[Qemu-devel] [PATCH] softmmu: fixing usage of cpu_st/ld* from helpers

[Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>]

MMU helper functions are called from generated code and other helper
functions. In both cases they try to get function's return address for
using it while restoring virtual CPU state.

When MMU helper is called from some other helper function
(like helper_maskmov_xmm) through cpu_st* function, the return address
will point to that helper. That is why CPU state cannot be restored in
the case of MMU fault.

This bug can occur when maskmov instruction is located in the middle of the
translation block.

Execution sequence for this example:

TB start:
PC1: instr1
     instr2
PC2: maskmov <page fault>
     <page fault processing>
PC1: instr1
     instr2
     maskmov

At the start of TB execution guest PC points to instr1. When page fault occurs
QEMU tries to restore guest PC (which should be equal to PC2). It reads host PC
from the call stack and checks whether it points to TB or not. Bug in ldst
helpers implementation provides incorrect host PC, which is not located within
the TB. That's why QEMU cannot recover guest PC and it remains the same (PC1).
After page fault processing QEMU restarts TB and executes instr1 and instr2
for the second time, because guest PC was not recovered.

This patch introduces several inline helpers to load return address
which points to the right place. Correct return address allows correct
restoring of the guest PC.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
---
 include/exec/cpu_ldst_template.h |   31 +++++++++++++++++++++++++++----
 include/exec/exec-all.h          |   27 +++++++++++++++++++++++++++
 softmmu_template.h               |   18 ++++++++++++++++++
 3 files changed, 72 insertions(+), 4 deletions(-)

diff --git a/include/exec/cpu_ldst_template.h b/include/exec/cpu_ldst_template.h
index 006093a..2658955 100644
--- a/include/exec/cpu_ldst_template.h
+++ b/include/exec/cpu_ldst_template.h
@@ -61,6 +61,17 @@
 #define MMUSUFFIX _mmu
 #endif
 
+/* inline helper ld function */
+
+static inline DATA_TYPE
+glue(glue(helper_inline_ld, SUFFIX), MEMSUFFIX)(CPUArchState *env,
+                                                target_ulong addr,
+                                                int mmu_idx)
+{
+    return glue(glue(helper_call_ld, SUFFIX), MMUSUFFIX)(env, addr, mmu_idx,
+                                                         GETRA());
+}
+
 /* generic load/store macros */
 
 static inline RES_TYPE
@@ -76,7 +87,8 @@ glue(glue(cpu_ld, USUFFIX), MEMSUFFIX)(CPUArchState *env, target_ulong ptr)
     mmu_idx = CPU_MMU_INDEX;
     if (unlikely(env->tlb_table[mmu_idx][page_index].ADDR_READ !=
                  (addr & (TARGET_PAGE_MASK | (DATA_SIZE - 1))))) {
-        res = glue(glue(helper_ld, SUFFIX), MMUSUFFIX)(env, addr, mmu_idx);
+        res = glue(glue(helper_inline_ld, SUFFIX), MEMSUFFIX)(env, addr,
+                                                              mmu_idx);
     } else {
         uintptr_t hostaddr = addr + env->tlb_table[mmu_idx][page_index].addend;
         res = glue(glue(ld, USUFFIX), _raw)(hostaddr);
@@ -97,8 +109,8 @@ glue(glue(cpu_lds, SUFFIX), MEMSUFFIX)(CPUArchState *env, target_ulong ptr)
     mmu_idx = CPU_MMU_INDEX;
     if (unlikely(env->tlb_table[mmu_idx][page_index].ADDR_READ !=
                  (addr & (TARGET_PAGE_MASK | (DATA_SIZE - 1))))) {
-        res = (DATA_STYPE)glue(glue(helper_ld, SUFFIX),
-                               MMUSUFFIX)(env, addr, mmu_idx);
+        res = (DATA_STYPE)glue(glue(helper_inline_ld, SUFFIX),
+                               MEMSUFFIX)(env, addr, mmu_idx);
     } else {
         uintptr_t hostaddr = addr + env->tlb_table[mmu_idx][page_index].addend;
         res = glue(glue(lds, SUFFIX), _raw)(hostaddr);
@@ -109,6 +121,17 @@ glue(glue(cpu_lds, SUFFIX), MEMSUFFIX)(CPUArchState *env, target_ulong ptr)
 
