273 lines
6.1 KiB
ArmAsm
273 lines
6.1 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Purgatory setup code
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*
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* Copyright IBM Corp. 2018
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*
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* Author(s): Philipp Rudo <prudo@linux.vnet.ibm.com>
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*/
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#include <linux/linkage.h>
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#include <asm/asm-offsets.h>
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#include <asm/page.h>
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#include <asm/sigp.h>
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#include <asm/ptrace.h>
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/* The purgatory is the code running between two kernels. It's main purpose
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* is to verify that the next kernel was not corrupted after load and to
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* start it.
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*
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* If the next kernel is a crash kernel there are some peculiarities to
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* consider:
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*
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* First the purgatory is called twice. Once only to verify the
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* sha digest. So if the crash kernel got corrupted the old kernel can try
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* to trigger a stand-alone dumper. And once to actually load the crash kernel.
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*
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* Second the purgatory also has to swap the crash memory region with its
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* destination at address 0. As the purgatory is part of crash memory this
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* requires some finesse. The tactic here is that the purgatory first copies
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* itself to the end of the destination and then swaps the rest of the
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* memory running from there.
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*/
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#define bufsz purgatory_end-stack
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.macro MEMCPY dst,src,len
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lgr %r0,\dst
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lgr %r1,\len
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lgr %r2,\src
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lgr %r3,\len
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20: mvcle %r0,%r2,0
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jo 20b
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.endm
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.macro MEMSWAP dst,src,buf,len
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10: cghi \len,bufsz
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jh 11f
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lgr %r4,\len
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j 12f
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11: lghi %r4,bufsz
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12: MEMCPY \buf,\dst,%r4
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MEMCPY \dst,\src,%r4
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MEMCPY \src,\buf,%r4
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agr \dst,%r4
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agr \src,%r4
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sgr \len,%r4
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cghi \len,0
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jh 10b
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.endm
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.macro START_NEXT_KERNEL base
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lg %r4,kernel_entry-\base(%r13)
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lg %r5,load_psw_mask-\base(%r13)
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ogr %r4,%r5
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stg %r4,0(%r0)
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xgr %r0,%r0
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diag %r0,%r0,0x308
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.endm
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.text
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.align PAGE_SIZE
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ENTRY(purgatory_start)
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/* The purgatory might be called after a diag308 so better set
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* architecture and addressing mode.
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*/
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lhi %r1,1
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sigp %r1,%r0,SIGP_SET_ARCHITECTURE
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sam64
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larl %r5,gprregs
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stmg %r6,%r15,0(%r5)
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basr %r13,0
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.base_crash:
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/* Setup stack */
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larl %r15,purgatory_end-STACK_FRAME_OVERHEAD
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/* If the next kernel is KEXEC_TYPE_CRASH the purgatory is called
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* directly with a flag passed in %r2 whether the purgatory shall do
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* checksum verification only (%r2 = 0 -> verification only).
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*
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* Check now and preserve over C function call by storing in
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* %r10 whith
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* 1 -> checksum verification only
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* 0 -> load new kernel
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*/
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lghi %r10,0
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lg %r11,kernel_type-.base_crash(%r13)
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cghi %r11,1 /* KEXEC_TYPE_CRASH */
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jne .do_checksum_verification
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cghi %r2,0 /* checksum verification only */
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jne .do_checksum_verification
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lghi %r10,1
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.do_checksum_verification:
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brasl %r14,verify_sha256_digest
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cghi %r10,1 /* checksum verification only */
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je .return_old_kernel
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cghi %r2,0 /* checksum match */
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jne .disabled_wait
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/* If the next kernel is a crash kernel the purgatory has to swap
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* the mem regions first.
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*/
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cghi %r11,1 /* KEXEC_TYPE_CRASH */
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je .start_crash_kernel
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/* start normal kernel */
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START_NEXT_KERNEL .base_crash
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.return_old_kernel:
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lmg %r6,%r15,gprregs-.base_crash(%r13)
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br %r14
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.disabled_wait:
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lpswe disabled_wait_psw-.base_crash(%r13)
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.start_crash_kernel:
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/* Location of purgatory_start in crash memory */
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lgr %r8,%r13
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aghi %r8,-(.base_crash-purgatory_start)
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/* Destination for this code i.e. end of memory to be swapped. */
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lg %r9,crash_size-.base_crash(%r13)
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aghi %r9,-(purgatory_end-purgatory_start)
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/* Destination in crash memory, i.e. same as r9 but in crash memory. */
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lg %r10,crash_start-.base_crash(%r13)
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agr %r10,%r9
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/* Buffer location (in crash memory) and size. As the purgatory is
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* behind the point of no return it can re-use the stack as buffer.
