s390/startup: add initial pgm check handler (da9ed30d) · Commits · 戴 / test

The startup code is getting more complicated with features like kaslr and secure boot in place. In a potential unexpected startup code crash case the system would end up in a pgm check loop at address 0, overwriting pgm check old psw value and just making debugging more complicated. To avoid that introduce startup program check handler which is active immediately after kernel start and until early_pgm_check_handler is set in kernel/early.c. So it covers kernel relocation phase and transition to it. This pgm check handler simply saves general/control registers and psw in the save area which should guarantee that we still have something to look at when standalone dumper is called without saving registers. And it does disabled wait with a faulty address in the end. Acked-by:

Ilya Leoshkevich <iii@linux.ibm.com> Signed-off-by:

Vasily Gorbik <gor@linux.ibm.com>

arch/s390/boot/head.S

+23 −1

Original line number	Diff line number	Diff line
		@@ -60,8 +60,10 @@ __HEAD
		.long 0x02000690,0x60000050
		.long 0x020006e0,0x20000050

		.org 0x1a0
		.org __LC_RST_NEW_PSW # 0x1a0
		.quad 0,iplstart
		.org __LC_PGM_NEW_PSW # 0x1d0
		.quad 0x0000000180000000,startup_pgm_check_handler

		.org 0x200

		@@ -351,6 +353,26 @@ ENTRY(startup_kdump)

		#include "head_kdump.S"

		#
		# This program check is active immediately after kernel start
		# and until early_pgm_check_handler is set in kernel/early.c
		# It simply saves general/control registers and psw in
		# the save area and does disabled wait with a faulty address.
		#
		ENTRY(startup_pgm_check_handler)
		stmg %r0,%r15,__LC_SAVE_AREA_SYNC
		la %r1,4095
		stctg %c0,%c15,__LC_CREGS_SAVE_AREA-4095(%r1)
		mvc __LC_GPREGS_SAVE_AREA-4095(128,%r1),__LC_SAVE_AREA_SYNC
		mvc __LC_PSW_SAVE_AREA-4095(16,%r1),__LC_PGM_OLD_PSW
		lg %r1,__LC_SAVE_AREA_SYNC+8
		mvc __LC_RETURN_PSW(16),__LC_PGM_OLD_PSW
		ni __LC_RETURN_PSW,0xfc # remove IO and EX bits
		ni __LC_RETURN_PSW+1,0xfb # remove MCHK bit
		oi __LC_RETURN_PSW+1,0x2 # set wait state bit
		lpswe __LC_RETURN_PSW # disabled wait
		ENDPROC(startup_pgm_check_handler)

		#
		# params at 10400 (setup.h)
		# Must be keept in sync with struct parmarea in setup.h

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