[Qemu-devel] [PATCH v2 27/32] s390x/tcg: Provide probe_write helper

[David Hildenbrand <david@redhat.com>]

Instead of checking e.g. the first access on every touched page, we should
check the actual access, otherwise we might get false positives when Low
Address Protection (LAP) is active. As probe_write() can only deal with
accesses to one page, we have to loop.

Use i64 for the length, although not needed - easier to reuse
TCG temps we already have in the translation functions where this will
be used. Also allow it to be used from other helpers.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 target/s390x/helper.h     |  1 +
 target/s390x/internal.h   |  2 ++
 target/s390x/mem_helper.c | 21 +++++++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/target/s390x/helper.h b/target/s390x/helper.h
index 577edb384f..e2710f4fb3 100644
--- a/target/s390x/helper.h
+++ b/target/s390x/helper.h
@@ -123,6 +123,7 @@ DEF_HELPER_4(cu42, i32, env, i32, i32, i32)
 DEF_HELPER_5(msa, i32, env, i32, i32, i32, i32)
 DEF_HELPER_FLAGS_1(stpt, TCG_CALL_NO_RWG, i64, env)
 DEF_HELPER_FLAGS_1(stck, TCG_CALL_NO_RWG_SE, i64, env)
+DEF_HELPER_FLAGS_3(probe_write_access, TCG_CALL_NO_WG, void, env, i64, i64)
 
 /* === Vector Support Instructions === */
 DEF_HELPER_FLAGS_4(vll, TCG_CALL_NO_WG, void, env, ptr, i64, i64)
diff --git a/target/s390x/internal.h b/target/s390x/internal.h
index 7baf0e2404..848d6c36d0 100644
--- a/target/s390x/internal.h
+++ b/target/s390x/internal.h
@@ -386,6 +386,8 @@ void ioinst_handle_sal(S390CPU *cpu, uint64_t reg1, uintptr_t ra);
 
 /* mem_helper.c */
 target_ulong mmu_real2abs(CPUS390XState *env, target_ulong raddr);
+void probe_write_access(CPUS390XState *env, uint64_t addr, uint64_t len,
+                        uintptr_t ra);
 
 
 /* mmu_helper.c */
diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c
index a506d9ef99..efd5256ebf 100644
--- a/target/s390x/mem_helper.c
+++ b/target/s390x/mem_helper.c
@@ -2623,3 +2623,24 @@ uint32_t HELPER(cu42)(CPUS390XState *env, uint32_t r1, uint32_t r2, uint32_t m3)
     return convert_unicode(env, r1, r2, m3, GETPC(),
                            decode_utf32, encode_utf16);
 }
+
+void probe_write_access(CPUS390XState *env, uint64_t addr, uint64_t len,
+                        uintptr_t ra)
+{
+#ifndef CONFIG_USER_ONLY
+    /* test the actual access, not just any access to the page due to LAP */
+    while (len) {
+        uint64_t curlen = MIN(TARGET_PAGE_SIZE - (addr % TARGET_PAGE_SIZE),
+                              len);
+
+        probe_write(env, addr, curlen, cpu_mmu_index(env, false), ra);
+        addr = wrap_address(env, addr + curlen);
+        len -= curlen;
+    }
+#endif
+}
+
+void HELPER(probe_write_access)(CPUS390XState *env, uint64_t addr, uint64_t len)
+{
+    probe_write_access(env, addr, len, GETPC());
+}
-- 
2.17.2