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*/
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lghi %r11,bufsz
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larl %r12,stack
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MEMCPY %r12,%r9,%r11 /* dst -> (crash) buf */
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MEMCPY %r9,%r8,%r11 /* self -> dst */
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/* Jump to new location. */
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lgr %r7,%r9
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aghi %r7,.jump_to_dst-purgatory_start
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br %r7
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.jump_to_dst:
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basr %r13,0
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.base_dst:
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/* clear buffer */
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MEMCPY %r12,%r10,%r11 /* (crash) buf -> (crash) dst */
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/* Load new buffer location after jump */
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larl %r7,stack
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aghi %r10,stack-purgatory_start
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MEMCPY %r10,%r7,%r11 /* (new) buf -> (crash) buf */
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/* Now the code is set up to run from its designated location. Start
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* swapping the rest of crash memory now.
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*
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* The registers will be used as follow:
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*
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* %r0-%r4 reserved for macros defined above
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* %r5-%r6 tmp registers
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* %r7 pointer to current struct sha region
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* %r8 index to iterate over all sha regions
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* %r9 pointer in crash memory
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* %r10 pointer in old kernel
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* %r11 total size (still) to be moved
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* %r12 pointer to buffer
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*/
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lgr %r12,%r7
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lgr %r11,%r9
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lghi %r10,0
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lg %r9,crash_start-.base_dst(%r13)
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lghi %r8,16 /* KEXEC_SEGMENTS_MAX */
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larl %r7,purgatory_sha_regions
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j .loop_first
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/* Loop over all purgatory_sha_regions. */
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.loop_next:
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aghi %r8,-1
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cghi %r8,0
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je .loop_out
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aghi %r7,__KEXEC_SHA_REGION_SIZE
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.loop_first:
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lg %r5,__KEXEC_SHA_REGION_START(%r7)
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cghi %r5,0
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je .loop_next
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/* Copy [end last sha region, start current sha region) */
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/* Note: kexec_sha_region->start points in crash memory */
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sgr %r5,%r9
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MEMCPY %r9,%r10,%r5
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agr %r9,%r5
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agr %r10,%r5
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sgr %r11,%r5
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/* Swap sha region */
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lg %r6,__KEXEC_SHA_REGION_LEN(%r7)
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MEMSWAP %r9,%r10,%r12,%r6
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sg %r11,__KEXEC_SHA_REGION_LEN(%r7)
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j .loop_next
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.loop_out:
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/* Copy rest of crash memory */
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MEMCPY %r9,%r10,%r11
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/* start crash kernel */
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START_NEXT_KERNEL .base_dst
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load_psw_mask:
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.long 0x00080000,0x80000000
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.align 8
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disabled_wait_psw:
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.quad 0x0002000180000000
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.quad 0x0000000000000000 + .do_checksum_verification
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gprregs:
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.rept 10
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.quad 0
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.endr
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/* Macro to define a global variable with name and size (in bytes) to be
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* shared with C code.
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*
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* Add the .size and .type attribute to satisfy checks on the Elf_Sym during
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* purgatory load.
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*/
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.macro GLOBAL_VARIABLE name,size
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\name:
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.global \name
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.size \name,\size
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.type \name,object
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.skip \size,0
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.endm
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GLOBAL_VARIABLE purgatory_sha256_digest,32
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GLOBAL_VARIABLE purgatory_sha_regions,16*__KEXEC_SHA_REGION_SIZE
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GLOBAL_VARIABLE kernel_entry,8
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GLOBAL_VARIABLE kernel_type,8
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GLOBAL_VARIABLE crash_start,8
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GLOBAL_VARIABLE crash_size,8
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.align PAGE_SIZE
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stack:
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/* The buffer to move this code must be as big as the code. */
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.skip stack-purgatory_start
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.align PAGE_SIZE
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purgatory_end:
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