/*
* S390 IPL (boot) from a real DASD device via vfio framework.
*
* Copyright (c) 2019 Jason J. Herne <jjherne@us.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or (at
* your option) any later version. See the COPYING file in the top-level
* directory.
*/
#include "libc.h"
#include "s390-ccw.h"
#include "s390-arch.h"
#include "dasd-ipl.h"
#include "helper.h"
static char prefix_page[PAGE_SIZE * 2]
__attribute__((__aligned__(PAGE_SIZE * 2)));
static void enable_prefixing(void)
{
memcpy(&prefix_page, lowcore, 4096);
set_prefix(ptr2u32(&prefix_page));
}
static void disable_prefixing(void)
{
set_prefix(0);
/* Copy io interrupt info back to low core */
memcpy((void *)&lowcore->subchannel_id, prefix_page + 0xB8, 12);
}
static bool is_read_tic_ccw_chain(Ccw0 *ccw)
{
Ccw0 *next_ccw = ccw + 1;
return ((ccw->cmd_code == CCW_CMD_DASD_READ ||
ccw->cmd_code == CCW_CMD_DASD_READ_MT) &&
ccw->chain && next_ccw->cmd_code == CCW_CMD_TIC);
}
static bool dynamic_cp_fixup(uint32_t ccw_addr, uint32_t *next_cpa)
{
Ccw0 *cur_ccw = (Ccw0 *)(uint64_t)ccw_addr;
Ccw0 *tic_ccw;
while (true) {
/* Skip over inline TIC (it might not have the chain bit on) */
if (cur_ccw->cmd_code == CCW_CMD_TIC &&
cur_ccw->cda == ptr2u32(cur_ccw) - 8) {
cur_ccw += 1;
continue;
}
if (!cur_ccw->chain) {
break;
}
if (is_read_tic_ccw_chain(cur_ccw)) {
/*
* Breaking a chain of CCWs may alter the semantics or even the
* validity of a channel program. The heuristic implemented below
* seems to work well in practice for the channel programs
* generated by zipl.
*/
tic_ccw = cur_ccw + 1;
*next_cpa = tic_ccw->cda;
cur_ccw->chain = 0;
return true;
}
cur_ccw += 1;
}
return false;
}
static int run_dynamic_ccw_program(SubChannelId schid, uint16_t cutype,
uint32_t cpa)
{
bool has_next;
uint32_t next_cpa = 0;
int rc;
do {
has_next = dynamic_cp_fixup(cpa, &next_cpa);
print_int("executing ccw chain at ", cpa);
enable_prefixing();
rc = do_cio(schid, cutype, cpa, CCW_FMT0);
disable_prefixing();
if (rc) {
break;
}
cpa = next_cpa;
} while (has_next);
return rc;
}
static void make_readipl(void)
{
Ccw0 *ccwIplRead = (Ccw0 *)0x00;
/* Clear out any existing data */
memset(ccwIplRead, 0, sizeof(Ccw0));
/* Create Read IPL ccw at address 0 */
ccwIplRead->cmd_code = CCW_CMD_READ_IPL;
ccwIplRead->cda = 0x00; /* Read into address 0x00 in main memory */
ccwIplRead->chain = 0; /* Chain flag */
ccwIplRead->count = 0x18; /* Read 0x18 bytes of data */
}
static void run_readipl(SubChannelId schid, uint16_t cutype)
{
if (do_cio(schid, cutype, 0x00, CCW_FMT0)) {
panic("dasd-ipl: Failed to run Read IPL channel program\n");
}
}
/*
* The architecture states that IPL1 data should consist of a psw followed by
* format-0 READ and TIC CCWs. Let's sanity check.
