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ARC: Process-creation/scheduling/idle-loop 

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Vineet Gupta 2013-01-18 15:12:18 +05:30
parent 4adeefe161
commit bf90e1eab6
10 changed files with 484 additions and 8 deletions
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2
arch/arc/Kconfig
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@ -17,6 +17,8 @@ config ARC
select GENERIC_FIND_FIRST_BIT
# for now, we don't need GENERIC_IRQ_PROBE, CONFIG_GENERIC_IRQ_CHIP
select GENERIC_IRQ_SHOW
select GENERIC_KERNEL_EXECVE
select GENERIC_KERNEL_THREAD
select GENERIC_PENDING_IRQ if SMP
select GENERIC_SMP_IDLE_THREAD
select HAVE_GENERIC_HARDIRQS

20
arch/arc/include/asm/arcregs.h
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@ -47,6 +47,17 @@
#define AUX_ITRIGGER 0x40d
#define AUX_IPULSE 0x415
/*
* Floating Pt Registers
* Status regs are read-only (build-time) so need not be saved/restored
*/
#define ARC_AUX_FP_STAT 0x300
#define ARC_AUX_DPFP_1L 0x301
#define ARC_AUX_DPFP_1H 0x302
#define ARC_AUX_DPFP_2L 0x303
#define ARC_AUX_DPFP_2H 0x304
#define ARC_AUX_DPFP_STAT 0x305
#ifndef __ASSEMBLY__
/*
@ -110,6 +121,15 @@
#endif
#ifdef CONFIG_ARC_FPU_SAVE_RESTORE
/* These DPFP regs need to be saved/restored across ctx-sw */
struct arc_fpu {
struct {
unsigned int l, h;
} aux_dpfp[2];
};
#endif
#endif /* __ASEMBLY__ */
#endif /* __KERNEL__ */

9
arch/arc/include/asm/processor.h
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@ -29,6 +29,9 @@ struct thread_struct {
unsigned long callee_reg; /* pointer to callee regs */
unsigned long fault_address; /* dbls as brkpt holder as well */
unsigned long cause_code; /* Exception Cause Code (ECR) */
#ifdef CONFIG_ARC_FPU_SAVE_RESTORE
struct arc_fpu fpu;
#endif
};
#define INIT_THREAD { \
@ -54,12 +57,6 @@ unsigned long thread_saved_pc(struct task_struct *t);
#define cpu_relax() do { } while (0)
/*
* Create a new kernel thread
*/
extern int kernel_thread(int (*fn) (void *), void *arg, unsigned long flags);
#define copy_segments(tsk, mm) do { } while (0)
#define release_segments(mm) do { } while (0)

8
arch/arc/include/asm/ptrace.h
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@ -91,6 +91,14 @@ struct callee_regs {
#define in_syscall(regs) (((regs->orig_r8) >= 0 && \
(regs->orig_r8 <= NR_syscalls)) ? 1 : 0)
#define current_pt_regs() \
({ \
/* open-coded current_thread_info() */ \
register unsigned long sp asm ("sp"); \
unsigned long pg_start = (sp & ~(THREAD_SIZE - 1)); \
(struct pt_regs *)(pg_start + THREAD_SIZE - 4) - 1; \
})
#endif /* !__ASSEMBLY__ */
#endif /* __KERNEL__ */

41
arch/arc/include/asm/switch_to.h Normal file
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@ -0,0 +1,41 @@
/*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef _ASM_ARC_SWITCH_TO_H
#define _ASM_ARC_SWITCH_TO_H
#ifndef __ASSEMBLY__
#include <linux/sched.h>
#ifdef CONFIG_ARC_FPU_SAVE_RESTORE
extern void fpu_save_restore(struct task_struct *p, struct task_struct *n);
#define ARC_FPU_PREV(p, n) fpu_save_restore(p, n)
#define ARC_FPU_NEXT(t)
#else
#define ARC_FPU_PREV(p, n)
#define ARC_FPU_NEXT(n)
#endif /* !CONFIG_ARC_FPU_SAVE_RESTORE */
struct task_struct *__switch_to(struct task_struct *p, struct task_struct *n);
#define switch_to(prev, next, last) \
do { \
ARC_FPU_PREV(prev, next); \
last = __switch_to(prev, next);\
ARC_FPU_NEXT(next); \
mb(); \
} while (0)
#endif
#endif

