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arm: Add support for using VFP in kernel

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Add missing logic to allow in-kernel VFP usage for ARMv7 NEON.
The implementation is strongly based on arm64 code.
It introduces a family of fpu_kern_* functions to enable the usage
of VFP instructions in kernel.
Apart from that the existing armv7 VFP logic was modified,
taking into account that the state of the VFP registers can now
be modified in the kernel.

Co-developed by: Wojciech Macek <wma@FreeBSD.org>
Sponsored by:	Stormshield
Obtained from:	Semihalf
Reviewed by:	andrew
Differential Revision: https://reviews.freebsd.org/D37419
This commit is contained in:
Kornel Dulęba 2023-02-04 13:59:30 +01:00
parent 767964fd86
commit 6926e2699a
12 changed files with 293 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
lib/libthread_db/arch/arm/libpthread_md.c
View File

@ -87,22 +87,25 @@ pt_ucontext_to_reg(const ucontext_t *uc, struct reg *r)
}
void
pt_fpreg_to_ucontext(const struct fpreg *r __unused, ucontext_t *uc)
pt_fpreg_to_ucontext(const struct fpreg *r, ucontext_t *uc)
{
mcontext_t *mc = &uc->uc_mcontext;
mcontext_vfp_t *mc_vfp;
/* XXX */
mc->mc_vfp_size = 0;
mc->mc_vfp_ptr = NULL;
memset(mc->mc_spare, 0, sizeof(mc->mc_spare));
mc_vfp = uc->uc_mcontext.mc_vfp_ptr;
if (mc_vfp != NULL)
memcpy(mc_vfp, r, sizeof(*r));
}
void
pt_ucontext_to_fpreg(const ucontext_t *uc __unused, struct fpreg *r)
pt_ucontext_to_fpreg(const ucontext_t *uc, struct fpreg *r)
{
mcontext_vfp_t *mc_vfp;
/* XXX */
memset(r, 0, sizeof(*r));
mc_vfp = uc->uc_mcontext.mc_vfp_ptr;
if (mc_vfp != NULL)
memcpy(r, &mc_vfp, sizeof(*r));
}
void

49
sys/arm/arm/exec_machdep.c
View File

@ -100,16 +100,18 @@ get_vfpcontext(struct thread *td, mcontext_vfp_t *vfp)
{
struct pcb *pcb;
MPASS(td == curthread);
pcb = td->td_pcb;
if (td == curthread) {
if ((pcb->pcb_fpflags & PCB_FP_STARTED) != 0) {
critical_enter();
vfp_store(&pcb->pcb_vfpstate, false);
critical_exit();
} else
MPASS(TD_IS_SUSPENDED(td));
memset(vfp, 0, sizeof(*vfp));
}
KASSERT(pcb->pcb_vfpsaved == &pcb->pcb_vfpstate,
("Called get_vfpcontext while the kernel is using the VFP"));
memcpy(vfp->mcv_reg, pcb->pcb_vfpstate.reg,
sizeof(vfp->mcv_reg));
sizeof(vfp->mcv_reg));
vfp->mcv_fpscr = pcb->pcb_vfpstate.fpscr;
}
@ -121,15 +123,18 @@ set_vfpcontext(struct thread *td, mcontext_vfp_t *vfp)
{
struct pcb *pcb;
MPASS(td == curthread);
pcb = td->td_pcb;
if (td == curthread) {
if ((pcb->pcb_fpflags & PCB_FP_STARTED) != 0) {
critical_enter();
vfp_discard(td);
critical_exit();
} else
MPASS(TD_IS_SUSPENDED(td));
}
KASSERT(pcb->pcb_vfpsaved == &pcb->pcb_vfpstate,
("Called set_vfpcontext while the kernel is using the VFP"));
memcpy(pcb->pcb_vfpstate.reg, vfp->mcv_reg,
sizeof(pcb->pcb_vfpstate.reg));
sizeof(pcb->pcb_vfpstate.reg));
pcb->pcb_vfpstate.fpscr = vfp->mcv_fpscr;
}
#endif
@ -166,6 +171,8 @@ get_mcontext(struct thread *td, mcontext_t *mcp, int clear_ret)
{
struct trapframe *tf = td->td_frame;
__greg_t *gr = mcp->__gregs;
mcontext_vfp_t mcontext_vfp;
int rv;
if (clear_ret & GET_MC_CLEAR_RET) {
gr[_REG_R0] = 0;
@ -190,9 +197,19 @@ get_mcontext(struct thread *td, mcontext_t *mcp, int clear_ret)
gr[_REG_LR] = tf->tf_usr_lr;
gr[_REG_PC] = tf->tf_pc;
mcp->mc_vfp_size = 0;
mcp->mc_vfp_ptr = NULL;
memset(&mcp->mc_spare, 0, sizeof(mcp->mc_spare));
#ifdef VFP
if (mcp->mc_vfp_size != sizeof(mcontext_vfp_t))
return (EINVAL);
get_vfpcontext(td, &mcontext_vfp);
#else
bzero(&mcontext_vfp, sizeof(mcontext_vfp));
#endif
if (mcp->mc_vfp_ptr != NULL) {
rv = copyout(&mcontext_vfp, mcp->mc_vfp_ptr, sizeof(mcontext_vfp));
if (rv != 0)
return (rv);
}
return (0);
}
@ -306,14 +323,6 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
/* Populate the siginfo frame. */
bzero(&frame, sizeof(frame));
get_mcontext(td, &frame.sf_uc.uc_mcontext, 0);
#ifdef VFP
get_vfpcontext(td, &frame.sf_vfp);
frame.sf_uc.uc_mcontext.mc_vfp_size = sizeof(fp->sf_vfp);
frame.sf_uc.uc_mcontext.mc_vfp_ptr = &fp->sf_vfp;
#else
frame.sf_uc.uc_mcontext.mc_vfp_size = 0;
frame.sf_uc.uc_mcontext.mc_vfp_ptr = NULL;
#endif
frame.sf_si = ksi->ksi_info;
frame.sf_uc.uc_sigmask = *mask;
frame.sf_uc.uc_stack = td->td_sigstk;

