* [Qemu-devel] [PULL for-4.1 4/7] tcg: Introduce set/clear_helper_retaddr
2019-07-14 11:12 [Qemu-devel] [PULL for-4.1 0/7] tcg patch queue Richard Henderson
` (2 preceding siblings ...)
2019-07-14 11:12 ` [Qemu-devel] [PULL for-4.1 3/7] include/qemu/atomic.h: Add signal_barrier Richard Henderson
@ 2019-07-14 11:12 ` Richard Henderson
2019-07-14 11:12 ` [Qemu-devel] [PULL for-4.1 5/7] tcg: Remove cpu_ld*_code_ra Richard Henderson
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: Richard Henderson @ 2019-07-14 11:12 UTC (permalink / raw)
To: qemu-devel; +Cc: peter.maydell
At present we have a potential error in that helper_retaddr contains
data for handle_cpu_signal, but we have not ensured that those stores
will be scheduled properly before the operation that may fault.
It might be that these races are not in practice observable, due to
our use of -fno-strict-aliasing, but better safe than sorry.
Adjust all of the setters of helper_retaddr.
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
include/exec/cpu_ldst.h | 20 +++++++++++
include/exec/cpu_ldst_useronly_template.h | 12 +++----
accel/tcg/user-exec.c | 11 +++---
target/arm/helper-a64.c | 8 ++---
target/arm/sve_helper.c | 43 +++++++++++------------
5 files changed, 57 insertions(+), 37 deletions(-)
diff --git a/include/exec/cpu_ldst.h b/include/exec/cpu_ldst.h
index a08b11bd2c..9de8c93303 100644
--- a/include/exec/cpu_ldst.h
+++ b/include/exec/cpu_ldst.h
@@ -89,6 +89,26 @@ typedef target_ulong abi_ptr;
extern __thread uintptr_t helper_retaddr;
+static inline void set_helper_retaddr(uintptr_t ra)
+{
+ helper_retaddr = ra;
+ /*
+ * Ensure that this write is visible to the SIGSEGV handler that
+ * may be invoked due to a subsequent invalid memory operation.
+ */
+ signal_barrier();
+}
+
+static inline void clear_helper_retaddr(void)
+{
+ /*
+ * Ensure that previous memory operations have succeeded before
+ * removing the data visible to the signal handler.
+ */
+ signal_barrier();
+ helper_retaddr = 0;
+}
+
/* In user-only mode we provide only the _code and _data accessors. */
#define MEMSUFFIX _data
diff --git a/include/exec/cpu_ldst_useronly_template.h b/include/exec/cpu_ldst_useronly_template.h
index bc45e2b8d4..e65733f7e2 100644
--- a/include/exec/cpu_ldst_useronly_template.h
+++ b/include/exec/cpu_ldst_useronly_template.h
@@ -78,9 +78,9 @@ glue(glue(glue(cpu_ld, USUFFIX), MEMSUFFIX), _ra)(CPUArchState *env,
uintptr_t retaddr)
{
RES_TYPE ret;
- helper_retaddr = retaddr;
+ set_helper_retaddr(retaddr);
ret = glue(glue(cpu_ld, USUFFIX), MEMSUFFIX)(env, ptr);
- helper_retaddr = 0;
+ clear_helper_retaddr();
return ret;
}
@@ -102,9 +102,9 @@ glue(glue(glue(cpu_lds, SUFFIX), MEMSUFFIX), _ra)(CPUArchState *env,
uintptr_t retaddr)
{
int ret;
- helper_retaddr = retaddr;
+ set_helper_retaddr(retaddr);
ret = glue(glue(cpu_lds, SUFFIX), MEMSUFFIX)(env, ptr);
- helper_retaddr = 0;
+ clear_helper_retaddr();
return ret;
}
#endif
@@ -128,9 +128,9 @@ glue(glue(glue(cpu_st, SUFFIX), MEMSUFFIX), _ra)(CPUArchState *env,
RES_TYPE v,
uintptr_t retaddr)
{
- helper_retaddr = retaddr;
+ set_helper_retaddr(retaddr);
glue(glue(cpu_st, SUFFIX), MEMSUFFIX)(env, ptr, v);
- helper_retaddr = 0;
+ clear_helper_retaddr();
}
#endif
diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
index cb5f4b19c5..4384b59a4d 100644
--- a/accel/tcg/user-exec.c
+++ b/accel/tcg/user-exec.c
@@ -134,7 +134,7 @@ static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info,
* currently executing TB was modified and must be exited
* immediately. Clear helper_retaddr for next execution.
