s390: critical section cleanup vs. machine checks (6551fbdf) · Commits · 戴 / test

The current machine check code uses the registers stored by the machine in the lowcore at __LC_GPREGS_SAVE_AREA as the registers of the interrupted context. The registers 0-7 of a user process can get clobbered if a machine checks interrupts the execution of a critical section in entry[64].S. The reason is that the critical section cleanup code may need to modify the PSW and the registers for the previous context to get to the end of a critical section. If registers 0-7 have to be replaced the relevant copy will be in the registers, which invalidates the copy in the lowcore. The machine check handler needs to explicitly store registers 0-7 to the stack. Cc: stable@vger.kernel.org Signed-off-by:

Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/entry.S

+2 −1

Original line number	Diff line number	Diff line
		@@ -636,7 +636,8 @@ ENTRY(mcck_int_handler)
		UPDATE_VTIME %r14,%r15,__LC_MCCK_ENTER_TIMER
		mcck_skip:
		SWITCH_ASYNC __LC_GPREGS_SAVE_AREA+32,__LC_PANIC_STACK,PAGE_SHIFT
		mvc __PT_R0(64,%r11),__LC_GPREGS_SAVE_AREA
		stm %r0,%r7,__PT_R0(%r11)
		mvc __PT_R8(32,%r11),__LC_GPREGS_SAVE_AREA+32
		stm %r8,%r9,__PT_PSW(%r11)
		xc __SF_BACKCHAIN(4,%r15),__SF_BACKCHAIN(%r15)
		l %r1,BASED(.Ldo_machine_check)

arch/s390/kernel/entry64.S

+3 −2

Original line number	Diff line number	Diff line
		@@ -678,8 +678,9 @@ ENTRY(mcck_int_handler)
		UPDATE_VTIME %r14,__LC_MCCK_ENTER_TIMER
		LAST_BREAK %r14
		mcck_skip:
		lghi %r14,__LC_GPREGS_SAVE_AREA
		mvc __PT_R0(128,%r11),0(%r14)
		lghi %r14,__LC_GPREGS_SAVE_AREA+64
		stmg %r0,%r7,__PT_R0(%r11)
		mvc __PT_R8(64,%r11),0(%r14)
		stmg %r8,%r9,__PT_PSW(%r11)
		xc __SF_BACKCHAIN(8,%r15),__SF_BACKCHAIN(%r15)
		lgr %r2,%r11 # pass pointer to pt_regs

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