Avoid a race condition with munmap in another thread.
Use around blocks that exclusively use "host_fn".
Keep the blocks as small as possible, but without setting
and clearing for every operation on one page.
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
target/arm/tcg/sme_helper.c | 16 ++++++++++++++
target/arm/tcg/sve_helper.c | 42 +++++++++++++++++++++++++++++--------
2 files changed, 49 insertions(+), 9 deletions(-)
diff --git a/target/arm/tcg/sme_helper.c b/target/arm/tcg/sme_helper.c
index e2e0575039..ab40ced38f 100644
--- a/target/arm/tcg/sme_helper.c
+++ b/target/arm/tcg/sme_helper.c
@@ -517,6 +517,8 @@ void sme_ld1(CPUARMState *env, void *za, uint64_t *vg,
clr_fn(za, 0, reg_off);
}
+ set_helper_retaddr(ra);
+
while (reg_off <= reg_last) {
uint64_t pg = vg[reg_off >> 6];
do {
@@ -529,6 +531,8 @@ void sme_ld1(CPUARMState *env, void *za, uint64_t *vg,
} while (reg_off <= reg_last && (reg_off & 63));
}
+ clear_helper_retaddr();
+
/*
* Use the slow path to manage the cross-page misalignment.
* But we know this is RAM and cannot trap.
@@ -543,6 +547,8 @@ void sme_ld1(CPUARMState *env, void *za, uint64_t *vg,
reg_last = info.reg_off_last[1];
host = info.page[1].host;
+ set_helper_retaddr(ra);
+
do {
uint64_t pg = vg[reg_off >> 6];
do {
@@ -554,6 +560,8 @@ void sme_ld1(CPUARMState *env, void *za, uint64_t *vg,
reg_off += esize;
} while (reg_off & 63);
} while (reg_off <= reg_last);
+
+ clear_helper_retaddr();
}
}
@@ -701,6 +709,8 @@ void sme_st1(CPUARMState *env, void *za, uint64_t *vg,
reg_last = info.reg_off_last[0];
host = info.page[0].host;
+ set_helper_retaddr(ra);
+
while (reg_off <= reg_last) {
uint64_t pg = vg[reg_off >> 6];
do {
@@ -711,6 +721,8 @@ void sme_st1(CPUARMState *env, void *za, uint64_t *vg,
} while (reg_off <= reg_last && (reg_off & 63));
}
+ clear_helper_retaddr();
+
/*
* Use the slow path to manage the cross-page misalignment.
* But we know this is RAM and cannot trap.
@@ -725,6 +737,8 @@ void sme_st1(CPUARMState *env, void *za, uint64_t *vg,
reg_last = info.reg_off_last[1];
host = info.page[1].host;
+ set_helper_retaddr(ra);
+
do {
uint64_t pg = vg[reg_off >> 6];
do {
@@ -734,6 +748,8 @@ void sme_st1(CPUARMState *env, void *za, uint64_t *vg,
reg_off += 1 << esz;
} while (reg_off & 63);
} while (reg_off <= reg_last);
+
+ clear_helper_retaddr();
}
}
diff --git a/target/arm/tcg/sve_helper.c b/target/arm/tcg/sve_helper.c
index dd49e67d7a..f1ee0e060f 100644
--- a/target/arm/tcg/sve_helper.c
+++ b/target/arm/tcg/sve_helper.c
@@ -5738,6 +5738,8 @@ void sve_ldN_r(CPUARMState *env, uint64_t *vg, const
target_ulong addr,
reg_last = info.reg_off_last[0];
host = info.page[0].host;
+ set_helper_retaddr(retaddr);
+
while (reg_off <= reg_last) {
uint64_t pg = vg[reg_off >> 6];
do {
@@ -5752,6 +5754,8 @@ void sve_ldN_r(CPUARMState *env, uint64_t *vg, const
target_ulong addr,
} while (reg_off <= reg_last && (reg_off & 63));
}
+ clear_helper_retaddr();
+
/*
* Use the slow path to manage the cross-page misalignment.
* But we know this is RAM and cannot trap.
@@ -5771,6 +5775,8 @@ void sve_ldN_r(CPUARMState *env, uint64_t *vg, const
target_ulong addr,
reg_last = info.reg_off_last[1];
host = info.page[1].host;
+ set_helper_retaddr(retaddr);
+
do {
uint64_t pg = vg[reg_off >> 6];
do {
@@ -5784,6 +5790,8 @@ void sve_ldN_r(CPUARMState *env, uint64_t *vg, const
target_ulong addr,
mem_off += N << msz;
} while (reg_off & 63);
} while (reg_off <= reg_last);
+
+ clear_helper_retaddr();
}
}
@@ -5934,15 +5942,11 @@ DO_LDN_2(4, dd, MO_64)
/*
* Load contiguous data, first-fault and no-fault.