*/
- helper_retaddr = 0;
+ clear_helper_retaddr();
cpu_exit_tb_from_sighandler(cpu, old_set);
/* NORETURN */
@@ -152,7 +152,7 @@ static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info,
* an exception. Undo signal and retaddr state prior to longjmp.
*/
sigprocmask(SIG_SETMASK, old_set, NULL);
- helper_retaddr = 0;
+ clear_helper_retaddr();
cc = CPU_GET_CLASS(cpu);
access_type = is_write ? MMU_DATA_STORE : MMU_DATA_LOAD;
@@ -682,14 +682,15 @@ static void *atomic_mmu_lookup(CPUArchState *env, target_ulong addr,
if (unlikely(addr & (size - 1))) {
cpu_loop_exit_atomic(env_cpu(env), retaddr);
}
- helper_retaddr = retaddr;
- return g2h(addr);
+ void *ret = g2h(addr);
+ set_helper_retaddr(retaddr);
+ return ret;
}
/* Macro to call the above, with local variables from the use context. */
#define ATOMIC_MMU_DECLS do {} while (0)
#define ATOMIC_MMU_LOOKUP atomic_mmu_lookup(env, addr, DATA_SIZE, GETPC())
-#define ATOMIC_MMU_CLEANUP do { helper_retaddr = 0; } while (0)
+#define ATOMIC_MMU_CLEANUP do { clear_helper_retaddr(); } while (0)
#define ATOMIC_NAME(X) HELPER(glue(glue(atomic_ ## X, SUFFIX), END))
#define EXTRA_ARGS
diff --git a/target/arm/helper-a64.c b/target/arm/helper-a64.c
index 44e45a8037..060699b901 100644
--- a/target/arm/helper-a64.c
+++ b/target/arm/helper-a64.c
@@ -554,7 +554,7 @@ uint64_t HELPER(paired_cmpxchg64_le)(CPUARMState *env, uint64_t addr,
/* ??? Enforce alignment. */
uint64_t *haddr = g2h(addr);
- helper_retaddr = ra;
+ set_helper_retaddr(ra);
o0 = ldq_le_p(haddr + 0);
o1 = ldq_le_p(haddr + 1);
oldv = int128_make128(o0, o1);
@@ -564,7 +564,7 @@ uint64_t HELPER(paired_cmpxchg64_le)(CPUARMState *env, uint64_t addr,
stq_le_p(haddr + 0, int128_getlo(newv));
stq_le_p(haddr + 1, int128_gethi(newv));
}
- helper_retaddr = 0;
+ clear_helper_retaddr();
#else
int mem_idx = cpu_mmu_index(env, false);
TCGMemOpIdx oi0 = make_memop_idx(MO_LEQ | MO_ALIGN_16, mem_idx);
@@ -624,7 +624,7 @@ uint64_t HELPER(paired_cmpxchg64_be)(CPUARMState *env, uint64_t addr,
/* ??? Enforce alignment. */
uint64_t *haddr = g2h(addr);
- helper_retaddr = ra;
+ set_helper_retaddr(ra);
o1 = ldq_be_p(haddr + 0);
o0 = ldq_be_p(haddr + 1);
oldv = int128_make128(o0, o1);
@@ -634,7 +634,7 @@ uint64_t HELPER(paired_cmpxchg64_be)(CPUARMState *env, uint64_t addr,
stq_be_p(haddr + 0, int128_gethi(newv));
stq_be_p(haddr + 1, int128_getlo(newv));
}
- helper_retaddr = 0;
+ clear_helper_retaddr();
#else
int mem_idx = cpu_mmu_index(env, false);
TCGMemOpIdx oi0 = make_memop_idx(MO_BEQ | MO_ALIGN_16, mem_idx);
diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c
index fd434c66ea..fc0c1755d2 100644
--- a/target/arm/sve_helper.c
+++ b/target/arm/sve_helper.c
@@ -4125,12 +4125,11 @@ static intptr_t max_for_page(target_ulong base, intptr_t mem_off,
return MIN(split, mem_max - mem_off) + mem_off;
}
-static inline void set_helper_retaddr(uintptr_t ra)
-{
-#ifdef CONFIG_USER_ONLY
- helper_retaddr = ra;
+#ifndef CONFIG_USER_ONLY
+/* These are normally defined only for CONFIG_USER_ONLY in <exec/cpu_ldst.h> */
+static inline void set_helper_retaddr(uintptr_t ra) { }
+static inline void clear_helper_retaddr(void) { }
#endif
-}
/*
* The result of tlb_vaddr_to_host for user-only is just g2h(x),
@@ -4188,7 +4187,7 @@ static void sve_ld1_r(CPUARMState *env, void *vg, const target_ulong addr,
if (test_host_page(host)) {
mem_off = host_fn(vd, vg, host - mem_off, mem_off, mem_max);
