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But instead of landing it in arm64, land the result into lib/vdso and unify both implementations to simplify future maintenance. Rename seq_count to tb_seq_count. Rename tk_is_cntvct to use_syscall. Rename cs_mult to cs_mono_mult. All to align with the variables in the arm64 vdso datapage. Rework vdso_read_begin() and vdso_read_retry() functions to reflect modern access patterns for tb_seq_count field. Update copyright message to reflect the start of the contributions in this series. Signed-off-by: Mark Salyzyn Cc: James Morse Cc: Russell King Cc: Catalin Marinas Cc: Will Deacon Cc: Andy Lutomirski Cc: Dmitry Safonov Cc: John Stultz Cc: Mark Rutland Cc: Laura Abbott Cc: Kees Cook Cc: Ard Biesheuvel Cc: Andy Gross Cc: Kevin Brodsky Cc: Andrew Pinski Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org v2: - split first CL into 1 of 7 pieces v4: - update commit message to reflect reasoning --- arch/arm/include/asm/vdso_datapage.h | 6 ++-- arch/arm/kernel/vdso.c | 17 +++++----- arch/arm/vdso/vgettimeofday.c | 61 +++++++++++++++++++----------------- 3 files changed, 45 insertions(+), 39 deletions(-) diff --git a/arch/arm/include/asm/vdso_datapage.h b/arch/arm/include/asm/vdso_datapage.h index 9be259442fca..fa3e1856244d 100644 --- a/arch/arm/include/asm/vdso_datapage.h +++ b/arch/arm/include/asm/vdso_datapage.h @@ -29,8 +29,8 @@ * 32 bytes. */ struct vdso_data { - u32 seq_count; /* sequence count - odd during updates */ - u16 tk_is_cntvct; /* fall back to syscall if false */ + u32 tb_seq_count; /* sequence count - odd during updates */ + u16 use_syscall; /* fall back to syscall if true */ u16 cs_shift; /* clocksource shift */ u32 xtime_coarse_sec; /* coarse time */ u32 xtime_coarse_nsec; @@ -38,7 +38,7 @@ struct vdso_data { u32 wtm_clock_sec; /* wall to monotonic offset */ u32 wtm_clock_nsec; u32 xtime_clock_sec; /* CLOCK_REALTIME - seconds */ - u32 cs_mult; /* clocksource multiplier */ + u32 cs_mono_mult; /* clocksource multiplier */ u64 cs_cycle_last; /* last cycle value */ u64 cs_mask; /* clocksource mask */ diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c index a4d6dc0f2427..aed84b659cc5 100644 --- a/arch/arm/kernel/vdso.c +++ b/arch/arm/kernel/vdso.c @@ -274,14 +274,14 @@ void arm_install_vdso(struct mm_struct *mm, unsigned long addr) static void vdso_write_begin(struct vdso_data *vdata) { - ++vdso_data->seq_count; + ++vdso_data->tb_seq_count; smp_wmb(); /* Pairs with smp_rmb in vdso_read_retry */ } static void vdso_write_end(struct vdso_data *vdata) { smp_wmb(); /* Pairs with smp_rmb in vdso_read_begin */ - ++vdso_data->seq_count; + ++vdso_data->tb_seq_count; } static bool tk_is_cntvct(const struct timekeeper *tk) @@ -305,10 +305,10 @@ static bool tk_is_cntvct(const struct timekeeper *tk) * counter again, making it even, indicating to userspace that the * update is finished. * - * Userspace is expected to sample seq_count before reading any other - * fields from the data page. If seq_count is odd, userspace is + * Userspace is expected to sample tb_seq_count before reading any other + * fields from the data page. If tb_seq_count is odd, userspace is * expected to wait until it becomes even. After copying data from - * the page, userspace must sample seq_count again; if it has changed + * the page, userspace must sample tb_seq_count again; if it has changed * from its previous value, userspace must retry the whole sequence. * * Calls to update_vsyscall are serialized by the timekeeping core. @@ -326,18 +326,19 @@ void update_vsyscall(struct timekeeper *tk) vdso_write_begin(vdso_data); - vdso_data->tk_is_cntvct = tk_is_cntvct(tk); + vdso_data->use_syscall = !tk_is_cntvct(tk); vdso_data->xtime_coarse_sec = tk->xtime_sec; vdso_data->xtime_coarse_nsec = (u32)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift); vdso_data->wtm_clock_sec = wtm->tv_sec; vdso_data->wtm_clock_nsec = wtm->tv_nsec; - if (vdso_data->tk_is_cntvct) { + if (!vdso_data->use_syscall) { vdso_data->cs_cycle_last = tk->tkr_mono.cycle_last; vdso_data->xtime_clock_sec = tk->xtime_sec; vdso_data->xtime_clock_snsec = tk->tkr_mono.xtime_nsec; - vdso_data->cs_mult = tk->tkr_mono.mult; + vdso_data->cs_mono_mult = tk->tkr_mono.mult; + /* tkr_mono.shift == tkr_raw.shift */ vdso_data->cs_shift = tk->tkr_mono.shift; vdso_data->cs_mask = tk->tkr_mono.mask; } diff --git a/arch/arm/vdso/vgettimeofday.c b/arch/arm/vdso/vgettimeofday.c index 79214d5ff097..8cf13af1323c 100644 --- a/arch/arm/vdso/vgettimeofday.c +++ b/arch/arm/vdso/vgettimeofday.c @@ -1,18 +1,25 @@ /* - * Copyright 2015 Mentor Graphics Corporation. + * Userspace implementations of gettimeofday() and friends. * - * This program is free software; you can redistribute it and/or - * modify it under the terms of the GNU General Public License - * as published by the Free Software Foundation; version 2 of the - * License. + * Copyright (C) 2017 Cavium, Inc. + * Copyright (C) 2015 Mentor Graphics Corporation + * Copyright (C) 2012 ARM Limited * - * 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. + * 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 . + * + * Author: Will Deacon + * Rewriten from arch64 version into C by: Andrew Pinski + * Reworked and rebased over arm version by: Mark Salyzyn */ #include @@ -31,32 +38,30 @@ extern struct vdso_data *__get_datapage(void); -static notrace u32 __vdso_read_begin(const struct vdso_data *vdata) -{ - u32 seq; -repeat: - seq = ACCESS_ONCE(vdata->seq_count); - if (seq & 1) { - cpu_relax(); - goto repeat; - } - return seq; -} - static notrace u32 vdso_read_begin(const struct vdso_data *vdata) { u32 seq; - seq = __vdso_read_begin(vdata); + do { + seq = READ_ONCE(vdata->tb_seq_count); + + if ((seq & 1) == 0) + break; - smp_rmb(); /* Pairs with smp_wmb in vdso_write_end */ + cpu_relax(); + } while (true); + + smp_rmb(); /* Pairs with second smp_wmb in update_vsyscall */ return seq; } static notrace int vdso_read_retry(const struct vdso_data *vdata, u32 start) { - smp_rmb(); /* Pairs with smp_wmb in vdso_write_begin */ - return vdata->seq_count != start; + u32 seq; + + smp_rmb(); /* Pairs with first smp_wmb in update_vsyscall */ + seq = READ_ONCE(vdata->tb_seq_count); + return seq != start; } static notrace long clock_gettime_fallback(clockid_t _clkid, @@ -127,7 +132,7 @@ static notrace u64 get_ns(struct vdso_data *vdata) cycle_delta = (cycle_now - vdata->cs_cycle_last) & vdata->cs_mask; - nsec = (cycle_delta * vdata->cs_mult) + vdata->xtime_clock_snsec; + nsec = (cycle_delta * vdata->cs_mono_mult) + vdata->xtime_clock_snsec; nsec >>= vdata->cs_shift; return nsec; @@ -141,7 +146,7 @@ static notrace int do_realtime(struct timespec *ts, struct vdso_data *vdata) do { seq = vdso_read_begin(vdata); - if (!vdata->tk_is_cntvct) + if (vdata->use_syscall) return -1; ts->tv_sec = vdata->xtime_clock_sec; @@ -164,7 +169,7 @@ static notrace int do_monotonic(struct timespec *ts, struct vdso_data *vdata) do { seq = vdso_read_begin(vdata); - if (!vdata->tk_is_cntvct) + if (vdata->use_syscall) return -1; ts->tv_sec = vdata->xtime_clock_sec;