kallsyms.c

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/*
 * kallsyms.c: in-kernel printing of symbolic oopses and stack traces.
 *
 * Rewritten and vastly simplified by Rusty Russell for in-kernel
 * module loader:
 *   Copyright 2002 Rusty Russell <[email protected]> IBM Corporation
 *
 * ChangeLog:
 *
 * (25/Aug/2004) Paulo Marques <[email protected]>
 *      Changed the compression method from stem compression to "table lookup"
 *      compression (see scripts/kallsyms.c for a more complete description)
 */
#include <linux/kallsyms.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/seq_file.h>
#include <linux/fs.h>
#include <linux/kdb.h>
#include <linux/err.h>
#include <linux/proc_fs.h>
#include <linux/sched.h>    /* for cond_resched */
#include <linux/mm.h>
#include <linux/ctype.h>
#include <linux/slab.h>

#include <asm/sections.h>

#ifdef CONFIG_KALLSYMS_ALL
#define all_var 1
#else
#define all_var 0
#endif

/*
 * These will be re-linked against their real values
 * during the second link stage.
 */
extern const unsigned long kallsyms_addresses[] __attribute__((weak));
extern const u8 kallsyms_names[] __attribute__((weak));

/*
 * Tell the compiler that the count isn't in the small data section if the arch
 * has one (eg: FRV).
 */
extern const unsigned long kallsyms_num_syms
__attribute__((weak, section(".rodata")));

extern const u8 kallsyms_token_table[] __attribute__((weak));
extern const u16 kallsyms_token_index[] __attribute__((weak));

extern const unsigned long kallsyms_markers[] __attribute__((weak));

static inline int is_kernel_inittext(unsigned long addr)
{
    if (addr >= (unsigned long)_sinittext
        && addr <= (unsigned long)_einittext)
        return 1;
    return 0;
}

static inline int is_kernel_text(unsigned long addr)
{
    if ((addr >= (unsigned long)_stext && addr <= (unsigned long)_etext) ||
        arch_is_kernel_text(addr))
        return 1;
    return in_gate_area_no_mm(addr);
}

static inline int is_kernel(unsigned long addr)
{
    if (addr >= (unsigned long)_stext && addr <= (unsigned long)_end)
        return 1;
    return in_gate_area_no_mm(addr);
}

static int is_ksym_addr(unsigned long addr)
{
    if (all_var)
        return is_kernel(addr);

    return is_kernel_text(addr) || is_kernel_inittext(addr);
}

/*
 * Expand a compressed symbol data into the resulting uncompressed string,
 * given the offset to where the symbol is in the compressed stream.
 */
static unsigned int kallsyms_expand_symbol(unsigned int off, char *result)
{
    int len, skipped_first = 0;
    const u8 *tptr, *data;

    /* Get the compressed symbol length from the first symbol byte. */
    data = &kallsyms_names[off];
    len = *data;
    data++;

    /*
     * Update the offset to return the offset for the next symbol on
     * the compressed stream.
     */
    off += len + 1;

    /*
     * For every byte on the compressed symbol data, copy the table
     * entry for that byte.
     */
    while (len) {
        tptr = &kallsyms_token_table[kallsyms_token_index[*data]];
        data++;
        len--;

        while (*tptr) {
            if (skipped_first) {
                *result = *tptr;
                result++;
            } else
                skipped_first = 1;
            tptr++;
        }
    }

    *result = '\0';

    /* Return to offset to the next symbol. */
    return off;
}

/*
 * Get symbol type information. This is encoded as a single char at the
 * beginning of the symbol name.
 */
static char kallsyms_get_symbol_type(unsigned int off)
{
    /*
     * Get just the first code, look it up in the token table,
     * and return the first char from this token.
     */
    return kallsyms_token_table[kallsyms_token_index[kallsyms_names[off + 1]]];
}


/*
 * Find the offset on the compressed stream given and index in the
 * kallsyms array.
 */
static unsigned int get_symbol_offset(unsigned long pos)
{
    const u8 *name;
    int i;

