	/*
	 * Guard against null symbols
	 */
	if (!symbolStart || !instrLow || !instrHigh) {
		kprintf("dtrace: %s has an invalid address\n", symbolName);
		return;
	}

	/*
	 * Assume the compiler doesn't schedule instructions in the prologue.
	 */

	foundPushLR = 0;
	savedRegs = -1;
	limit = (machine_inst_t *)instrHigh;

	assert(sizeof(*instr) == 4);

	for (j = 0, instr = symbolStart, theInstr = 0;
	     (j < 8) && ((uintptr_t)instr >= instrLow) && (instrHigh > (uintptr_t)(instr)); j++, instr++)
	{
		/*
		 * Count the number of time we pushed something onto the stack
		 * before hitting a frame push. That will give us an estimation
		 * of how many stack pops we should expect when looking for the
		 * RET instruction.
		 */
		theInstr = *instr;
		if (FBT_IS_ARM64_FRAME_PUSH(theInstr)) {
			foundPushLR = 1;
			pushinstr = instr;
		}

		if (foundPushLR && (FBT_IS_ARM64_ADD_FP_SP(theInstr)))
			/* Guard against a random setting of fp from sp, we make sure we found the push first */
			break;
		if (FBT_IS_ARM64_RET(theInstr)) /* We've gone too far, bail. */
			break;
		if (FBT_IS_ARM64_FRAME_POP(theInstr)) /* We've gone too far, bail. */
			break;
	}

	if (!(foundPushLR && (FBT_IS_ARM64_ADD_FP_SP(theInstr)))) {
		return;
	}

	thisid = dtrace_probe_lookup(fbt_id, modname, symbolName, FBT_ENTRY);
	newfbt = kmem_zalloc(sizeof(fbt_probe_t), KM_SLEEP);
	newfbt->fbtp_next = NULL;
	strlcpy( (char *)&(newfbt->fbtp_name), symbolName, MAX_FBTP_NAME_CHARS );
		
	if (thisid != 0) {
		/*
		 * The dtrace_probe previously existed, so we have to hook
		 * the newfbt entry onto the end of the existing fbt's
		 * chain.
		 * If we find an fbt entry that was previously patched to
		 * fire, (as indicated by the current patched value), then
		 * we want to enable this newfbt on the spot.
		 */
		entryfbt = dtrace_probe_arg (fbt_id, thisid);
		ASSERT (entryfbt != NULL);
		for(; entryfbt != NULL; entryfbt = entryfbt->fbtp_next) {
			if (entryfbt->fbtp_currentval == entryfbt->fbtp_patchval)
				doenable++;

			if (entryfbt->fbtp_next == NULL) {
				entryfbt->fbtp_next = newfbt;
				newfbt->fbtp_id = entryfbt->fbtp_id;
				break;
			}
		}
	}
	else {
		/*
		 * The dtrace_probe did not previously exist, so we
		 * create it and hook in the newfbt.  Since the probe is
		 * new, we obviously do not need to enable it on the spot.
		 */
		newfbt->fbtp_id = dtrace_probe_create(fbt_id, modname, symbolName, FBT_ENTRY, FBT_AFRAMES_ENTRY, newfbt);
		doenable = 0;
	}

	newfbt->fbtp_patchpoint = instr;
	newfbt->fbtp_ctl = ctl;
	newfbt->fbtp_loadcnt = ctl->mod_loadcnt;
	newfbt->fbtp_rval = DTRACE_INVOP_PUSH_FRAME;
	newfbt->fbtp_savedval = theInstr;
	newfbt->fbtp_patchval = FBT_PATCHVAL;
	newfbt->fbtp_currentval = 0;
	newfbt->fbtp_hashnext = fbt_probetab[FBT_ADDR2NDX(instr)];
	fbt_probetab[FBT_ADDR2NDX(instr)] = newfbt;

	if (doenable)
		fbt_enable(NULL, newfbt->fbtp_id, newfbt);

	/*
	 * The fbt entry chain is in place, one entry point per symbol.
	 * The fbt return chain can have multiple return points per
	 * symbol.
	 * Here we find the end of the fbt return chain.
	 */

	doenable=0;

	thisid = dtrace_probe_lookup(fbt_id, modname, symbolName, FBT_RETURN);
		
	if (thisid != 0) {
		/* The dtrace_probe previously existed, so we have to
		 * find the end of the existing fbt chain.  If we find
		 * an fbt return that was previously patched to fire,
		 * (as indicated by the currrent patched value), then
		 * we want to enable any new fbts on the spot.
		 */
		retfbt = dtrace_probe_arg (fbt_id, thisid);
		ASSERT(retfbt != NULL);
		for (;  retfbt != NULL; retfbt =  retfbt->fbtp_next) {
			if (retfbt->fbtp_currentval == retfbt->fbtp_patchval)
				doenable++;
			if(retfbt->fbtp_next == NULL)
				break;
		}
	}
	else {
		doenable = 0;
		retfbt = NULL;
	}

	/*
	 * Go back to the start of the function, in case
	 * the compiler emitted pcrel data loads
	 * before FP was adjusted.
	 */
	instr = pushinstr + 1;
again:
	if (instr >= limit)
		return;

	/* XXX FIXME ... extra jump table detection? */

	/*
	 * OK, it's an instruction.
	 */
	theInstr = *instr;
		
	/* Walked onto the start of the next routine? If so, bail out from this function */
	if (FBT_IS_ARM64_FRAME_PUSH(theInstr)) {
		if (!retfbt)
			kprintf("dtrace: fbt: No return probe for %s, walked to next routine at 0x%016llx\n",symbolName,(uint64_t)instr);
		return;
	}

