问题
I am trying to determine when optional ARMv8 cpu features are available on iOS at runtime. On OS X desktops, like i686, x86_64, PPC and PPC64 we can use sysctl. See, for example, PR 3108, SIGILL-free processor capabilities detection on MacOS X.
The "SIGILL-free processor capabilities" part is important because SIGILL-based feature probes corrupt memory on Apple platforms. At least three projects I follow have had problems with it, including Crypto++ and OpenSSL. Another part of the problem is questions like Does Apple Clang lack CRC32 for ARMv8/Aarch64 under Xcode 10?, where core ARMv8 features that should be present seem to be missing or unsupported.
I've looked for the iOS equivalent of the OS X desktops but I cannot find them (see below).
We really prefer to avoid Apple frameworks like CommonCrypto. We try hard to stay platform agnostic. We don't use CommonCrypto, but I would consider using an Apple functions like below if there's nothing agnostic available (I'm making them up):
BOOL CCHasAes();
BOOL CCHasSHA1();
BOOL CCHasSHA2();
Does Apple publish a method to determine cpu features at runtime?
How do we determine cpu features at runtime on iOS?
These may be related, but I'm not sure if that's the best we have, or if that's the only thing we have, or if there are other ways to approach it.
- Calling “sysctlbyname(…)” with “hw.machine” flag in iOS9.
- How to get device make and model on iOS?
Below I am looking for CRC-32, CRC-32C, AES, PMULL, SHA1 and SHA2 features. I don't see any hits that resemble what I am looking for. Apple supports ARMv8 since Xcode 7, so 8.2 supports the CPU.
$ grep -IR CTL_ /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.2.sdk | \
sed 's|/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS8.2.sdk/usr/include|...|g'
.../c++/4.2.1/bits/c++config.h:#define _GLIBCXX_HAVE_SYS_IOCTL_H 1
.../netinet/in.h:#define IPCTL_FORWARDING 1 /* act as router */
.../netinet/in.h:#define IPCTL_SENDREDIRECTS 2 /* may send redirects when forwarding */
.../netinet/in.h:#define IPCTL_DEFTTL 3 /* default TTL */
.../netinet/in.h:#define IPCTL_DEFMTU 4 /* default MTU */
.../netinet/in.h:#define IPCTL_RTEXPIRE 5 /* cloned route expiration time */
.../netinet/in.h:#define IPCTL_RTMINEXPIRE 6 /* min value for expiration time */
.../netinet/in.h:#define IPCTL_RTMAXCACHE 7 /* trigger level for dynamic expire */
.../netinet/in.h:#define IPCTL_SOURCEROUTE 8 /* may perform source routes */
.../netinet/in.h:#define IPCTL_DIRECTEDBROADCAST 9 /* may re-broadcast received packets */
.../netinet/in.h:#define IPCTL_INTRQMAXLEN 10 /* max length of netisr queue */
.../netinet/in.h:#define IPCTL_INTRQDROPS 11 /* number of netisr q drops */
.../netinet/in.h:#define IPCTL_STATS 12 /* ipstat structure */
.../netinet/in.h:#define IPCTL_ACCEPTSOURCEROUTE 13 /* may accept source routed packets */
.../netinet/in.h:#define IPCTL_FASTFORWARDING 14 /* use fast IP forwarding code */
.../netinet/in.h:#define IPCTL_KEEPFAITH 15 /* deprecated */
.../netinet/in.h:#define IPCTL_GIF_TTL 16 /* default TTL for gif encap packet */
.../netinet/in.h:#define IPCTL_MAXID 17
.../netinet6/in6.h:#define IPV6CTL_FORWARDING 1 /* act as router */
.../netinet6/in6.h:#define IPV6CTL_SENDREDIRECTS 2 /* may send redirects when forwarding */
.../netinet6/in6.h:#define IPV6CTL_DEFHLIM 3 /* default Hop-Limit */
.../netinet6/in6.h:#define IPV6CTL_DEFMTU 4 /* default MTU */
.../netinet6/in6.h:#define IPV6CTL_FORWSRCRT 5 /* forward source-routed dgrams */
.../netinet6/in6.h:#define IPV6CTL_STATS 6 /* stats */
.../netinet6/in6.h:#define IPV6CTL_MRTSTATS 7 /* multicast forwarding stats */
.../netinet6/in6.h:#define IPV6CTL_MRTPROTO 8 /* multicast routing protocol */
.../netinet6/in6.h:#define IPV6CTL_MAXFRAGPACKETS 9 /* max packets reassembly queue */