tcg_debug_assert(mem_off == mem_max);
- set_helper_retaddr(0);
+ clear_helper_retaddr();
/* After having taken any fault, zero leading inactive elements. */
swap_memzero(vd, reg_off);
return;
@@ -4239,7 +4238,7 @@ static void sve_ld1_r(CPUARMState *env, void *vg, const target_ulong addr,
}
#endif
- set_helper_retaddr(0);
+ clear_helper_retaddr();
memcpy(vd, &scratch, reg_max);
}
@@ -4312,7 +4311,7 @@ static void sve_ld2_r(CPUARMState *env, void *vg, target_ulong addr,
addr += 2 * size;
} while (i & 15);
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
/* Wait until all exceptions have been raised to write back. */
memcpy(&env->vfp.zregs[rd], &scratch[0], oprsz);
@@ -4341,7 +4340,7 @@ static void sve_ld3_r(CPUARMState *env, void *vg, target_ulong addr,
addr += 3 * size;
} while (i & 15);
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
/* Wait until all exceptions have been raised to write back. */
memcpy(&env->vfp.zregs[rd], &scratch[0], oprsz);
@@ -4372,7 +4371,7 @@ static void sve_ld4_r(CPUARMState *env, void *vg, target_ulong addr,
addr += 4 * size;
} while (i & 15);
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
/* Wait until all exceptions have been raised to write back. */
memcpy(&env->vfp.zregs[rd], &scratch[0], oprsz);
@@ -4494,7 +4493,7 @@ static void sve_ldff1_r(CPUARMState *env, void *vg, const target_ulong addr,
if (test_host_page(host)) {
mem_off = host_fn(vd, vg, host - mem_off, mem_off, mem_max);
tcg_debug_assert(mem_off == mem_max);
- set_helper_retaddr(0);
+ clear_helper_retaddr();
/* After any fault, zero any leading inactive elements. */
swap_memzero(vd, reg_off);
return;
@@ -4537,7 +4536,7 @@ static void sve_ldff1_r(CPUARMState *env, void *vg, const target_ulong addr,
}
#endif
- set_helper_retaddr(0);
+ clear_helper_retaddr();
record_fault(env, reg_off, reg_max);
}
@@ -4740,7 +4739,7 @@ static void sve_st1_r(CPUARMState *env, void *vg, target_ulong addr,
addr += msize;
} while (i & 15);
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
}
static void sve_st2_r(CPUARMState *env, void *vg, target_ulong addr,
@@ -4766,7 +4765,7 @@ static void sve_st2_r(CPUARMState *env, void *vg, target_ulong addr,
addr += 2 * msize;
} while (i & 15);
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
}
static void sve_st3_r(CPUARMState *env, void *vg, target_ulong addr,
@@ -4794,7 +4793,7 @@ static void sve_st3_r(CPUARMState *env, void *vg, target_ulong addr,
addr += 3 * msize;
} while (i & 15);
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
}
static void sve_st4_r(CPUARMState *env, void *vg, target_ulong addr,
@@ -4824,7 +4823,7 @@ static void sve_st4_r(CPUARMState *env, void *vg, target_ulong addr,
addr += 4 * msize;
} while (i & 15);
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
}
#define DO_STN_1(N, NAME, ESIZE) \
@@ -4932,7 +4931,7 @@ static void sve_ld1_zs(CPUARMState *env, void *vd, void *vg, void *vm,
i += 4, pg >>= 4;
} while (i & 15);
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
/* Wait until all exceptions have been raised to write back. */
memcpy(vd, &scratch, oprsz);
@@ -4955,7 +4954,7 @@ static void sve_ld1_zd(CPUARMState *env, void *vd, void *vg, void *vm,
tlb_fn(env, &scratch, i * 8, base + (off << scale), oi, ra);
}
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
/* Wait until all exceptions have been raised to write back. */
memcpy(vd, &scratch, oprsz * 8);
