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Diffstat (limited to 'arch/s390/purgatory/head.S')
| -rw-r--r-- | arch/s390/purgatory/head.S | 273 |
1 files changed, 273 insertions, 0 deletions
diff --git a/arch/s390/purgatory/head.S b/arch/s390/purgatory/head.S new file mode 100644 index 000000000..9b2d7a71f --- /dev/null +++ b/arch/s390/purgatory/head.S @@ -0,0 +1,273 @@ +/* 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> + +/* 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: cghi \len,bufsz + jh 11f + lgr %r4,\len + j 12f +11: lghi %r4,bufsz + +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 + aghi %r15,-160 + + /* 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 */ + lgr %r8,%r13 + aghi %r8,-(.base_crash-purgatory_start) + + /* Destination for this code i.e. end of memory to be swapped. */ + lg %r9,crash_size-.base_crash(%r13) + aghi %r9,-(purgatory_end-purgatory_start) + + /* 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. + */ + lghi %r11,bufsz + larl %r12,stack + + MEMCPY %r12,%r9,%r11 /* dst -> (crash) buf */ + MEMCPY %r9,%r8,%r11 /* self -> dst */ + + /* Jump to new location. */ + lgr %r7,%r9 + aghi %r7,.jump_to_dst-purgatory_start + 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 + aghi %r10,stack-purgatory_start + 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: |