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Date: Thu, 24 Jan 2013 16:20:20 +0530
From: Vineet Gupta <Vineet.Gupta1@...opsys.com>
To: <linux-arch@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <arnd@...db.de>, Vineet Gupta <Vineet.Gupta1@...opsys.com>,
Al Viro <viro@...IV.linux.org.uk>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v3 18/71] ARC: Process-creation/scheduling/idle-loop
Signed-off-by: Vineet Gupta <vgupta@...opsys.com>
Cc: Al Viro <viro@...IV.linux.org.uk>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
arch/arc/Kconfig | 2 +
arch/arc/include/asm/arcregs.h | 20 ++++
arch/arc/include/asm/processor.h | 9 +-
arch/arc/include/asm/ptrace.h | 8 ++
arch/arc/include/asm/switch_to.h | 41 ++++++++
arch/arc/kernel/ctx_sw.c | 91 ++++++++++++++++++
arch/arc/kernel/ctx_sw_asm.S | 58 +++++++++++
arch/arc/kernel/entry.S | 15 +++-
arch/arc/kernel/fpu.c | 55 +++++++++++
arch/arc/kernel/process.c | 193 ++++++++++++++++++++++++++++++++++++++
10 files changed, 484 insertions(+), 8 deletions(-)
create mode 100644 arch/arc/include/asm/switch_to.h
create mode 100644 arch/arc/kernel/ctx_sw.c
create mode 100644 arch/arc/kernel/ctx_sw_asm.S
create mode 100644 arch/arc/kernel/fpu.c
diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 8789de1..a4e9806 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -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
diff --git a/arch/arc/include/asm/arcregs.h b/arch/arc/include/asm/arcregs.h
index 3fccb04..d764118 100644
--- a/arch/arc/include/asm/arcregs.h
+++ b/arch/arc/include/asm/arcregs.h
@@ -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__ */
diff --git a/arch/arc/include/asm/processor.h b/arch/arc/include/asm/processor.h
index bf88cfb..860252e 100644
--- a/arch/arc/include/asm/processor.h
+++ b/arch/arc/include/asm/processor.h
@@ -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)
diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h
index 9abbb7c..72754a2 100644
--- a/arch/arc/include/asm/ptrace.h
+++ b/arch/arc/include/asm/ptrace.h
@@ -130,6 +130,14 @@ struct user_regs_struct {
#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__ */
diff --git a/arch/arc/include/asm/switch_to.h b/arch/arc/include/asm/switch_to.h
new file mode 100644
index 0000000..1b171ab
--- /dev/null
+++ b/arch/arc/include/asm/switch_to.h
@@ -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
diff --git a/arch/arc/kernel/ctx_sw.c b/arch/arc/kernel/ctx_sw.c
new file mode 100644
index 0000000..647e37a
--- /dev/null
+++ b/arch/arc/kernel/ctx_sw.c
@@ -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;
+}
diff --git a/arch/arc/kernel/ctx_sw_asm.S b/arch/arc/kernel/ctx_sw_asm.S
new file mode 100644
index 0000000..d897234
--- /dev/null
+++ b/arch/arc/kernel/ctx_sw_asm.S
@@ -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
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index 0b0a190..ed08ac1 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -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 ##########################
diff --git a/arch/arc/kernel/fpu.c b/arch/arc/kernel/fpu.c
new file mode 100644
index 0000000..f352e51
--- /dev/null
+++ b/arch/arc/kernel/fpu.c
@@ -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))
+ );
+}
diff --git a/arch/arc/kernel/process.c b/arch/arc/kernel/process.c
index 4d14e56..279e080 100644
--- a/arch/arc/kernel/process.c
+++ b/arch/arc/kernel/process.c
@@ -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);
--
1.7.4.1
--
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