1
sys/arm/arm/machdep.c
View File

@ -377,6 +377,7 @@ init_proc0(vm_offset_t kstack)
thread0.td_pcb = (struct pcb *)(thread0.td_kstack +
thread0.td_kstack_pages * PAGE_SIZE) - 1;
thread0.td_pcb->pcb_flags = 0;
thread0.td_pcb->pcb_fpflags = 0;
thread0.td_pcb->pcb_vfpcpu = -1;
thread0.td_pcb->pcb_vfpstate.fpscr = VFPSCR_DN;
thread0.td_frame = &proc0_tf;

31
sys/arm/arm/machdep_kdb.c
View File

@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$");
#include <sys/systm.h>
#include <machine/cpu.h>
#include <machine/pcb.h>
#ifdef DDB
#include <ddb/ddb.h>
@ -105,7 +106,26 @@ fill_regs(struct thread *td, struct reg *regs)
int
fill_fpregs(struct thread *td, struct fpreg *regs)
{
bzero(regs, sizeof(*regs));
#ifdef VFP
struct pcb *pcb;
pcb = td->td_pcb;
if ((pcb->pcb_fpflags & PCB_FP_STARTED) != 0) {
/*
* If we have just been running VFP instructions we will
* need to save the state to memcpy it below.
*/
if (td == curthread)
vfp_save_state(td, pcb);
}
KASSERT(pcb->pcb_vfpsaved == &pcb->pcb_vfpstate,
("Called fill_fpregs while the kernel is using the VFP"));
memcpy(regs->fpr_r, pcb->pcb_vfpstate.reg,
sizeof(regs->fpr_r));
regs->fpr_fpscr = pcb->pcb_vfpstate.fpscr;
#else
memset(regs, 0, sizeof(*regs));
#endif
return (0);
}
@ -126,6 +146,15 @@ set_regs(struct thread *td, struct reg *regs)
int
set_fpregs(struct thread *td, struct fpreg *regs)
{
#ifdef VFP
struct pcb *pcb;
pcb = td->td_pcb;
KASSERT(pcb->pcb_vfpsaved == &pcb->pcb_vfpstate,
("Called set_fpregs while the kernel is using the VFP"));
memcpy(pcb->pcb_vfpstate.reg, regs->fpr_r, sizeof(regs->fpr_r));
pcb->pcb_vfpstate.fpscr = regs->fpr_fpscr;
#endif
return (0);
}

