path: root/erts/emulator/beam/beam_ranges.c

/*
 * %CopyrightBegin%
 *
 * Copyright Ericsson AB 2012. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * %CopyrightEnd%
 */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#include "sys.h"
#include "erl_vm.h"
#include "global.h"
#include "beam_load.h"

typedef struct {
    BeamInstr* start;		/* Pointer to start of module. */
    erts_smp_atomic_t end; /* (BeamInstr*) Points one word beyond last function in module. */
} Range;

/* Range 'end' needs to be atomic as we purge module
    by setting end=start in active code_ix */
#define RANGE_END(R) ((BeamInstr*)erts_smp_atomic_read_nob(&(R)->end))

static Range* find_range(BeamInstr* pc);
static void lookup_loc(FunctionInfo* fi, const BeamInstr* pc,
		       BeamCodeHeader*, int idx);

/*
 * The following variables keep a sorted list of address ranges for
 * each module.  It allows us to quickly find a function given an
 * instruction pointer.
 */
struct ranges {
    Range* modules;	       /* Sorted lists of module addresses. */
    Sint n;		       /* Number of range entries. */
    Sint allocated;	       /* Number of allocated entries. */
    erts_smp_atomic_t mid;     /* Cached search start point */
};
static struct ranges r[ERTS_NUM_CODE_IX];
static erts_smp_atomic_t mem_used;
static Range* write_ptr;

#ifdef HARD_DEBUG
static void check_consistency(struct ranges* p)
{
    int i;

    ASSERT(p->n <= p->allocated);
    ASSERT((Uint)(p->mid - p->modules) < p->n ||
	   (p->mid == p->modules && p->n == 0));
    for (i = 0; i < p->n; i++) {
	ASSERT(p->modules[i].start <= RANGE_END(&p->modules[i]));
	ASSERT(!i || RANGE_END(&p->modules[i-1]) < p->modules[i].start);
    }
}
#  define CHECK(r) check_consistency(r)
#else
#  define CHECK(r)
#endif /* HARD_DEBUG */

static int
rangecompare(Range* a, Range* b)
{
    if (a->start < b->start) {
	return -1;
    } else if (a->start == b->start) {
	return 0;
    } else {
	return 1;
    }
}

void
erts_init_ranges(void)
{
    Sint i;

    erts_smp_atomic_init_nob(&mem_used, 0);
    for (i = 0; i < ERTS_NUM_CODE_IX; i++) {
	r[i].modules = 0;
	r[i].n = 0;
	r[i].allocated = 0;
	erts_smp_atomic_init_nob(&r[i].mid, 0);
    }
}

void
erts_start_staging_ranges(int num_new)
{
    ErtsCodeIndex src = erts_active_code_ix();
    ErtsCodeIndex dst = erts_staging_code_ix();
    Sint need;

    if (r[dst].modules) {
	erts_smp_atomic_add_nob(&mem_used, -r[dst].allocated);
	erts_free(ERTS_ALC_T_MODULE_REFS, r[dst].modules);
    }

    need = r[dst].allocated = r[src].n + num_new;
    erts_smp_atomic_add_nob(&mem_used, need);
    write_ptr = erts_alloc(ERTS_ALC_T_MODULE_REFS,
			   need * sizeof(Range));
    r[dst].modules = write_ptr;
}

void
erts_end_staging_ranges(int commit)
{
    if (commit) {
	Sint i;
	ErtsCodeIndex src = erts_active_code_ix();
	ErtsCodeIndex dst = erts_staging_code_ix();
	Range* mp;
	Sint num_inserted;

	mp = r[dst].modules;
	num_inserted = write_ptr - mp;
	for (i = 0; i < r[src].n; i++) {
	    Range* rp = r[src].modules+i;
	    if (rp->start < RANGE_END(rp)) {
		/* Only insert a module that has not been purged. */
		write_ptr->start = rp->start;
		erts_smp_atomic_init_nob(&write_ptr->end,
					 (erts_aint_t)(RANGE_END(rp)));
		write_ptr++;
	    }
	}

	/*
	 * There are num_inserted new range entries (unsorted) at the
	 * beginning of the modules array, followed by the old entries
	 * (sorted). We must now sort the entire array.
	 */

	r[dst].n = write_ptr - mp;
	if (num_inserted > 1) {
	    qsort(mp, r[dst].n, sizeof(Range),
		  (int (*)(const void *, const void *)) rangecompare);
	} else if (num_inserted == 1) {
	    /* Sift the new range into place. This is faster than qsort(). */
	    Range t = mp[0];
	    for (i = 0; i < r[dst].n-1 && t.start > mp[i+1].start; i++) {
		mp[i] = mp[i+1];
	    }
	    mp[i] = t;
	}
	r[dst].modules = mp;
	CHECK(&r[dst]);
	erts_smp_atomic_set_nob(&r[dst].mid,
				(erts_aint_t) (r[dst].modules +
					       r[dst].n / 2));
    }
}

void
erts_update_ranges(BeamInstr* code, Uint size)
{
    ErtsCodeIndex dst = erts_staging_code_ix();
    ErtsCodeIndex src = erts_active_code_ix();

    if (src == dst) {
	ASSERT(!erts_initialized);

