Commit ba9c1d65 authored by Max Filippov's avatar Max Filippov
Browse files

xtensa: rearrange syscall tracing 



system_call saves and restores syscall number across system call to make
clone and execv entry and exit tracing match. This complicates things
when syscall code may be changed by ptrace.
Preserve syscall code in copy_thread and start_thread directly instead of
doing tricks in system_call.

Signed-off-by: default avatarMax Filippov <jcmvbkbc@gmail.com>
parent c2d9aa3b

arch/xtensa/include/asm/processor.h

+2 −1
Original line number Diff line number Diff line
@@ -195,6 +195,7 @@ struct thread_struct { 
/* Clearing a0 terminates the backtrace. */

#define start_thread(regs, new_pc, new_sp) \

	do { \

		unsigned long syscall = (regs)->syscall; \

		memset((regs), 0, sizeof(*(regs))); \

		(regs)->pc = (new_pc); \

		(regs)->ps = USER_PS_VALUE; \
@@ -204,7 +205,7 @@ struct thread_struct { 
		(regs)->depc = 0; \

		(regs)->windowbase = 0; \

		(regs)->windowstart = 1; \

		(regs)->syscall = NO_SYSCALL; \

		(regs)->syscall = syscall; \

	} while (0)



/* Forward declaration */

arch/xtensa/kernel/entry.S

+0 −6
Original line number Diff line number Diff line
@@ -1895,8 +1895,6 @@ ENTRY(system_call) 
	l32i	a7, a2, PT_SYSCALL



1:

	s32i	a7, a1, 4



	/* syscall = sys_call_table[syscall_nr] */



	movi	a4, sys_call_table
@@ -1930,12 +1928,8 @@ ENTRY(system_call) 
	abi_ret(4)



1:

	l32i	a4, a1, 4

	l32i	a3, a2, PT_SYSCALL

	s32i	a4, a2, PT_SYSCALL

	mov	a6, a2

	call4	do_syscall_trace_leave

	s32i	a3, a2, PT_SYSCALL

	abi_ret(4)



ENDPROC(system_call)

arch/xtensa/kernel/process.c

+2 −0
Original line number Diff line number Diff line
@@ -264,6 +264,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn, 
			       &regs->areg[XCHAL_NUM_AREGS - len/4], len);

		}



		childregs->syscall = regs->syscall;



		/* The thread pointer is passed in the '4th argument' (= a5) */

		if (clone_flags & CLONE_SETTLS)

			childregs->threadptr = childregs->areg[5];

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