mirror of
https://github.com/morgan9e/systemd
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d15811d7e5
Sometimes it's nice being able to store dev_t as pointer values in hashmaps/tables, instead of having to allocate memory for them and using devt_hash_ops. After all dev_t is weird on Linux/glibc: glibc defines it as 64bit entity (which hence appears as something we cannot encode in a pointer value for compat with 32bit archs) but it actually is 32bit in the kernel apis. Hence we can safely cut off the upper 32bit, and still retain compat with all archs. But let's hide this in new macros, and validate this is all correct via a test.
63 lines
2.7 KiB
C
63 lines
2.7 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#pragma once
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#include <inttypes.h>
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#include <stdbool.h>
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#include <sys/types.h>
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#include "stdio-util.h"
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int parse_devnum(const char *s, dev_t *ret);
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#define DEVNUM_MAJOR_MAX ((UINT32_C(1) << 12) - 1U)
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#define DEVNUM_MINOR_MAX ((UINT32_C(1) << 20) - 1U)
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/* glibc and the Linux kernel have different ideas about the major/minor size. These calls will check whether the
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* specified major is valid by the Linux kernel's standards, not by glibc's. Linux has 20bits of minor, and 12 bits of
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* major space. See MINORBITS in linux/kdev_t.h in the kernel sources. (If you wonder why we define _y here, instead of
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* comparing directly >= 0: it's to trick out -Wtype-limits, which would otherwise complain if the type is unsigned, as
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* such a test would be pointless in such a case.) */
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#define DEVICE_MAJOR_VALID(x) \
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({ \
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typeof(x) _x = (x), _y = 0; \
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_x >= _y && _x <= DEVNUM_MAJOR_MAX; \
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\
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})
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#define DEVICE_MINOR_VALID(x) \
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({ \
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typeof(x) _x = (x), _y = 0; \
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_x >= _y && _x <= DEVNUM_MINOR_MAX; \
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})
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int device_path_make_major_minor(mode_t mode, dev_t devnum, char **ret);
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int device_path_make_inaccessible(mode_t mode, char **ret);
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int device_path_make_canonical(mode_t mode, dev_t devnum, char **ret);
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int device_path_parse_major_minor(const char *path, mode_t *ret_mode, dev_t *ret_devnum);
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static inline bool devnum_set_and_equal(dev_t a, dev_t b) {
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/* Returns true if a and b definitely refer to the same device. If either is zero, this means "don't
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* know" and we'll return false */
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return a == b && a != 0;
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}
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/* Maximum string length for a major:minor string. (Note that DECIMAL_STR_MAX includes space for a trailing NUL) */
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#define DEVNUM_STR_MAX (DECIMAL_STR_MAX(dev_t)-1+1+DECIMAL_STR_MAX(dev_t))
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#define DEVNUM_FORMAT_STR "%u:%u"
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#define DEVNUM_FORMAT_VAL(d) major(d), minor(d)
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static inline char *format_devnum(dev_t d, char buf[static DEVNUM_STR_MAX]) {
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return ASSERT_PTR(snprintf_ok(buf, DEVNUM_STR_MAX, DEVNUM_FORMAT_STR, DEVNUM_FORMAT_VAL(d)));
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}
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#define FORMAT_DEVNUM(d) format_devnum((d), (char[DEVNUM_STR_MAX]) {})
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static inline bool devnum_is_zero(dev_t d) {
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return major(d) == 0 && minor(d) == 0;
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}
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#define DEVNUM_TO_PTR(u) ((void*) (uintptr_t) (u))
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#define PTR_TO_DEVNUM(p) ((dev_t) ((uintptr_t) (p)))
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