Trigger breakpoints before beginning translation of a TB that would begin with a BP. Thus we never generate code for the BP at all.
Single-step instructions within a page containing a BP so that we are sure to check each insn for the BP as above. We no longer need to flush any TBs when changing BPs. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/286 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/404 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/489 Reviewed-by: Alex Bennée <alex.ben...@linaro.org> Signed-off-by: Richard Henderson <richard.hender...@linaro.org> --- accel/tcg/cpu-exec.c | 91 ++++++++++++++++++++++++++++++++++++++++-- accel/tcg/translator.c | 24 +---------- cpu.c | 20 ---------- 3 files changed, 89 insertions(+), 46 deletions(-) diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c index cde7069eb7..5cc6363f4c 100644 --- a/accel/tcg/cpu-exec.c +++ b/accel/tcg/cpu-exec.c @@ -222,6 +222,76 @@ static inline void log_cpu_exec(target_ulong pc, CPUState *cpu, } } +static bool check_for_breakpoints(CPUState *cpu, target_ulong pc, + uint32_t *cflags) +{ + CPUBreakpoint *bp; + bool match_page = false; + + if (likely(QTAILQ_EMPTY(&cpu->breakpoints))) { + return false; + } + + /* + * Singlestep overrides breakpoints. + * This requirement is visible in the record-replay tests, where + * we would fail to make forward progress in reverse-continue. + * + * TODO: gdb singlestep should only override gdb breakpoints, + * so that one could (gdb) singlestep into the guest kernel's + * architectural breakpoint handler. + */ + if (cpu->singlestep_enabled) { + return false; + } + + QTAILQ_FOREACH(bp, &cpu->breakpoints, entry) { + /* + * If we have an exact pc match, trigger the breakpoint. + * Otherwise, note matches within the page. + */ + if (pc == bp->pc) { + bool match_bp = false; + + if (bp->flags & BP_GDB) { + match_bp = true; + } else if (bp->flags & BP_CPU) { +#ifdef CONFIG_USER_ONLY + g_assert_not_reached(); +#else + CPUClass *cc = CPU_GET_CLASS(cpu); + assert(cc->tcg_ops->debug_check_breakpoint); + match_bp = cc->tcg_ops->debug_check_breakpoint(cpu); +#endif + } + + if (match_bp) { + cpu->exception_index = EXCP_DEBUG; + return true; + } + } else if (((pc ^ bp->pc) & TARGET_PAGE_MASK) == 0) { + match_page = true; + } + } + + /* + * Within the same page as a breakpoint, single-step, + * returning to helper_lookup_tb_ptr after each insn looking + * for the actual breakpoint. + * + * TODO: Perhaps better to record all of the TBs associated + * with a given virtual page that contains a breakpoint, and + * then invalidate them when a new overlapping breakpoint is + * set on the page. Non-overlapping TBs would not be + * invalidated, nor would any TB need to be invalidated as + * breakpoints are removed. + */ + if (match_page) { + *cflags = (*cflags & ~CF_COUNT_MASK) | CF_NO_GOTO_TB | 1; + } + return false; +} + /** * helper_lookup_tb_ptr: quick check for next tb * @env: current cpu state @@ -235,11 +305,16 @@ const void *HELPER(lookup_tb_ptr)(CPUArchState *env) CPUState *cpu = env_cpu(env); TranslationBlock *tb; target_ulong cs_base, pc; - uint32_t flags; + uint32_t flags, cflags; cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags); - tb = tb_lookup(cpu, pc, cs_base, flags, curr_cflags(cpu)); + cflags = curr_cflags(cpu); + if (check_for_breakpoints(cpu, pc, &cflags)) { + cpu_loop_exit(cpu); + } + + tb = tb_lookup(cpu, pc, cs_base, flags, cflags); if (tb == NULL) { return tcg_code_gen_epilogue; } @@ -346,6 +421,12 @@ void cpu_exec_step_atomic(CPUState *cpu) cflags &= ~CF_PARALLEL; /* After 1 insn, return and release the exclusive lock. */ cflags |= CF_NO_GOTO_TB | CF_NO_GOTO_PTR | 1; + /* + * No need to check_for_breakpoints here. + * We only arrive in cpu_exec_step_atomic after beginning execution + * of an insn that includes an atomic operation