x86/speculation/mmio: Enable CPU Fill buffer clearing on idle

[mirror_ubuntu-jammy-kernel.git] / lib / string_helpers.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Helpers for formatting and printing strings
 *
 * Copyright 31 August 2008 James Bottomley
 * Copyright (C) 2013, Intel Corporation
 */
#include <linux/bug.h>
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/export.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/limits.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/string_helpers.h>

/**
 * string_get_size - get the size in the specified units
 * @size:       The size to be converted in blocks
 * @blk_size:   Size of the block (use 1 for size in bytes)
 * @units:      units to use (powers of 1000 or 1024)
 * @buf:        buffer to format to
 * @len:        length of buffer
 *
 * This function returns a string formatted to 3 significant figures
 * giving the size in the required units.  @buf should have room for
 * at least 9 bytes and will always be zero terminated.
 *
 */
void string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
                     char *buf, int len)
{
        static const char *const units_10[] = {
                "B", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"
        };
        static const char *const units_2[] = {
                "B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"
        };
        static const char *const *const units_str[] = {
                [STRING_UNITS_10] = units_10,
                [STRING_UNITS_2] = units_2,
        };
        static const unsigned int divisor[] = {
                [STRING_UNITS_10] = 1000,
                [STRING_UNITS_2] = 1024,
        };
        static const unsigned int rounding[] = { 500, 50, 5 };
        int i = 0, j;
        u32 remainder = 0, sf_cap;
        char tmp[8];
        const char *unit;

        tmp[0] = '\0';

        if (blk_size == 0)
                size = 0;
        if (size == 0)
                goto out;

        /* This is Napier's algorithm.  Reduce the original block size to
         *
         * coefficient * divisor[units]^i
         *
         * we do the reduction so both coefficients are just under 32 bits so
         * that multiplying them together won't overflow 64 bits and we keep
         * as much precision as possible in the numbers.
         *
         * Note: it's safe to throw away the remainders here because all the
         * precision is in the coefficients.
         */
        while (blk_size >> 32) {
                do_div(blk_size, divisor[units]);
                i++;
        }

        while (size >> 32) {
                do_div(size, divisor[units]);
                i++;
        }

        /* now perform the actual multiplication keeping i as the sum of the
         * two logarithms */
        size *= blk_size;

        /* and logarithmically reduce it until it's just under the divisor */
        while (size >= divisor[units]) {
                remainder = do_div(size, divisor[units]);
                i++;
        }

        /* work out in j how many digits of precision we need from the
         * remainder */
        sf_cap = size;
        for (j = 0; sf_cap*10 < 1000; j++)
                sf_cap *= 10;

        if (units == STRING_UNITS_2) {
                /* express the remainder as a decimal.  It's currently the
                 * numerator of a fraction whose denominator is
                 * divisor[units], which is 1 << 10 for STRING_UNITS_2 */
                remainder *= 1000;
                remainder >>= 10;
        }

        /* add a 5 to the digit below what will be printed to ensure
         * an arithmetical round up and carry it through to size */
        remainder += rounding[j];
        if (remainder >= 1000) {
                remainder -= 1000;
                size += 1;
        }

        if (j) {
                snprintf(tmp, sizeof(tmp), ".%03u", remainder);
                tmp[j+1] = '\0';
        }

 out:
        if (i >= ARRAY_SIZE(units_2))
                unit = "UNK";
        else
                unit = units_str[units][i];

        snprintf(buf, len, "%u%s %s", (u32)size,
                 tmp, unit);
}
EXPORT_SYMBOL(string_get_size);

static bool unescape_space(char **src, char **dst)
{
        char *p = *dst, *q = *src;

        switch (*q) {
        case 'n':
                *p = '\n';
                break;
        case 'r':
                *p = '\r';
                break;
        case 't':
                *p = '\t';
                break;
        case 'v':
                *p = '\v';
                break;
        case 'f':
                *p = '\f';
                break;
        default:
                return false;
        }
        *dst += 1;
        *src += 1;
        return true;
}

