Commit 3f2829a3 authored by Nicolas Pitre's avatar Nicolas Pitre Committed by Russell King
Browse files

[ARM] 3105/4: ARM EABI: new syscall entry convention 



Patch from Nicolas Pitre

For a while we wanted to change the way syscalls were called on ARM.
Instead of encoding the syscall number in the swi instruction which
requires reading back the instruction from memory to extract that number
and polluting the data cache, it was decided that simply storing the
syscall number into r7 would be more efficient. Since this represents
an ABI change then making that change at the same time as EABI support
is the right thing to do.

It is now expected that EABI user space binaries put the syscall number
into r7 and use "swi 0" to call the kernel. Syscall register argument
are also expected to have "EABI arrangement" i.e. 64-bit arguments
should be put in a pair of registers from an even register number.

Example with long ftruncate64(unsigned int fd, loff_t length):

	legacy ABI:
	- put fd into r0
	- put length into r1-r2
	- use "swi #(0x900000 + 194)" to call the kernel

	new ARM EABI:
	- put fd into r0
	- put length into r2-r3 (skipping over r1)
	- put 194 into r7
	- use "swi 0" to call the kernel

Note that it is important to use 0 for the swi argument as backward
compatibility with legacy ABI user space relies on this.
The syscall macros in asm-arm/unistd.h were also updated to support
both ABIs and implement the right call method automatically.

Signed-off-by: default avatarNicolas Pitre <nico@cam.org>
Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent ba95e4e4

arch/arm/kernel/entry-common.S

+21 −14
Original line number Diff line number Diff line
@@ -98,20 +98,14 @@ ENTRY(ret_from_fork) 
	   run on an ARM7 and we can save a couple of instructions.  

								--pb */

#ifdef CONFIG_CPU_ARM710

	.macro	arm710_bug_check, instr, temp

	and	\temp, \instr, #0x0f000000	@ check for SWI

	teq	\temp, #0x0f000000

	bne	.Larm700bug

	.endm



.Larm700bug:

#define A710(code...) code

.Larm710bug:

	ldmia	sp, {r0 - lr}^			@ Get calling r0 - lr

	mov	r0, r0

	add	sp, sp, #S_FRAME_SIZE

	subs	pc, lr, #4

#else

	.macro	arm710_bug_check, instr, temp

	.endm

#define A710(code...)

#endif



	.align	5
@@ -129,14 +123,24 @@ ENTRY(vector_swi) 
	/*

	 * Get the system call number.

	 */

#ifdef CONFIG_ARM_THUMB

#if defined(CONFIG_AEABI)



	@ syscall number is in scno (r7) already.



  A710(	ldr	ip, [lr, #-4]			@ get SWI instruction	)

  A710(	and	ip, ip, #0x0f000000		@ check for SWI		)

  A710(	teq	ip, #0x0f000000						)

  A710(	bne	.Larm710bug						)

#elif defined(CONFIG_ARM_THUMB)

	tst	r8, #PSR_T_BIT			@ this is SPSR from save_user_regs

	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in

	ldreq	scno, [lr, #-4]

#else

	ldr	scno, [lr, #-4]			@ get SWI instruction

  A710(	and	ip, scno, #0x0f000000		@ check for SWI		)

  A710(	teq	ip, #0x0f000000						)

  A710(	bne	.Larm710bug						)

#endif

	arm710_bug_check scno, ip



#ifdef CONFIG_ALIGNMENT_TRAP

	ldr	ip, __cr_alignment
@@ -145,18 +149,19 @@ ENTRY(vector_swi) 
#endif

	enable_irq



	stmdb	sp!, {r4, r5}			@ push fifth and sixth args



	get_thread_info tsk

	ldr	ip, [tsk, #TI_FLAGS]		@ check for syscall tracing

#ifndef CONFIG_AEABI

	bic	scno, scno, #0xff000000		@ mask off SWI op-code

	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number

#endif

	adr	tbl, sys_call_table		@ load syscall table pointer

	stmdb	sp!, {r4, r5}			@ push fifth and sixth args

	tst	ip, #_TIF_SYSCALL_TRACE		@ are we tracing syscalls?

