From 5c53bb812152c3d7919cadfd47c210b181bf89ac Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Fri, 28 Mar 2014 15:29:48 +0000 Subject: [PATCH] tcg: Avoid undefined behaviour patching code at unaligned addresses MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Peter Maydell Signed-off-by: Richard Henderson --- 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 34ece1f80b..9a585ab5ec 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 293f00bc5a..31a5d48d03 100644 --- a/tcg/tcg.c +++ b/tcg/tcg.c @@ -122,6 +122,11 @@ static inline void tcg_out8(TCGContext *s, uint8_t 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) { 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; } +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) { 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; } +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) { 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; } +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,