8
sys/arm/arm/swtch-v6.S
View File

@ -323,11 +323,9 @@ ENTRY(cpu_switch)
#ifdef VFP
ldr r3, [r10, #(TD_PCB)]
fmrx r0, fpexc /* If the VFP is enabled */
tst r0, #(VFPEXC_EN) /* the current thread has */
movne r1, #1 /* used it, so go save */
addne r0, r3, #(PCB_VFPSTATE) /* the state into the PCB */
blne _C_LABEL(vfp_store) /* and disable the VFP. */
mov r1, r3
mov r0, r10
blne _C_LABEL(vfp_save_state)
#endif
/*

8
sys/arm/arm/swtch.S
View File

@ -99,11 +99,9 @@ ENTRY(savectx)
add r3, r0, #(PCB_R4)
stmia r3, {r4-r12, sp, lr, pc}
#ifdef VFP
fmrx r2, fpexc /* If the VFP is enabled */
tst r2, #(VFPEXC_EN) /* the current thread has */
movne r1, #1 /* used it, so go save */
addne r0, r0, #(PCB_VFPSTATE) /* the state into the PCB */
blne _C_LABEL(vfp_store) /* and disable the VFP. */
mov r1, r0
mov r0, #0
blne _C_LABEL(vfp_save_state)
#endif
add sp, sp, #4;
ldmfd sp!, {pc}