static bool unescape_octal(char **src, char **dst)
{
        char *p = *dst, *q = *src;
        u8 num;

        if (isodigit(*q) == 0)
                return false;

        num = (*q++) & 7;
        while (num < 32 && isodigit(*q) && (q - *src < 3)) {
                num <<= 3;
                num += (*q++) & 7;
        }
        *p = num;
        *dst += 1;
        *src = q;
        return true;
}

static bool unescape_hex(char **src, char **dst)
{
        char *p = *dst, *q = *src;
        int digit;
        u8 num;

        if (*q++ != 'x')
                return false;

        num = digit = hex_to_bin(*q++);
        if (digit < 0)
                return false;

        digit = hex_to_bin(*q);
        if (digit >= 0) {
                q++;
                num = (num << 4) | digit;
        }
        *p = num;
        *dst += 1;
        *src = q;
        return true;
}

static bool unescape_special(char **src, char **dst)
{
        char *p = *dst, *q = *src;

        switch (*q) {
        case '\"':
                *p = '\"';
                break;
        case '\\':
                *p = '\\';
                break;
        case 'a':
                *p = '\a';
                break;
        case 'e':
                *p = '\e';
                break;
        default:
                return false;
        }
        *dst += 1;
        *src += 1;
        return true;
}

/**
 * string_unescape - unquote characters in the given string
 * @src:        source buffer (escaped)
 * @dst:        destination buffer (unescaped)
 * @size:       size of the destination buffer (0 to unlimit)
 * @flags:      combination of the flags.
 *
 * Description:
 * The function unquotes characters in the given string.
 *
 * Because the size of the output will be the same as or less than the size of
 * the input, the transformation may be performed in place.
 *
 * Caller must provide valid source and destination pointers. Be aware that
 * destination buffer will always be NULL-terminated. Source string must be
 * NULL-terminated as well.  The supported flags are::
 *
 *      UNESCAPE_SPACE:
 *              '\f' - form feed
 *              '\n' - new line
 *              '\r' - carriage return
 *              '\t' - horizontal tab
 *              '\v' - vertical tab
 *      UNESCAPE_OCTAL:
 *              '\NNN' - byte with octal value NNN (1 to 3 digits)
 *      UNESCAPE_HEX:
 *              '\xHH' - byte with hexadecimal value HH (1 to 2 digits)
 *      UNESCAPE_SPECIAL:
 *              '\"' - double quote
 *              '\\' - backslash
 *              '\a' - alert (BEL)
 *              '\e' - escape
 *      UNESCAPE_ANY:
 *              all previous together
 *
 * Return:
 * The amount of the characters processed to the destination buffer excluding
 * trailing '\0' is returned.
 */
int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
{
        char *out = dst;

        while (*src && --size) {
                if (src[0] == '\\' && src[1] != '\0' && size > 1) {
                        src++;
                        size--;

                        if (flags & UNESCAPE_SPACE &&
                                        unescape_space(&src, &out))
                                continue;

                        if (flags & UNESCAPE_OCTAL &&
                                        unescape_octal(&src, &out))
                                continue;

                        if (flags & UNESCAPE_HEX &&
                                        unescape_hex(&src, &out))
                                continue;

                        if (flags & UNESCAPE_SPECIAL &&
                                        unescape_special(&src, &out))
                                continue;

                        *out++ = '\\';
                }
                *out++ = *src++;
        }
        *out = '\0';

        return out - dst;
}
EXPORT_SYMBOL(string_unescape);

static bool escape_passthrough(unsigned char c, char **dst, char *end)
{
        char *out = *dst;

        if (out < end)
                *out = c;
        *dst = out + 1;
        return true;
}

static bool escape_space(unsigned char c, char **dst, char *end)
{
        char *out = *dst;
        unsigned char to;

        switch (c) {
        case '\n':
                to = 'n';
                break;
        case '\r':
                to = 'r';
                break;
        case '\t':
                to = 't';
                break;
        case '\v':
                to = 'v';
                break;
        case '\f':
                to = 'f';
                break;
        default:
                return false;
        }

        if (out < end)
                *out = '\\';
        ++out;
        if (out < end)
                *out = to;
        ++out;

