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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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8ec7f15b8c
Fix incorrect calculation in do_monotonic() and do_monotonic_coarse() function that in turn caused incorrect values returned by the vdso version of system call clock_gettime() on mips64 if its system clock ID parameter was CLOCK_MONOTONIC or CLOCK_MONOTONIC_COARSE. Consider these variables and their types on mips32 and mips64: tk->wall_to_monotonic.tv_sec s64, s64 (kernel/vdso.c) vdso_data.wall_to_mono_sec u32, u32 (kernel/vdso.c) to_mono_sec u32, u32 (vdso/gettimeofday.c) ts->tv_sec s32, s64 (vdso/gettimeofday.c) For mips64 case, u32 vdso_data.wall_to_mono_sec variable is updated from the 64-bit signed variable tk->wall_to_monotonic.tv_sec (kernel/vdso.c:76) which is a negative number holding the time passed from 1970-01-01 to the time boot started. This 64-bit signed value is currently around 47+ years, in seconds. For instance, let this value be: -1489757461 or 11111111111111111111111111111111 10100111001101000001101011101011 By updating 32-bit vdso_data.wall_to_mono_sec variable, we lose upper 32 bits (signed 1's). to_mono_sec variable is a parameter of do_monotonic() and do_monotonic_coarse() functions which holds vdso_data.wall_to_mono_sec value. Its value needs to be added (or subtracted considering it holds negative value from the tk->wall_to_monotonic.tv_sec) to the current time passed from 1970-01-01 (ts->tv_sec), which is again something like 47+ years, but increased by the time passed from the boot to the current time. ts->tv_sec is 32-bit long in case of 32-bit architecture and 64-bit long in case of 64-bit architecture. Consider the update of ts->tv_sec (vdso/gettimeofday.c:55 & 167): ts->tv_sec += to_mono_sec; mips32 case: This update will be performed correctly, since both ts->tv_sec and to_mono_sec are 32-bit long and the sign in to_mono_sec is preserved. Implicit conversion from u32 to s32 will be done correctly. mips64 case: This update will be wrong, since the implicit conversion will not be done correctly. The reason is that the conversion will be from u32 to s64. This is because to_mono_sec is 32-bit long for both mips32 and mips64 cases and s64..33 bits of converted to_mono_sec variable will be zeros. So, in order to make MIPS64 implementation work properly for MONOTONIC and MONOTONIC_COARSE clock ids on mips64, the size of wall_to_mono_sec variable in mips_vdso_data union and respective parameters in do_monotonic() and do_monotonic_coarse() functions should be changed from u32 to u64. Because of consistency, this size change from u32 and u64 is also done for wall_to_mono_nsec variable and corresponding function parameters. As far as similar situations for other architectures are concerned, let's take a look at arm. Arm has two distinct vdso_data structures for 32-bit & 64-bit cases, and arm's wall_to_mono_sec and wall_to_mono_nsec are u32 for 32-bit and u64 for 64-bit cases. On the other hand, MIPS has only one structure (mips_vdso_data), hence the need for changing the size of above mentioned parameters. Signed-off-by: Goran Ferenc <goran.ferenc@imgtec.com> Signed-off-by: Miodrag Dinic <miodrag.dinic@imgtec.com> Signed-off-by: Aleksandar Markovic <aleksandar.markovic@imgtec.com> Cc: Douglas Leung <douglas.leung@imgtec.com> Cc: James Hogan <james.hogan@imgtec.com> Cc: Paul Burton <paul.burton@imgtec.com> Cc: Petar Jovanovic <petar.jovanovic@imgtec.com> Cc: Raghu Gandham <raghu.gandham@imgtec.com> Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/16638/ Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
137 lines
3.7 KiB
C
137 lines
3.7 KiB
C
/*
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* Copyright (C) 2015 Imagination Technologies
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* Author: Alex Smith <alex.smith@imgtec.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*/
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#ifndef __ASM_VDSO_H
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#define __ASM_VDSO_H
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#include <linux/mm_types.h>
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#include <asm/barrier.h>
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/**
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* struct mips_vdso_image - Details of a VDSO image.
