3d6519968b
A Linux binary will have the string "S390EP" at address 0x10008, which is important in getting the guest up off the ground. In the case of a reboot (specifically chreipl going to a new device), we should defer to the PSW at address zero for the new config, which will re-write "S390EP" from the new image. Let's clear it out at this point so that a reipl to, say, a DASD passthrough device drives the IPL path from scratch without disrupting disrupting the order of operations for other boots. Rather than hardcoding the address of this magic (again), let's define it somewhere so that the two users are visibly related. Signed-off-by: Eric Farman <farman@linux.ibm.com> Message-Id: <20201120160117.59366-3-farman@linux.ibm.com> Signed-off-by: Thomas Huth <thuth@redhat.com>
98 lines
2.7 KiB
C
98 lines
2.7 KiB
C
/*
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* QEMU s390-ccw firmware - jump to IPL code
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or (at
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* your option) any later version. See the COPYING file in the top-level
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* directory.
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*/
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#include "libc.h"
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#include "s390-ccw.h"
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#include "s390-arch.h"
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#define KERN_IMAGE_START 0x010000UL
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#define RESET_PSW_MASK (PSW_MASK_SHORTPSW | PSW_MASK_64)
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#define RESET_PSW ((uint64_t)&jump_to_IPL_addr | RESET_PSW_MASK)
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static uint64_t *reset_psw = 0, save_psw, ipl_continue;
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void write_reset_psw(uint64_t psw)
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{
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*reset_psw = psw;
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}
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static void jump_to_IPL_addr(void)
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{
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__attribute__((noreturn)) void (*ipl)(void) = (void *)ipl_continue;
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/* Restore reset PSW */
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write_reset_psw(save_psw);
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ipl();
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/* should not return */
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}
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void jump_to_IPL_code(uint64_t address)
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{
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/* store the subsystem information _after_ the bootmap was loaded */
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write_subsystem_identification();
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write_iplb_location();
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/* prevent unknown IPL types in the guest */
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if (iplb.pbt == S390_IPL_TYPE_QEMU_SCSI) {
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iplb.pbt = S390_IPL_TYPE_CCW;
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set_iplb(&iplb);
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}
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/*
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* The IPL PSW is at address 0. We also must not overwrite the
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* content of non-BIOS memory after we loaded the guest, so we
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* save the original content and restore it in jump_to_IPL_2.
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*/
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if (address) {
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save_psw = *reset_psw;
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write_reset_psw(RESET_PSW);
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ipl_continue = address;
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}
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debug_print_int("set IPL addr to", address ?: *reset_psw & PSW_MASK_SHORT_ADDR);
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/* Ensure the guest output starts fresh */
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sclp_print("\n");
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/*
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* HACK ALERT.
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* We use the load normal reset to keep r15 unchanged. jump_to_IPL_2
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* can then use r15 as its stack pointer.
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*/
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asm volatile("lghi 1,1\n\t"
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"diag 1,1,0x308\n\t"
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: : : "1", "memory");
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panic("\n! IPL returns !\n");
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}
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void jump_to_low_kernel(void)
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{
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/*
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* If it looks like a Linux binary, i.e. there is the "S390EP" magic from
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* arch/s390/kernel/head.S here, then let's jump to the well-known Linux
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* kernel start address (when jumping to the PSW-at-zero address instead,
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* the kernel startup code fails when we booted from a network device).
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*/
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if (!memcmp((char *)S390EP, "S390EP", 6)) {
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jump_to_IPL_code(KERN_IMAGE_START);
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}
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/* Trying to get PSW at zero address */
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if (*((uint64_t *)0) & RESET_PSW_MASK) {
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/*
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* Surely nobody will try running directly from lowcore, so
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* let's use 0 as an indication that we want to load the reset
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* psw at 0x0 and not jump to the entry.
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*/
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jump_to_IPL_code(0);
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}
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/* No other option left, so use the Linux kernel start address */
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jump_to_IPL_code(KERN_IMAGE_START);
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}
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