	bne	__sys_trace



	adr	lr, ret_fast_syscall		@ return address

	cmp	scno, #NR_syscalls		@ check upper syscall limit

	adr	lr, ret_fast_syscall		@ return address

	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine



	add	r1, sp, #S_OFF
@@ -207,6 +212,7 @@ ENTRY(sys_call_table) 
@ r8 = syscall table

		.type	sys_syscall, #function

sys_syscall:

#ifndef CONFIG_AEABI

		eor	scno, r0, #__NR_SYSCALL_BASE

		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE

		cmpne	scno, #NR_syscalls	@ check range
@@ -216,6 +222,7 @@ sys_syscall: 
		movlo	r2, r3

		movlo	r3, r4

		ldrlo	pc, [tbl, scno, lsl #2]

#endif

		b	sys_ni_syscall



sys_fork_wrapper:

arch/arm/kernel/traps.c

+1 −1
Original line number Diff line number Diff line
@@ -404,7 +404,7 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs) 
	struct thread_info *thread = current_thread_info();

	siginfo_t info;



	if ((no >> 16) != 0x9f)

	if ((no >> 16) != (__ARM_NR_BASE>> 16))

		return bad_syscall(no, regs);



	switch (no & 0xffff) {

include/asm-arm/unistd.h

+26 −22
Original line number Diff line number Diff line
@@ -15,10 +15,12 @@ 


#include <linux/linkage.h>



#if defined(__thumb__)

#define __NR_OABI_SYSCALL_BASE	0x900000



#if defined(__thumb__) || defined(__ARM_EABI__)

#define __NR_SYSCALL_BASE	0

#else

#define __NR_SYSCALL_BASE	0x900000

#define __NR_SYSCALL_BASE	__NR_OABI_SYSCALL_BASE

#endif



/*
@@ -373,13 +375,13 @@ 
#define __sys1(x) __sys2(x)



#ifndef __syscall

#if defined(__thumb__)

#define __syscall(name)					\

	"push	{r7}\n\t"				\

	"mov	r7, #" __sys1(__NR_##name) "\n\t"	\

	"swi	0\n\t"					\

	"pop	{r7}"

#if defined(__thumb__) || defined(__ARM_EABI__)

#define __SYS_REG(name) register long __sysreg __asm__("r7") = __NR_##name;

#define __SYS_REG_LIST(regs...) "r" (__sysreg) , ##regs

#define __syscall(name) "swi\t0"

#else

#define __SYS_REG(name)

#define __SYS_REG_LIST(regs...) regs

#define __syscall(name) "swi\t" __sys1(__NR_##name) ""

#endif

#endif
@@ -395,33 +397,34 @@ do { \ 


#define _syscall0(type,name)						\

type name(void) {							\

  __SYS_REG(name)							\

  register long __res_r0 __asm__("r0");					\

  long __res;								\

  __asm__ __volatile__ (						\

  __syscall(name)							\

	: "=r" (__res_r0)						\

	:								\

	: "lr");							\

	: __SYS_REG_LIST() );						\

  __res = __res_r0;							\

  __syscall_return(type,__res);						\

}



#define _syscall1(type,name,type1,arg1) 				\

type name(type1 arg1) { 						\

  __SYS_REG(name)							\

  register long __r0 __asm__("r0") = (long)arg1;			\

  register long __res_r0 __asm__("r0");					\

  long __res;								\

  __asm__ __volatile__ (						\

  __syscall(name)							\

	: "=r" (__res_r0)						\

	: "r" (__r0)							\

	: "lr");							\

	: __SYS_REG_LIST( "0" (__r0) ) );				\

  __res = __res_r0;							\

  __syscall_return(type,__res);						\

}



#define _syscall2(type,name,type1,arg1,type2,arg2)			\

type name(type1 arg1,type2 arg2) {					\

  __SYS_REG(name)							\

  register long __r0 __asm__("r0") = (long)arg1;			\

  register long __r1 __asm__("r1") = (long)arg2;			\

  register long __res_r0 __asm__("r0");					\
@@ -429,8 +432,7 @@ type name(type1 arg1,type2 arg2) { \ 
  __asm__ __volatile__ (						\

