Commit 4c7a0f6f authored by Richard Henderson's avatar Richard Henderson Committed by Laurent Vivier
Browse files

target/m68k: Improve ending TB at page boundaries 



Rather than limit total TB size to PAGE-32 bytes, end the TB when
near the end of a page.  This should provide proper semantics of
SIGSEGV when executing near the end of a page.

Signed-off-by: default avatarRichard Henderson <richard.henderson@linaro.org>
Message-Id: <20180512050250.12774-9-richard.henderson@linaro.org>
Signed-off-by: default avatarLaurent Vivier <laurent@vivier.eu>
parent 11ab74b0

target/m68k/translate.c

+19 −3
Original line number Diff line number Diff line
@@ -6105,11 +6105,27 @@ static void m68k_tr_translate_insn(DisasContextBase *dcbase, CPUState *cpu) 
    disas_m68k_insn(cpu->env_ptr, dc);

    dc->base.pc_next = dc->pc;



    if (dc->base.is_jmp == DISAS_NEXT

        && dc->pc - dc->base.pc_first >= TARGET_PAGE_SIZE - 32) {

    if (dc->base.is_jmp == DISAS_NEXT) {

        /* Stop translation when the next insn might touch a new page.

         * This ensures that prefetch aborts at the right place.

         *

         * We cannot determine the size of the next insn without

         * completely decoding it.  However, the maximum insn size

         * is 32 bytes, so end if we do not have that much remaining.

         * This may produce several small TBs at the end of each page,

         * but they will all be linked with goto_tb.

         *

         * ??? ColdFire maximum is 4 bytes; MC68000's maximum is also

         * smaller than MC68020's.

         */

        target_ulong start_page_offset

            = dc->pc - (dc->base.pc_first & TARGET_PAGE_MASK);



        if (start_page_offset >= TARGET_PAGE_SIZE - 32) {

            dc->base.is_jmp = DISAS_TOO_MANY;

        }

    }

}



static void m68k_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu)

{