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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
+.align PAGE_SIZE
+ENTRY(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 whith
+ * 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 re-use 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
+
+
+load_psw_mask:
+ .long 0x00080000,0x80000000
+
+ .align 8
+disabled_wait_psw:
+ .quad 0x0002000180000000
+ .quad 0x0000000000000000 + .do_checksum_verification
+
+gprregs:
+ .rept 10
+ .quad 0
+ .endr
+
+/* Macro to define a global variable with name and size (in bytes) to be
+ * shared with C code.
+ *
+ * Add the .size and .type attribute to satisfy checks on the Elf_Sym during
+ * purgatory load.
+ */
+.macro GLOBAL_VARIABLE name,size
+\name:
+ .global \name
+ .size \name,\size
+ .type \name,object
+ .skip \size,0
+.endm
+
+GLOBAL_VARIABLE purgatory_sha256_digest,32
+GLOBAL_VARIABLE purgatory_sha_regions,16*__KEXEC_SHA_REGION_SIZE
+GLOBAL_VARIABLE kernel_entry,8
+GLOBAL_VARIABLE kernel_type,8
+GLOBAL_VARIABLE crash_start,8
+GLOBAL_VARIABLE crash_size,8
+
+ .align PAGE_SIZE
+stack:
+ /* The buffer to move this code must be as big as the code. */
+ .skip stack-purgatory_start
+ .align PAGE_SIZE
+purgatory_end: