Commit e0969e0c authored by Stuart Menefy's avatar Stuart Menefy Committed by Paul Mundt
Browse files

sh: Fix syscall tracing ordering. 



The implementation of system call tracing in the kernel has a
couple of ordering problems:

 - the validity of the system call number is checked before
   calling out to system call tracing code, and should be
   done after

 - the system call number used when tracing is the one the
   system call was invoked with, while the system call tracing
   code can legitimatly change the call number (for example
   strace permutes fork into clone)

This patch fixes both of these problems, and also reoders the
code slightly to make the direct path through the code the
common case.

Signed-off-by: default avatarStuart Menefy <stuart.menefy@st.com>
Signed-off-by: default avatarPaul Mundt <lethal@linux-sh.org>
parent c9f0b1c1

arch/sh/kernel/entry-common.S

+22 −23
Original line number Diff line number Diff line
@@ -256,8 +256,7 @@ syscall_trace_entry: 
	mov.l	@(OFF_R6,r15), r6

	mov.l	@(OFF_R7,r15), r7   ! arg3

	mov.l	@(OFF_R3,r15), r3   ! syscall_nr

	!   	    	    Arrange for do_syscall_trace to be called

	!   	    	    again as the system call returns.

	!

	mov.l	2f, r10			! Number of syscalls

	cmp/hs	r10, r3

	bf	syscall_call
@@ -273,6 +272,18 @@ __restore_all: 
	.align	2

1:	.long	restore_all



	.align	2

not_syscall_tra:	

	bra	debug_trap

	 nop



	.align	2

syscall_badsys:			! Bad syscall number

	mov	#-ENOSYS, r0

	bra	resume_userspace

	 mov.l	r0, @(OFF_R0,r15)	! Return value

	



/*

 * Syscall interface:

 *
@@ -316,39 +327,27 @@ ENTRY(system_call) 
	! Is the trap argument >= 0x20? (TRA will be >= 0x80)

	mov	#0x7f, r9

	cmp/hi	r9, r8

	bt/s	0f

	bt/s	not_syscall_tra

	 mov	#OFF_TRA, r9

	add	r15, r9

	!

	mov.l	r8, @r9			! set TRA value to tra

	sti

	!   	    	    Call the system call handler through the table.

	!   	    	    First check for bad syscall number

	mov	r3, r9

	mov.l	2f, r8			! Number of syscalls

	cmp/hs	r8, r9

	get_current_thread_info r8, r10

	bf	good_system_call

syscall_badsys:			! Bad syscall number

	mov	#-ENOSYS, r0

	bra	resume_userspace

	 mov.l	r0, @(OFF_R0,r15)	! Return value

	!

0:

	bra	debug_trap

	 nop

	!

good_system_call:		! Good syscall number

	get_current_thread_info r8, r10

	mov.l	@(TI_FLAGS,r8), r8

	mov	#_TIF_SYSCALL_TRACE, r10

	tst	r10, r8

	bf	syscall_trace_entry

	!

	mov.l	2f, r8			! Number of syscalls

	cmp/hs	r8, r3

	bt	syscall_badsys

	!

syscall_call:

	shll2	r9		! x4

	shll2	r3		! x4

	mov.l	3f, r8		! Load the address of sys_call_table

	add	r8, r9

	mov.l	@r9, r8

	add	r8, r3

	mov.l	@r3, r8

	jsr	@r8	    	! jump to specific syscall handler

	 nop

	mov.l	@(OFF_R0,r15), r12		! save r0

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