  __syscall(name)							\

	: "=r" (__res_r0)						\

	: "r" (__r0),"r" (__r1) 					\

	: "lr");							\

	: __SYS_REG_LIST( "0" (__r0), "r" (__r1) ) );			\

  __res = __res_r0;							\

  __syscall_return(type,__res);						\

}
@@ -438,6 +440,7 @@ type name(type1 arg1,type2 arg2) { \ 


#define _syscall3(type,name,type1,arg1,type2,arg2,type3,arg3)		\

type name(type1 arg1,type2 arg2,type3 arg3) {				\

  __SYS_REG(name)							\

  register long __r0 __asm__("r0") = (long)arg1;			\

  register long __r1 __asm__("r1") = (long)arg2;			\

  register long __r2 __asm__("r2") = (long)arg3;			\
@@ -446,8 +449,7 @@ type name(type1 arg1,type2 arg2,type3 arg3) { \ 
  __asm__ __volatile__ (						\

  __syscall(name)							\

	: "=r" (__res_r0)						\

	: "r" (__r0),"r" (__r1),"r" (__r2)				\

	: "lr");							\

	: __SYS_REG_LIST( "0" (__r0), "r" (__r1), "r" (__r2) ) );	\

  __res = __res_r0;							\

  __syscall_return(type,__res);						\

}
@@ -455,6 +457,7 @@ type name(type1 arg1,type2 arg2,type3 arg3) { \ 


#define _syscall4(type,name,type1,arg1,type2,arg2,type3,arg3,type4,arg4)\

type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4) {		\

  __SYS_REG(name)							\

  register long __r0 __asm__("r0") = (long)arg1;			\

  register long __r1 __asm__("r1") = (long)arg2;			\

  register long __r2 __asm__("r2") = (long)arg3;			\
@@ -464,8 +467,7 @@ type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4) { \ 
  __asm__ __volatile__ (						\

  __syscall(name)							\

	: "=r" (__res_r0)						\

	: "r" (__r0),"r" (__r1),"r" (__r2),"r" (__r3)			\

	: "lr");							\

	: __SYS_REG_LIST( "0" (__r0), "r" (__r1), "r" (__r2), "r" (__r3) ) ); \

  __res = __res_r0;							\

  __syscall_return(type,__res);						\

}
@@ -473,6 +475,7 @@ type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4) { \ 


#define _syscall5(type,name,type1,arg1,type2,arg2,type3,arg3,type4,arg4,type5,arg5)	\

type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4, type5 arg5) {	\

  __SYS_REG(name)							\

  register long __r0 __asm__("r0") = (long)arg1;			\

  register long __r1 __asm__("r1") = (long)arg2;			\

  register long __r2 __asm__("r2") = (long)arg3;			\
@@ -483,14 +486,15 @@ type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4, type5 arg5) { \ 
  __asm__ __volatile__ (						\

  __syscall(name)							\

	: "=r" (__res_r0)						\

	: "r" (__r0),"r" (__r1),"r" (__r2),"r" (__r3),"r" (__r4)	\

	: "lr");							\

	: __SYS_REG_LIST( "0" (__r0), "r" (__r1), "r" (__r2),		\

			  "r" (__r3), "r" (__r4) ) );			\

  __res = __res_r0;							\

  __syscall_return(type,__res);						\

}



#define _syscall6(type,name,type1,arg1,type2,arg2,type3,arg3,type4,arg4,type5,arg5,type6,arg6)	\

type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4, type5 arg5, type6 arg6) {	\

  __SYS_REG(name)							\

  register long __r0 __asm__("r0") = (long)arg1;			\

  register long __r1 __asm__("r1") = (long)arg2;			\

  register long __r2 __asm__("r2") = (long)arg3;			\
@@ -502,8 +506,8 @@ type name(type1 arg1, type2 arg2, type3 arg3, type4 arg4, type5 arg5, type6 arg6 
  __asm__ __volatile__ (						\

  __syscall(name)							\

	: "=r" (__res_r0)						\

	: "r" (__r0),"r" (__r1),"r" (__r2),"r" (__r3), "r" (__r4),"r" (__r5)		\

	: "lr");							\

	: __SYS_REG_LIST( "0" (__r0), "r" (__r1), "r" (__r2),		\

			  "r" (__r3), "r" (__r4), "r" (__r5) ) );	\

  __res = __res_r0;							\

  __syscall_return(type,__res);						\

}

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