^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 1) ============================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 2) Kernel-provided User Helpers
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 3) ============================
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 4)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 5) These are segment of kernel provided user code reachable from user space
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 6) at a fixed address in kernel memory. This is used to provide user space
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 7) with some operations which require kernel help because of unimplemented
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 8) native feature and/or instructions in many ARM CPUs. The idea is for this
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 9) code to be executed directly in user mode for best efficiency but which is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 10) too intimate with the kernel counter part to be left to user libraries.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 11) In fact this code might even differ from one CPU to another depending on
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 12) the available instruction set, or whether it is a SMP systems. In other
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 13) words, the kernel reserves the right to change this code as needed without
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 14) warning. Only the entry points and their results as documented here are
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 15) guaranteed to be stable.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 16)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 17) This is different from (but doesn't preclude) a full blown VDSO
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 18) implementation, however a VDSO would prevent some assembly tricks with
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 19) constants that allows for efficient branching to those code segments. And
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 20) since those code segments only use a few cycles before returning to user
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 21) code, the overhead of a VDSO indirect far call would add a measurable
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 22) overhead to such minimalistic operations.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 23)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 24) User space is expected to bypass those helpers and implement those things
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 25) inline (either in the code emitted directly by the compiler, or part of
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 26) the implementation of a library call) when optimizing for a recent enough
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 27) processor that has the necessary native support, but only if resulting
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 28) binaries are already to be incompatible with earlier ARM processors due to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 29) usage of similar native instructions for other things. In other words
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 30) don't make binaries unable to run on earlier processors just for the sake
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 31) of not using these kernel helpers if your compiled code is not going to
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 32) use new instructions for other purpose.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 33)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 34) New helpers may be added over time, so an older kernel may be missing some
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 35) helpers present in a newer kernel. For this reason, programs must check
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 36) the value of __kuser_helper_version (see below) before assuming that it is
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 37) safe to call any particular helper. This check should ideally be
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 38) performed only once at process startup time, and execution aborted early
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 39) if the required helpers are not provided by the kernel version that
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 40) process is running on.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 41)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 42) kuser_helper_version
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 43) --------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 44)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 45) Location: 0xffff0ffc
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 46)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 47) Reference declaration::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 48)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 49) extern int32_t __kuser_helper_version;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 50)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 51) Definition:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 52)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 53) This field contains the number of helpers being implemented by the
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 54) running kernel. User space may read this to determine the availability
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 55) of a particular helper.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 56)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 57) Usage example::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 58)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 59) #define __kuser_helper_version (*(int32_t *)0xffff0ffc)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 60)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 61) void check_kuser_version(void)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 62) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 63) if (__kuser_helper_version < 2) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 64) fprintf(stderr, "can't do atomic operations, kernel too old\n");
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 65) abort();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 66) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 67) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 68)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 69) Notes:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 70)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 71) User space may assume that the value of this field never changes
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 72) during the lifetime of any single process. This means that this
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 73) field can be read once during the initialisation of a library or
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 74) startup phase of a program.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 75)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 76) kuser_get_tls
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 77) -------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 78)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 79) Location: 0xffff0fe0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 80)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 81) Reference prototype::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 82)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 83) void * __kuser_get_tls(void);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 84)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 85) Input:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 86)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 87) lr = return address
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 88)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 89) Output:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 90)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 91) r0 = TLS value
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 92)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 93) Clobbered registers:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 94)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 95) none
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 96)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 97) Definition:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 98)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 99) Get the TLS value as previously set via the __ARM_NR_set_tls syscall.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 100)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 101) Usage example::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 102)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 103) typedef void * (__kuser_get_tls_t)(void);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 104) #define __kuser_get_tls (*(__kuser_get_tls_t *)0xffff0fe0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 105)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 106) void foo()
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 107) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 108) void *tls = __kuser_get_tls();
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 109) printf("TLS = %p\n", tls);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 110) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 111)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 112) Notes:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 113)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 114) - Valid only if __kuser_helper_version >= 1 (from kernel version 2.6.12).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 115)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 116) kuser_cmpxchg
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 117) -------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 118)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 119) Location: 0xffff0fc0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 120)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 121) Reference prototype::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 122)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 123) int __kuser_cmpxchg(int32_t oldval, int32_t newval, volatile int32_t *ptr);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 124)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 125) Input:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 126)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 127) r0 = oldval