@@ -5133,7 +5132,7 @@ static inline void sve_ldff1_zs(CPUARMState *env, void *vd, void *vg, void *vm,
tlb_fn(env, vd, reg_off, addr, oi, ra);
/* The rest of the reads will be non-faulting. */
- set_helper_retaddr(0);
+ clear_helper_retaddr();
}
/* After any fault, zero the leading predicated false elements. */
@@ -5175,7 +5174,7 @@ static inline void sve_ldff1_zd(CPUARMState *env, void *vd, void *vg, void *vm,
tlb_fn(env, vd, reg_off, addr, oi, ra);
/* The rest of the reads will be non-faulting. */
- set_helper_retaddr(0);
+ clear_helper_retaddr();
}
/* After any fault, zero the leading predicated false elements. */
@@ -5299,7 +5298,7 @@ static void sve_st1_zs(CPUARMState *env, void *vd, void *vg, void *vm,
i += 4, pg >>= 4;
} while (i & 15);
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
}
static void sve_st1_zd(CPUARMState *env, void *vd, void *vg, void *vm,
@@ -5318,7 +5317,7 @@ static void sve_st1_zd(CPUARMState *env, void *vd, void *vg, void *vm,
tlb_fn(env, vd, i * 8, base + (off << scale), oi, ra);
}
}
- set_helper_retaddr(0);
+ clear_helper_retaddr();
}
#define DO_ST1_ZPZ_S(MEM, OFS) \
--
2.17.1
^ permalink raw reply related [flat|nested] 9+ messages in thread* [Qemu-devel] [PULL for-4.1 7/7] tcg: Release mmap_lock on translation fault
2019-07-14 11:12 [Qemu-devel] [PULL for-4.1 0/7] tcg patch queue Richard Henderson
` (5 preceding siblings ...)
2019-07-14 11:12 ` [Qemu-devel] [PULL for-4.1 6/7] tcg: Remove duplicate #if !defined(CODE_ACCESS) Richard Henderson
@ 2019-07-14 11:12 ` Richard Henderson
2019-07-15 9:40 ` [Qemu-devel] [PULL for-4.1 0/7] tcg patch queue Peter Maydell
7 siblings, 0 replies; 9+ messages in thread
From: Richard Henderson @ 2019-07-14 11:12 UTC (permalink / raw)
To: qemu-devel; +Cc: peter.maydell
Turn helper_retaddr into a multi-state flag that may now also
indicate when we're performing a read on behalf of the translator.
In this case, release the mmap_lock before the longjmp back to
the main cpu loop, and thereby avoid a failing assert therein.
Fixes: https://bugs.launchpad.net/qemu/+bug/1832353
Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
include/exec/cpu_ldst_useronly_template.h | 20 +++++--
accel/tcg/user-exec.c | 66 ++++++++++++++++-------
2 files changed, 63 insertions(+), 23 deletions(-)
diff --git a/include/exec/cpu_ldst_useronly_template.h b/include/exec/cpu_ldst_useronly_template.h
index d663826ac2..2378f2958c 100644
--- a/include/exec/cpu_ldst_useronly_template.h
+++ b/include/exec/cpu_ldst_useronly_template.h
@@ -64,12 +64,18 @@
static inline RES_TYPE
glue(glue(cpu_ld, USUFFIX), MEMSUFFIX)(CPUArchState *env, abi_ptr ptr)
{
-#if !defined(CODE_ACCESS)
+#ifdef CODE_ACCESS
+ RES_TYPE ret;
+ set_helper_retaddr(1);
+ ret = glue(glue(ld, USUFFIX), _p)(g2h(ptr));
+ clear_helper_retaddr();
+ return ret;
+#else
trace_guest_mem_before_exec(
env_cpu(env), ptr,
trace_mem_build_info(SHIFT, false, MO_TE, false));
-#endif
return glue(glue(ld, USUFFIX), _p)(g2h(ptr));
+#endif
}
#ifndef CODE_ACCESS
@@ -90,12 +96,18 @@ glue(glue(glue(cpu_ld, USUFFIX), MEMSUFFIX), _ra)(CPUArchState *env,
static inline int
glue(glue(cpu_lds, SUFFIX), MEMSUFFIX)(CPUArchState *env, abi_ptr ptr)
{
-#if !defined(CODE_ACCESS)
+#ifdef CODE_ACCESS
+ int ret;
+ set_helper_retaddr(1);
+ ret = glue(glue(lds, SUFFIX), _p)(g2h(ptr));
+ clear_helper_retaddr();
+ return ret;
+#else
trace_guest_mem_before_exec(
env_cpu(env), ptr,
