Commit 61649881 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390: system call path micro optimization 



Add a pointer to the system call table to the thread_info structure.
The TIF_31BIT bit is set or cleared by SET_PERSONALITY exactly once
for the lifetime of a process. With the pointer to the correct system
call table in thread_info the system call code in entry64.S path can
drop the check for TIF_31BIT which saves a couple of instructions.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent dc7ee00d

arch/s390/include/asm/elf.h

+18 −4
Original line number Diff line number Diff line
@@ -120,6 +120,7 @@ 


#include <asm/ptrace.h>

#include <asm/compat.h>

#include <asm/syscall.h>

#include <asm/user.h>



typedef s390_fp_regs elf_fpregset_t;
@@ -181,18 +182,31 @@ extern unsigned long elf_hwcap; 
extern char elf_platform[];

#define ELF_PLATFORM (elf_platform)



#ifdef CONFIG_64BIT

#ifndef CONFIG_COMPAT

#define SET_PERSONALITY(ex) \

do {								\

	set_personality(PER_LINUX |				\

		(current->personality & (~PER_MASK)));		\

	current_thread_info()->sys_call_table = 		\

		(unsigned long) &sys_call_table;		\

} while (0)

#else /* CONFIG_COMPAT */

#define SET_PERSONALITY(ex)					\

do {								\

	if (personality(current->personality) != PER_LINUX32)	\

		set_personality(PER_LINUX |			\

			(current->personality & ~PER_MASK));	\

	if ((ex).e_ident[EI_CLASS] == ELFCLASS32)		\

	if ((ex).e_ident[EI_CLASS] == ELFCLASS32) {		\

		set_thread_flag(TIF_31BIT);			\

	else							\

		current_thread_info()->sys_call_table =		\

			(unsigned long)	&sys_call_table_emu;	\

	} else {						\

		clear_thread_flag(TIF_31BIT);			\

		current_thread_info()->sys_call_table =		\

			(unsigned long) &sys_call_table;	\

	}							\

} while (0)

#endif /* CONFIG_64BIT */

#endif /* CONFIG_COMPAT */



#define STACK_RND_MASK	0x7ffUL

arch/s390/include/asm/syscall.h

+1 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
 * type here is what we want [need] for both 32 bit and 64 bit systems.

 */

extern const unsigned int sys_call_table[];

extern const unsigned int sys_call_table_emu[];



static inline long syscall_get_nr(struct task_struct *task,

				  struct pt_regs *regs)

arch/s390/include/asm/thread_info.h

+1 −0
Original line number Diff line number Diff line
@@ -41,6 +41,7 @@ struct thread_info { 
	struct task_struct	*task;		/* main task structure */

	struct exec_domain	*exec_domain;	/* execution domain */

	unsigned long		flags;		/* low level flags */

	unsigned long		sys_call_table;	/* System call table address */

	unsigned int		cpu;		/* current CPU */

	int			preempt_count;	/* 0 => preemptable, <0 => BUG */

	struct restart_block	restart_block;

arch/s390/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ int main(void) 
	DEFINE(__TI_task, offsetof(struct thread_info, task));

	DEFINE(__TI_domain, offsetof(struct thread_info, exec_domain));

	DEFINE(__TI_flags, offsetof(struct thread_info, flags));

	DEFINE(__TI_sysc_table, offsetof(struct thread_info, sys_call_table));

	DEFINE(__TI_cpu, offsetof(struct thread_info, cpu));

	DEFINE(__TI_precount, offsetof(struct thread_info, preempt_count));

	DEFINE(__TI_user_timer, offsetof(struct thread_info, user_timer));

arch/s390/kernel/entry.S

+1 −2
Original line number Diff line number Diff line
@@ -188,6 +188,7 @@ sysc_vtime: 
	mvc	__PT_INT_CODE(4,%r11),__LC_SVC_ILC

sysc_do_svc:

	oi	__TI_flags+3(%r12),_TIF_SYSCALL

	l	%r10,__TI_sysc_table(%r12)	# 31 bit system call table

	lh	%r8,__PT_INT_CODE+2(%r11)

	sla	%r8,2				# shift and test for svc0

	jnz	sysc_nr_ok
@@ -198,7 +199,6 @@ sysc_do_svc: 
	lr	%r8,%r1

	sla	%r8,2

sysc_nr_ok:

	l	%r10,BASED(.Lsys_call_table)	# 31 bit system call table

	xc	__SF_BACKCHAIN(4,%r15),__SF_BACKCHAIN(%r15)

	st	%r2,__PT_ORIG_GPR2(%r11)

	st	%r7,STACK_FRAME_OVERHEAD(%r15)
@@ -906,7 +906,6 @@ cleanup_idle_wait: 
.Ltrace_enter:		.long	do_syscall_trace_enter

.Ltrace_exit:		.long	do_syscall_trace_exit

.Lschedule_tail:	.long	schedule_tail

.Lsys_call_table:	.long	sys_call_table

.Lsysc_per:		.long	sysc_per + 0x80000000

#ifdef CONFIG_TRACE_IRQFLAGS

.Lhardirqs_on:		.long	trace_hardirqs_on_caller

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