.../netinet6/in6.h:#define IPV6CTL_SOURCECHECK 10 /* verify source route and intf */
.../netinet6/in6.h:#define IPV6CTL_SOURCECHECK_LOGINT 11 /* minimume logging interval */
.../netinet6/in6.h:#define IPV6CTL_ACCEPT_RTADV 12
.../netinet6/in6.h:#define IPV6CTL_KEEPFAITH 13 /* deprecated */
.../netinet6/in6.h:#define IPV6CTL_LOG_INTERVAL 14
.../netinet6/in6.h:#define IPV6CTL_HDRNESTLIMIT 15
.../netinet6/in6.h:#define IPV6CTL_DAD_COUNT 16
.../netinet6/in6.h:#define IPV6CTL_AUTO_FLOWLABEL 17
.../netinet6/in6.h:#define IPV6CTL_DEFMCASTHLIM 18
.../netinet6/in6.h:#define IPV6CTL_GIF_HLIM 19 /* default HLIM for gif encap packet */
.../netinet6/in6.h:#define IPV6CTL_KAME_VERSION 20
.../netinet6/in6.h:#define IPV6CTL_USE_DEPRECATED 21 /* use deprec addr (RFC2462 5.5.4) */
.../netinet6/in6.h:#define IPV6CTL_RR_PRUNE 22 /* walk timer for router renumbering */
.../netinet6/in6.h:#define IPV6CTL_MAPPED_ADDR 23
.../netinet6/in6.h:#define IPV6CTL_V6ONLY 24
.../netinet6/in6.h:#define IPV6CTL_RTEXPIRE 25 /* cloned route expiration time */
.../netinet6/in6.h:#define IPV6CTL_RTMINEXPIRE 26 /* min value for expiration time */
.../netinet6/in6.h:#define IPV6CTL_RTMAXCACHE 27 /* trigger level for dynamic expire */
.../netinet6/in6.h:#define IPV6CTL_USETEMPADDR 32 /* use temporary addresses [RFC 4941] */
.../netinet6/in6.h:#define IPV6CTL_TEMPPLTIME 33 /* preferred lifetime for tmpaddrs */
.../netinet6/in6.h:#define IPV6CTL_TEMPVLTIME 34 /* valid lifetime for tmpaddrs */
.../netinet6/in6.h:#define IPV6CTL_AUTO_LINKLOCAL 35 /* automatic link-local addr assign */
.../netinet6/in6.h:#define IPV6CTL_RIP6STATS 36 /* raw_ip6 stats */
.../netinet6/in6.h:#define IPV6CTL_PREFER_TEMPADDR 37 /* prefer temporary addr as src */
.../netinet6/in6.h:#define IPV6CTL_ADDRCTLPOLICY 38 /* get/set address selection policy */
.../netinet6/in6.h:#define IPV6CTL_USE_DEFAULTZONE 39 /* use default scope zone */
.../netinet6/in6.h:#define IPV6CTL_MAXFRAGS 41 /* max fragments */
.../netinet6/in6.h:#define IPV6CTL_MCAST_PMTU 44 /* enable pMTU discovery for mcast? */
.../netinet6/in6.h:#define IPV6CTL_NEIGHBORGCTHRESH 46
.../netinet6/in6.h:#define IPV6CTL_MAXIFPREFIXES 47
.../netinet6/in6.h:#define IPV6CTL_MAXIFDEFROUTERS 48
.../netinet6/in6.h:#define IPV6CTL_MAXDYNROUTES 49
.../netinet6/in6.h:#define ICMPV6CTL_ND6_ONLINKNSRFC4861 50
.../netinet6/in6.h:/* New entries should be added here from current IPV6CTL_MAXID value. */
.../netinet6/in6.h:#define IPV6CTL_MAXID 51
.../sys/ioctl.h:#ifndef _SYS_IOCTL_H_
.../sys/ioctl.h:#define _SYS_IOCTL_H_
.../sys/ioctl.h:#endif /* !_SYS_IOCTL_H_ */
.../sys/ioctl.h: * Keep outside _SYS_IOCTL_H_
.../sys/ioctl.h:#endif /* !_SYS_IOCTL_H_ */
.../sys/mount.h: * Sysctl CTL_VFS definitions.
.../sys/mount.h: int vc_vers; /* should be VFSIDCTL_VERS1 (below) */
.../sys/mount.h:#define VFS_CTL_VERS1 0x01
.../sys/mount.h:#define VFS_CTL_STATFS 0x00010001 /* statfs */
.../sys/mount.h:#define VFS_CTL_UMOUNT 0x00010002 /* unmount */
.../sys/mount.h:#define VFS_CTL_QUERY 0x00010003 /* anything wrong? (vfsquery) */
.../sys/mount.h:#define VFS_CTL_NEWADDR 0x00010004 /* reconnect to new address */
.../sys/mount.h:#define VFS_CTL_TIMEO 0x00010005 /* set timeout for vfs notification */
.../sys/mount.h:#define VFS_CTL_NOLOCKS 0x00010006 /* disable file locking */
.../sys/mount.h:#define VFS_CTL_SADDR 0x00010007 /* get server address */
.../sys/mount.h:#define VFS_CTL_DISC 0x00010008 /* server disconnected */
.../sys/mount.h:#define VFS_CTL_SERVERINFO 0x00010009 /* information about fs server */
.../sys/mount.h:#define VFS_CTL_NSTATUS 0x0001000A /* netfs mount status */
.../sys/mount.h: * NetFS mount status - returned by VFS_CTL_NSTATUS
.../sys/socket.h: * Definitions for network related sysctl, CTL_NET.
