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/* SPDX-License-Identifier: GPL-2.0 */
/*
* Purgatory setup code
*
* Copyright IBM Corp. 2018
*
* Author(s): Philipp Rudo <prudo@linux.vnet.ibm.com>
*/
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/page.h>
#include <asm/sigp.h>
#include <asm/ptrace.h>
/* The purgatory is the code running between two kernels. It's main purpose
* is to verify that the next kernel was not corrupted after load and to
* start it.
*
* If the next kernel is a crash kernel there are some peculiarities to
* consider:
*
* First the purgatory is called twice. Once only to verify the
* sha digest. So if the crash kernel got corrupted the old kernel can try
* to trigger a stand-alone dumper. And once to actually load the crash kernel.
*
* Second the purgatory also has to swap the crash memory region with its
* destination at address 0. As the purgatory is part of crash memory this
* requires some finesse. The tactic here is that the purgatory first copies
* itself to the end of the destination and then swaps the rest of the
* memory running from there.
*/
#define bufsz purgatory_end-stack
.macro MEMCPY dst,src,len
lgr %r0,\dst
lgr %r1,\len
lgr %r2,\src
lgr %r3,\len
20: mvcle %r0,%r2,0
jo 20b
.endm
.macro MEMSWAP dst,src,buf,len
10: larl %r0,purgatory_end
larl %r1,stack
slgr %r0,%r1
cgr \len,%r0
jh 11f
lgr %r4,\len
j 12f
11: lgr %r4,%r0
12: MEMCPY \buf,\dst,%r4
MEMCPY \dst,\src,%r4
MEMCPY \src,\buf,%r4
agr \dst,%r4
agr \src,%r4
sgr \len,%r4
cghi \len,0
jh 10b
.endm
.macro START_NEXT_KERNEL base subcode
lg %r4,kernel_entry-\base(%r13)
lg %r5,load_psw_mask-\base(%r13)
ogr %r4,%r5
stg %r4,0(%r0)
xgr %r0,%r0
lghi %r1,\subcode
diag %r0,%r1,0x308
.endm
.text
.balign PAGE_SIZE
SYM_CODE_START(purgatory_start)
/* The purgatory might be called after a diag308 so better set
* architecture and addressing mode.
*/
lhi %r1,1
sigp %r1,%r0,SIGP_SET_ARCHITECTURE
sam64
larl %r5,gprregs
stmg %r6,%r15,0(%r5)
basr %r13,0
.base_crash:
/* Setup stack */
larl %r15,purgatory_end-STACK_FRAME_OVERHEAD
/* If the next kernel is KEXEC_TYPE_CRASH the purgatory is called
* directly with a flag passed in %r2 whether the purgatory shall do
* checksum verification only (%r2 = 0 -> verification only).
*
* Check now and preserve over C function call by storing in
* %r10 with
* 1 -> checksum verification only
* 0 -> load new kernel
*/
lghi %r10,0
lg %r11,kernel_type-.base_crash(%r13)
cghi %r11,1 /* KEXEC_TYPE_CRASH */
jne .do_checksum_verification
cghi %r2,0 /* checksum verification only */
jne .do_checksum_verification
lghi %r10,1
.do_checksum_verification:
brasl %r14,verify_sha256_digest
cghi %r10,1 /* checksum verification only */
je .return_old_kernel
cghi %r2,0 /* checksum match */
jne .disabled_wait
/* If the next kernel is a crash kernel the purgatory has to swap
* the mem regions first.
*/
cghi %r11,1 /* KEXEC_TYPE_CRASH */
je .start_crash_kernel
/* start normal kernel */
START_NEXT_KERNEL .base_crash 0
.return_old_kernel:
lmg %r6,%r15,gprregs-.base_crash(%r13)
br %r14
.disabled_wait:
lpswe disabled_wait_psw-.base_crash(%r13)
.start_crash_kernel:
/* Location of purgatory_start in crash memory */
larl %r0,.base_crash
larl %r1,purgatory_start
slgr %r0,%r1
lgr %r8,%r13
sgr %r8,%r0
/* Destination for this code i.e. end of memory to be swapped. */
larl %r0,purgatory_end
larl %r1,purgatory_start
slgr %r0,%r1
lg %r9,crash_size-.base_crash(%r13)
sgr %r9,%r0
/* Destination in crash memory, i.e. same as r9 but in crash memory. */
lg %r10,crash_start-.base_crash(%r13)
agr %r10,%r9
/* Buffer location (in crash memory) and size. As the purgatory is
* behind the point of no return it can reuse the stack as buffer.