    /*
     * Use the closest marker we have. We have markers every 256 positions,
     * so that should be close enough.
     */
    name = &kallsyms_names[kallsyms_markers[pos >> 8]];

    /*
     * Sequentially scan all the symbols up to the point we're searching
     * for. Every symbol is stored in a [<len>][<len> bytes of data] format,
     * so we just need to add the len to the current pointer for every
     * symbol we wish to skip.
     */
    for (i = 0; i < (pos & 0xFF); i++)
        name = name + (*name) + 1;

    return name - kallsyms_names;
}

/* Lookup the address for this symbol. Returns 0 if not found. */
unsigned long kallsyms_lookup_name(const char *name)
{
    char namebuf[KSYM_NAME_LEN];
    unsigned long i;
    unsigned int off;

    for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
        off = kallsyms_expand_symbol(off, namebuf);

        if (strcmp(namebuf, name) == 0)
            return kallsyms_addresses[i];
    }
    return module_kallsyms_lookup_name(name);
}
EXPORT_SYMBOL_GPL(kallsyms_lookup_name);

int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
                      unsigned long),
                void *data)
{
    char namebuf[KSYM_NAME_LEN];
    unsigned long i;
    unsigned int off;
    int ret;

    for (i = 0, off = 0; i < kallsyms_num_syms; i++) {
        off = kallsyms_expand_symbol(off, namebuf);
        ret = fn(data, namebuf, NULL, kallsyms_addresses[i]);
        if (ret != 0)
            return ret;
    }
    return module_kallsyms_on_each_symbol(fn, data);
}
EXPORT_SYMBOL_GPL(kallsyms_on_each_symbol);

static unsigned long get_symbol_pos(unsigned long addr,
                    unsigned long *symbolsize,
                    unsigned long *offset)
{
    unsigned long symbol_start = 0, symbol_end = 0;
    unsigned long i, low, high, mid;

    /* This kernel should never had been booted. */
    BUG_ON(!kallsyms_addresses);

    /* Do a binary search on the sorted kallsyms_addresses array. */
    low = 0;
    high = kallsyms_num_syms;

    while (high - low > 1) {
        mid = low + (high - low) / 2;
        if (kallsyms_addresses[mid] <= addr)
            low = mid;
        else
            high = mid;
    }

    /*
     * Search for the first aliased symbol. Aliased
     * symbols are symbols with the same address.
     */
    while (low && kallsyms_addresses[low-1] == kallsyms_addresses[low])
        --low;

    symbol_start = kallsyms_addresses[low];

    /* Search for next non-aliased symbol. */
    for (i = low + 1; i < kallsyms_num_syms; i++) {
        if (kallsyms_addresses[i] > symbol_start) {
            symbol_end = kallsyms_addresses[i];
            break;
        }
    }

    /* If we found no next symbol, we use the end of the section. */
    if (!symbol_end) {
        if (is_kernel_inittext(addr))
            symbol_end = (unsigned long)_einittext;
        else if (all_var)
            symbol_end = (unsigned long)_end;
        else
            symbol_end = (unsigned long)_etext;
    }

    if (symbolsize)
        *symbolsize = symbol_end - symbol_start;
    if (offset)
        *offset = addr - symbol_start;

    return low;
}

/*
 * Lookup an address but don't bother to find any names.
 */
int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
                unsigned long *offset)
{
    char namebuf[KSYM_NAME_LEN];
    if (is_ksym_addr(addr))
        return !!get_symbol_pos(addr, symbolsize, offset);

    return !!module_address_lookup(addr, symbolsize, offset, NULL, namebuf);
}

/*
 * Lookup an address
 * - modname is set to NULL if it's in the kernel.
 * - We guarantee that the returned name is valid until we reschedule even if.
 *   It resides in a module.
 * - We also guarantee that modname will be valid until rescheduled.
 */
const char *kallsyms_lookup(unsigned long addr,
                unsigned long *symbolsize,
                unsigned long *offset,
                char **modname, char *namebuf)
{
    namebuf[KSYM_NAME_LEN - 1] = 0;
    namebuf[0] = 0;

    if (is_ksym_addr(addr)) {
        unsigned long pos;

        pos = get_symbol_pos(addr, symbolsize, offset);
        /* Grab name */
        kallsyms_expand_symbol(get_symbol_offset(pos), namebuf);
        if (modname)
            *modname = NULL;
        return namebuf;
    }

