Re: [kvm-unit-tests PATCH v4 3/3] s390x: SCLP unit test

Janosch Frank
2019-11-27T18:21:33Z

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On 11/19/19 10:53 AM, Claudio Imbrenda wrote:
> SCLP unit test. Testing the following:
>
> * Correctly ignoring instruction bits that should be ignored
> * Privileged instruction check
> * Check for addressing exceptions
> * Specification exceptions:
> - SCCB size less than 8
> - SCCB unaligned
> - SCCB overlaps prefix or lowcore
> - SCCB address higher than 2GB
> * Return codes for
> - Invalid command
> - SCCB too short (but at least 8)
> - SCCB page boundary violation
>
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
> s390x/Makefile | 1 +
> s390x/sclp.c | 465 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> s390x/unittests.cfg | 3 +
> 3 files changed, 469 insertions(+)
> create mode 100644 s390x/sclp.c
>
> diff --git a/s390x/Makefile b/s390x/Makefile
> index 3744372..ddb4b48 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -16,6 +16,7 @@ tests += $(TEST_DIR)/diag288.elf
> tests += $(TEST_DIR)/stsi.elf
> tests += $(TEST_DIR)/skrf.elf
> tests += $(TEST_DIR)/smp.elf
> +tests += $(TEST_DIR)/sclp.elf
> tests_binary = $(patsubst %.elf,%.bin,$(tests))
>
> all: directories test_cases test_cases_binary
> diff --git a/s390x/sclp.c b/s390x/sclp.c
> new file mode 100644
> index 0000000..aeb0b04
> --- /dev/null
> +++ b/s390x/sclp.c
> @@ -0,0 +1,465 @@
> +/*
> + * Service Call tests
> + *
> + * Copyright (c) 2019 IBM Corp
> + *
> + * Authors:
> + * Claudio Imbrenda <imbrenda@linux.ibm.com>
> + *
> + * This code is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2.
> + */
> +
> +#include <libcflat.h>
> +#include <asm/page.h>
> +#include <asm/asm-offsets.h>
> +#include <asm/interrupt.h>
> +#include <sclp.h>
> +
> +#define PGM_NONE 1
> +#define PGM_BIT_SPEC (1ULL << PGM_INT_CODE_SPECIFICATION)
> +#define PGM_BIT_ADDR (1ULL << PGM_INT_CODE_ADDRESSING)
> +#define PGM_BIT_PRIV (1ULL << PGM_INT_CODE_PRIVILEGED_OPERATION)
> +#define MKPTR(x) ((void *)(uint64_t)(x))
> +
> +/* two pages of scratch memory to be used for some of the tests */
> +static uint8_t pagebuf[PAGE_SIZE * 2] __attribute__((aligned(PAGE_SIZE * 2)));
> +/* used as prefix when testing prefix access, to guarantee that prefix != 0 */
> +static uint8_t prefix_buf[PAGE_SIZE * 2] __attribute__((aligned(PAGE_SIZE * 2)));

"to guarantee that prefix != 0" ... also returns in an error when used
as a sccb address?

> +/* SCCB template used to */

Used to what? :-)

> +static uint8_t sccb_template[PAGE_SIZE];

> +/* the valid command code to use for getting SCP information */

/* The sccb command code we'll use for the "read info" command. */

> +static uint32_t valid_code;

That's an unfortunate name for this variable.
How about: read_info_cmd_code?

> +/* points to lowcore (real address 0) */
> +static struct lowcore *lc;

I'd guess that a comment for this variable is a bit pointless.

I find this hard to read with all the comments above.

