linux-kernel - [PATCH v8 2/3] rseq/selftests: add rseq_offset_deref

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Message-Id: <20200923233618.2572849-2-posk@google.com>
Date:   Wed, 23 Sep 2020 16:36:17 -0700
From:   Peter Oskolkov <posk@...gle.com>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Boqun Feng <boqun.feng@...il.com>, linux-kernel@...r.kernel.org
Cc:     Paul Turner <pjt@...gle.com>,
        Chris Kennelly <ckennelly@...gle.com>,
        Peter Oskolkov <posk@...k.io>, Shuah Khan <shuah@...nel.org>,
        linux-kselftest@...r.kernel.org, Peter Oskolkov <posk@...gle.com>
Subject: [PATCH v8 2/3] rseq/selftests: add rseq_offset_deref_addv

This patch adds rseq_offset_deref_addv function to
tools/testing/selftests/rseq/rseq-x86.h, to be used
in a selftest in the next patch in the patchset.

v7->v8: this patch split out of the v7 selftest patch.

Signed-off-by: Peter Oskolkov <posk@...gle.com>
---
 tools/testing/selftests/rseq/rseq-x86.h | 57 +++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/tools/testing/selftests/rseq/rseq-x86.h b/tools/testing/selftests/rseq/rseq-x86.h
index b2da6004fe30..640411518e46 100644
--- a/tools/testing/selftests/rseq/rseq-x86.h
+++ b/tools/testing/selftests/rseq/rseq-x86.h
@@ -279,6 +279,63 @@ int rseq_addv(intptr_t *v, intptr_t count, int cpu)
 #endif
 }
 
+#define RSEQ_ARCH_HAS_OFFSET_DEREF_ADDV
+
+/*
+ *   pval = *(ptr+off)
+ *  *pval += inc;
+ */
+static inline __attribute__((always_inline))
+int rseq_offset_deref_addv(intptr_t *ptr, off_t off, intptr_t inc, int cpu)
+{
+	RSEQ_INJECT_C(9)
+
+	__asm__ __volatile__ goto (
+		RSEQ_ASM_DEFINE_TABLE(3, 1f, 2f, 4f) /* start, commit, abort */
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[error1])
+#endif
+		/* Start rseq by storing table entry pointer into rseq_cs. */
+		RSEQ_ASM_STORE_RSEQ_CS(1, 3b, RSEQ_CS_OFFSET(%[rseq_abi]))
+		RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), 4f)
+		RSEQ_INJECT_ASM(3)
+#ifdef RSEQ_COMPARE_TWICE
+		RSEQ_ASM_CMP_CPU_ID(cpu_id, RSEQ_CPU_ID_OFFSET(%[rseq_abi]), %l[error1])
+#endif
+		/* get p+v */
+		"movq %[ptr], %%rbx\n\t"
+		"addq %[off], %%rbx\n\t"
+		/* get pv */
+		"movq (%%rbx), %%rcx\n\t"
+		/* *pv += inc */
+		"addq %[inc], (%%rcx)\n\t"
+		"2:\n\t"
+		RSEQ_INJECT_ASM(4)
+		RSEQ_ASM_DEFINE_ABORT(4, "", abort)
+		: /* gcc asm goto does not allow outputs */
+		: [cpu_id]		"r" (cpu),
+		  [rseq_abi]		"r" (&__rseq_abi),
+		  /* final store input */
+		  [ptr]			"m" (*ptr),
+		  [off]			"er" (off),
+		  [inc]			"er" (inc)
+		: "memory", "cc", "rax", "rbx", "rcx"
+		  RSEQ_INJECT_CLOBBER
+		: abort
+#ifdef RSEQ_COMPARE_TWICE
+		  , error1
+#endif
+	);
+	return 0;
+abort:
+	RSEQ_INJECT_FAILED
+	return -1;
+#ifdef RSEQ_COMPARE_TWICE
+error1:
+	rseq_bug("cpu_id comparison failed");
+#endif
+}
+
 static inline __attribute__((always_inline))
 int rseq_cmpeqv_trystorev_storev(intptr_t *v, intptr_t expect,
 				 intptr_t *v2, intptr_t newv2,
-- 
2.28.0.709.gb0816b6eb0-goog