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Commit c0e50d41 authored by Chris Zankel's avatar Chris Zankel
Browse files

xtensa: fix fast_syscall_spill_registers 



The original implementation could clobber registers under certain conditions.

The Xtensa processor architecture uses windowed registers and the original
implementation was using a4 as a temporary register, which under certain
conditions could be register a0 of the oldest window frame, and didn't always
restore the content correctly.

By moving the _spill_registers routine inside the fast system call, it frees
up one more register (the return address is not required anymore) for the
spill routine.

Signed-off-by: default avatarChris Zankel <chris@zankel.net>
parent 6b5a1f74

arch/xtensa/kernel/vectors.S

+1 −1
Original line number Diff line number Diff line
@@ -235,7 +235,7 @@ ENTRY(_DoubleExceptionVector) 


	/* Check for overflow/underflow exception, jump if overflow. */



	_bbci.l	a0, 6, _DoubleExceptionVector_WindowOverflow

	bbci.l	a0, 6, _DoubleExceptionVector_WindowOverflow



	/*

	 * Restart window underflow exception.

arch/xtensa/kernel/xtensa_ksyms.c

+0 −2
Original line number Diff line number Diff line
@@ -122,9 +122,7 @@ EXPORT_SYMBOL(insw); 
EXPORT_SYMBOL(insl);



extern long common_exception_return;

extern long _spill_registers;

EXPORT_SYMBOL(common_exception_return);

EXPORT_SYMBOL(_spill_registers);



#ifdef CONFIG_FUNCTION_TRACER

EXPORT_SYMBOL(_mcount);