Date: Tue, 11 Jun 2019 00:03:24 -0400 From: Mitchell Horne <mhorne@freebsd.org> To: Ian Lepore <ian@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r348886 - in head/sys/riscv: include riscv Message-ID: <CADeAsy3irQA5=Bj6HyB=24cBvKXjjEm2bFXFvkb94J-8Tgr3tg@mail.gmail.com> In-Reply-To: <b0cd8506da0817b55319cae5db9677a1f64ef382.camel@freebsd.org> References: <201906110055.x5B0tsOM089231@repo.freebsd.org> <b0cd8506da0817b55319cae5db9677a1f64ef382.camel@freebsd.org>
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On Mon, Jun 10, 2019 at 9:12 PM Ian Lepore <ian@freebsd.org> wrote: > > On Tue, 2019-06-11 at 00:55 +0000, Mitchell Horne wrote: > > Author: mhorne > > Date: Tue Jun 11 00:55:54 2019 > > New Revision: 348886 > > URL: https://svnweb.freebsd.org/changeset/base/348886 > > > > Log: > > RISC-V: expose extension bits in AT_HWCAP > > > > AT_HWCAP is a field in the elf auxiliary vector meant to describe > > cpu-specific hardware features. For RISC-V we want to use this to > > indicate the presence of any standard extensions supported by the > > CPU. > > This allows userland applications to query the system for supported > > extensions using elf_aux_info(3). > > > > Support for an extension is indicated by the presence of its > > corresponding bit in AT_HWCAP -- e.g. systems supporting the 'c' > > extension (compressed instructions) will have the second bit set. > > > > Extensions advertised through AT_HWCAP are only those that are > > supported > > by all harts in the system. > > > > A word of advice from the arm world (a don't make the mistakes we did > kind of thing): If linux has already defined AT_HWCAP values for > riscv, life may be better in the long run if our values match theirs as > much as possible. It will especially help with ports. > > -- Ian That's good advice. Rest assured that in this case we are mimicking the behaviour that's been implemented in Linux. Mitchell > > > Reviewed by: jhb, markj > > Approved by: markj (mentor) > > MFC after: 2 weeks > > Differential Revision: https://reviews.freebsd.org/D20493 > > > > Modified: > > head/sys/riscv/include/elf.h > > head/sys/riscv/include/md_var.h > > head/sys/riscv/riscv/elf_machdep.c > > head/sys/riscv/riscv/identcpu.c > > > > Modified: head/sys/riscv/include/elf.h > > ===================================================================== > > ========= > > --- head/sys/riscv/include/elf.h Mon Jun 10 23:25:40 2019 (r348 > > 885) > > +++ head/sys/riscv/include/elf.h Tue Jun 11 00:55:54 2019 (r348 > > 886) > > @@ -74,4 +74,15 @@ __ElfType(Auxinfo); > > /* TODO: set correct value */ > > #define ET_DYN_LOAD_ADDR 0x100000 > > > > +/* Flags passed in AT_HWCAP */ > > +#define HWCAP_ISA_BIT(c) (1 << ((c) - 'A')) > > +#define HWCAP_ISA_I HWCAP_ISA_BIT('I') > > +#define HWCAP_ISA_M HWCAP_ISA_BIT('M') > > +#define HWCAP_ISA_A HWCAP_ISA_BIT('A') > > +#define HWCAP_ISA_F HWCAP_ISA_BIT('F') > > +#define HWCAP_ISA_D HWCAP_ISA_BIT('D') > > +#define HWCAP_ISA_C HWCAP_ISA_BIT('C') > > +#define HWCAP_ISA_G \ > > + (HWCAP_ISA_I | HWCAP_ISA_M | HWCAP_ISA_A | HWCAP_ISA_F | > > HWCAP_ISA_D) > > + > > #endif /* !_MACHINE_ELF_H_ */ > > > > Modified: head/sys/riscv/include/md_var.h > > ===================================================================== > > ========= > > --- head/sys/riscv/include/md_var.h Mon Jun 10 23:25:40 2019 (r348 > > 885) > > +++ head/sys/riscv/include/md_var.h Tue Jun 11 00:55:54 2019 (r348 > > 886) > > @@ -38,6 +38,7 @@ extern char sigcode[]; > > extern int szsigcode; > > extern uint64_t *vm_page_dump; > > extern int vm_page_dump_size; > > +extern u_long elf_hwcap; > > > > struct dumperinfo; > > > > > > Modified: head/sys/riscv/riscv/elf_machdep.c > > ===================================================================== > > ========= > > --- head/sys/riscv/riscv/elf_machdep.c Mon Jun 10 23:25:40 > > 2019 (r348885) > > +++ head/sys/riscv/riscv/elf_machdep.c Tue Jun 11 00:55:54 > > 2019 (r348886) > > @@ -58,6 +58,8 @@ __FBSDID("$FreeBSD$"); > > #include <machine/elf.h> > > #include <machine/md_var.h> > > > > +u_long elf_hwcap; > > + > > struct sysentvec elf64_freebsd_sysvec = { > > .sv_size = SYS_MAXSYSCALL, > > .sv_table = sysent, > > @@ -90,6 +92,7 @@ struct sysentvec elf64_freebsd_sysvec = { > > .sv_schedtail = NULL, > > .sv_thread_detach = NULL, > > .sv_trap = NULL, > > + .sv_hwcap = &elf_hwcap, > > }; > > INIT_SYSENTVEC(elf64_sysvec, &elf64_freebsd_sysvec); > > > > > > Modified: head/sys/riscv/riscv/identcpu.c > > ===================================================================== > > ========= > > --- head/sys/riscv/riscv/identcpu.c Mon Jun 10 23:25:40 2019 (r348 > > 885) > > +++ head/sys/riscv/riscv/identcpu.c Tue Jun 11 00:55:54 2019 (r348 > > 886) > > @@ -32,18 +32,28 @@ > > * SUCH DAMAGE. > > */ > > > > +#include "opt_platform.h" > > + > > #include <sys/cdefs.h> > > __FBSDID("$FreeBSD$"); > > > > #include <sys/param.h> > > +#include <sys/systm.h> > > +#include <sys/kernel.h> > > #include <sys/pcpu.h> > > #include <sys/sysctl.h> > > -#include <sys/systm.h> > > > > #include <machine/cpu.h> > > #include <machine/cpufunc.h> > > +#include <machine/elf.h> > > +#include <machine/md_var.h> > > #include <machine/trap.h> > > > > +#ifdef FDT > > +#include <dev/fdt/fdt_common.h> > > +#include <dev/ofw/openfirm.h> > > +#endif > > + > > char machine[] = "riscv"; > > > > SYSCTL_STRING(_hw, HW_MACHINE, machine, CTLFLAG_RD, machine, 0, > > @@ -87,6 +97,84 @@ const struct cpu_implementers cpu_implementers[] = > > { > > { CPU_IMPL_UCB_ROCKET, "UC Berkeley Rocket" }, > > CPU_IMPLEMENTER_NONE, > > }; > > + > > +#ifdef FDT > > +/* > > + * The ISA string is made up of a small prefix (e.g. rv64) and up to > > 26 letters > > + * indicating the presence of the 26 possible standard extensions. > > Therefore 32 > > + * characters will be sufficient. > > + */ > > +#define ISA_NAME_MAXLEN 32 > > +#define ISA_PREFIX ("rv" > > __XSTRING(__riscv_xlen)) > > +#define ISA_PREFIX_LEN (sizeof(ISA_PREFIX) - 1) > > + > > +static void > > +fill_elf_hwcap(void *dummy __unused) > > +{ > > + u_long caps[256] = {0}; > > + char isa[ISA_NAME_MAXLEN]; > > + u_long hwcap; > > + phandle_t node; > > + ssize_t len; > > + int i; > > + > > + caps['i'] = caps['I'] = HWCAP_ISA_I; > > + caps['m'] = caps['M'] = HWCAP_ISA_M; > > + caps['a'] = caps['A'] = HWCAP_ISA_A; > > +#ifdef FPE > > + caps['f'] = caps['F'] = HWCAP_ISA_F; > > + caps['d'] = caps['D'] = HWCAP_ISA_D; > > +#endif > > + caps['c'] = caps['C'] = HWCAP_ISA_C; > > + > > + node = OF_finddevice("/cpus"); > > + if (node == -1) { > > + if (bootverbose) > > + printf("fill_elf_hwcap: Can't find cpus > > node\n"); > > + return; > > + } > > + > > + /* > > + * Iterate through the CPUs and examine their ISA string. While > > we > > + * could assign elf_hwcap to be whatever the boot CPU supports, > > to > > + * handle the (unusual) case of running a system with > > hetergeneous > > + * ISAs, keep only the extension bits that are common to all > > harts. > > + */ > > + for (node = OF_child(node); node > 0; node = OF_peer(node)) { > > + if (!fdt_is_compatible_strict(node, "riscv")) { > > + if (bootverbose) > > + printf("fill_elf_hwcap: Can't find > > cpu\n"); > > + return; > > + } > > + > > + len = OF_getprop(node, "riscv,isa", isa, sizeof(isa)); > > + KASSERT(len <= ISA_NAME_MAXLEN, ("ISA string > > truncated")); > > + if (len == -1) { > > + if (bootverbose) > > + printf("fill_elf_hwcap: " > > + "Can't find riscv,isa property\n"); > > + return; > > + } else if (strncmp(isa, ISA_PREFIX, ISA_PREFIX_LEN) != > > 0) { > > + if (bootverbose) > > + printf("fill_elf_hwcap: " > > + "Unsupported ISA string: %s\n", > > isa); > > + return; > > + } > > + > > + hwcap = 0; > > + for (i = ISA_PREFIX_LEN; i < len; i++) > > + hwcap |= caps[(unsigned char)isa[i]]; > > + > > + if (elf_hwcap != 0) > > + elf_hwcap &= hwcap; > > + else > > + elf_hwcap = hwcap; > > + > > + } > > +} > > + > > +SYSINIT(identcpu, SI_SUB_CPU, SI_ORDER_ANY, fill_elf_hwcap, NULL); > > +#endif > > > > void > > identify_cpu(void) > > >
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