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[Qemu-devel] [PATCH 8/9] target/m68k: Improve ending TB at page boundari
From: |
Richard Henderson |
Subject: |
[Qemu-devel] [PATCH 8/9] target/m68k: Improve ending TB at page boundaries |
Date: |
Fri, 11 May 2018 22:02:49 -0700 |
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 <address@hidden>
---
target/m68k/translate.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/target/m68k/translate.c b/target/m68k/translate.c
index 0ab9ab1148..069558bc28 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;
+ }
}
}
--
2.17.0
- [Qemu-devel] [PATCH v1.1 0/9] target/m68k: Convert to TranslatorOps, Richard Henderson, 2018/05/12
- [Qemu-devel] [PATCH 3/9] target/m68k: Remove DISAS_JUMP_NEXT as unused, Richard Henderson, 2018/05/12
- [Qemu-devel] [PATCH 1/9] target/m68k: Use DISAS_NORETURN for exceptions, Richard Henderson, 2018/05/12
- [Qemu-devel] [PATCH 5/9] target/m68k: Rename DISAS_UPDATE and gen_lookup_tb, Richard Henderson, 2018/05/12
- [Qemu-devel] [PATCH 4/9] target/m68k: Use lookup_and_goto_tb for DISAS_JUMP, Richard Henderson, 2018/05/12
- [Qemu-devel] [PATCH 2/9] target/m68k: Replace DISAS_TB_JUMP with DISAS_NORETURN, Richard Henderson, 2018/05/12
- [Qemu-devel] [PATCH 8/9] target/m68k: Improve ending TB at page boundaries,
Richard Henderson <=
- [Qemu-devel] [PATCH 7/9] target/m68k: Convert to TranslatorOps, Richard Henderson, 2018/05/12
- [Qemu-devel] [PATCH 6/9] target/m68k: Convert to DisasContextBase, Richard Henderson, 2018/05/12
- [Qemu-devel] [PATCH 9/9] target/m68k: Merge disas_m68k_insn into m68k_tr_translate_insn, Richard Henderson, 2018/05/12
- Re: [Qemu-devel] [PATCH v1.1 0/9] target/m68k: Convert to TranslatorOps, no-reply, 2018/05/12
- Re: [Qemu-devel] [PATCH v1.1 0/9] target/m68k: Convert to TranslatorOps, Laurent Vivier, 2018/05/13