*/
larl %r11,purgatory_end
larl %r12,stack
slgr %r11,%r12
MEMCPY %r12,%r9,%r11 /* dst -> (crash) buf */
MEMCPY %r9,%r8,%r11 /* self -> dst */
/* Jump to new location. */
lgr %r7,%r9
larl %r0,.jump_to_dst
larl %r1,purgatory_start
slgr %r0,%r1
agr %r7,%r0
br %r7
.jump_to_dst:
basr %r13,0
.base_dst:
/* clear buffer */
MEMCPY %r12,%r10,%r11 /* (crash) buf -> (crash) dst */
/* Load new buffer location after jump */
larl %r7,stack
lgr %r0,%r7
larl %r1,purgatory_start
slgr %r0,%r1
agr %r10,%r0
MEMCPY %r10,%r7,%r11 /* (new) buf -> (crash) buf */
/* Now the code is set up to run from its designated location. Start
* swapping the rest of crash memory now.
*
* The registers will be used as follow:
*
* %r0-%r4 reserved for macros defined above
* %r5-%r6 tmp registers
* %r7 pointer to current struct sha region
* %r8 index to iterate over all sha regions
* %r9 pointer in crash memory
* %r10 pointer in old kernel
* %r11 total size (still) to be moved
* %r12 pointer to buffer
*/
lgr %r12,%r7
lgr %r11,%r9
lghi %r10,0
lg %r9,crash_start-.base_dst(%r13)
lghi %r8,16 /* KEXEC_SEGMENTS_MAX */
larl %r7,purgatory_sha_regions
j .loop_first
/* Loop over all purgatory_sha_regions. */
.loop_next:
aghi %r8,-1
cghi %r8,0
je .loop_out
aghi %r7,__KEXEC_SHA_REGION_SIZE
.loop_first:
lg %r5,__KEXEC_SHA_REGION_START(%r7)
cghi %r5,0
je .loop_next
/* Copy [end last sha region, start current sha region) */
/* Note: kexec_sha_region->start points in crash memory */
sgr %r5,%r9
MEMCPY %r9,%r10,%r5
agr %r9,%r5
agr %r10,%r5
sgr %r11,%r5
/* Swap sha region */
lg %r6,__KEXEC_SHA_REGION_LEN(%r7)
MEMSWAP %r9,%r10,%r12,%r6
sg %r11,__KEXEC_SHA_REGION_LEN(%r7)
j .loop_next
.loop_out:
/* Copy rest of crash memory */
MEMCPY %r9,%r10,%r11
/* start crash kernel */
START_NEXT_KERNEL .base_dst 1
SYM_CODE_END(purgatory_start)
SYM_DATA_LOCAL(load_psw_mask, .long 0x00080000,0x80000000)
.balign 8
SYM_DATA_LOCAL(disabled_wait_psw, .quad 0x0002000180000000,.do_checksum_verification)
SYM_DATA_LOCAL(gprregs, .fill 10,8,0)
SYM_DATA(purgatory_sha256_digest, .skip 32)
SYM_DATA(purgatory_sha_regions, .skip 16*__KEXEC_SHA_REGION_SIZE)
SYM_DATA(kernel_entry, .skip 8)
SYM_DATA(kernel_type, .skip 8)
SYM_DATA(crash_start, .skip 8)
SYM_DATA(crash_size, .skip 8)
.balign PAGE_SIZE
SYM_DATA_START_LOCAL(stack)
/* The buffer to move this code must be as big as the code. */
.skip stack-purgatory_start
.balign PAGE_SIZE
SYM_DATA_END_LABEL(stack, SYM_L_LOCAL, purgatory_end)
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