	/*
	 * During start-up of system, the indices are the same
	 * and erts_start_staging_ranges() has not been called.
	 */
	if (r[dst].modules == NULL) {
	    Sint need = 128;
	    erts_smp_atomic_add_nob(&mem_used, need);
	    r[dst].modules = erts_alloc(ERTS_ALC_T_MODULE_REFS,
					need * sizeof(Range));
	    r[dst].allocated = need;
	    write_ptr = r[dst].modules;
	}
    }

    ASSERT(r[dst].modules);
    write_ptr->start = code;
    erts_smp_atomic_init_nob(&(write_ptr->end),
			     (erts_aint_t)(((byte *)code) + size));
    write_ptr++;
}

void
erts_remove_from_ranges(BeamInstr* code)
{
    Range* rp = find_range(code);
    erts_smp_atomic_set_nob(&rp->end, (erts_aint_t)rp->start);
}

UWord
erts_ranges_sz(void)
{
    return erts_smp_atomic_read_nob(&mem_used) * sizeof(Range);
}

/*
 * Find a function from the given pc and fill information in
 * the FunctionInfo struct. If the full_info is non-zero, fill
 * in all available information (including location in the
 * source code). If no function is found, the 'current' field
 * will be set to NULL.
 */

void
erts_lookup_function_info(FunctionInfo* fi, BeamInstr* pc, int full_info)
{
    BeamInstr** low;
    BeamInstr** high;
    BeamInstr** mid;
    Range* rp;
    BeamCodeHeader* hdr;

    fi->current = NULL;
    fi->needed = 5;
    fi->loc = LINE_INVALID_LOCATION;
    rp = find_range(pc);
    if (rp == 0) {
	return;
    }
    hdr = (BeamCodeHeader*) rp->start;

    low = hdr->functions;
    high = low + hdr->num_functions;
    while (low < high) {
	mid = low + (high-low) / 2;
	if (pc < mid[0]) {
	    high = mid;
	} else if (pc < mid[1]) {
	    fi->current = mid[0]+2;
	    if (full_info) {
		BeamInstr** fp = hdr->functions;
		int idx = mid - fp;
		lookup_loc(fi, pc, hdr, idx);
	    }
	    return;
	} else {
	    low = mid + 1;
	}
    }
}

static Range*
find_range(BeamInstr* pc)
{
    ErtsCodeIndex active = erts_active_code_ix();
    Range* low = r[active].modules;
    Range* high = low + r[active].n;
    Range* mid = (Range *) erts_smp_atomic_read_nob(&r[active].mid);

    CHECK(&r[active]);
    while (low < high) {
	if (pc < mid->start) {
	    high = mid;
	} else if (pc >= RANGE_END(mid)) {
	    low = mid + 1;
	} else {
	    erts_smp_atomic_set_nob(&r[active].mid, (erts_aint_t) mid);
	    return mid;
	}
	mid = low + (high-low) / 2;
    }
    return 0;
}

static void
lookup_loc(FunctionInfo* fi, const BeamInstr* pc,
           BeamCodeHeader* code_hdr, int idx)
{
    BeamCodeLineTab* lt = code_hdr->line_table;
    const BeamInstr** low;
    const BeamInstr** high;
    const BeamInstr** mid;

    if (lt == NULL) {
	return;
    }

    fi->fname_ptr = lt->fname_ptr;
    low = lt->func_tab[idx];
    high = lt->func_tab[idx+1];
    while (high > low) {
	mid = low + (high-low) / 2;
	if (pc < mid[0]) {
	    high = mid;
	} else if (pc < mid[1]) {
	    int file;
	    int index = mid - lt->func_tab[0];

	    if (lt->loc_size == 2) {
		fi->loc = lt->loc_tab.p2[index];
	    } else {
		ASSERT(lt->loc_size == 4);
		fi->loc = lt->loc_tab.p4[index];
	    }
	    if (fi->loc == LINE_INVALID_LOCATION) {
		return;
	    }
	    fi->needed += 3+2+3+2;
	    file = LOC_FILE(fi->loc);
	    if (file == 0) {
		/* Special case: Module name with ".erl" appended */
		Atom* mod_atom = atom_tab(atom_val(fi->current[0]));
		fi->needed += 2*(mod_atom->len+4);
	    } else {
		Atom* ap = atom_tab(atom_val((fi->fname_ptr)[file-1]));
		fi->needed += 2*ap->len;
	    }
	    return;
	} else {
	    low = mid + 1;
	}
    }
}