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linux/arch/s390/kernel/swsusp.S
Martin Schwidefsky ce3dc44749 s390: add support for virtually mapped kernel stacks 
With virtually mapped kernel stacks the kernel stack overflow detection
is now fault based, every stack has a guard page in the vmalloc space.
The panic_stack is renamed to nodat_stack and is used for all function
that need to run without DAT, e.g. memcpy_real or do_start_kdump.

The main effect is a reduction in the kernel image size as with vmap
stacks the old style overflow checking that adds two instructions per
function is not needed anymore. Result from bloat-o-meter:

add/remove: 20/1 grow/shrink: 13/26854 up/down: 2198/-216240 (-214042)

In regard to performance the micro-benchmark for fork has a hit of a
few microseconds, allocating 4 pages in vmalloc space is more expensive
compare to an order-2 page allocation. But with real workload I could
not find a noticeable difference.

Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2018-10-09 11:20:57 +02:00

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/* SPDX-License-Identifier: GPL-2.0 */
/*
* S390 64-bit swsusp implementation
*
* Copyright IBM Corp. 2009
*
* Author(s): Hans-Joachim Picht <hans@linux.vnet.ibm.com>
* Michael Holzheu <holzheu@linux.vnet.ibm.com>
*/
#include <linux/linkage.h>
#include <asm/page.h>
#include <asm/ptrace.h>
#include <asm/thread_info.h>
#include <asm/asm-offsets.h>
#include <asm/nospec-insn.h>
#include <asm/sigp.h>
/*
* Save register context in absolute 0 lowcore and call swsusp_save() to
* create in-memory kernel image. The context is saved in the designated
* "store status" memory locations (see POP).
* We return from this function twice. The first time during the suspend to
* disk process. The second time via the swsusp_arch_resume() function
* (see below) in the resume process.
* This function runs with disabled interrupts.
*/
GEN_BR_THUNK %r14
.section .text
ENTRY(swsusp_arch_suspend)
lg %r1,__LC_NODAT_STACK
aghi %r1,-STACK_FRAME_OVERHEAD
stmg %r6,%r15,__SF_GPRS(%r1)
stg %r15,__SF_BACKCHAIN(%r1)
lgr %r1,%r15
/* Store FPU registers */
brasl %r14,save_fpu_regs
/* Deactivate DAT */
stnsm __SF_EMPTY(%r15),0xfb
/* Store prefix register on stack */
stpx __SF_EMPTY(%r15)
/* Save prefix register contents for lowcore copy */
llgf %r10,__SF_EMPTY(%r15)
/* Get pointer to save area */
lghi %r1,0x1000
/* Save CPU address */
stap __LC_EXT_CPU_ADDR(%r0)
/* Store registers */
mvc 0x318(4,%r1),__SF_EMPTY(%r15) /* move prefix to lowcore */
stam %a0,%a15,0x340(%r1) /* store access registers */
stctg %c0,%c15,0x380(%r1) /* store control registers */
stmg %r0,%r15,0x280(%r1) /* store general registers */
stpt 0x328(%r1) /* store timer */
stck __SF_EMPTY(%r15) /* store clock */
stckc 0x330(%r1) /* store clock comparator */
/* Update cputime accounting before going to sleep */
lg %r0,__LC_LAST_UPDATE_TIMER
slg %r0,0x328(%r1)
alg %r0,__LC_SYSTEM_TIMER
stg %r0,__LC_SYSTEM_TIMER
mvc __LC_LAST_UPDATE_TIMER(8),0x328(%r1)
lg %r0,__LC_LAST_UPDATE_CLOCK
slg %r0,__SF_EMPTY(%r15)
alg %r0,__LC_STEAL_TIMER
stg %r0,__LC_STEAL_TIMER
mvc __LC_LAST_UPDATE_CLOCK(8),__SF_EMPTY(%r15)
/* Activate DAT */
stosm __SF_EMPTY(%r15),0x04
/* Set prefix page to zero */
xc __SF_EMPTY(4,%r15),__SF_EMPTY(%r15)
spx __SF_EMPTY(%r15)
/* Save absolute zero pages */
larl %r2,suspend_zero_pages
lg %r2,0(%r2)
lghi %r4,0
lghi %r3,2*PAGE_SIZE
lghi %r5,2*PAGE_SIZE
1: mvcle %r2,%r4,0
jo 1b
/* Copy lowcore to absolute zero lowcore */
lghi %r2,0
lgr %r4,%r10
lghi %r3,2*PAGE_SIZE
lghi %r5,2*PAGE_SIZE
1: mvcle %r2,%r4,0
jo 1b
/* Save image */
brasl %r14,swsusp_save
/* Restore prefix register and return */
lghi %r1,0x1000
spx 0x318(%r1)
lmg %r6,%r15,STACK_FRAME_OVERHEAD + __SF_GPRS(%r15)
lghi %r2,0
BR_EX %r14
/*
* Restore saved memory image to correct place and restore register context.