91
arch/arc/kernel/ctx_sw.c Normal file
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@ -0,0 +1,91 @@
/*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Vineetg: Aug 2009
* -"C" version of lowest level context switch asm macro called by schedular
* gcc doesn't generate the dward CFI info for hand written asm, hence can't
* backtrace out of it (e.g. tasks sleeping in kernel).
* So we cheat a bit by writing almost similar code in inline-asm.
* -This is a hacky way of doing things, but there is no other simple way.
* I don't want/intend to extend unwinding code to understand raw asm
*/
#include <asm/asm-offsets.h>
#include <linux/sched.h>
struct task_struct *__sched
__switch_to(struct task_struct *prev_task, struct task_struct *next_task)
{
unsigned int tmp;
unsigned int prev = (unsigned int)prev_task;
unsigned int next = (unsigned int)next_task;
int num_words_to_skip = 1;
__asm__ __volatile__(
/* FP/BLINK save generated by gcc (standard function prologue */
"st.a r13, [sp, -4] \n\t"
"st.a r14, [sp, -4] \n\t"
"st.a r15, [sp, -4] \n\t"
"st.a r16, [sp, -4] \n\t"
"st.a r17, [sp, -4] \n\t"
"st.a r18, [sp, -4] \n\t"
"st.a r19, [sp, -4] \n\t"
"st.a r20, [sp, -4] \n\t"
"st.a r21, [sp, -4] \n\t"
"st.a r22, [sp, -4] \n\t"
"st.a r23, [sp, -4] \n\t"
"st.a r24, [sp, -4] \n\t"
"st.a r25, [sp, -4] \n\t"
"sub sp, sp, %4 \n\t" /* create gutter at top */
/* set ksp of outgoing task in tsk->thread.ksp */
"st.as sp, [%3, %1] \n\t"
"sync \n\t"
/*
* setup _current_task with incoming tsk.
* optionally, set r25 to that as well
* For SMP extra work to get to &_current_task[cpu]
* (open coded SET_CURR_TASK_ON_CPU)
*/
"st %2, [@_current_task] \n\t"
/* get ksp of incoming task from tsk->thread.ksp */
"ld.as sp, [%2, %1] \n\t"
/* start loading it's CALLEE reg file */
"add sp, sp, %4 \n\t" /* skip gutter at top */
"ld.ab r25, [sp, 4] \n\t"
"ld.ab r24, [sp, 4] \n\t"
"ld.ab r23, [sp, 4] \n\t"
"ld.ab r22, [sp, 4] \n\t"
"ld.ab r21, [sp, 4] \n\t"
"ld.ab r20, [sp, 4] \n\t"
"ld.ab r19, [sp, 4] \n\t"
"ld.ab r18, [sp, 4] \n\t"
"ld.ab r17, [sp, 4] \n\t"
"ld.ab r16, [sp, 4] \n\t"
"ld.ab r15, [sp, 4] \n\t"
"ld.ab r14, [sp, 4] \n\t"
"ld.ab r13, [sp, 4] \n\t"
/* last (ret value) = prev : although for ARC it mov r0, r0 */
"mov %0, %3 \n\t"
/* FP/BLINK restore generated by gcc (standard func epilogue */
: "=r"(tmp)
: "n"((TASK_THREAD + THREAD_KSP) / 4), "r"(next), "r"(prev),
"n"(num_words_to_skip * 4)
: "blink"
);
return (struct task_struct *)tmp;
}

58
arch/arc/kernel/ctx_sw_asm.S Normal file
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@ -0,0 +1,58 @@
/*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Vineetg: Aug 2009
* -Moved core context switch macro out of entry.S into this file.
* -This is the more "natural" hand written assembler
*/
#include <asm/entry.h> /* For the SAVE_* macros */
#include <asm/asm-offsets.h>
#include <asm/linkage.h>
;################### Low Level Context Switch ##########################
.section .sched.text,"ax",@progbits
.align 4
.global __switch_to
.type __switch_to, @function
__switch_to:
/* Save regs on kernel mode stack of task */
st.a blink, [sp, -4]
st.a fp, [sp, -4]
SAVE_CALLEE_SAVED_KERNEL
/* Save the now KSP in task->thread.ksp */
st.as sp, [r0, (TASK_THREAD + THREAD_KSP)/4]
/*
* Return last task in r0 (return reg)
* On ARC, Return reg = First Arg reg = r0.
* Since we already have last task in r0,
* don't need to do anything special to return it
*/
/* hardware memory barrier */
sync
/*
* switch to new task, contained in r1
* Temp reg r3 is required to get the ptr to store val
*/
SET_CURR_TASK_ON_CPU r1, r3
/* reload SP with kernel mode stack pointer in task->thread.ksp */
ld.as sp, [r1, (TASK_THREAD + THREAD_KSP)/4]
/* restore the registers */
RESTORE_CALLEE_SAVED_KERNEL
ld.ab fp, [sp, 4]
ld.ab blink, [sp, 4]
j [blink]
ARC_EXIT __switch_to

