Re: [kvm-unit-tests PATCH v8 6/6] s390x: SCLP unit test

[David Hildenbrand <david@redhat.com>]

On 22.01.20 11:40, David Hildenbrand wrote:
> On 22.01.20 11:39, Thomas Huth wrote:
>> On 22/01/2020 11.32, David Hildenbrand wrote:
>>> On 22.01.20 11:31, Thomas Huth wrote:
>>>> On 22/01/2020 11.22, David Hildenbrand wrote:
>>>>> On 22.01.20 11:10, David Hildenbrand wrote:
>>>>>> On 20.01.20 19:42, 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>
>>>>>>> Reviewed-by: Thomas Huth <thuth@redhat.com>
>>>>>>> Acked-by: Janosch Frank <frankja@linux.ibm.com>
>>>>>>> ---
>>>>>>>  s390x/Makefile      |   1 +
>>>>>>>  s390x/sclp.c        | 474 ++++++++++++++++++++++++++++++++++++++++++++
>>>>>>>  s390x/unittests.cfg |   8 +
>>>>>>>  3 files changed, 483 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..215347e
>>>>>>> --- /dev/null
>>>>>>> +++ b/s390x/sclp.c
>>>>>>> @@ -0,0 +1,474 @@
>>>>>>> +/*
>>>>>>> + * 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))
>>>>>>> +
>>>>>>> +#define LC_SIZE (2 * PAGE_SIZE)
>>>>>>> +
>>>>>>> +static uint8_t pagebuf[LC_SIZE] __attribute__((aligned(LC_SIZE)));	/* scratch pages used for some tests */
>>>>>>> +static uint8_t prefix_buf[LC_SIZE] __attribute__((aligned(LC_SIZE)));	/* temporary lowcore for test_sccb_prefix */
>>>>>>> +static uint8_t sccb_template[PAGE_SIZE];				/* SCCB template to be used */
>>>>>>> +static uint32_t valid_code;						/* valid command code for READ SCP INFO */
>>>>>>> +static struct lowcore *lc;
>>>>>>> +
>>>>>>> +/**
>>>>>>> + * 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);
>>>>>>> +	if (exp_pgm != PGM_NONE)
>>>>>>> +		expect_pgm_int();
>>>>>>> +	/* perform the actual call */
>>>>>>> +	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 be used when the template should not be
>>>>>>> + * copied and the memory address should not be touched.
>>>>>>> + */
>>>>>>> +static bool test_one_ro(uint32_t cmd, uint8_t *addr, uint64_t exp_pgm, uint16_t exp_rc)
>>>>>>> +{
>>>>>>> +	return test_one_sccb(cmd, addr, 0, exp_pgm, exp_rc);
>>>>>>> +}
>>>>>>> +
>>>>>>> +/**
>>>>>>> + * 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);
>>>>>>
>>>>>> Doing a fresh ./configure + make on RHEL7 gives me
>>>>>>
>>>>>> [linux1@rhkvm01 kvm-unit-tests]$ make
>>>>>> gcc  -std=gnu99 -ffreestanding -I /home/linux1/git/kvm-unit-tests/lib -I /home/linux1/git/kvm-unit-tests/lib/s390x -I lib -O2 -march=zEC12 -fno-delete-null-pointer-checks -g -MMD -MF s390x/.sclp.d -Wall -Wwrite-strings -Wempty-body -Wuninitialized -Wignored-qualifiers -Werror  -fomit-frame-pointer    -Wno-frame-address   -fno-pic    -Wclobbered  -Wunused-but-set-parameter  -Wmissing-parameter-type  -Wold-style-declaration -Woverride-init -Wmissing-prototypes -Wstrict-prototypes   -c -o s390x/sclp.o s390x/sclp.c
>>>>>> s390x/sclp.c: In function 'test_one_simple':
>>>>>> s390x/sclp.c:121:2: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
>>>>>>   ((SCCBHeader *)sccb_template)->length = sccb_len;
>>>>>>   ^
>>>>>> s390x/sclp.c: At top level:
>>>>>> cc1: error: unrecognized command line option "-Wno-frame-address" [-Werror]
>>>>>> cc1: all warnings being treated as errors
>>>>>> make: *** [s390x/sclp.o] Error 1
>>>>>
>>>>> The following makes it work:
>>>>>
>>>>>
>>>>> diff --git a/s390x/sclp.c b/s390x/sclp.c
>>>>> index c13fa60..0b8117a 100644
>>>>> --- a/s390x/sclp.c
>>>>> +++ b/s390x/sclp.c
>>>>> @@ -117,8 +117,10 @@ static bool test_one_ro(uint32_t cmd, uint8_t *addr, uint64_t exp_pgm, uint16_t
>>>>>  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)
>>>>>  {
>>>>> +       SCCBHeader *header = (void *)sccb_template;
>>>>> +
>>>>>         memset(sccb_template, 0, sizeof(sccb_template));
>>>>> -       ((SCCBHeader *)sccb_template)->length = sccb_len;
>>>>> +       header->length = sccb_len;
>>>>
>>>> While that might silence the compiler warning, we still might get
>>>> aliasing problems here, I think.
>>>> The right way to solve this problem is to turn sccb_template into a
>>>> union of the various structs/arrays that you want to use and then access
>>>> the fields through the union instead ("type-punning through union").
>>>
>>> We do have the exact same thing in lib/s390x/sclp.c already, no?
>>
>> Maybe we should carefully check that code, too...
>>
>>> Especially, new compilers don't seem to care?
>>
>> I've seen horrible bugs due to these aliasing problems in the past -
>> without compiler warnings showing up! Certain versions of GCC assume
>> that they can re-order code with pointers that point to types of
>> different sizes, i.e. in the above example, I think they could assume
>> that they could re-order the memset() and the header->length = ... line.
>> I'd feel better if we play safe and use a union here.
> 
> Should we simply allow type-punning?