.../sys/sysctl.h:#ifndef _SYS_SYSCTL_H_
.../sys/sysctl.h:#define _SYS_SYSCTL_H_
.../sys/sysctl.h:#define CTL_MAXNAME 12 /* largest number of components supported */
.../sys/sysctl.h: * SYSCTL_OUT(rey, local buffer, length)
.../sys/sysctl.h: * e.g. SYSCTL_INT(_parent, OID_AUTO, name, CTLFLAG_RW, &variable, 0, "");
.../sys/sysctl.h:#define SYSCTL_DEF_ENABLED
.../sys/sysctl.h:#ifdef SYSCTL_DEF_ENABLED
.../sys/sysctl.h:#define CTL_UNSPEC 0 /* unused */
.../sys/sysctl.h:#define CTL_KERN 1 /* "high kernel": proc, limits */
.../sys/sysctl.h:#define CTL_VM 2 /* virtual memory */
.../sys/sysctl.h:#define CTL_VFS 3 /* file system, mount type is next */
.../sys/sysctl.h:#define CTL_NET 4 /* network, see socket.h */
.../sys/sysctl.h:#define CTL_DEBUG 5 /* debugging parameters */
.../sys/sysctl.h:#define CTL_HW 6 /* generic cpu/io */
.../sys/sysctl.h:#define CTL_MACHDEP 7 /* machine dependent */
.../sys/sysctl.h:#define CTL_USER 8 /* user-level */
.../sys/sysctl.h:#define CTL_MAXID 9 /* number of valid top-level ids */
.../sys/sysctl.h:#define CTL_NAMES { \
.../sys/sysctl.h: * CTL_KERN identifiers
.../sys/sysctl.h: * Don't add any more sysctls like this. Instead, use the SYSCTL_*() macros
.../sys/sysctl.h:#define CTL_KERN_NAMES { \
.../sys/sysctl.h: * CTL_VFS identifiers
.../sys/sysctl.h:#define CTL_VFS_NAMES { \
.../sys/sysctl.h: * CTL_VM identifiers
.../sys/sysctl.h:#define CTL_VM_NAMES { \
.../sys/sysctl.h: * CTL_HW identifiers
.../sys/sysctl.h:#define CTL_HW_NAMES { \
.../sys/sysctl.h: * CTL_USER definitions
.../sys/sysctl.h:#define CTL_USER_NAMES { \
.../sys/sysctl.h: * CTL_DEBUG definitions
.../sys/sysctl.h:#define CTL_DEBUG_NAME 0 /* string: variable name */
.../sys/sysctl.h:#define CTL_DEBUG_VALUE 1 /* int: variable value */
.../sys/sysctl.h:#define CTL_DEBUG_MAXID 20
.../sys/sysctl.h:#if (CTL_MAXID != 9) || (KERN_MAXID != 72) || (VM_MAXID != 6) || (HW_MAXID != 26) || (USER_MAXID != 21) || (CTL_DEBUG_MAXID != 20)
.../sys/sysctl.h:#error Use the SYSCTL_*() macros and OID_AUTO instead!
.../sys/sysctl.h:#endif /* SYSCTL_DEF_ENABLED */
.../sys/sysctl.h:#endif /* !_SYS_SYSCTL_H_ */
.../sys/termios.h:#if !defined(_SYS_IOCTL_COMPAT_H_) || __DARWIN_UNIX03
.../sys/termios.h:#endif /* !_SYS_IOCTL_COMPAT_H_ */
回答1:
As far as I know Apple is going to remove the support to 32-bit chips this year. Since Apple A7 processors Apple uses ArmV8-A cores for its SoCs...so maybe you cannot choose them with the new APIs because you have nothing to choose...Apple usually is cryptic about those kind of things and uses automatic switching for certain features on mobile platforms. However basically every iOS 11 SoC will have the same basic hardware features except for the number of cores and the energy management (which is different for SoC >= A10 Fusion). I was searching for the same thing some month ago but apparently on iOS you have to be in the hands of the OS.
来源：https://stackoverflow.com/questions/45637888/how-to-determine-armv8-features-at-runtime-on-ios