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tcg: Avoid undefined behaviour patching code at unaligned addresses

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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.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <rth@twiddle.net>
This commit is contained in:
Peter Maydell 2014-03-28 15:29:48 +00:00 committed by Richard Henderson
parent 4387345a96
commit 5c53bb8121
2 changed files with 26 additions and 6 deletions
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12
tcg/i386/tcg-target.c
View File

@ -151,14 +151,14 @@ static void patch_reloc(uint8_t *code_ptr, int type,
if (value != (int32_t)value) { if (value != (int32_t)value) {
tcg_abort(); tcg_abort();
} }
*(uint32_t *)code_ptr = value; tcg_patch32(code_ptr, value);
break; break;
case R_386_PC8: case R_386_PC8:
value -= (uintptr_t)code_ptr; value -= (uintptr_t)code_ptr;
if (value != (int8_t)value) { if (value != (int8_t)value) {
tcg_abort(); tcg_abort();
} }
*(uint8_t *)code_ptr = value; tcg_patch8(code_ptr, value);
break; break;
default: default:
tcg_abort(); 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]; uint8_t **label_ptr = &l->label_ptr[0];
/* resolve label address */ /* 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) { 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) { if (TCG_TARGET_REG_BITS == 32) {
@ -1360,9 +1360,9 @@ static void tcg_out_qemu_st_slow_path(TCGContext *s, TCGLabelQemuLdst *l)
TCGReg retaddr; TCGReg retaddr;
/* resolve label address */ /* 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) { 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) { if (TCG_TARGET_REG_BITS == 32) {

20
tcg/tcg.c
View File

@ -122,6 +122,11 @@ static inline void tcg_out8(TCGContext *s, uint8_t v)
*s->code_ptr++ = v; *s->code_ptr++ = v;
} }
static inline void tcg_patch8(uint8_t *p, uint8_t v)
{
memcpy(p, &v, sizeof(v));
}
static inline void tcg_out16(TCGContext *s, uint16_t v) static inline void tcg_out16(TCGContext *s, uint16_t v)
{ {
uint8_t *p = s->code_ptr; uint8_t *p = s->code_ptr;
@ -129,6 +134,11 @@ static inline void tcg_out16(TCGContext *s, uint16_t v)
s->code_ptr = p + 2; s->code_ptr = p + 2;
} }
static inline void tcg_patch16(uint8_t *p, uint16_t v)
{
memcpy(p, &v, sizeof(v));
}
static inline void tcg_out32(TCGContext *s, uint32_t v) static inline void tcg_out32(TCGContext *s, uint32_t v)
{ {
uint8_t *p = s->code_ptr; uint8_t *p = s->code_ptr;
@ -136,6 +146,11 @@ static inline void tcg_out32(TCGContext *s, uint32_t v)
s->code_ptr = p + 4; s->code_ptr = p + 4;
} }
static inline void tcg_patch32(uint8_t *p, uint32_t v)
{
memcpy(p, &v, sizeof(v));
}
static inline void tcg_out64(TCGContext *s, uint64_t v) static inline void tcg_out64(TCGContext *s, uint64_t v)
{ {
uint8_t *p = s->code_ptr; uint8_t *p = s->code_ptr;
@ -143,6 +158,11 @@ static inline void tcg_out64(TCGContext *s, uint64_t v)
s->code_ptr = p + 8; s->code_ptr = p + 8;
} }
static inline void tcg_patch64(uint8_t *p, uint64_t v)
{
memcpy(p, &v, sizeof(v));
}
/* label relocation processing */ /* label relocation processing */
static void tcg_out_reloc(TCGContext *s, uint8_t *code_ptr, int type, static void tcg_out_reloc(TCGContext *s, uint8_t *code_ptr, int type,