    /* See if it's in a module. */
    return module_address_lookup(addr, symbolsize, offset, modname,
                     namebuf);
}

int lookup_symbol_name(unsigned long addr, char *symname)
{
    symname[0] = '\0';
    symname[KSYM_NAME_LEN - 1] = '\0';

    if (is_ksym_addr(addr)) {
        unsigned long pos;

        pos = get_symbol_pos(addr, NULL, NULL);
        /* Grab name */
        kallsyms_expand_symbol(get_symbol_offset(pos), symname);
        return 0;
    }
    /* See if it's in a module. */
    return lookup_module_symbol_name(addr, symname);
}

int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
            unsigned long *offset, char *modname, char *name)
{
    name[0] = '\0';
    name[KSYM_NAME_LEN - 1] = '\0';

    if (is_ksym_addr(addr)) {
        unsigned long pos;

        pos = get_symbol_pos(addr, size, offset);
        /* Grab name */
        kallsyms_expand_symbol(get_symbol_offset(pos), name);
        modname[0] = '\0';
        return 0;
    }
    /* See if it's in a module. */
    return lookup_module_symbol_attrs(addr, size, offset, modname, name);
}

/* Look up a kernel symbol and return it in a text buffer. */
static int __sprint_symbol(char *buffer, unsigned long address,
               int symbol_offset, int add_offset)
{
    char *modname;
    const char *name;
    unsigned long offset, size;
    int len;

    address += symbol_offset;
    name = kallsyms_lookup(address, &size, &offset, &modname, buffer);
    if (!name)
        return sprintf(buffer, "0x%lx", address);

    if (name != buffer)
        strcpy(buffer, name);
    len = strlen(buffer);
    offset -= symbol_offset;

    if (add_offset)
        len += sprintf(buffer + len, "+%#lx/%#lx", offset, size);

    if (modname)
        len += sprintf(buffer + len, " [%s]", modname);

    return len;
}

int sprint_symbol(char *buffer, unsigned long address)
{
    return __sprint_symbol(buffer, address, 0, 1);
}
EXPORT_SYMBOL_GPL(sprint_symbol);

int sprint_symbol_no_offset(char *buffer, unsigned long address)
{
    return __sprint_symbol(buffer, address, 0, 0);
}
EXPORT_SYMBOL_GPL(sprint_symbol_no_offset);

int sprint_backtrace(char *buffer, unsigned long address)
{
    return __sprint_symbol(buffer, address, -1, 1);
}

/* Look up a kernel symbol and print it to the kernel messages. */
void __print_symbol(const char *fmt, unsigned long address)
{
    char buffer[KSYM_SYMBOL_LEN];

    sprint_symbol(buffer, address);

    printk(fmt, buffer);
}
EXPORT_SYMBOL(__print_symbol);

/* To avoid using get_symbol_offset for every symbol, we carry prefix along. */
struct kallsym_iter {
    loff_t pos;
    unsigned long value;
    unsigned int nameoff; /* If iterating in core kernel symbols. */
    char type;
    char name[KSYM_NAME_LEN];
    char module_name[MODULE_NAME_LEN];
    int exported;
};

static int get_ksymbol_mod(struct kallsym_iter *iter)
{
    if (module_get_kallsym(iter->pos - kallsyms_num_syms, &iter->value,
                &iter->type, iter->name, iter->module_name,
                &iter->exported) < 0)
        return 0;
    return 1;
}