15
arch/arc/kernel/entry.S
View File

@ -566,8 +566,19 @@ ARC_ENTRY ret_from_fork
; when the forked child comes here from the __switch_to function
; r0 has the last task pointer.
; put last task in scheduler queue
bl @schedule_tail
b @ret_from_exception
bl @schedule_tail
; If kernel thread, jump to it's entry-point
ld r9, [sp, PT_status32]
brne r9, 0, 1f
jl.d [r14]
mov r0, r13 ; arg to payload
1:
; special case of kernel_thread entry point returning back due to
; kernel_execve() - pretend return from syscall to ret to userland
b ret_from_exception
ARC_EXIT ret_from_fork
;################### Special Sys Call Wrappers ##########################

55
arch/arc/kernel/fpu.c Normal file
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@ -0,0 +1,55 @@
/*
* fpu.c - save/restore of Floating Point Unit Registers on task switch
*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/sched.h>
#include <asm/switch_to.h>
/*
* To save/restore FPU regs, simplest scheme would use LR/SR insns.
* However since SR serializes the pipeline, an alternate "hack" can be used
* which uses the FPU Exchange insn (DEXCL) to r/w FPU regs.
*
* Store to 64bit dpfp1 reg from a pair of core regs:
* dexcl1 0, r1, r0 ; where r1:r0 is the 64 bit val
*
* Read from dpfp1 into pair of core regs (w/o clobbering dpfp1)
* mov_s r3, 0
* daddh11 r1, r3, r3 ; get "hi" into r1 (dpfp1 unchanged)
* dexcl1 r0, r1, r3 ; get "low" into r0 (dpfp1 low clobbered)
* dexcl1 0, r1, r0 ; restore dpfp1 to orig value
*
* However we can tweak the read, so that read-out of outgoing task's FPU regs
* and write of incoming task's regs happen in one shot. So all the work is
* done before context switch
*/
void fpu_save_restore(struct task_struct *prev, struct task_struct *next)
{
unsigned int *saveto = &prev->thread.fpu.aux_dpfp[0].l;
unsigned int *readfrom = &next->thread.fpu.aux_dpfp[0].l;
const unsigned int zero = 0;
__asm__ __volatile__(
"daddh11 %0, %2, %2\n"
"dexcl1 %1, %3, %4\n"
: "=&r" (*(saveto + 1)), /* early clobber must here */
"=&r" (*(saveto))
: "r" (zero), "r" (*(readfrom + 1)), "r" (*(readfrom))
);
__asm__ __volatile__(
"daddh22 %0, %2, %2\n"
"dexcl2 %1, %3, %4\n"
: "=&r"(*(saveto + 3)), /* early clobber must here */
"=&r"(*(saveto + 2))
: "r" (zero), "r" (*(readfrom + 3)), "r" (*(readfrom + 2))
);
}

