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Tue, 1 Oct 2024 15:06:21 +0000 (GMT) Received: from smtpav04.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 7748C20040; Tue, 1 Oct 2024 15:06:21 +0000 (GMT) Received: from heavy.ibm.com (unknown [9.179.29.119]) by smtpav04.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 1 Oct 2024 15:06:21 +0000 (GMT) From: Ilya Leoshkevich To: Paolo Bonzini , Richard Henderson , Eduardo Habkost Cc: qemu-devel@nongnu.org, Ilya Leoshkevich Subject: [PATCH v4] tests/tcg/x86_64: Add cross-modifying code test Date: Tue, 1 Oct 2024 17:03:48 +0200 Message-ID: <20241001150617.9977-1-iii@linux.ibm.com> X-Mailer: git-send-email 2.46.2 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: q4nyWSi_LyRbhWVICPM5JqOUz85LeDxB X-Proofpoint-ORIG-GUID: ZVx-MogHAU_Jkab79SNZ7QHp5tY8tCdj X-Proofpoint-UnRewURL: 0 URL was un-rewritten MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-01_11,2024-09-30_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 mlxscore=0 lowpriorityscore=0 clxscore=1015 bulkscore=0 spamscore=0 phishscore=0 mlxlogscore=999 adultscore=0 priorityscore=1501 malwarescore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2408220000 definitions=main-2410010096 Received-SPF: pass client-ip=148.163.158.5; envelope-from=iii@linux.ibm.com; helo=mx0b-001b2d01.pphosted.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org commit f025692c992c ("accel/tcg: Clear PAGE_WRITE before translation") fixed cross-modifying code handling, but did not add a test. The changed code was further improved recently [1], and I was not sure whether these modifications were safe (spoiler: they were fine). Add a test to make sure there are no regressions. [1] https://lists.gnu.org/archive/html/qemu-devel/2022-09/msg00034.html Signed-off-by: Ilya Leoshkevich Reviewed-by: Richard Henderson --- v3: https://lore.kernel.org/qemu-devel/20230316214711.318339-1-iii@linux.ibm.com/ v3 -> v4: Rebase. I've been looking into the .NET failures under QEMU again and what this test looks for was a suspect. It turned out to be https://gitlab.com/qemu-project/qemu/-/issues/2600 but it would be good to have this test upstream to ensure there are no regressions. v2: https://patchew.org/QEMU/20220905154944.1284289-1-iii@linux.ibm.com/ v2 -> v3: Resend with a trivial rebase. v1: https://lists.gnu.org/archive/html/qemu-devel/2022-09/msg00455.html v1 -> v2: Fix tweaking the flags (Alex). Keep the custom build rule for now. tests/tcg/x86_64/Makefile.target | 4 ++ tests/tcg/x86_64/cross-modifying-code.c | 80 +++++++++++++++++++++++++ 2 files changed, 84 insertions(+) create mode 100644 tests/tcg/x86_64/cross-modifying-code.c diff --git a/tests/tcg/x86_64/Makefile.target b/tests/tcg/x86_64/Makefile.target index 783ab5b21ad..d6dff559c7d 100644 --- a/tests/tcg/x86_64/Makefile.target +++ b/tests/tcg/x86_64/Makefile.target @@ -17,6 +17,7 @@ X86_64_TESTS += cmpxchg X86_64_TESTS += adox X86_64_TESTS += test-1648 X86_64_TESTS += test-2175 +X86_64_TESTS += cross-modifying-code TESTS=$(MULTIARCH_TESTS) $(X86_64_TESTS) test-x86_64 else TESTS=$(MULTIARCH_TESTS) @@ -27,6 +28,9 @@ adox: CFLAGS=-O2 run-test-i386-ssse3: QEMU_OPTS += -cpu max run-plugin-test-i386-ssse3-%: QEMU_OPTS += -cpu max +cross-modifying-code: CFLAGS+=-pthread +cross-modifying-code: LDFLAGS+=-pthread + test-x86_64: LDFLAGS+=-lm -lc test-x86_64: test-i386.c test-i386.h test-i386-shift.h test-i386-muldiv.h $(CC) $(CFLAGS) $< -o $@ $(LDFLAGS) diff --git a/tests/tcg/x86_64/cross-modifying-code.c b/tests/tcg/x86_64/cross-modifying-code.c new file mode 100644 index 00000000000..2704df6061c --- /dev/null +++ b/tests/tcg/x86_64/cross-modifying-code.c @@ -0,0 +1,80 @@ +/* + * Test patching code, running in one thread, from another thread. + * + * Intel SDM calls this "cross-modifying code" and recommends a special + * sequence, which requires both threads to cooperate. + * + * Linux kernel uses a different sequence that does not require cooperation and + * involves patching the first byte with int3. + * + * Finally, there is user-mode software out there that simply uses atomics, and + * that seems to be good enough in practice. Test that QEMU has no problems + * with this as well. + */ + +#include +#include +#include +#include + +void add1_or_nop(long *x); +asm(".pushsection .rwx,\"awx\",@progbits\n" + ".globl add1_or_nop\n" + /* addq $0x1,(%rdi) */ + "add1_or_nop: .byte 0x48, 0x83, 0x07, 0x01\n" + "ret\n" + ".popsection\n"); + +#define THREAD_WAIT 0 +#define THREAD_PATCH 1 +#define THREAD_STOP 2 + +static void *thread_func(void *arg) +{ + int val = 0x0026748d; /* nop */ + + while (true) { + switch (__atomic_load_n((int *)arg, __ATOMIC_SEQ_CST)) { + case THREAD_WAIT: + break; + case THREAD_PATCH: + val = __atomic_exchange_n((int *)&add1_or_nop, val, + __ATOMIC_SEQ_CST); + break; + case THREAD_STOP: + return NULL; + default: + assert(false); + __builtin_unreachable(); + } + } +} + +#define INITIAL 42 +#define COUNT 1000000 + +int main(void) +{ + int command = THREAD_WAIT; + pthread_t thread; + long x = 0; + int err; + int i; + + err = pthread_create(&thread, NULL, &thread_func, &command); + assert(err == 0); + + __atomic_store_n(&command, THREAD_PATCH, __ATOMIC_SEQ_CST); + for (i = 0; i < COUNT; i++) { + add1_or_nop(&x); + } + __atomic_store_n(&command, THREAD_STOP, __ATOMIC_SEQ_CST); + + err = pthread_join(thread, NULL); + assert(err == 0); + + assert(x >= INITIAL); + assert(x <= INITIAL + COUNT); + + return EXIT_SUCCESS; +}