diff options
Diffstat (limited to 'arch/arm64/kernel/vdso/gettimeofday.S')
| -rw-r--r-- | arch/arm64/kernel/vdso/gettimeofday.S | 248 |
1 files changed, 248 insertions, 0 deletions
diff --git a/arch/arm64/kernel/vdso/gettimeofday.S b/arch/arm64/kernel/vdso/gettimeofday.S new file mode 100644 index 000000000..efa79e8d4 --- /dev/null +++ b/arch/arm64/kernel/vdso/gettimeofday.S @@ -0,0 +1,248 @@ +/* + * Userspace implementations of gettimeofday() and friends. + * + * Copyright (C) 2012 ARM Limited + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see <http://www.gnu.org/licenses/>. + * + * Author: Will Deacon <will.deacon@arm.com> + */ + +#include <linux/linkage.h> +#include <asm/asm-offsets.h> +#include <asm/unistd.h> + +#define NSEC_PER_SEC_LO16 0xca00 +#define NSEC_PER_SEC_HI16 0x3b9a + +vdso_data .req x6 +use_syscall .req w7 +seqcnt .req w8 + + .macro seqcnt_acquire +9999: ldr seqcnt, [vdso_data, #VDSO_TB_SEQ_COUNT] + tbnz seqcnt, #0, 9999b + dmb ishld + ldr use_syscall, [vdso_data, #VDSO_USE_SYSCALL] + .endm + + .macro seqcnt_read, cnt + dmb ishld + ldr \cnt, [vdso_data, #VDSO_TB_SEQ_COUNT] + .endm + + .macro seqcnt_check, cnt, fail + cmp \cnt, seqcnt + b.ne \fail + .endm + + .text + +/* int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz); */ +ENTRY(__kernel_gettimeofday) + .cfi_startproc + mov x2, x30 + .cfi_register x30, x2 + + /* Acquire the sequence counter and get the timespec. */ + adr vdso_data, _vdso_data +1: seqcnt_acquire + cbnz use_syscall, 4f + + /* If tv is NULL, skip to the timezone code. */ + cbz x0, 2f + bl __do_get_tspec + seqcnt_check w9, 1b + + /* Convert ns to us. */ + mov x13, #1000 + lsl x13, x13, x12 + udiv x11, x11, x13 + stp x10, x11, [x0, #TVAL_TV_SEC] +2: + /* If tz is NULL, return 0. */ + cbz x1, 3f + ldp w4, w5, [vdso_data, #VDSO_TZ_MINWEST] + stp w4, w5, [x1, #TZ_MINWEST] +3: + mov x0, xzr + ret x2 +4: + /* Syscall fallback. */ + mov x8, #__NR_gettimeofday + svc #0 + ret x2 + .cfi_endproc +ENDPROC(__kernel_gettimeofday) + +/* int __kernel_clock_gettime(clockid_t clock_id, struct timespec *tp); */ +ENTRY(__kernel_clock_gettime) + .cfi_startproc + cmp w0, #CLOCK_REALTIME + ccmp w0, #CLOCK_MONOTONIC, #0x4, ne + b.ne 2f + + mov x2, x30 + .cfi_register x30, x2 + + /* Get kernel timespec. */ + adr vdso_data, _vdso_data +1: seqcnt_acquire + cbnz use_syscall, 7f + + bl __do_get_tspec + seqcnt_check w9, 1b + + mov x30, x2 + + cmp w0, #CLOCK_MONOTONIC + b.ne 6f + + /* Get wtm timespec. */ + ldp x13, x14, [vdso_data, #VDSO_WTM_CLK_SEC] + + /* Check the sequence counter. */ + seqcnt_read w9 + seqcnt_check w9, 1b + b 4f +2: + cmp w0, #CLOCK_REALTIME_COARSE + ccmp w0, #CLOCK_MONOTONIC_COARSE, #0x4, ne + b.ne 8f + + /* xtime_coarse_nsec is already right-shifted */ + mov x12, #0 + + /* Get coarse timespec. */ + adr vdso_data, _vdso_data +3: seqcnt_acquire + ldp x10, x11, [vdso_data, #VDSO_XTIME_CRS_SEC] + + /* Get wtm timespec. */ + ldp x13, x14, [vdso_data, #VDSO_WTM_CLK_SEC] + + /* Check the sequence counter. */ + seqcnt_read w9 + seqcnt_check w9, 3b + + cmp w0, #CLOCK_MONOTONIC_COARSE + b.ne 6f +4: + /* Add on wtm timespec. */ + add x10, x10, x13 + lsl x14, x14, x12 + add x11, x11, x14 + + /* Normalise the new timespec. */ + mov x15, #NSEC_PER_SEC_LO16 + movk x15, #NSEC_PER_SEC_HI16, lsl #16 + lsl x15, x15, x12 + cmp x11, x15 + b.lt 5f + sub x11, x11, x15 + add x10, x10, #1 +5: + cmp x11, #0 + b.ge 6f + add x11, x11, x15 + sub x10, x10, #1 + +6: /* Store to the user timespec. */ + lsr x11, x11, x12 + stp x10, x11, [x1, #TSPEC_TV_SEC] + mov x0, xzr + ret +7: + mov x30, x2 +8: /* Syscall fallback. */ + mov x8, #__NR_clock_gettime + svc #0 + ret + .cfi_endproc +ENDPROC(__kernel_clock_gettime) + +/* int __kernel_clock_getres(clockid_t clock_id, struct timespec *res); */ +ENTRY(__kernel_clock_getres) + .cfi_startproc + cmp w0, #CLOCK_REALTIME + ccmp w0, #CLOCK_MONOTONIC, #0x4, ne + b.ne 1f + + ldr x2, 5f + b 2f +1: + cmp w0, #CLOCK_REALTIME_COARSE + ccmp w0, #CLOCK_MONOTONIC_COARSE, #0x4, ne + b.ne 4f + ldr x2, 6f +2: + cbz w1, 3f + stp xzr, x2, [x1] + +3: /* res == NULL. */ + mov w0, wzr + ret + +4: /* Syscall fallback. */ + mov x8, #__NR_clock_getres + svc #0 + ret +5: + .quad CLOCK_REALTIME_RES +6: + .quad CLOCK_COARSE_RES + .cfi_endproc +ENDPROC(__kernel_clock_getres) + +/* + * Read the current time from the architected counter. + * Expects vdso_data to be initialised. + * Clobbers the temporary registers (x9 - x15). + * Returns: + * - w9 = vDSO sequence counter + * - (x10, x11) = (ts->tv_sec, shifted ts->tv_nsec) + * - w12 = cs_shift + */ +ENTRY(__do_get_tspec) + .cfi_startproc + + /* Read from the vDSO data page. */ + ldr x10, [vdso_data, #VDSO_CS_CYCLE_LAST] + ldp x13, x14, [vdso_data, #VDSO_XTIME_CLK_SEC] + ldp w11, w12, [vdso_data, #VDSO_CS_MULT] + seqcnt_read w9 + + /* Read the virtual counter. */ + isb + mrs x15, cntvct_el0 + + /* Calculate cycle delta and convert to ns. */ + sub x10, x15, x10 + /* We can only guarantee 56 bits of precision. */ + movn x15, #0xff00, lsl #48 + and x10, x15, x10 + mul x10, x10, x11 + + /* Use the kernel time to calculate the new timespec. */ + mov x11, #NSEC_PER_SEC_LO16 + movk x11, #NSEC_PER_SEC_HI16, lsl #16 + lsl x11, x11, x12 + add x15, x10, x14 + udiv x14, x15, x11 + add x10, x13, x14 + mul x13, x14, x11 + sub x11, x15, x13 + + ret + .cfi_endproc +ENDPROC(__do_get_tspec) |