> +
> +/**
> + * Perform one service call, handling exceptions and interrupts.
> + */
> +static int sclp_service_call_test(unsigned int command, void *sccb)
> +{
> + int cc;
> +
> + sclp_mark_busy();
> + sclp_setup_int();
> + cc = servc(command, __pa(sccb));
> + if (lc->pgm_int_code) {
> + sclp_handle_ext();
> + return 0;
> + }
> + if (!cc)
> + sclp_wait_busy();
> + return cc;
> +}
> +
> +/**
> + * Perform one test at the given address, optionally using the SCCB template,
> + * checking for the expected program interrupts and return codes.
> + *
> + * The parameter buf_len indicates the number of bytes of the template that
> + * should be copied to the test address, and should be 0 when the test
> + * address is invalid, in which case nothing is copied.
> + *
> + * The template is used to simplify tests where the same buffer content is
> + * used many times in a row, at different addresses.
> + *
> + * Returns true in case of success or false in case of failure
> + */
> +static bool test_one_sccb(uint32_t cmd, uint8_t *addr, uint16_t buf_len, uint64_t exp_pgm, uint16_t exp_rc)
> +{
> + SCCBHeader *h = (SCCBHeader *)addr;
> + int res, pgm;
> +
> + /* Copy the template to the test address if needed */
> + if (buf_len)
> + memcpy(addr, sccb_template, buf_len);
> + expect_pgm_int();
> + /* perform the actuall call */

s/actuall/actual/

> + res = sclp_service_call_test(cmd, h);
> + if (res) {
> + report_info("SCLP not ready (command %#x, address %p, cc %d)", cmd, addr, res);
> + return false;
> + }
> + pgm = clear_pgm_int();
> + /* Check if the program exception was one of the expected ones */
> + if (!((1ULL << pgm) & exp_pgm)) {
> + report_info("First failure at addr %p, buf_len %d, cmd %#x, pgm code %d",
> + addr, buf_len, cmd, pgm);
> + return false;
> + }
> + /* Check if the response code is the one expected */
> + if (exp_rc && exp_rc != h->response_code) {
> + report_info("First failure at addr %p, buf_len %d, cmd %#x, resp code %#x",
> + addr, buf_len, cmd, h->response_code);
> + return false;
> + }
> + return true;
> +}
> +
> +/**
> + * Wrapper for test_one_sccb to set up a simple SCCB template.
> + *
> + * The parameter sccb_len indicates the value that will be saved in the SCCB
> + * length field of the SCCB, buf_len indicates the number of bytes of
> + * template that need to be copied to the actual test address. In many cases
> + * it's enough to clear/copy the first 8 bytes of the buffer, while the SCCB
> + * itself can be larger.
> + *
> + * Returns true in case of success or false in case of failure
> + */
> +static bool test_one_simple(uint32_t cmd, uint8_t *addr, uint16_t sccb_len,
> + uint16_t buf_len, uint64_t exp_pgm, uint16_t exp_rc)
> +{
> + memset(sccb_template, 0, sizeof(sccb_template));
> + ((SCCBHeader *)sccb_template)->length = sccb_len;
> + return test_one_sccb(cmd, addr, buf_len, exp_pgm, exp_rc);
> +}
> +
> +/**
> + * Test SCCB lengths < 8.
> + */
> +static void test_sccb_too_short(void)
> +{
> + int len;
> +
> + for (len = 0; len < 8; len++)
> + if (!test_one_simple(valid_code, pagebuf, len, 8, PGM_BIT_SPEC, 0))
> + break;
> +
> + report("SCCB too short", len == 8);
> +}
> +
> +/**
> + * Test SCCBs that are not 64-bit aligned.
> + */
> +static void test_sccb_unaligned(void)
> +{
> + int offset;
> +
> + for (offset = 1; offset < 8; offset++)
> + if (!test_one_simple(valid_code, offset + pagebuf, 8, 8, PGM_BIT_SPEC, 0))
> + break;
> + report("SCCB unaligned", offset == 8);
> +}
> +
> +/**
> + * Test SCCBs whose address is in the lowcore or prefix area.
> + */
> +static void test_sccb_prefix(void)
> +{
> + uint8_t scratch[2 * PAGE_SIZE];
> + uint32_t prefix, new_prefix;
> + int offset;
> +
> + /*
> + * copy the current lowcore to the future new location, otherwise we
> + * will not have a valid lowcore after setting the new prefix.
> + */
> + memcpy(prefix_buf, 0, 2 * PAGE_SIZE);
> + /* save the current prefix (it's probably going to be 0) */
> + asm volatile("stpx %0" : "=Q" (prefix));

s390x/intercept.c already uses it, maybe we can move it to the library
along with spx?