we can't handle. + * Any breakpoint for this insn will have been recognized earlier. + */ tb = tb_lookup(cpu, pc, cs_base, flags, cflags); if (tb == NULL) { @@ -837,6 +918,8 @@ int cpu_exec(CPUState *cpu) target_ulong cs_base, pc; uint32_t flags, cflags; + cpu_get_tb_cpu_state(cpu->env_ptr, &pc, &cs_base, &flags); + /* * When requested, use an exact setting for cflags for the next * execution. This is used for icount, precise smc, and stop- @@ -851,7 +934,9 @@ int cpu_exec(CPUState *cpu) cpu->cflags_next_tb = -1; } - cpu_get_tb_cpu_state(cpu->env_ptr, &pc, &cs_base, &flags); + if (check_for_breakpoints(cpu, pc, &cflags)) { + break; + } tb = tb_lookup(cpu, pc, cs_base, flags, cflags); if (tb == NULL) { diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c index a59eb7c11b..4f3728c278 100644 --- a/accel/tcg/translator.c +++ b/accel/tcg/translator.c @@ -50,7 +50,6 @@ bool translator_use_goto_tb(DisasContextBase *db, target_ulong dest) void translator_loop(const TranslatorOps *ops, DisasContextBase *db, CPUState *cpu, TranslationBlock *tb, int max_insns) { - int bp_insn = 0; bool plugin_enabled; /* Initialize DisasContext */ @@ -85,27 +84,6 @@ void translator_loop(const TranslatorOps *ops, DisasContextBase *db, plugin_gen_insn_start(cpu, db); } - /* Pass breakpoint hits to target for further processing */ - if (!db->singlestep_enabled - && unlikely(!QTAILQ_EMPTY(&cpu->breakpoints))) { - CPUBreakpoint *bp; - QTAILQ_FOREACH(bp, &cpu->breakpoints, entry) { - if (bp->pc == db->pc_next) { - if (ops->breakpoint_check(db, cpu, bp)) { - bp_insn = 1; - break; - } - } - } - /* The breakpoint_check hook may use DISAS_TOO_MANY to indicate - that only one more instruction is to be executed. Otherwise - it should use DISAS_NORETURN when generating an exception, - but may use a DISAS_TARGET_* value for Something Else. */ - if (db->is_jmp > DISAS_TOO_MANY) { - break; - } - } - /* Disassemble one instruction. The translate_insn hook should update db->pc_next and db->is_jmp to indicate what should be done next -- either exiting this loop or locate the start of @@ -144,7 +122,7 @@ void translator_loop(const TranslatorOps *ops, DisasContextBase *db, /* Emit code to exit the TB, as indicated by db->is_jmp. */ ops->tb_stop(db, cpu); - gen_tb_end(db->tb, db->num_insns - bp_insn); + gen_tb_end(db->tb, db->num_insns); if (plugin_enabled) { plugin_gen_tb_end(cpu); diff --git a/cpu.c b/cpu.c index 91d9e38acb..d6ae5ae581 100644 --- a/cpu.c +++ b/cpu.c @@ -225,11 +225,6 @@ void tb_invalidate_phys_addr(target_ulong addr) tb_invalidate_phys_page_range(addr, addr + 1); mmap_unlock(); } - -static void breakpoint_invalidate(CPUState *cpu, target_ulong pc) -{ - tb_invalidate_phys_addr(pc); -} #else void tb_invalidate_phys_addr(AddressSpace *as, hwaddr addr, MemTxAttrs attrs) { @@ -250,17 +245,6 @@ void tb_invalidate_phys_addr(AddressSpace *as, hwaddr addr, MemTxAttrs attrs) ram_addr = memory_region_get_ram_addr(mr) + addr; tb_invalidate_phys_page_range(ram_addr, ram_addr + 1); } - -static void breakpoint_invalidate(CPUState *cpu, target_ulong pc) -{ - /* - * There may not be a virtual to physical translation for the pc - * right now, but there may exist cached TB for this pc. - * Flush the whole TB cache to force re-translation of such TBs. - * This is heavyweight, but we're debugging anyway. - */ - tb_flush(cpu); -} #endif /* Add a breakpoint. */ @@ -286,8 +270,6 @@ int cpu_breakpoint_insert(CPUState *cpu, vaddr pc, int flags, QTAILQ_INSERT_TAIL(&cpu->breakpoints, bp, entry); } - breakpoint_invalidate(cpu, pc); - if (breakpoint) { *breakpoint = bp; } @@ -320,8 +302,6 @@ void cpu_breakpoint_remove_by_ref(CPUState *cpu, CPUBreakpoint *bp) { QTAILQ_REMOVE(&cpu->breakpoints, bp, entry); - breakpoint_invalidate(cpu, bp->pc); - trace_breakpoint_remove(cpu->cpu_index, bp->pc, bp->flags); g_free(bp); } -- 2.25.1
