d/freebsd-nq
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Reuse gp register for pcpu pointer.

Browse Source 
gp (global pointer) is used by compiler in userland only,
so re-use it for pcpup in kernel, save it on stack on switching
out to userland and load back on return to kernel.

Discussed with:	jhb, andrew, kib
Sponsored by:	DARPA, AFRL
Sponsored by:	HEIF5
Differential Revision:	https://reviews.freebsd.org/D5178
This commit is contained in:
Ruslan Bukin 2016-02-04 12:49:28 +00:00
parent 0b5afe4aea
commit 4d50647d52
6 changed files with 38 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
sys/riscv/include/pcpu.h
View File

@ -47,8 +47,11 @@ extern struct pcpu *pcpup;
static inline struct pcpu *
get_pcpu(void)
{
struct pcpu *pcpu;
return (pcpup);
__asm __volatile("mv %0, gp" : "=&r"(pcpu));
return (pcpu);
}
static inline struct thread *
@ -56,7 +59,7 @@ get_curthread(void)
{
struct thread *td;
td = (struct thread *)*(uint64_t *)pcpup;
__asm __volatile("ld %0, 0(gp)" : "=&r"(td));
return (td);
}

17
sys/riscv/riscv/exception.S
View File

@ -41,12 +41,16 @@ __FBSDID("$FreeBSD$");
#include <machine/riscvreg.h>
.macro save_registers el
addi sp, sp, -280
addi sp, sp, -(TF_SIZE)
sd ra, (TF_RA)(sp)
sd gp, (TF_GP)(sp)
sd tp, (TF_TP)(sp)
.if \el == 0 /* We came from userspace. Load our pcpu */
sd gp, (TF_GP)(sp)
ld gp, (TF_SIZE)(sp)
.endif
sd t0, (TF_T + 0 * 8)(sp)
sd t1, (TF_T + 1 * 8)(sp)
sd t2, (TF_T + 2 * 8)(sp)
@ -127,13 +131,16 @@ __FBSDID("$FreeBSD$");
csrw sepc, t0
.if \el == 0
/* Load user sp */
/* We go to userspace. Load user sp */
ld t0, (TF_SP)(sp)
csrw sscratch, t0
/* And store our pcpu */
sd gp, (TF_SIZE)(sp)
ld gp, (TF_GP)(sp)
.endif
ld ra, (TF_RA)(sp)
ld gp, (TF_GP)(sp)
ld tp, (TF_TP)(sp)
ld t0, (TF_T + 0 * 8)(sp)
@ -166,7 +173,7 @@ __FBSDID("$FreeBSD$");
ld a6, (TF_A + 6 * 8)(sp)
ld a7, (TF_A + 7 * 8)(sp)
addi sp, sp, 280
addi sp, sp, (TF_SIZE)
.endm
.macro do_ast

1
sys/riscv/riscv/genassym.c
View File

@ -85,6 +85,7 @@ ASSYM(TD_FRAME, offsetof(struct thread, td_frame));
ASSYM(TD_MD, offsetof(struct thread, td_md));
ASSYM(TD_LOCK, offsetof(struct thread, td_lock));
ASSYM(TF_SIZE, sizeof(struct trapframe));
ASSYM(TF_RA, offsetof(struct trapframe, tf_ra));
ASSYM(TF_SP, offsetof(struct trapframe, tf_sp));
ASSYM(TF_GP, offsetof(struct trapframe, tf_gp));

11
sys/riscv/riscv/machdep.c
View File

@ -256,7 +256,9 @@ ptrace_clear_single_step(struct thread *td)
void
exec_setregs(struct thread *td, struct image_params *imgp, u_long stack)
{
struct trapframe *tf = td->td_frame;
struct trapframe *tf;
tf = td->td_frame;
memset(tf, 0, sizeof(struct trapframe));
@ -563,6 +565,7 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
static void
init_proc0(vm_offset_t kstack)
{
pcpup = &__pcpu[0];
proc_linkup0(&proc0, &thread0);
@ -760,11 +763,7 @@ initriscv(struct riscv_bootparams *rvbp)
pcpu_init(pcpup, 0, sizeof(struct pcpu));
/* Set the pcpu pointer */
#if 0
/* SMP TODO: try re-use gp for pcpu pointer */
__asm __volatile(
"mv gp, %0" :: "r"(pcpup));
#endif
__asm __volatile("mv gp, %0" :: "r"(pcpup));
PCPU_SET(curthread, &thread0);

23
sys/riscv/riscv/swtch.S
View File

@ -74,8 +74,6 @@ ENTRY(cpu_throw)
/* Load registers */
ld ra, (PCB_RA)(x13)
ld sp, (PCB_SP)(x13)
ld gp, (PCB_GP)(x13)
ld tp, (PCB_TP)(x13)
/* s[0-11] */
ld s0, (PCB_S + 0 * 8)(x13)
@ -120,8 +118,6 @@ ENTRY(cpu_switch)
/* Store the callee-saved registers */
sd ra, (PCB_RA)(x13)
sd sp, (PCB_SP)(x13)
sd gp, (PCB_GP)(x13)
sd tp, (PCB_TP)(x13)
/* We use these in fork_trampoline */
sd t0, (PCB_T + 0 * 8)(x13)
@ -176,8 +172,6 @@ ENTRY(cpu_switch)
/* Restore the registers */
ld ra, (PCB_RA)(x13)
ld sp, (PCB_SP)(x13)
ld gp, (PCB_GP)(x13)
ld tp, (PCB_TP)(x13)
/* We use these in fork_trampoline */
ld t0, (PCB_T + 0 * 8)(x13)
@ -254,12 +248,23 @@ ENTRY(fork_trampoline)
ld a6, (TF_A + 6 * 8)(sp)
ld a7, (TF_A + 7 * 8)(sp)
/* Load user ra and sp */
ld tp, (TF_TP)(sp)
ld ra, (TF_RA)(sp)
/*
* Store our pcpup on stack, we will load it back
* on kernel mode trap.
*/
sd gp, (TF_SIZE)(sp)
ld gp, (TF_GP)(sp)
/* Save kernel stack so we can use it doing a user trap */
addi sp, sp, TF_SIZE
csrw sscratch, sp
/* Load user ra and sp */
ld ra, (TF_RA)(sp)
ld sp, (TF_SP)(sp)
/* Load user stack */
ld sp, (TF_SP - TF_SIZE)(sp)
eret
END(fork_trampoline)

2
sys/riscv/riscv/vm_machdep.c
View File

@ -218,7 +218,7 @@ cpu_thread_alloc(struct thread *td)
td->td_pcb = (struct pcb *)(td->td_kstack +
td->td_kstack_pages * PAGE_SIZE) - 1;
td->td_frame = (struct trapframe *)STACKALIGN(
td->td_pcb - 1);
(caddr_t)td->td_pcb - 8 - sizeof(struct trapframe));
}
void