> + /*
> + * save the current content of absolute pages 0 and 1, so we can
> + * restore them after we trash them later on
> + */
> + memcpy(scratch, (void *)(intptr_t)prefix, 2 * PAGE_SIZE);
> + /* set the new prefix to prefix_buf */
> + new_prefix = (uint32_t)(intptr_t)prefix_buf;
> + asm volatile("spx %0" : : "Q" (new_prefix) : "memory");
> +
> + /*
> + * testing with SCCB addresses in the lowcore; since we can't
> + * actually trash the lowcore (unsurprisingly, things break if we
> + * do), this will be a read-only test.
> + */
> + for (offset = 0; offset < 2 * PAGE_SIZE; offset += 8)
> + if (!test_one_sccb(valid_code, MKPTR(offset), 0, PGM_BIT_SPEC, 0))
> + break;
> + report("SCCB low pages", offset == 2 * PAGE_SIZE);
> +
> + /*
> + * this will trash the contents of the two pages at absolute
> + * address 0; we will need to restore them later.
> + */
> + for (offset = 0; offset < 2 * PAGE_SIZE; offset += 8)
> + if (!test_one_simple(valid_code, MKPTR(new_prefix + offset), 8, 8, PGM_BIT_SPEC, 0))
> + break;
> + report("SCCB prefix pages", offset == 2 * PAGE_SIZE);
> +
> + /* restore the previous contents of absolute pages 0 and 1 */
> + memcpy(prefix_buf, 0, 2 * PAGE_SIZE);
> + /* restore the prefix to the original value */
> + asm volatile("spx %0" : : "Q" (prefix) : "memory");
> +}
> +
> +/**
> + * Test SCCBs that are above 2GB. If outside of memory, an addressing
> + * exception is also allowed.
> + */
> +static void test_sccb_high(void)
> +{
> + SCCBHeader *h = (SCCBHeader *)pagebuf;
> + uintptr_t a[33 * 4 * 2 + 2]; /* for the list of addresses to test */
> +
> + uint64_t maxram;
> + int i, pgm, len = 0;
> +
> + h->length = 8;
> + /* addresses with 1 bit set in the first 33 bits */
> + for (i = 0; i < 33; i++)
> + a[len++] = 1UL << (i + 31);
> + /* addresses with 2 consecutive bits set in the first 33 bits */
> + for (i = 0; i < 33; i++)
> + a[len++] = 3UL << (i + 31);
> + /* addresses with all bits set in bits 0..N */
> + for (i = 0; i < 33; i++)
> + a[len++] = 0xffffffff80000000UL << i;
> + /* addresses with all bits set in bits N..33 */
> + a[len++] = 0x80000000;
> + for (i = 1; i < 33; i++, len++)
> + a[len] = a[len - 1] | (1UL << (i + 31));
> + /* all the addresses above, but adding the offset of a valid buffer */
> + for (i = 0; i < len; i++)
> + a[len + i] = a[i] + (intptr_t)h;
> + len += i;
> + /* two more hand-crafted addresses */
> + a[len++] = 0xdeadbeef00000000;
> + a[len++] = 0xdeaddeadbeef0000;
> +
> + maxram = get_ram_size();
> + for (i = 0; i < len; i++) {
> + pgm = PGM_BIT_SPEC | (a[i] >= maxram ? PGM_BIT_ADDR : 0);
> + if (!test_one_sccb(valid_code, (void *)a[i], 0, pgm, 0))
> + break;
> + }
> + report("SCCB high addresses", i == len);
> +}
> +
> +/**
> + * Test invalid commands, both invalid command detail codes and valid
> + * ones with invalid command class code.
> + */
> +static void test_inval(void)
> +{
> + const uint16_t res = SCLP_RC_INVALID_SCLP_COMMAND;
> + uint32_t cmd;
> + int i;
> +
> + report_prefix_push("Invalid command");
> + for (i = 0; i < 65536; i++) {
> + cmd = 0xdead0000 | i;
> + if (!test_one_simple(cmd, pagebuf, PAGE_SIZE, PAGE_SIZE, PGM_NONE, res))
> + break;
> + }
> + report("Command detail code", i == 65536);
> +
> + for (i = 0; i < 256; i++) {
> + cmd = (valid_code & ~0xff) | i;
> + if (cmd == valid_code)
> + continue;
> + if (!test_one_simple(cmd, pagebuf, PAGE_SIZE, PAGE_SIZE, PGM_NONE, res))
> + break;
> + }
> + report("Command class code", i == 256);
> + report_prefix_pop();
> +}
> +
> +
> +/**
> + * Test short SCCBs (but larger than 8).
> + */
> +static void test_short(void)
> +{
> + const uint16_t res = SCLP_RC_INSUFFICIENT_SCCB_LENGTH;
> + int len;
> +
> + for (len = 8; len < 144; len++)
> + if (!test_one_simple(valid_code, pagebuf, len, len, PGM_NONE, res))
> + break;
> + report("Insufficient SCCB length (Read SCP info)", len == 144);
> +
> + for (len = 8; len < 40; len++)
> + if (!test_one_simple(SCLP_READ_CPU_INFO, pagebuf, len, len, PGM_NONE, res))
> + break;
