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This routine returns a monotonic count of the number of nanoseconds elapsed since the previous call. On arm64 it uses the generic system timer. The implementation multiplies the counter value by 10**9 then divides by the counter frequency, but this multiplication can overflow. This can result in trace records with non-monotonic timestamps, which breaks libdtrace's temporal ordering algorithm. An easy fix is to reverse the order of operations, since the counter frequency will in general be smaller than 10**9. (In fact, it's mandated to be 1Ghz in ARMv9, which makes life simple.) However, this can give a fair bit of error. Adopt the calculation used on amd64, with tweaks to handle frequencies as low as 1MHz: the ARM generic timer documentation suggests that ARMv8 timers are typically in the 1MHz-50MHz range, which is true on arm64 systems that I have access to. MFC after: 2 weeks Sponsored by: Innovate UK Differential Revision: https://reviews.freebsd.org/D49244 (cherry picked from commit 36ae5ce2f2fda35763c2655a19bf1b0ee22fdf3c) |
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| .. | ||
| amd64 | ||
| arm | ||
| arm64 | ||
| bsm | ||
| cam | ||
| cddl | ||
| compat | ||
| conf | ||
| contrib | ||
| crypto | ||
| ddb | ||
| dev | ||
| dts | ||
| fs | ||
| gdb | ||
| geom | ||
| gnu | ||
| i386 | ||
| isa | ||
| kern | ||
| kgssapi | ||
| libkern | ||
| modules | ||
| net | ||
| net80211 | ||
| netgraph | ||
| netinet | ||
| netinet6 | ||
| netipsec | ||
| netlink | ||
| netpfil | ||
| netsmb | ||
| nfs | ||
| nfsclient | ||
| nfsserver | ||
| nlm | ||
| ofed | ||
| opencrypto | ||
| powerpc | ||
| riscv | ||
| rpc | ||
| security | ||
| sys | ||
| teken | ||
| tests | ||
| tools | ||
| ufs | ||
| vm | ||
| x86 | ||
| xdr | ||
| xen | ||
| Makefile | ||
| README.md | ||
FreeBSD Kernel Source:
This directory contains the source files and build glue that make up the FreeBSD kernel and its modules, including both original and contributed software.
Kernel configuration files are located in the conf/ subdirectory of each
architecture. GENERIC is the configuration used in release builds. NOTES
contains documentation of all possible entries. LINT is a compile-only
configuration used to maximize build coverage and detect regressions.
Documentation:
Source code documentation is maintained in a set of man pages, under section 9.
These pages are located in share/man/man9, from the
top-level of the src tree. Consult intro(9)
for an overview of existing pages.
Some additional high-level documentation of the kernel is maintained in the Architecture Handbook.
Source Roadmap:
| Directory | Description |
|---|---|
| amd64 | AMD64 (64-bit x86) architecture support |
| arm | 32-bit ARM architecture support |
| arm64 | 64-bit ARM (AArch64) architecture support |
| cam | Common Access Method storage subsystem - cam(4) and ctl(4) |
| cddl | CDDL-licensed optional sources such as DTrace |
| conf | kernel build glue |
| compat | Linux compatibility layer, FreeBSD 32-bit compatibility |
| contrib | 3rd-party imported software such as OpenZFS |
| crypto | crypto drivers |
| ddb | interactive kernel debugger - ddb(4) |
| fs | most filesystems, excluding UFS, NFS, and ZFS |
| dev | device drivers and other arch independent code |
| gdb | kernel remote GDB stub - gdb(4) |
| geom | GEOM framework - geom(4) |
| i386 | i386 (32-bit x86) architecture support |
| kern | main part of the kernel |
| libkern | libc-like and other support functions for kernel use |
| modules | kernel module infrastructure |
| net | core networking code |
| net80211 | wireless networking (IEEE 802.11) - net80211(4) |
| netgraph | graph-based networking subsystem - netgraph(4) |
| netinet | IPv4 protocol implementation - inet(4) |
| netinet6 | IPv6 protocol implementation - inet6(4) |
| netipsec | IPsec protocol implementation - ipsec(4) |
| netpfil | packet filters - ipfw(4), pf(4), and ipfilter(4) |
| opencrypto | OpenCrypto framework - crypto(7) |
| powerpc | PowerPC/POWER (32 and 64-bit) architecture support |
| riscv | 64-bit RISC-V architecture support |
| security | security facilities - audit(4) and mac(4) |
| sys | kernel headers |
| tests | kernel unit tests |
| ufs | Unix File System - ffs(7) |
| vm | virtual memory system |
| x86 | code shared by AMD64 and i386 architectures |