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[Qemu-devel] [RFC 3/3] tcg: Avoid undefined behaviour patching code at u
From: |
Peter Maydell |
Subject: |
[Qemu-devel] [RFC 3/3] tcg: Avoid undefined behaviour patching code at unaligned addresses |
Date: |
Fri, 28 Mar 2014 15:29:48 +0000 |
To avoid C undefined behaviour when patching generated code,
provide wrappers tcg_patch8/16/32/64 which use the usual memcpy
trick, and use them in the i386 backend.
Signed-off-by: Peter Maydell <address@hidden>
---
tcg/i386/tcg-target.c | 12 ++++++------
tcg/tcg.c | 20 ++++++++++++++++++++
2 files changed, 26 insertions(+), 6 deletions(-)
diff --git a/tcg/i386/tcg-target.c b/tcg/i386/tcg-target.c
index f832282..a0f9dff 100644
--- a/tcg/i386/tcg-target.c
+++ b/tcg/i386/tcg-target.c
@@ -151,14 +151,14 @@ static void patch_reloc(uint8_t *code_ptr, int type,
if (value != (int32_t)value) {
tcg_abort();
}
- *(uint32_t *)code_ptr = value;
+ tcg_patch32(code_ptr, value);
break;
case R_386_PC8:
value -= (uintptr_t)code_ptr;
if (value != (int8_t)value) {
tcg_abort();
}
- *(uint8_t *)code_ptr = value;
+ tcg_patch8(code_ptr, value);
break;
default:
tcg_abort();
@@ -1276,9 +1276,9 @@ static void tcg_out_qemu_ld_slow_path(TCGContext *s,
TCGLabelQemuLdst *l)
uint8_t **label_ptr = &l->label_ptr[0];
/* resolve label address */
- *(uint32_t *)label_ptr[0] = (uint32_t)(s->code_ptr - label_ptr[0] - 4);
+ tcg_patch32(label_ptr[0], s->code_ptr - label_ptr[0] - 4);
if (TARGET_LONG_BITS > TCG_TARGET_REG_BITS) {
- *(uint32_t *)label_ptr[1] = (uint32_t)(s->code_ptr - label_ptr[1] - 4);
+ tcg_patch32(label_ptr[1], s->code_ptr - label_ptr[1] - 4);
}
if (TCG_TARGET_REG_BITS == 32) {
@@ -1360,9 +1360,9 @@ static void tcg_out_qemu_st_slow_path(TCGContext *s,
TCGLabelQemuLdst *l)
TCGReg retaddr;
/* resolve label address */
- *(uint32_t *)label_ptr[0] = (uint32_t)(s->code_ptr - label_ptr[0] - 4);
+ tcg_patch32(label_ptr[0], s->code_ptr - label_ptr[0] - 4);
if (TARGET_LONG_BITS > TCG_TARGET_REG_BITS) {
- *(uint32_t *)label_ptr[1] = (uint32_t)(s->code_ptr - label_ptr[1] - 4);
+ tcg_patch32(label_ptr[1], s->code_ptr - label_ptr[1] - 4);
}
if (TCG_TARGET_REG_BITS == 32) {
diff --git a/tcg/tcg.c b/tcg/tcg.c
index 60f06c5..727112d 100644
--- a/tcg/tcg.c
+++ b/tcg/tcg.c
@@ -143,6 +143,26 @@ static inline void tcg_out64(TCGContext *s, uint64_t v)
s->code_ptr = p + 8;
}
+static inline void tcg_patch8(uint8_t *p, uint8_t v)
+{
+ memcpy(p, &v, sizeof(v));
+}
+
+static inline void tcg_patch16(uint8_t *p, uint16_t v)
+{
+ memcpy(p, &v, sizeof(v));
+}
+
+static inline void tcg_patch32(uint8_t *p, uint32_t v)
+{
+ memcpy(p, &v, sizeof(v));
+}
+
+static inline void tcg_patch64(uint8_t *p, uint64_t v)
+{
+ memcpy(p, &v, sizeof(v));
+}
+
/* label relocation processing */
static void tcg_out_reloc(TCGContext *s, uint8_t *code_ptr, int type,
--
1.9.0