        *dst = out;
        return true;
}

static bool escape_special(unsigned char c, char **dst, char *end)
{
        char *out = *dst;
        unsigned char to;

        switch (c) {
        case '\\':
                to = '\\';
                break;
        case '\a':
                to = 'a';
                break;
        case '\e':
                to = 'e';
                break;
        case '"':
                to = '"';
                break;
        default:
                return false;
        }

        if (out < end)
                *out = '\\';
        ++out;
        if (out < end)
                *out = to;
        ++out;

        *dst = out;
        return true;
}

static bool escape_null(unsigned char c, char **dst, char *end)
{
        char *out = *dst;

        if (c)
                return false;

        if (out < end)
                *out = '\\';
        ++out;
        if (out < end)
                *out = '0';
        ++out;

        *dst = out;
        return true;
}

static bool escape_octal(unsigned char c, char **dst, char *end)
{
        char *out = *dst;

        if (out < end)
                *out = '\\';
        ++out;
        if (out < end)
                *out = ((c >> 6) & 0x07) + '0';
        ++out;
        if (out < end)
                *out = ((c >> 3) & 0x07) + '0';
        ++out;
        if (out < end)
                *out = ((c >> 0) & 0x07) + '0';
        ++out;

        *dst = out;
        return true;
}

static bool escape_hex(unsigned char c, char **dst, char *end)
{
        char *out = *dst;

        if (out < end)
                *out = '\\';
        ++out;
        if (out < end)
                *out = 'x';
        ++out;
        if (out < end)
                *out = hex_asc_hi(c);
        ++out;
        if (out < end)
                *out = hex_asc_lo(c);
        ++out;

        *dst = out;
        return true;
}

/**
 * string_escape_mem - quote characters in the given memory buffer
 * @src:        source buffer (unescaped)
 * @isz:        source buffer size
 * @dst:        destination buffer (escaped)
 * @osz:        destination buffer size
 * @flags:      combination of the flags
 * @only:       NULL-terminated string containing characters used to limit
 *              the selected escape class. If characters are included in @only
 *              that would not normally be escaped by the classes selected
 *              in @flags, they will be copied to @dst unescaped.
 *
 * Description:
 * The process of escaping byte buffer includes several parts. They are applied
 * in the following sequence.
 *
 *      1. The character is not matched to the one from @only string and thus
 *         must go as-is to the output.
 *      2. The character is matched to the printable and ASCII classes, if asked,
 *         and in case of match it passes through to the output.
 *      3. The character is matched to the printable or ASCII class, if asked,
 *         and in case of match it passes through to the output.
 *      4. The character is checked if it falls into the class given by @flags.
 *         %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any
 *         character. Note that they actually can't go together, otherwise
 *         %ESCAPE_HEX will be ignored.
 *
 * Caller must provide valid source and destination pointers. Be aware that
 * destination buffer will not be NULL-terminated, thus caller have to append
 * it if needs. The supported flags are::
 *
 *      %ESCAPE_SPACE: (special white space, not space itself)
 *              '\f' - form feed
 *              '\n' - new line
 *              '\r' - carriage return
 *              '\t' - horizontal tab
 *              '\v' - vertical tab
 *      %ESCAPE_SPECIAL:
 *              '\"' - double quote
 *              '\\' - backslash
 *              '\a' - alert (BEL)
 *              '\e' - escape
 *      %ESCAPE_NULL:
 *              '\0' - null
 *      %ESCAPE_OCTAL:
 *              '\NNN' - byte with octal value NNN (3 digits)
 *      %ESCAPE_ANY:
 *              all previous together
 *      %ESCAPE_NP:
 *              escape only non-printable characters, checked by isprint()
 *      %ESCAPE_ANY_NP:
 *              all previous together
 *      %ESCAPE_HEX:
 *              '\xHH' - byte with hexadecimal value HH (2 digits)
 *      %ESCAPE_NA:
 *              escape only non-ascii characters, checked by isascii()
 *      %ESCAPE_NAP:
 *              escape only non-printable or non-ascii characters
 *      %ESCAPE_APPEND:
 *              append characters from @only to be escaped by the given classes
 *
 * %ESCAPE_APPEND would help to pass additional characters to the escaped, when
 * one of %ESCAPE_NP, %ESCAPE_NA, or %ESCAPE_NAP is provided.
 *
 * One notable caveat, the %ESCAPE_NAP, %ESCAPE_NP and %ESCAPE_NA have the
 * higher priority than the rest of the flags (%ESCAPE_NAP is the highest).
 * It doesn't make much sense to use either of them without %ESCAPE_OCTAL
 * or %ESCAPE_HEX, because they cover most of the other character classes.
 * %ESCAPE_NAP can utilize %ESCAPE_SPACE or %ESCAPE_SPECIAL in addition to
 * the above.
 *
 * Return:
 * The total size of the escaped output that would be generated for
 * the given input and flags. To check whether the output was
 * truncated, compare the return value to osz. There is room left in
 * dst for a '\0' terminator if and only if ret < osz.
 */
int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
                      unsigned int flags, const char *only)
{
        char *p = dst;
        char *end = p + osz;
        bool is_dict = only && *only;
        bool is_append = flags & ESCAPE_APPEND;