*/
static void check_ipl1(void)
{
Ccw0 *ccwread = (Ccw0 *)0x08;
Ccw0 *ccwtic = (Ccw0 *)0x10;
if (ccwread->cmd_code != CCW_CMD_DASD_READ ||
ccwtic->cmd_code != CCW_CMD_TIC) {
panic("dasd-ipl: IPL1 data invalid. Is this disk really bootable?\n");
}
}
static void check_ipl2(uint32_t ipl2_addr)
{
Ccw0 *ccw = u32toptr(ipl2_addr);
if (ipl2_addr == 0x00) {
panic("IPL2 address invalid. Is this disk really bootable?\n");
}
if (ccw->cmd_code == 0x00) {
panic("IPL2 ccw data invalid. Is this disk really bootable?\n");
}
}
static uint32_t read_ipl2_addr(void)
{
Ccw0 *ccwtic = (Ccw0 *)0x10;
return ccwtic->cda;
}
static void ipl1_fixup(void)
{
Ccw0 *ccwSeek = (Ccw0 *) 0x08;
Ccw0 *ccwSearchID = (Ccw0 *) 0x10;
Ccw0 *ccwSearchTic = (Ccw0 *) 0x18;
Ccw0 *ccwRead = (Ccw0 *) 0x20;
CcwSeekData *seekData = (CcwSeekData *) 0x30;
CcwSearchIdData *searchData = (CcwSearchIdData *) 0x38;
/* move IPL1 CCWs to make room for CCWs needed to locate record 2 */
memcpy(ccwRead, (void *)0x08, 16);
/* Disable chaining so we don't TIC to IPL2 channel program */
ccwRead->chain = 0x00;
ccwSeek->cmd_code = CCW_CMD_DASD_SEEK;
ccwSeek->cda = ptr2u32(seekData);
ccwSeek->chain = 1;
ccwSeek->count = sizeof(*seekData);
seekData->reserved = 0x00;
seekData->cyl = 0x00;
seekData->head = 0x00;
ccwSearchID->cmd_code = CCW_CMD_DASD_SEARCH_ID_EQ;
ccwSearchID->cda = ptr2u32(searchData);
ccwSearchID->chain = 1;
ccwSearchID->count = sizeof(*searchData);
searchData->cyl = 0;
searchData->head = 0;
searchData->record = 2;
/* Go back to Search CCW if correct record not yet found */
ccwSearchTic->cmd_code = CCW_CMD_TIC;
ccwSearchTic->cda = ptr2u32(ccwSearchID);
}
static void run_ipl1(SubChannelId schid, uint16_t cutype)
{
uint32_t startAddr = 0x08;
if (do_cio(schid, cutype, startAddr, CCW_FMT0)) {
panic("dasd-ipl: Failed to run IPL1 channel program\n");
}
}
static void run_ipl2(SubChannelId schid, uint16_t cutype, uint32_t addr)
{
if (run_dynamic_ccw_program(schid, cutype, addr)) {
panic("dasd-ipl: Failed to run IPL2 channel program\n");
}
}
/*
* Limitations in vfio-ccw support complicate the IPL process. Details can
* be found in docs/devel/s390-dasd-ipl.rst
*/
void dasd_ipl(SubChannelId schid, uint16_t cutype)
{
PSWLegacy *pswl = (PSWLegacy *) 0x00;
uint32_t ipl2_addr;
/* Construct Read IPL CCW and run it to read IPL1 from boot disk */
make_readipl();
run_readipl(schid, cutype);
ipl2_addr = read_ipl2_addr();
check_ipl1();
/*
* Fixup IPL1 channel program to account for vfio-ccw limitations, then run
* it to read IPL2 channel program from boot disk.
*/
ipl1_fixup();
run_ipl1(schid, cutype);
check_ipl2(ipl2_addr);
/*
* Run IPL2 channel program to read operating system code from boot disk
*/
run_ipl2(schid, cutype, ipl2_addr);
/* Transfer control to the guest operating system */
pswl->mask |= PSW_MASK_EAMODE; /* Force z-mode */
pswl->addr |= PSW_MASK_BAMODE; /* ... */
jump_to_low_kernel();
}