* Then we return to the function that called swsusp_arch_suspend().
* swsusp_arch_resume() runs with disabled interrupts.
*/
ENTRY(swsusp_arch_resume)
stmg %r6,%r15,__SF_GPRS(%r15)
lgr %r1,%r15
aghi %r15,-STACK_FRAME_OVERHEAD
stg %r1,__SF_BACKCHAIN(%r15)
/* Make all free pages stable */
lghi %r2,1
brasl %r14,arch_set_page_states
/* Deactivate DAT */
stnsm __SF_EMPTY(%r15),0xfb
/* Set prefix page to zero */
xc __SF_EMPTY(4,%r15),__SF_EMPTY(%r15)
spx __SF_EMPTY(%r15)
/* Restore saved image */
larl %r1,restore_pblist
lg %r1,0(%r1)
ltgr %r1,%r1
jz 2f
0:
lg %r2,8(%r1)
lg %r4,0(%r1)
iske %r0,%r4
lghi %r3,PAGE_SIZE
lghi %r5,PAGE_SIZE
1:
mvcle %r2,%r4,0
jo 1b
lg %r2,8(%r1)
sske %r0,%r2
lg %r1,16(%r1)
ltgr %r1,%r1
jnz 0b
2:
ptlb /* flush tlb */
/* Reset System */
larl %r1,restart_entry
larl %r2,.Lrestart_diag308_psw
og %r1,0(%r2)
stg %r1,0(%r0)
larl %r1,.Lnew_pgm_check_psw
epsw %r2,%r3
stm %r2,%r3,0(%r1)
mvc __LC_PGM_NEW_PSW(16,%r0),0(%r1)
lghi %r0,0
diag %r0,%r0,0x308
restart_entry:
lhi %r1,1
sigp %r1,%r0,SIGP_SET_ARCHITECTURE
sam64
#ifdef CONFIG_SMP
larl %r1,smp_cpu_mt_shift
icm %r1,15,0(%r1)
jz smt_done
llgfr %r1,%r1
smt_loop:
sigp %r1,%r0,SIGP_SET_MULTI_THREADING
brc 8,smt_done /* accepted */
brc 2,smt_loop /* busy, try again */
smt_done:
#endif
larl %r1,.Lnew_pgm_check_psw
lpswe 0(%r1)
pgm_check_entry:
/* Switch to original suspend CPU */
larl %r1,.Lresume_cpu /* Resume CPU address: r2 */
stap 0(%r1)
llgh %r2,0(%r1)
llgh %r1,__LC_EXT_CPU_ADDR(%r0) /* Suspend CPU address: r1 */
cgr %r1,%r2
je restore_registers /* r1 = r2 -> nothing to do */
larl %r4,.Lrestart_suspend_psw /* Set new restart PSW */
mvc __LC_RST_NEW_PSW(16,%r0),0(%r4)
3:
sigp %r9,%r1,SIGP_INITIAL_CPU_RESET /* sigp initial cpu reset */
brc 8,4f /* accepted */
brc 2,3b /* busy, try again */
/* Suspend CPU not available -> panic */
larl %r15,init_thread_union+THREAD_SIZE-STACK_FRAME_OVERHEAD
larl %r2,.Lpanic_string
brasl %r14,sclp_early_printk_force
larl %r3,.Ldisabled_wait_31
lpsw 0(%r3)
4:
/* Switch to suspend CPU */
sigp %r9,%r1,SIGP_RESTART /* sigp restart to suspend CPU */
brc 2,4b /* busy, try again */
5:
sigp %r9,%r2,SIGP_STOP /* sigp stop to current resume CPU */
brc 2,5b /* busy, try again */
6: j 6b
restart_suspend:
larl %r1,.Lresume_cpu
llgh %r2,0(%r1)
7:
sigp %r9,%r2,SIGP_SENSE /* sigp sense, wait for resume CPU */
brc 8,7b /* accepted, status 0, still running */
brc 2,7b /* busy, try again */
tmll %r9,0x40 /* Test if resume CPU is stopped */
jz 7b
restore_registers:
/* Restore registers */
lghi %r13,0x1000 /* %r1 = pointer to save area */
/* Ignore time spent in suspended state. */
llgf %r1,0x318(%r13)
stck __LC_LAST_UPDATE_CLOCK(%r1)
spt 0x328(%r13) /* reprogram timer */
//sckc 0x330(%r13) /* set clock comparator */
lctlg %c0,%c15,0x380(%r13) /* load control registers */
lam %a0,%a15,0x340(%r13) /* load access registers */
/* Load old stack */
lg %r15,0x2f8(%r13)
/* Save prefix register */
mvc __SF_EMPTY(4,%r15),0x318(%r13)
/* Restore absolute zero pages */
lghi %r2,0
larl %r4,suspend_zero_pages
lg %r4,0(%r4)
lghi %r3,2*PAGE_SIZE
lghi %r5,2*PAGE_SIZE
1: mvcle %r2,%r4,0
jo 1b
/* Restore prefix register */
spx __SF_EMPTY(%r15)
/* Activate DAT */
stosm __SF_EMPTY(%r15),0x04
/* Make all free pages unstable */
lghi %r2,0
brasl %r14,arch_set_page_states
/* Call arch specific early resume code */
brasl %r14,s390_early_resume
/* Return 0 */
lmg %r6,%r15,STACK_FRAME_OVERHEAD + __SF_GPRS(%r15)
lghi %r2,0
BR_EX %r14
.section .data..nosave,"aw",@progbits
.align 8
.Ldisabled_wait_31:
.long 0x000a0000,0x00000000
.Lpanic_string:
.asciz "Resume not possible because suspend CPU is no longer available\n"
.align 8
.Lrestart_diag308_psw:
.long 0x00080000,0x80000000
.Lrestart_suspend_psw:
.quad 0x0000000180000000,restart_suspend
.Lnew_pgm_check_psw:
.quad 0,pgm_check_entry
.Lresume_cpu:
.byte 0,0
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