        while (isz--) {
                unsigned char c = *src++;
                bool in_dict = is_dict && strchr(only, c);

                /*
                 * Apply rules in the following sequence:
                 *      - the @only string is supplied and does not contain a
                 *        character under question
                 *      - the character is printable and ASCII, when @flags has
                 *        %ESCAPE_NAP bit set
                 *      - the character is printable, when @flags has
                 *        %ESCAPE_NP bit set
                 *      - the character is ASCII, when @flags has
                 *        %ESCAPE_NA bit set
                 *      - the character doesn't fall into a class of symbols
                 *        defined by given @flags
                 * In these cases we just pass through a character to the
                 * output buffer.
                 *
                 * When %ESCAPE_APPEND is passed, the characters from @only
                 * have been excluded from the %ESCAPE_NAP, %ESCAPE_NP, and
                 * %ESCAPE_NA cases.
                 */
                if (!(is_append || in_dict) && is_dict &&
                                          escape_passthrough(c, &p, end))
                        continue;

                if (!(is_append && in_dict) && isascii(c) && isprint(c) &&
                    flags & ESCAPE_NAP && escape_passthrough(c, &p, end))
                        continue;

                if (!(is_append && in_dict) && isprint(c) &&
                    flags & ESCAPE_NP && escape_passthrough(c, &p, end))
                        continue;

                if (!(is_append && in_dict) && isascii(c) &&
                    flags & ESCAPE_NA && escape_passthrough(c, &p, end))
                        continue;

                if (flags & ESCAPE_SPACE && escape_space(c, &p, end))
                        continue;

                if (flags & ESCAPE_SPECIAL && escape_special(c, &p, end))
                        continue;

                if (flags & ESCAPE_NULL && escape_null(c, &p, end))
                        continue;

                /* ESCAPE_OCTAL and ESCAPE_HEX always go last */
                if (flags & ESCAPE_OCTAL && escape_octal(c, &p, end))
                        continue;

                if (flags & ESCAPE_HEX && escape_hex(c, &p, end))
                        continue;

                escape_passthrough(c, &p, end);
        }

        return p - dst;
}
EXPORT_SYMBOL(string_escape_mem);

