x86_64: Add rseq_offset_deref_addv()

This patch adds rseq_offset_deref_addv() function to
rseq-x86.h, to be used in a selftest in the next patch in the patchset.

  Once an architecture adds support for this function they should define
  "RSEQ_ARCH_HAS_OFFSET_DEREF_ADDV".

[ Contribution from Peter Oskolkov <posk@google.com>. ]

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: Ia32b27c909a7e41b4262dca3e86b6fb83d0b3bee

diff --git a/include/rseq/rseq-x86.h b/include/rseq/rseq-x86.h
index c2251c768fdcc8ca23ef652071621526370e0ec7..b2f13ee5031955c8ac94e7de6784af683e416770 100644 (file)
--- a/include/rseq/rseq-x86.h
+++ b/include/rseq/rseq-x86.h
@@ -293,6 +293,66 @@ error1:
 #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_get_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
+       );
+       rseq_after_asm_goto();
+       return 0;
+abort:
+       rseq_after_asm_goto();
+       RSEQ_INJECT_FAILED
+       return -1;
+#ifdef RSEQ_COMPARE_TWICE
+error1:
+       rseq_after_asm_goto();
+       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,