trace_mem_build_info(SHIFT, true, MO_TE, false));
-#endif
return glue(glue(lds, SUFFIX), _p)(g2h(ptr));
+#endif
}
#ifndef CODE_ACCESS
diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
index 4384b59a4d..897d1571c4 100644
--- a/accel/tcg/user-exec.c
+++ b/accel/tcg/user-exec.c
@@ -64,27 +64,56 @@ static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info,
CPUState *cpu = current_cpu;
CPUClass *cc;
unsigned long address = (unsigned long)info->si_addr;
- MMUAccessType access_type;
+ MMUAccessType access_type = is_write ? MMU_DATA_STORE : MMU_DATA_LOAD;
- /* We must handle PC addresses from two different sources:
- * a call return address and a signal frame address.
- *
- * Within cpu_restore_state_from_tb we assume the former and adjust
- * the address by -GETPC_ADJ so that the address is within the call
- * insn so that addr does not accidentally match the beginning of the
- * next guest insn.
- *
- * However, when the PC comes from the signal frame, it points to
- * the actual faulting host insn and not a call insn. Subtracting
- * GETPC_ADJ in that case may accidentally match the previous guest insn.
- *
- * So for the later case, adjust forward to compensate for what
- * will be done later by cpu_restore_state_from_tb.
- */
- if (helper_retaddr) {
+ switch (helper_retaddr) {
+ default:
+ /*
+ * Fault during host memory operation within a helper function.
+ * The helper's host return address, saved here, gives us a
+ * pointer into the generated code that will unwind to the
+ * correct guest pc.
+ */
pc = helper_retaddr;
- } else {
+ break;
+
+ case 0:
+ /*
+ * Fault during host memory operation within generated code.
+ * (Or, a unrelated bug within qemu, but we can't tell from here).
+ *
+ * We take the host pc from the signal frame. However, we cannot
+ * use that value directly. Within cpu_restore_state_from_tb, we
+ * assume PC comes from GETPC(), as used by the helper functions,
+ * so we adjust the address by -GETPC_ADJ to form an address that
+ * is within the call insn, so that the address does not accidentially
+ * match the beginning of the next guest insn. However, when the
+ * pc comes from the signal frame it points to the actual faulting
+ * host memory insn and not the return from a call insn.
+ *
+ * Therefore, adjust to compensate for what will be done later
+ * by cpu_restore_state_from_tb.
+ */
pc += GETPC_ADJ;
+ break;
+
+ case 1:
+ /*
+ * Fault during host read for translation, or loosely, "execution".
+ *
+ * The guest pc is already pointing to the start of the TB for which
+ * code is being generated. If the guest translator manages the
+ * page crossings correctly, this is exactly the correct address
+ * (and if the translator doesn't handle page boundaries correctly
+ * there's little we can do about that here). Therefore, do not
+ * trigger the unwinder.
+ *
+ * Like tb_gen_code, release the memory lock before cpu_loop_exit.
+ */
+ pc = 0;
+ access_type = MMU_INST_FETCH;
+ mmap_unlock();
+ break;
}
/* For synchronous signals we expect to be coming from the vCPU
@@ -155,7 +184,6 @@ static inline int handle_cpu_signal(uintptr_t pc, siginfo_t *info,
clear_helper_retaddr();
cc = CPU_GET_CLASS(cpu);
- access_type = is_write ? MMU_DATA_STORE : MMU_DATA_LOAD;
cc->tlb_fill(cpu, address, 0, access_type, MMU_USER_IDX, false, pc);
g_assert_not_reached();
}
--
2.17.1
^ permalink raw reply related [flat|nested] 9+ messages in thread