target/i386: Make sure that vsyscall's tb->size != 0

tb_gen_code() assumes that tb->size must never be zero, otherwise it
may produce spurious exceptions. For x86_64 this may happen when
creating a translation block for the vsyscall page.

Fix by pretending that vsyscall translation blocks have at least one
instruction.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210519045738.1335210-2-iii@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

diff --git a/target/i386/tcg/translate.c b/target/i386/tcg/translate.c
index db56a483435dc721e54e3affcf96fbc91cc15a03..3ab8c238556056710dc93925b502cfca404808d4 100644 (file)
--- a/target/i386/tcg/translate.c
+++ b/target/i386/tcg/translate.c
@@ -8583,6 +8583,7 @@ static void i386_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu)
      */
     if ((dc->base.pc_next & TARGET_PAGE_MASK) == TARGET_VSYSCALL_PAGE) {
         gen_exception(dc, EXCP_VSYSCALL, dc->base.pc_next);
+        dc->base.pc_next = dc->pc + 1;
         return;
     }
 #endif