s390: fix fpu restore in entry.S (1179f170) · Commits · 戴 / test

We need to disable interrupts in load_fpu_regs(). Otherwise an interrupt might come in after the registers are loaded, but before CIF_FPU is cleared in load_fpu_regs(). When the interrupt returns, CIF_FPU will be cleared and the registers will never be restored. The entry.S code usually saves the interrupt state in __SF_EMPTY on the stack when disabling/restoring interrupts. sie64a however saves the pointer to the sie control block in __SF_SIE_CONTROL, which references the same location. This is non-obvious to the reader. To avoid thrashing the sie control block pointer in load_fpu_regs(), move the __SIE_* offsets eight bytes after __SF_EMPTY on the stack. Cc: <stable@vger.kernel.org> # 5.8 Fixes: ("s390: remove critical section cleanup from entry.S") Reported-by:

Pierre Morel <pmorel@linux.ibm.com> Signed-off-by:

Sven Schnelle <svens@linux.ibm.com> Acked-by:

Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by:

Heiko Carstens <hca@linux.ibm.com> Signed-off-by:

Heiko Carstens <hca@linux.ibm.com>

arch/s390/kernel/asm-offsets.c

+5 −5

Original line number	Diff line number	Diff line
		@@ -53,11 +53,11 @@ int main(void)
		/* stack_frame offsets */
		OFFSET(__SF_BACKCHAIN, stack_frame, back_chain);
		OFFSET(__SF_GPRS, stack_frame, gprs);
		OFFSET(__SF_EMPTY, stack_frame, empty1);
		OFFSET(__SF_SIE_CONTROL, stack_frame, empty1[0]);
		OFFSET(__SF_SIE_SAVEAREA, stack_frame, empty1[1]);
		OFFSET(__SF_SIE_REASON, stack_frame, empty1[2]);
		OFFSET(__SF_SIE_FLAGS, stack_frame, empty1[3]);
		OFFSET(__SF_EMPTY, stack_frame, empty1[0]);
		OFFSET(__SF_SIE_CONTROL, stack_frame, empty1[1]);
		OFFSET(__SF_SIE_SAVEAREA, stack_frame, empty1[2]);
		OFFSET(__SF_SIE_REASON, stack_frame, empty1[3]);
		OFFSET(__SF_SIE_FLAGS, stack_frame, empty1[4]);
		BLANK();
		OFFSET(__VDSO_GETCPU_VAL, vdso_per_cpu_data, getcpu_val);
		BLANK();

arch/s390/kernel/entry.S

+2 −0

Original line number	Diff line number	Diff line
		@@ -1068,6 +1068,7 @@ EXPORT_SYMBOL(save_fpu_regs)
		* %r4
		*/
		load_fpu_regs:
		stnsm __SF_EMPTY(%r15),0xfc
		lg %r4,__LC_CURRENT
		aghi %r4,__TASK_thread
		TSTMSK __LC_CPU_FLAGS,_CIF_FPU
		@@ -1099,6 +1100,7 @@ load_fpu_regs:
		.Lload_fpu_regs_done:
		ni __LC_CPU_FLAGS+7,255-_CIF_FPU
		.Lload_fpu_regs_exit:
		ssm __SF_EMPTY(%r15)
		BR_EX %r14
		.Lload_fpu_regs_end:
		ENDPROC(load_fpu_regs)

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