193
arch/arc/kernel/process.c
View File

@ -40,3 +40,196 @@ SYSCALL_DEFINE0(arc_gettls)
{
return task_thread_info(current)->thr_ptr;
}
static inline void arch_idle(void)
{
/* sleep, but enable all interrupts before committing */
__asm__("sleep 0x3");
}
void cpu_idle(void)
{
/* Since we SLEEP in idle loop, TIF_POLLING_NRFLAG can't be set */
/* endless idle loop with no priority at all */
while (1) {
tick_nohz_idle_enter();
rcu_idle_enter();
doze:
local_irq_disable();
if (!need_resched()) {
arch_idle();
goto doze;
} else {
local_irq_enable();
}
rcu_idle_exit();
tick_nohz_idle_exit();
schedule_preempt_disabled();
}
}
asmlinkage void ret_from_fork(void);
/* Layout of Child kernel mode stack as setup at the end of this function is
*
* | ... |
* | ... |
* | unused |
* | |
* ------------------ <==== top of Stack (thread.ksp)
* | UNUSED 1 word|
* ------------------
* | r25 |
* ~ ~
* | --to-- | (CALLEE Regs of user mode)
* | r13 |
* ------------------
* | fp |
* | blink | @ret_from_fork
* ------------------
* | |
* ~ ~
* ~ ~
* | |
* ------------------
* | r12 |
* ~ ~
* | --to-- | (scratch Regs of user mode)
* | r0 |
* ------------------
* | UNUSED 1 word|
* ------------------ <===== END of PAGE
*/
int copy_thread(unsigned long clone_flags,
unsigned long usp, unsigned long arg,
struct task_struct *p)
{
struct pt_regs *c_regs; /* child's pt_regs */
unsigned long *childksp; /* to unwind out of __switch_to() */
struct callee_regs *c_callee; /* child's callee regs */
struct callee_regs *parent_callee; /* paren't callee */
struct pt_regs *regs = current_pt_regs();
/* Mark the specific anchors to begin with (see pic above) */
c_regs = task_pt_regs(p);
childksp = (unsigned long *)c_regs - 2; /* 2 words for FP/BLINK */
c_callee = ((struct callee_regs *)childksp) - 1;
/*
* __switch_to() uses thread.ksp to start unwinding stack
* For kernel threads we don't need to create callee regs, the
* stack layout nevertheless needs to remain the same.
* Also, since __switch_to anyways unwinds callee regs, we use
* this to populate kernel thread entry-pt/args into callee regs,
* so that ret_from_kernel_thread() becomes simpler.
*/
p->thread.ksp = (unsigned long)c_callee; /* THREAD_KSP */
/* __switch_to expects FP(0), BLINK(return addr) at top */
childksp[0] = 0; /* fp */
childksp[1] = (unsigned long)ret_from_fork; /* blink */
if (unlikely(p->flags & PF_KTHREAD)) {
memset(c_regs, 0, sizeof(struct pt_regs));
c_callee->r13 = arg; /* argument to kernel thread */
c_callee->r14 = usp; /* function */
return 0;
}
/*--------- User Task Only --------------*/
/* __switch_to expects FP(0), BLINK(return addr) at top of stack */
childksp[0] = 0; /* for POP fp */
childksp[1] = (unsigned long)ret_from_fork; /* for POP blink */
/* Copy parents pt regs on child's kernel mode stack */
*c_regs = *regs;
if (usp)
c_regs->sp = usp;
c_regs->r0 = 0; /* fork returns 0 in child */
parent_callee = ((struct callee_regs *)regs) - 1;
*c_callee = *parent_callee;
if (unlikely(clone_flags & CLONE_SETTLS)) {
/*
* set task's userland tls data ptr from 4th arg
* clone C-lib call is difft from clone sys-call
*/
task_thread_info(p)->thr_ptr = regs->r3;
} else {
/* Normal fork case: set parent's TLS ptr in child */
task_thread_info(p)->thr_ptr =
task_thread_info(current)->thr_ptr;
}
return 0;
}
/*
* Some archs flush debug and FPU info here
*/
void flush_thread(void)
{
}
/*
* Free any architecture-specific thread data structures, etc.
*/
void exit_thread(void)
{
}
int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
{
return 0;
}
/*
* API: expected by schedular Code: If thread is sleeping where is that.
* What is this good for? it will be always the scheduler or ret_from_fork.
* So we hard code that anyways.
*/
unsigned long thread_saved_pc(struct task_struct *t)
{
struct pt_regs *regs = task_pt_regs(t);
unsigned long blink = 0;
/*
* If the thread being queried for in not itself calling this, then it
* implies it is not executing, which in turn implies it is sleeping,
* which in turn implies it got switched OUT by the schedular.
* In that case, it's kernel mode blink can reliably retrieved as per
* the picture above (right above pt_regs).
*/
if (t != current && t->state != TASK_RUNNING)
blink = *((unsigned int *)regs - 1);
return blink;
}
int elf_check_arch(const struct elf32_hdr *x)
{
unsigned int eflags;
if (x->e_machine != EM_ARCOMPACT)
return 0;
eflags = x->e_flags;
if ((eflags & EF_ARC_OSABI_MSK) < EF_ARC_OSABI_V2) {
pr_err("ABI mismatch - you need newer toolchain\n");
force_sigsegv(SIGSEGV, current);
return 0;
}
return 1;
}
EXPORT_SYMBOL(elf_check_arch);