For now I squashed

diff --git a/s390x/sclp.c b/s390x/sclp.c
index c13fa60..7d92bf3 100644
--- a/s390x/sclp.c
+++ b/s390x/sclp.c
@@ -26,7 +26,12 @@

 static uint8_t pagebuf[LC_SIZE] __attribute__((aligned(LC_SIZE)));	/*
scratch pages used for some tests */
 static uint8_t prefix_buf[LC_SIZE] __attribute__((aligned(LC_SIZE)));
/* temporary lowcore for test_sccb_prefix */
-static uint8_t sccb_template[PAGE_SIZE];				/* SCCB template to be used */
+/* SCCB template to be used */
+static union {
+	uint8_t raw[PAGE_SIZE];
+	SCCBHeader header;
+	WriteEventData data;
+} sccb_template;
 static uint32_t valid_code;						/* valid command code for READ SCP INFO */
 static struct lowcore *lc;

@@ -69,7 +74,7 @@ static bool test_one_sccb(uint32_t cmd, uint8_t *addr,
uint16_t buf_len, uint64_

 	/* Copy the template to the test address if needed */
 	if (buf_len)
-		memcpy(addr, sccb_template, buf_len);
+		memcpy(addr, sccb_template.raw, buf_len);
 	if (exp_pgm != PGM_NONE)
 		expect_pgm_int();
 	/* perform the actual call */
@@ -117,8 +122,8 @@ static bool test_one_ro(uint32_t cmd, uint8_t *addr,
uint64_t exp_pgm, uint16_t
 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;
+	memset(sccb_template.raw, 0, sizeof(sccb_template.raw));
+	sccb_template.header.length = sccb_len;
 	return test_one_sccb(cmd, addr, buf_len, exp_pgm, exp_rc);
 }

@@ -299,10 +304,10 @@ 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;
+	WriteEventData *sccb = &sccb_template.data;
 	int len, offset;

-	memset(sccb_template, 0, sizeof(sccb_template));
+	memset(sccb_template.raw, 0, sizeof(sccb_template.raw));
 	sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
 	for (len = 32; len <= 4096; len++) {
 		offset = len & 7 ? len & ~7 : len - 8;
@@ -323,10 +328,10 @@ 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;
+	WriteEventData *sccb = &sccb_template.data;
 	int len;

-	memset(sccb_template, 0, sizeof(sccb_template));
+	memset(sccb_template.raw, 0, sizeof(sccb_template.raw));
 	sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
 	for (len = 4097; len < 8192; len++) {
 		sccb->h.length = len;
-- 
2.24.1




-- 
Thanks,

David / dhildenb