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* @data: Pointer to VDSO image data (page-aligned).
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* @size: Size of the VDSO image data (page-aligned).
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* @off_sigreturn: Offset of the sigreturn() trampoline.
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* @off_rt_sigreturn: Offset of the rt_sigreturn() trampoline.
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* @mapping: Special mapping structure.
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*
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* This structure contains details of a VDSO image, including the image data
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* and offsets of certain symbols required by the kernel. It is generated as
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* part of the VDSO build process, aside from the mapping page array, which is
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* populated at runtime.
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*/
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struct mips_vdso_image {
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void *data;
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unsigned long size;
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unsigned long off_sigreturn;
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unsigned long off_rt_sigreturn;
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struct vm_special_mapping mapping;
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};
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/*
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* The following structures are auto-generated as part of the build for each
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* ABI by genvdso, see arch/mips/vdso/Makefile.
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*/
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extern struct mips_vdso_image vdso_image;
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#ifdef CONFIG_MIPS32_O32
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extern struct mips_vdso_image vdso_image_o32;
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#endif
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#ifdef CONFIG_MIPS32_N32
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extern struct mips_vdso_image vdso_image_n32;
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#endif
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/**
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* union mips_vdso_data - Data provided by the kernel for the VDSO.
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* @xtime_sec: Current real time (seconds part).
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* @xtime_nsec: Current real time (nanoseconds part, shifted).
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* @wall_to_mono_sec: Wall-to-monotonic offset (seconds part).
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* @wall_to_mono_nsec: Wall-to-monotonic offset (nanoseconds part).
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* @seq_count: Counter to synchronise updates (odd = updating).
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* @cs_shift: Clocksource shift value.
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* @clock_mode: Clocksource to use for time functions.
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* @cs_mult: Clocksource multiplier value.
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* @cs_cycle_last: Clock cycle value at last update.
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* @cs_mask: Clocksource mask value.
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* @tz_minuteswest: Minutes west of Greenwich (from timezone).
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* @tz_dsttime: Type of DST correction (from timezone).
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*
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* This structure contains data needed by functions within the VDSO. It is
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* populated by the kernel and mapped read-only into user memory. The time
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* fields are mirrors of internal data from the timekeeping infrastructure.
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*
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* Note: Care should be taken when modifying as the layout must remain the same
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* for both 64- and 32-bit (for 32-bit userland on 64-bit kernel).
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*/
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union mips_vdso_data {
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struct {
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u64 xtime_sec;
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u64 xtime_nsec;
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u64 wall_to_mono_sec;
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u64 wall_to_mono_nsec;
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u32 seq_count;
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u32 cs_shift;
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u8 clock_mode;
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u32 cs_mult;
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u64 cs_cycle_last;
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u64 cs_mask;
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s32 tz_minuteswest;
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s32 tz_dsttime;
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};
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u8 page[PAGE_SIZE];
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};
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static inline u32 vdso_data_read_begin(const union mips_vdso_data *data)
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{
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u32 seq;
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while (true) {
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seq = ACCESS_ONCE(data->seq_count);
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if (likely(!(seq & 1))) {
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/* Paired with smp_wmb() in vdso_data_write_*(). */
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smp_rmb();
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return seq;
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}
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cpu_relax();
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}
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}
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static inline bool vdso_data_read_retry(const union mips_vdso_data *data,
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u32 start_seq)
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{
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/* Paired with smp_wmb() in vdso_data_write_*(). */
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smp_rmb();
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return unlikely(data->seq_count != start_seq);
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}
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static inline void vdso_data_write_begin(union mips_vdso_data *data)
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{
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++data->seq_count;
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/* Ensure sequence update is written before other data page values. */
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smp_wmb();
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}
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static inline void vdso_data_write_end(union mips_vdso_data *data)
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{
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/* Ensure data values are written before updating sequence again. */
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smp_wmb();
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++data->seq_count;
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}
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#endif /* __ASM_VDSO_H */
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