 #ifndef SOFTMMU_CODE_ACCESS
 
+/* inline helper st function */
+
+static inline void
+glue(glue(helper_inline_st, SUFFIX), MEMSUFFIX)(CPUArchState *env,
+                                                target_ulong addr,
+                                                DATA_TYPE val, int mmu_idx)
+{
+    glue(glue(helper_call_st, SUFFIX), MMUSUFFIX)(env, addr, val, mmu_idx,
+                                                  GETRA());
+}
+
 /* generic store macro */
 
 static inline void
@@ -124,7 +147,7 @@ glue(glue(cpu_st, SUFFIX), MEMSUFFIX)(CPUArchState *env, target_ulong ptr,
     mmu_idx = CPU_MMU_INDEX;
     if (unlikely(env->tlb_table[mmu_idx][page_index].addr_write !=
                  (addr & (TARGET_PAGE_MASK | (DATA_SIZE - 1))))) {
-        glue(glue(helper_st, SUFFIX), MMUSUFFIX)(env, addr, v, mmu_idx);
+        glue(glue(helper_inline_st, SUFFIX), MEMSUFFIX)(env, addr, v, mmu_idx);
     } else {
         uintptr_t hostaddr = addr + env->tlb_table[mmu_idx][page_index].addend;
         glue(glue(st, SUFFIX), _raw)(hostaddr, v);
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 5e5d86e..528928f 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -344,6 +344,33 @@ bool io_mem_write(struct MemoryRegion *mr, hwaddr addr,
 void tlb_fill(CPUState *cpu, target_ulong addr, int is_write, int mmu_idx,
               uintptr_t retaddr);
 
+uint8_t helper_call_ldb_cmmu(CPUArchState *env, target_ulong addr,
+                             int mmu_idx, uintptr_t retaddr);
+uint16_t helper_call_ldw_cmmu(CPUArchState *env, target_ulong addr,
+                              int mmu_idx, uintptr_t retaddr);
+uint32_t helper_call_ldl_cmmu(CPUArchState *env, target_ulong addr,
+                              int mmu_idx, uintptr_t retaddr);
+uint64_t helper_call_ldq_cmmu(CPUArchState *env, target_ulong addr,
+                              int mmu_idx, uintptr_t retaddr);
+
+uint8_t helper_call_ldb_mmu(CPUArchState *env, target_ulong addr,
+                            int mmu_idx, uintptr_t retaddr);
+uint16_t helper_call_ldw_mmu(CPUArchState *env, target_ulong addr,
+                             int mmu_idx, uintptr_t retaddr);
+uint32_t helper_call_ldl_mmu(CPUArchState *env, target_ulong addr,
+                             int mmu_idx, uintptr_t retaddr);
+uint64_t helper_call_ldq_mmu(CPUArchState *env, target_ulong addr,
+                             int mmu_idx, uintptr_t retaddr);
+
+void helper_call_stb_mmu(CPUArchState *env, target_ulong addr,
+                         uint8_t val, int mmu_idx, uintptr_t retaddr);
+void helper_call_stw_mmu(CPUArchState *env, target_ulong addr,
+                         uint16_t val, int mmu_idx, uintptr_t retaddr);
+void helper_call_stl_mmu(CPUArchState *env, target_ulong addr,
+                         uint32_t val, int mmu_idx, uintptr_t retaddr);
+void helper_call_stq_mmu(CPUArchState *env, target_ulong addr,
+                         uint64_t val, int mmu_idx, uintptr_t retaddr);
+
 #endif
 
 #if defined(CONFIG_USER_ONLY)
diff --git a/softmmu_template.h b/softmmu_template.h
index 5a07f99..1053cf3 100644
--- a/softmmu_template.h
+++ b/softmmu_template.h
@@ -311,6 +311,15 @@ glue(glue(helper_ld, SUFFIX), MMUSUFFIX)(CPUArchState *env, target_ulong addr,
     return helper_te_ld_name (env, addr, mmu_idx, GETRA());
 }
 
+DATA_TYPE
+glue(glue(helper_call_ld, SUFFIX), MMUSUFFIX)(CPUArchState *env,
+                                              target_ulong addr,
+                                              int mmu_idx,
+                                              uintptr_t retaddr)
+{
+    return helper_te_ld_name(env, addr, mmu_idx, retaddr);
+}
+
 #ifndef SOFTMMU_CODE_ACCESS
 
 /* Provide signed versions of the load routines as well.  We can of course
@@ -505,6 +514,15 @@ glue(glue(helper_st, SUFFIX), MMUSUFFIX)(CPUArchState *env, target_ulong addr,
     helper_te_st_name(env, addr, val, mmu_idx, GETRA());
 }
 
+void
+glue(glue(helper_call_st, SUFFIX), MMUSUFFIX)(CPUArchState *env,
+                                              target_ulong addr,
+                                              DATA_TYPE val, int mmu_idx,
+                                              uintptr_t retaddr)
+{
+    helper_te_st_name(env, addr, val, mmu_idx, retaddr);
+}
+
 #endif /* !defined(SOFTMMU_CODE_ACCESS) */
 
 #undef READ_ACCESS_TYPE