/* Returns space to next name. */
static unsigned long get_ksymbol_core(struct kallsym_iter *iter)
{
    unsigned off = iter->nameoff;

    iter->module_name[0] = '\0';
    iter->value = kallsyms_addresses[iter->pos];

    iter->type = kallsyms_get_symbol_type(off);

    off = kallsyms_expand_symbol(off, iter->name);

    return off - iter->nameoff;
}

static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
{
    iter->name[0] = '\0';
    iter->nameoff = get_symbol_offset(new_pos);
    iter->pos = new_pos;
}

/* Returns false if pos at or past end of file. */
static int update_iter(struct kallsym_iter *iter, loff_t pos)
{
    /* Module symbols can be accessed randomly. */
    if (pos >= kallsyms_num_syms) {
        iter->pos = pos;
        return get_ksymbol_mod(iter);
    }

    /* If we're not on the desired position, reset to new position. */
    if (pos != iter->pos)
        reset_iter(iter, pos);

    iter->nameoff += get_ksymbol_core(iter);
    iter->pos++;

    return 1;
}

static void *s_next(struct seq_file *m, void *p, loff_t *pos)
{
    (*pos)++;

    if (!update_iter(m->private, *pos))
        return NULL;
    return p;
}

static void *s_start(struct seq_file *m, loff_t *pos)
{
    if (!update_iter(m->private, *pos))
        return NULL;
    return m->private;
}

static void s_stop(struct seq_file *m, void *p)
{
}

static int s_show(struct seq_file *m, void *p)
{
    struct kallsym_iter *iter = m->private;

    /* Some debugging symbols have no name.  Ignore them. */
    if (!iter->name[0])
        return 0;

    if (iter->module_name[0]) {
        char type;

        /*
         * Label it "global" if it is exported,
         * "local" if not exported.
         */
        type = iter->exported ? toupper(iter->type) :
                    tolower(iter->type);
        seq_printf(m, "%pK %c %s\t[%s]\n", (void *)iter->value,
               type, iter->name, iter->module_name);
    } else
        seq_printf(m, "%pK %c %s\n", (void *)iter->value,
               iter->type, iter->name);
    return 0;
}

static const struct seq_operations kallsyms_op = {
    .start = s_start,
    .next = s_next,
    .stop = s_stop,
    .show = s_show
};

static int kallsyms_open(struct inode *inode, struct file *file)
{
    /*
     * We keep iterator in m->private, since normal case is to
     * s_start from where we left off, so we avoid doing
     * using get_symbol_offset for every symbol.
     */
    struct kallsym_iter *iter;
    int ret;

    iter = kmalloc(sizeof(*iter), GFP_KERNEL);
    if (!iter)
        return -ENOMEM;
    reset_iter(iter, 0);

    ret = seq_open(file, &kallsyms_op);
    if (ret == 0)
        ((struct seq_file *)file->private_data)->private = iter;
    else
        kfree(iter);
    return ret;
}

#ifdef  CONFIG_KGDB_KDB
const char *kdb_walk_kallsyms(loff_t *pos)
{
    static struct kallsym_iter kdb_walk_kallsyms_iter;
    if (*pos == 0) {
        memset(&kdb_walk_kallsyms_iter, 0,
               sizeof(kdb_walk_kallsyms_iter));
        reset_iter(&kdb_walk_kallsyms_iter, 0);
    }
    while (1) {
        if (!update_iter(&kdb_walk_kallsyms_iter, *pos))
            return NULL;
        ++*pos;
        /* Some debugging symbols have no name.  Ignore them. */
        if (kdb_walk_kallsyms_iter.name[0])
            return kdb_walk_kallsyms_iter.name;
    }
}
#endif  /* CONFIG_KGDB_KDB */

static const struct file_operations kallsyms_operations = {
    .open = kallsyms_open,
    .read = seq_read,
    .llseek = seq_lseek,
    .release = seq_release_private,
};

static int __init kallsyms_init(void)
{
    proc_create("kallsyms", 0444, NULL, &kallsyms_operations);
    return 0;
}
device_initcall(kallsyms_init);