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authorRichard Henderson <richard.henderson@linaro.org>2018-05-11 22:02:49 -0700
committerLaurent Vivier <laurent@vivier.eu>2018-06-11 12:43:42 +0200
commit4c7a0f6f34869b3dfe7091d28ff27a8dfbdd8b70 (patch)
treef779182e3805415456888bb8ba64b3e7d8c7c204 /target/m68k
parent11ab74b01e0a8ea4973eed89c6b90fa6e4fb9fb6 (diff)
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: Richard Henderson <richard.henderson@linaro.org> Message-Id: <20180512050250.12774-9-richard.henderson@linaro.org> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Diffstat (limited to 'target/m68k')
-rw-r--r--target/m68k/translate.c22
1 files changed, 19 insertions, 3 deletions
diff --git a/target/m68k/translate.c b/target/m68k/translate.c
index 62a96bedcd..ff3493d8ab 100644
--- a/target/m68k/translate.c
+++ b/target/m68k/translate.c
@@ -6105,9 +6105,25 @@ 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) {
- dc->base.is_jmp = DISAS_TOO_MANY;
+ 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;
+ }
}
}