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 128) r1 = newval
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 129) r2 = ptr
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 130) lr = return address
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 131)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 132) Output:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 133)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 134) r0 = success code (zero or non-zero)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 135) C flag = set if r0 == 0, clear if r0 != 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 136)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 137) Clobbered registers:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 138)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 139) r3, ip, flags
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 140)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 141) Definition:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 142)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 143) Atomically store newval in `*ptr` only if `*ptr` is equal to oldval.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 144) Return zero if `*ptr` was changed or non-zero if no exchange happened.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 145) The C flag is also set if `*ptr` was changed to allow for assembly
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 146) optimization in the calling code.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 147)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 148) Usage example::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 149)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 150) typedef int (__kuser_cmpxchg_t)(int oldval, int newval, volatile int *ptr);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 151) #define __kuser_cmpxchg (*(__kuser_cmpxchg_t *)0xffff0fc0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 152)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 153) int atomic_add(volatile int *ptr, int val)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 154) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 155) int old, new;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 156)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 157) do {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 158) old = *ptr;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 159) new = old + val;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 160) } while(__kuser_cmpxchg(old, new, ptr));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 161)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 162) return new;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 163) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 164)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 165) Notes:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 166)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 167) - This routine already includes memory barriers as needed.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 168)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 169) - Valid only if __kuser_helper_version >= 2 (from kernel version 2.6.12).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 170)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 171) kuser_memory_barrier
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 172) --------------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 173)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 174) Location: 0xffff0fa0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 175)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 176) Reference prototype::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 177)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 178) void __kuser_memory_barrier(void);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 179)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 180) Input:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 181)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 182) lr = return address
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 183)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 184) Output:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 185)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 186) none
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 187)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 188) Clobbered registers:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 189)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 190) none
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 191)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 192) Definition:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 193)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 194) Apply any needed memory barrier to preserve consistency with data modified
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 195) manually and __kuser_cmpxchg usage.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 196)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 197) Usage example::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 198)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 199) typedef void (__kuser_dmb_t)(void);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 200) #define __kuser_dmb (*(__kuser_dmb_t *)0xffff0fa0)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 201)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 202) Notes:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 203)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 204) - Valid only if __kuser_helper_version >= 3 (from kernel version 2.6.15).
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 205)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 206) kuser_cmpxchg64
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 207) ---------------
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 208)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 209) Location: 0xffff0f60
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 210)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 211) Reference prototype::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 212)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 213) int __kuser_cmpxchg64(const int64_t *oldval,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 214) const int64_t *newval,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 215) volatile int64_t *ptr);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 216)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 217) Input:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 218)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 219) r0 = pointer to oldval
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 220) r1 = pointer to newval
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 221) r2 = pointer to target value
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 222) lr = return address
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 223)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 224) Output:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 225)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 226) r0 = success code (zero or non-zero)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 227) C flag = set if r0 == 0, clear if r0 != 0
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 228)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 229) Clobbered registers:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 230)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 231) r3, lr, flags
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 232)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 233) Definition:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 234)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 235) Atomically store the 64-bit value pointed by `*newval` in `*ptr` only if `*ptr`
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 236) is equal to the 64-bit value pointed by `*oldval`. Return zero if `*ptr` was
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 237) changed or non-zero if no exchange happened.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 238)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 239) The C flag is also set if `*ptr` was changed to allow for assembly
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 240) optimization in the calling code.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 241)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 242) Usage example::
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 243)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 244) typedef int (__kuser_cmpxchg64_t)(const int64_t *oldval,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 245) const int64_t *newval,
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 246) volatile int64_t *ptr);
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 247) #define __kuser_cmpxchg64 (*(__kuser_cmpxchg64_t *)0xffff0f60)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 248)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 249) int64_t atomic_add64(volatile int64_t *ptr, int64_t val)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 250) {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 251) int64_t old, new;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 252)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 253) do {
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 254) old = *ptr;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 255) new = old + val;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 256) } while(__kuser_cmpxchg64(&old, &new, ptr));
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 257)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 258) return new;
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 259) }
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 260)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 261) Notes:
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 262)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 263) - This routine already includes memory barriers as needed.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 264)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 265) - Due to the length of this sequence, this spans 2 conventional kuser
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 266) "slots", therefore 0xffff0f80 is not used as a valid entry point.
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 267)
^8f3ce5b39 (kx 2023-10-28 12:00:06 +0300 268) - Valid only if __kuser_helper_version >= 5 (from kernel version 3.1).
Orange Pi5 kernel
Deprecated Linux kernel 5.10.110 for OrangePi 5/5B/5+ boards
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