182
sys/arm/arm/vfp.c
View File

@ -55,6 +55,14 @@ static struct undefined_handler vfp10_uh, vfp11_uh;
/* If true the VFP unit has 32 double registers, otherwise it has 16 */
static int is_d32;
struct fpu_kern_ctx {
struct vfp_state *prev;
#define FPU_KERN_CTX_DUMMY 0x01 /* avoided save for the kern thread */
#define FPU_KERN_CTX_INUSE 0x02
uint32_t flags;
struct vfp_state state;
};
/*
* About .fpu directives in this file...
*
@ -100,6 +108,26 @@ set_coprocessorACR(u_int val)
isb();
}
static void
vfp_enable(void)
{
uint32_t fpexc;
fpexc = fmrx(fpexc);
fmxr(fpexc, fpexc | VFPEXC_EN);
isb();
}
static void
vfp_disable(void)
{
uint32_t fpexc;
fpexc = fmrx(fpexc);
fmxr(fpexc, fpexc & ~VFPEXC_EN);
isb();
}
/* called for each cpu */
void
vfp_init(void)
@ -223,7 +251,9 @@ vfp_bounce(u_int addr, u_int insn, struct trapframe *frame, int code)
curpcb = curthread->td_pcb;
cpu = PCPU_GET(cpuid);
if (curpcb->pcb_vfpcpu != cpu || curthread != PCPU_GET(fpcurthread)) {
vfp_restore(&curpcb->pcb_vfpstate);
if (curpcb->pcb_vfpsaved == NULL)
curpcb->pcb_vfpsaved = &curpcb->pcb_vfpstate;
vfp_restore(curpcb->pcb_vfpsaved);
curpcb->pcb_vfpcpu = cpu;
PCPU_SET(fpcurthread, curthread);
}
@ -320,4 +350,154 @@ vfp_discard(struct thread *td)
fmxr(fpexc, tmp & ~VFPEXC_EN);
}
void
vfp_save_state(struct thread *td, struct pcb *pcb)
{
int32_t fpexc;
KASSERT(pcb != NULL, ("NULL vfp pcb"));
KASSERT(td == NULL || td->td_pcb == pcb, ("Invalid vfp pcb"));
/*
* savectx() will be called on panic with dumppcb as an argument,
* dumppcb doesn't have pcb_vfpsaved set, so set it to save
* the VFP registers.
*/
if (pcb->pcb_vfpsaved == NULL)
pcb->pcb_vfpsaved = &pcb->pcb_vfpstate;
if (td == NULL)
td = curthread;
critical_enter();
/*
* Only store the registers if the VFP is enabled,
* i.e. return if we are trapping on FP access.
*/
fpexc = fmrx(fpexc);
if (fpexc & VFPEXC_EN) {
KASSERT(PCPU_GET(fpcurthread) == td,
("Storing an invalid VFP state"));
vfp_store(pcb->pcb_vfpsaved, true);
}
critical_exit();
}
void
fpu_kern_enter(struct thread *td, struct fpu_kern_ctx *ctx, u_int flags)
{
struct pcb *pcb;
pcb = td->td_pcb;
KASSERT((flags & FPU_KERN_NOCTX) != 0 || ctx != NULL,
("ctx is required when !FPU_KERN_NOCTX"));
KASSERT(ctx == NULL || (ctx->flags & FPU_KERN_CTX_INUSE) == 0,
("using inuse ctx"));
KASSERT((pcb->pcb_fpflags & PCB_FP_NOSAVE) == 0,
("recursive fpu_kern_enter while in PCB_FP_NOSAVE state"));
if ((flags & FPU_KERN_NOCTX) != 0) {
critical_enter();
if (curthread == PCPU_GET(fpcurthread)) {
vfp_save_state(curthread, pcb);
}
PCPU_SET(fpcurthread, NULL);
vfp_enable();
pcb->pcb_fpflags |= PCB_FP_KERN | PCB_FP_NOSAVE |
PCB_FP_STARTED;
return;
}
if ((flags & FPU_KERN_KTHR) != 0 && is_fpu_kern_thread(0)) {
ctx->flags = FPU_KERN_CTX_DUMMY | FPU_KERN_CTX_INUSE;
return;
}
/*
* Check either we are already using the VFP in the kernel, or
* the the saved state points to the default user space.
*/
KASSERT((pcb->pcb_fpflags & PCB_FP_KERN) != 0 ||
pcb->pcb_vfpsaved == &pcb->pcb_vfpstate,
("Mangled pcb_vfpsaved %x %p %p", pcb->pcb_fpflags, pcb->pcb_vfpsaved,
&pcb->pcb_vfpstate));
ctx->flags = FPU_KERN_CTX_INUSE;
vfp_save_state(curthread, pcb);
ctx->prev = pcb->pcb_vfpsaved;
pcb->pcb_vfpsaved = &ctx->state;
pcb->pcb_fpflags |= PCB_FP_KERN;
pcb->pcb_fpflags &= ~PCB_FP_STARTED;
return;
}
int
fpu_kern_leave(struct thread *td, struct fpu_kern_ctx *ctx)
{
struct pcb *pcb;
pcb = td->td_pcb;
if ((pcb->pcb_fpflags & PCB_FP_NOSAVE) != 0) {
KASSERT(ctx == NULL, ("non-null ctx after FPU_KERN_NOCTX"));
KASSERT(PCPU_GET(fpcurthread) == NULL,
("non-NULL fpcurthread for PCB_FP_NOSAVE"));
CRITICAL_ASSERT(td);
vfp_disable();
pcb->pcb_fpflags &= ~(PCB_FP_NOSAVE | PCB_FP_STARTED);
critical_exit();
} else {
KASSERT((ctx->flags & FPU_KERN_CTX_INUSE) != 0,
("FPU context not inuse"));
ctx->flags &= ~FPU_KERN_CTX_INUSE;
if (is_fpu_kern_thread(0) &&
(ctx->flags & FPU_KERN_CTX_DUMMY) != 0)
return (0);
KASSERT((ctx->flags & FPU_KERN_CTX_DUMMY) == 0, ("dummy ctx"));
critical_enter();
vfp_discard(td);
critical_exit();
pcb->pcb_fpflags &= ~PCB_FP_STARTED;
pcb->pcb_vfpsaved = ctx->prev;
}
if (pcb->pcb_vfpsaved == &pcb->pcb_vfpstate) {
pcb->pcb_fpflags &= ~PCB_FP_KERN;
} else {
KASSERT((pcb->pcb_fpflags & PCB_FP_KERN) != 0,
("unpaired fpu_kern_leave"));
}
return (0);
}
int
fpu_kern_thread(u_int flags __unused)
{
struct pcb *pcb = curthread->td_pcb;
KASSERT((curthread->td_pflags & TDP_KTHREAD) != 0,
("Only kthread may use fpu_kern_thread"));
KASSERT(pcb->pcb_vfpsaved == &pcb->pcb_vfpstate,
("Mangled pcb_vfpsaved"));
KASSERT((pcb->pcb_fpflags & PCB_FP_KERN) == 0,
("Thread already setup for the VFP"));
pcb->pcb_fpflags |= PCB_FP_KERN;
return (0);
}
int
is_fpu_kern_thread(u_int flags __unused)
{
struct pcb *curpcb;
if ((curthread->td_pflags & TDP_KTHREAD) == 0)
return (0);
curpcb = curthread->td_pcb;
return ((curpcb->pcb_fpflags & PCB_FP_KERN) != 0);
}
#endif