/*
 * Return an allocated string that has been escaped of special characters
 * and double quotes, making it safe to log in quotes.
 */
char *kstrdup_quotable(const char *src, gfp_t gfp)
{
        size_t slen, dlen;
        char *dst;
        const int flags = ESCAPE_HEX;
        const char esc[] = "\f\n\r\t\v\a\e\\\"";

        if (!src)
                return NULL;
        slen = strlen(src);

        dlen = string_escape_mem(src, slen, NULL, 0, flags, esc);
        dst = kmalloc(dlen + 1, gfp);
        if (!dst)
                return NULL;

        WARN_ON(string_escape_mem(src, slen, dst, dlen, flags, esc) != dlen);
        dst[dlen] = '\0';

        return dst;
}
EXPORT_SYMBOL_GPL(kstrdup_quotable);

/*
 * Returns allocated NULL-terminated string containing process
 * command line, with inter-argument NULLs replaced with spaces,
 * and other special characters escaped.
 */
char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp)
{
        char *buffer, *quoted;
        int i, res;

        buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
        if (!buffer)
                return NULL;

        res = get_cmdline(task, buffer, PAGE_SIZE - 1);
        buffer[res] = '\0';

        /* Collapse trailing NULLs, leave res pointing to last non-NULL. */
        while (--res >= 0 && buffer[res] == '\0')
                ;

        /* Replace inter-argument NULLs. */
        for (i = 0; i <= res; i++)
                if (buffer[i] == '\0')
                        buffer[i] = ' ';

        /* Make sure result is printable. */
        quoted = kstrdup_quotable(buffer, gfp);
        kfree(buffer);
        return quoted;
}
EXPORT_SYMBOL_GPL(kstrdup_quotable_cmdline);

/*
 * Returns allocated NULL-terminated string containing pathname,
 * with special characters escaped, able to be safely logged. If
 * there is an error, the leading character will be "<".
 */
char *kstrdup_quotable_file(struct file *file, gfp_t gfp)
{
        char *temp, *pathname;

        if (!file)
                return kstrdup("<unknown>", gfp);

        /* We add 11 spaces for ' (deleted)' to be appended */
        temp = kmalloc(PATH_MAX + 11, GFP_KERNEL);
        if (!temp)
                return kstrdup("<no_memory>", gfp);

        pathname = file_path(file, temp, PATH_MAX + 11);
        if (IS_ERR(pathname))
                pathname = kstrdup("<too_long>", gfp);
        else
                pathname = kstrdup_quotable(pathname, gfp);

        kfree(temp);
        return pathname;
}
EXPORT_SYMBOL_GPL(kstrdup_quotable_file);

/**
 * kfree_strarray - free a number of dynamically allocated strings contained
 *                  in an array and the array itself
 *
 * @array: Dynamically allocated array of strings to free.
 * @n: Number of strings (starting from the beginning of the array) to free.
 *
 * Passing a non-NULL @array and @n == 0 as well as NULL @array are valid
 * use-cases. If @array is NULL, the function does nothing.
 */
void kfree_strarray(char **array, size_t n)
{
        unsigned int i;

        if (!array)
                return;

        for (i = 0; i < n; i++)
                kfree(array[i]);
        kfree(array);
}
EXPORT_SYMBOL_GPL(kfree_strarray);

/**
 * memcpy_and_pad - Copy one buffer to another with padding
 * @dest: Where to copy to
 * @dest_len: The destination buffer size
 * @src: Where to copy from
 * @count: The number of bytes to copy
 * @pad: Character to use for padding if space is left in destination.
 */
void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count,
                    int pad)
{
        if (dest_len > count) {
                memcpy(dest, src, count);
                memset(dest + count, pad,  dest_len - count);
        } else {
                memcpy(dest, src, dest_len);
        }
}
EXPORT_SYMBOL(memcpy_and_pad);