> + report("Insufficient SCCB length (Read CPU info)", len == 40);
> +}
> +
> +/**
> + * Test SCCB page boundary violations.
> + */
> +static void test_boundary(void)
> +{
> + const uint32_t cmd = SCLP_CMD_WRITE_EVENT_DATA;
> + const uint16_t res = SCLP_RC_SCCB_BOUNDARY_VIOLATION;
> + WriteEventData *sccb = (WriteEventData *)sccb_template;
> + int len, offset;
> +
> + memset(sccb_template, 0, sizeof(sccb_template));
> + sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
> + for (len = 32; len <= 4096; len++) {
> + offset = len & 7 ? len & ~7 : len - 8;
> + for (offset = 4096 - offset; offset < 4096; offset += 8) {
> + sccb->h.length = len;
> + if (!test_one_sccb(cmd, offset + pagebuf, len, PGM_NONE, res))
> + goto out;
> + }
> + }
> +out:
> + report("SCCB page boundary violation", len > 4096 && offset == 4096);
> +}
> +
> +/**
> + * Test excessively long SCCBs.
> + */
> +static void test_toolong(void)
> +{
> + const uint32_t cmd = SCLP_CMD_WRITE_EVENT_DATA;
> + const uint16_t res = SCLP_RC_SCCB_BOUNDARY_VIOLATION;
> + WriteEventData *sccb = (WriteEventData *)sccb_template;
> + int len;
> +
> + memset(sccb_template, 0, sizeof(sccb_template));
> + sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
> + for (len = 4097; len < 8192; len++) {
> + sccb->h.length = len;
> + if (!test_one_sccb(cmd, pagebuf, PAGE_SIZE, PGM_NONE, res))
> + break;
> + }
> + report("SCCB bigger than 4k", len == 8192);
> +}
> +
> +/**
> + * Test privileged operation.
> + */
> +static void test_priv(void)
> +{
> + SCCBHeader *h = (SCCBHeader *)pagebuf;
> +
> + report_prefix_push("Privileged operation");
> + h->length = 8;
> + expect_pgm_int();
> + enter_pstate();
> + servc(valid_code, __pa(h));
> + check_pgm_int_code(PGM_INT_CODE_PRIVILEGED_OPERATION);
> + report_prefix_pop();
> +}
> +
> +/**
> + * Test addressing exceptions. We need to test SCCB addresses between the
> + * end of available memory and 2GB, because after 2GB a specification
> + * exception is also allowed.
> + * Only applicable if the VM has less than 2GB of memory
> + */
> +static void test_addressing(void)
> +{
> + unsigned long i, maxram = get_ram_size();
> +
> + /* the VM has more than 2GB of memory */
> + if (maxram >= 0x80000000) {
> + report_skip("Invalid SCCB address");
> + return;
> + }
> + /* test all possible valid addresses immediately after the end of memory
> + * up to 64KB after the end of memory
> + */
> + for (i = 0; i < 0x10000 && i + maxram < 0x80000000; i += 8)
> + if (!test_one_sccb(valid_code, MKPTR(i + maxram), 0, PGM_BIT_ADDR, 0))
> + goto out;
> + /* test more addresses until we reach 1MB after end of memory;
> + * increment by a prime number (times 8) in order to test all
> + * possible valid offsets inside pages
> + */
> + for (; i < 0x100000 && i + maxram < 0x80000000 ; i += 808)
> + if (!test_one_sccb(valid_code, MKPTR(i + maxram), 0, PGM_BIT_ADDR, 0))
> + goto out;
> + /* test the remaining addresses until we reach address 2GB;
> + * increment by a prime number (times 8) in order to test all
> + * possible valid offsets inside pages
> + */
> + for (; i < 0x80000000; i += 800024)
> + if (!test_one_sccb(valid_code, MKPTR(i + maxram), 0, PGM_BIT_ADDR, 0))
> + goto out;
> +out:
> + report("Invalid SCCB address", i >= 0x80000000);
> +}
> +
> +/**
> + * Test some bits in the instruction format that are specified to be ignored.
> + */
> +static void test_instbits(void)
> +{
> + SCCBHeader *h = (SCCBHeader *)pagebuf;
> + int cc;
> +
> + expect_pgm_int();
> + sclp_mark_busy();
> + h->length = 8;
> + sclp_setup_int();
> +
> + asm volatile(
> + " .insn rre,0xb2204200,%1,%2\n" /* servc %1,%2 */
> + " ipm %0\n"
> + " srl %0,28"
> + : "=&d" (cc) : "d" (valid_code), "a" (__pa(pagebuf))
> + : "cc", "memory");
> + if (lc->pgm_int_code) {
> + sclp_handle_ext();
> + cc = 1;
> + } else if (!cc)
> + sclp_wait_busy();
> + report("Instruction format ignored bits", cc == 0);
> +}
> +
> +/**
> + * Find a valid SCLP command code; not all codes are always allowed, and
> + * probing should be performed in the right order.