*
- * For user-only, one could argue that we should hold the mmap_lock during
- * the operation so that there is no race between page_check_range and the
- * load operation. However, unmapping pages out from under a running thread
- * is extraordinarily unlikely. This theoretical race condition also affects
- * linux-user/ in its get_user/put_user macros.
- *
- * TODO: Construct some helpers, written in assembly, that interact with
- * host_signal_handler to produce memory ops which can properly report errors
- * without racing.
+ * For user-only, we control the race between page_check_range and
+ * another thread's munmap by using set/clear_helper_retaddr. Any
+ * SEGV that occurs between those markers is assumed to be because
+ * the guest page vanished. Keep that block as small as possible
+ * so that unrelated QEMU bugs are not blamed on the guest.
*/
/* Fault on byte I. All bits in FFR from I are cleared. The vector
@@ -6093,6 +6097,8 @@ void sve_ldnfff1_r(CPUARMState *env, void *vg, const
target_ulong addr,
reg_last = info.reg_off_last[0];
host = info.page[0].host;
+ set_helper_retaddr(retaddr);
+
do {
uint64_t pg = *(uint64_t *)(vg + (reg_off >> 3));
do {
@@ -6101,9 +6107,11 @@ void sve_ldnfff1_r(CPUARMState *env, void *vg, const
target_ulong addr,
(cpu_watchpoint_address_matches
(env_cpu(env), addr + mem_off, 1 << msz)
& BP_MEM_READ)) {
+ clear_helper_retaddr();
goto do_fault;
}
if (mtedesc && !mte_probe(env, mtedesc, addr + mem_off)) {
+ clear_helper_retaddr();
goto do_fault;
}
host_fn(vd, reg_off, host + mem_off);
@@ -6113,6 +6121,8 @@ void sve_ldnfff1_r(CPUARMState *env, void *vg, const
target_ulong addr,
} while (reg_off <= reg_last && (reg_off & 63));
} while (reg_off <= reg_last);
+ clear_helper_retaddr();
+
/*
* MemSingleNF is allowed to fail for any reason. We have special
* code above to handle the first element crossing a page boundary.
@@ -6348,6 +6358,8 @@ void sve_stN_r(CPUARMState *env, uint64_t *vg,
target_ulong addr,
reg_last = info.reg_off_last[0];
host = info.page[0].host;
+ set_helper_retaddr(retaddr);
+
while (reg_off <= reg_last) {
uint64_t pg = vg[reg_off >> 6];
do {
@@ -6362,6 +6374,8 @@ void sve_stN_r(CPUARMState *env, uint64_t *vg,
target_ulong addr,
} while (reg_off <= reg_last && (reg_off & 63));
}
+ clear_helper_retaddr();
+
/*
* Use the slow path to manage the cross-page misalignment.
* But we know this is RAM and cannot trap.
@@ -6381,6 +6395,8 @@ void sve_stN_r(CPUARMState *env, uint64_t *vg,
target_ulong addr,
reg_last = info.reg_off_last[1];
host = info.page[1].host;
+ set_helper_retaddr(retaddr);
+
do {
uint64_t pg = vg[reg_off >> 6];
do {
@@ -6394,6 +6410,8 @@ void sve_stN_r(CPUARMState *env, uint64_t *vg,
target_ulong addr,
mem_off += N << msz;
} while (reg_off & 63);
} while (reg_off <= reg_last);
+
+ clear_helper_retaddr();
}
}
@@ -6560,7 +6578,9 @@ void sve_ld1_z(CPUARMState *env, void *vd, uint64_t *vg,
void *vm,
if (unlikely(info.flags & TLB_MMIO)) {
tlb_fn(env, &scratch, reg_off, addr, retaddr);
} else {
+ set_helper_retaddr(retaddr);
host_fn(&scratch, reg_off, info.host);
+ clear_helper_retaddr();
}
} else {
/* Element crosses the page boundary. */
@@ -6782,7 +6802,9 @@ void sve_ldff1_z(CPUARMState *env, void *vd, uint64_t
*vg, void *vm,
goto fault;
}
+ set_helper_retaddr(retaddr);
host_fn(vd, reg_off, info.host);
+ clear_helper_retaddr();
}
reg_off += esize;
} while (reg_off & 63);
@@ -6986,7 +7008,9 @@ void sve_st1_z(CPUARMState *env, void *vd, uint64_t *vg,
void *vm,
do {
void *h = host[i];
if (likely(h != NULL)) {
+ set_helper_retaddr(retaddr);
host_fn(vd, reg_off, h);
+ clear_helper_retaddr();
} else if ((vg[reg_off >> 6] >> (reg_off & 63)) & 1) {
target_ulong addr = base + (off_fn(vm, reg_off) << scale);
tlb_fn(env, vd, reg_off, addr, retaddr);
--
2.43.0
