linux/arch/arc/kernel/ctx_sw_asm.S
Vineet Gupta 86effd0dc6 ARC: dw2 unwind: enable cfi pseudo ops in string lib
This uses a new set of annoations viz. ENTRY_CFI/END_CFI to enabel cfi
ops generation.

Note that we didn't change the normal ENTRY/EXIT as we don't actually
want unwind info in the trap/exception/interrutp handlers which use
these, as unwinder then gets confused (it keeps recursing vs. stopping).
Semantically these are leaf routines and unwinding should stop when it
hits those routines.

Before
------

    28.52%     1.19%          9929  hackbench  libuClibc-1.0.17.so   [.] __write_nocancel
            |
            ---__write_nocancel
               |--8.95%--EV_Trap
               |           --8.25%--sys_write
               |                     |--3.93%--sock_write_iter
     ...
               |--2.62%--memset   <==== [LEAF entry as no unwind info]
                         ^^^^^^

After
-----

    29.46%     1.24%         13622  hackbench  libuClibc-1.0.17.so   [.] __write_nocancel
            |
            ---__write_nocancel
               |--9.31%--EV_Trap
               |           --8.62%--sys_write
               |                     |--4.17%--sock_write_iter
     ...
               |--6.19%--sys_write
               |           --6.19%--sock_write_iter
               |                     unix_stream_sendmsg
               |                     |--1.62%--sock_alloc_send_pskb
               |                     |--0.89%--sock_def_readable
               |                     |--0.88%--_raw_spin_unlock_irqrestore
               |                     |--0.69%--memset
               |                     |         ^^^^^^     <==== [now in proper callframe]
               |                     |
               |                      --0.52%--skb_copy_datagram_from_iter

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
2016-09-30 14:48:22 -07:00

64 lines
1.7 KiB
ArmAsm

/*
* 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 <linux/linkage.h>
#include <asm/entry.h> /* For the SAVE_* macros */
#include <asm/asm-offsets.h>
#define KSP_WORD_OFF ((TASK_THREAD + THREAD_KSP) / 4)
;################### Low Level Context Switch ##########################
.section .sched.text,"ax",@progbits
.align 4
.global __switch_to
.type __switch_to, @function
__switch_to:
CFI_STARTPROC
/* 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 */
#if KSP_WORD_OFF <= 255
st.as sp, [r0, KSP_WORD_OFF]
#else
/* Workaround for NR_CPUS=4k as ST.as can only take s9 offset */
add2 r24, r0, KSP_WORD_OFF
st sp, [r24]
#endif
/*
* 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
*/
/*
* 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]
END_CFI(__switch_to)