6
sys/arm/arm/vm_machdep.c
View File

@ -108,9 +108,8 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
#ifdef VFP
/* Store actual state of VFP */
if (curthread == td1) {
critical_enter();
vfp_store(&td1->td_pcb->pcb_vfpstate, false);
critical_exit();
if ((td1->td_pcb->pcb_fpflags & PCB_FP_STARTED) != 0)
vfp_save_state(td1, td1->td_pcb);
}
#endif
td2->td_pcb = pcb2;
@ -139,6 +138,7 @@ cpu_fork(struct thread *td1, struct proc *p2, struct thread *td2, int flags)
pcb2->pcb_regs.sf_tpidrurw = (register_t)get_tls();
pcb2->pcb_vfpcpu = -1;
pcb2->pcb_vfpsaved = &pcb2->pcb_vfpstate;
pcb2->pcb_vfpstate.fpscr = initial_fpscr;
tf = td2->td_frame;

7
sys/arm/include/fpu.h Normal file
View File

@ -0,0 +1,7 @@
/*-
* This file is in the public domain.
*
* $FreeBSD$
*/
#include <machine/ucontext.h>
#include <machine/vfp.h>

5
sys/arm/include/pcb.h
View File

@ -66,6 +66,11 @@ struct pcb {
struct vfp_state pcb_vfpstate; /* VP/NEON state */
u_int pcb_vfpcpu; /* VP/NEON last cpu */
#define PCB_FP_STARTED 0x01
#define PCB_FP_KERN 0x02
#define PCB_FP_NOSAVE 0x04
struct vfp_state *pcb_vfpsaved; /* VP/NEON state */
int pcb_fpflags;
} __aligned(8); /*
* We need the PCB to be aligned on 8 bytes, as we may
* access it using ldrd/strd, and ARM ABI require it

12
sys/arm/include/reg.h
View File

@ -13,17 +13,9 @@ struct reg {
unsigned int r_cpsr;
};
struct fp_extended_precision {
__uint32_t fp_exponent;
__uint32_t fp_mantissa_hi;
__uint32_t fp_mantissa_lo;
};
typedef struct fp_extended_precision fp_reg_t;
struct fpreg {
unsigned int fpr_fpsr;
fp_reg_t fpr[8];
__uint64_t fpr_r[32];
__uint32_t fpr_fpscr;
};
struct dbreg {

17
sys/arm/include/vfp.h
View File

@ -139,6 +139,11 @@
#define COPROC10 (0x3 << 20)
#define COPROC11 (0x3 << 22)
#define FPU_KERN_NORMAL 0x0000
#define FPU_KERN_NOWAIT 0x0001
#define FPU_KERN_KTHR 0x0002
#define FPU_KERN_NOCTX 0x0004
#ifndef LOCORE
struct vfp_state {
uint64_t reg[32];
@ -154,6 +159,18 @@ void set_vfpcontext(struct thread *, mcontext_vfp_t *);
void vfp_init(void);
void vfp_store(struct vfp_state *, boolean_t);
void vfp_discard(struct thread *);
void vfp_restore_state(void);
void vfp_save_state(struct thread *, struct pcb *);
struct fpu_kern_ctx;
struct fpu_kern_ctx *fpu_kern_alloc_ctx(u_int);
void fpu_kern_free_ctx(struct fpu_kern_ctx *);
void fpu_kern_enter(struct thread *, struct fpu_kern_ctx *, u_int);
int fpu_kern_leave(struct thread *, struct fpu_kern_ctx *);
int fpu_kern_thread(u_int);
int is_fpu_kern_thread(u_int);
#endif /* _KERNEL */
#endif /* LOCORE */