Find valid READ INFO command code

> + */
> +static void find_valid_sclp_code(void)
> +{
> + const unsigned int commands[] = { SCLP_CMDW_READ_SCP_INFO_FORCED,
> + SCLP_CMDW_READ_SCP_INFO };
> + SCCBHeader *h = (SCCBHeader *)pagebuf;
> + int i, cc;
> +
> + for (i = 0; i < ARRAY_SIZE(commands); i++) {
> + sclp_mark_busy();
> + memset(h, 0, sizeof(*h));
> + h->length = 4096;
> +
> + valid_code = commands[i];
> + cc = sclp_service_call(commands[i], h);
> + if (cc)
> + break;
> + if (h->response_code == SCLP_RC_NORMAL_READ_COMPLETION)
> + return;
> + if (h->response_code != SCLP_RC_INVALID_SCLP_COMMAND)
> + break;
> + }
> + valid_code = 0;
> + report_abort("READ_SCP_INFO failed");
> +}
> +
> +int main(void)
> +{
> + report_prefix_push("sclp");
> + find_valid_sclp_code();
> +
> + /* Test some basic things */
> + test_instbits();
> + test_priv();
> + test_addressing();
> +
> + /* Test the specification exceptions */
> + test_sccb_too_short();
> + test_sccb_unaligned();
> + test_sccb_prefix();
> + test_sccb_high();
> +
> + /* Test the expected response codes */
> + test_inval();
> + test_short();
> + test_boundary();
> + test_toolong();
> +
> + return report_summary();
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index f1b07cd..75e3d37 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -75,3 +75,6 @@ file = stsi.elf
> [smp]
> file = smp.elf
> extra_params =-smp 2
> +
> +[sclp]
> +file = sclp.elf

I like Tomas' idea about the two tests.

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