	/* XXX fancy detection of end of function using PC-relative loads */

	/*
	 * Look for:
	 * 	ldp fp, lr, [sp], #val
	 * 	ldp fp, lr, [sp,  #val]
	 */
	if (!FBT_IS_ARM64_FRAME_POP(theInstr)) {
		instr++;
		goto again;
	}

	/* go to the next instruction */
	instr++;

	/* Scan ahead for a ret or a branch outside the function */
	for (; instr < limit; instr++) {
		theInstr = *instr;
		if (FBT_IS_ARM64_RET(theInstr))
			break;
		if (FBT_IS_ARM64_B_INSTR(theInstr)) {
			machine_inst_t *dest = instr + FBT_GET_ARM64_B_IMM(theInstr);
			/*
			 * Check whether the destination of the branch
			 * is outside of the function
			 */
			if (dest >= limit || dest < symbolStart)
				break;
		}
	}

	if (!FBT_IS_ARM64_RET(theInstr) && !FBT_IS_ARM64_B_INSTR(theInstr))
		return;

	newfbt = kmem_zalloc(sizeof(fbt_probe_t), KM_SLEEP);
	newfbt->fbtp_next = NULL;	
	strlcpy( (char *)&(newfbt->fbtp_name), symbolName, MAX_FBTP_NAME_CHARS );

	if (retfbt == NULL) {
		newfbt->fbtp_id = dtrace_probe_create(fbt_id, modname,
		    symbolName, FBT_RETURN, FBT_AFRAMES_RETURN, newfbt);
	} else {
		retfbt->fbtp_next = newfbt;
		newfbt->fbtp_id = retfbt->fbtp_id;
	}

	retfbt = newfbt;
	newfbt->fbtp_patchpoint = instr;
	newfbt->fbtp_ctl = ctl;
	newfbt->fbtp_loadcnt = ctl->mod_loadcnt;

	ASSERT(FBT_IS_ARM64_RET(theInstr));
	newfbt->fbtp_rval = DTRACE_INVOP_RET;
	newfbt->fbtp_roffset = (uintptr_t) ((uint8_t*) instr - (uint8_t *)symbolStart);
	newfbt->fbtp_savedval = theInstr;
	newfbt->fbtp_patchval = FBT_PATCHVAL;
	newfbt->fbtp_currentval = 0;
	newfbt->fbtp_hashnext = fbt_probetab[FBT_ADDR2NDX(instr)];
	fbt_probetab[FBT_ADDR2NDX(instr)] = newfbt;

	if (doenable)
		fbt_enable(NULL, newfbt->fbtp_id, newfbt);

	instr++;
	goto again;
}

void
fbt_provide_module_kernel_syms(struct modctl *ctl)
{
	kernel_mach_header_t		*mh;
	struct load_command		*cmd;
	kernel_segment_command_t	*orig_ts = NULL, *orig_le = NULL;
	struct symtab_command 		*orig_st = NULL;
	kernel_nlist_t			*sym = NULL;
	char				*strings;
	uintptr_t			instrLow, instrHigh;
	char				*modname;
	unsigned int			i;

	mh = (kernel_mach_header_t *)(ctl->mod_address);
	modname = ctl->mod_modname;
	
	/*
	 * Employees of dtrace and their families are ineligible.  Void
	 * where prohibited.
	 */

	if (mh->magic != MH_MAGIC_KERNEL)
		return;

	cmd = (struct load_command *) & mh[1];
	for (i = 0; i < mh->ncmds; i++) {
		if (cmd->cmd == LC_SEGMENT_KERNEL) {
			kernel_segment_command_t *orig_sg = (kernel_segment_command_t *) cmd;

			if (LIT_STRNEQL(orig_sg->segname, SEG_TEXT))
				orig_ts = orig_sg;
			else if (LIT_STRNEQL(orig_sg->segname, SEG_LINKEDIT))
				orig_le = orig_sg;
			else if (LIT_STRNEQL(orig_sg->segname, ""))
				orig_ts = orig_sg;	/* kexts have a single
							 * unnamed segment */
		} else if (cmd->cmd == LC_SYMTAB)
			orig_st = (struct symtab_command *) cmd;

		cmd = (struct load_command *) ((caddr_t) cmd + cmd->cmdsize);
	}

	if ((orig_ts == NULL) || (orig_st == NULL) || (orig_le == NULL))
		return;

	sym = (kernel_nlist_t *)(orig_le->vmaddr + orig_st->symoff - orig_le->fileoff);
	strings = (char *)(orig_le->vmaddr + orig_st->stroff - orig_le->fileoff);

	/* Find extent of the TEXT section */
	instrLow = (uintptr_t) orig_ts->vmaddr;
	instrHigh = (uintptr_t) (orig_ts->vmaddr + orig_ts->vmsize);

	for (i = 0; i < orig_st->nsyms; i++) {
		uint8_t         n_type = sym[i].n_type & (N_TYPE | N_EXT);
		char           *name = strings + sym[i].n_un.n_strx;

		/* Check that the symbol is a global and that it has a name. */
		if (((N_SECT | N_EXT) != n_type && (N_ABS | N_EXT) != n_type))
			continue;

		if (0 == sym[i].n_un.n_strx)	/* iff a null, "", name. */
			continue;

		/* Lop off omnipresent leading underscore. */
		if (*name == '_')
			name += 1;

                /*
		 * We're only blacklisting functions in the kernel for now.
		 */
		if (MOD_IS_MACH_KERNEL(ctl) && fbt_excluded(name))
			continue;

		fbt_provide_probe(ctl, instrLow, instrHigh, modname, name, (machine_inst_t*)sym[i].n_value);
	}
}