Re: [Qemu-devel] [PATCH v3 14/16] tcg/arm: Return false on failure from patch_reloc

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> This does require an extra two checks within the slow paths
> to replace the assert that we're moving.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

> ---
>  tcg/arm/tcg-target.inc.c | 22 ++++++++++++++++------
>  1 file changed, 16 insertions(+), 6 deletions(-)
>
> diff --git a/tcg/arm/tcg-target.inc.c b/tcg/arm/tcg-target.inc.c
> index deefa20fbf..49f57d655e 100644
> --- a/tcg/arm/tcg-target.inc.c
> +++ b/tcg/arm/tcg-target.inc.c
> @@ -187,10 +187,14 @@ static const uint8_t tcg_cond_to_arm_cond[] = {
>      [TCG_COND_GTU] = COND_HI,
>  };
>
> -static inline void reloc_pc24(tcg_insn_unit *code_ptr, tcg_insn_unit *target)
> +static inline bool reloc_pc24(tcg_insn_unit *code_ptr, tcg_insn_unit *target)
>  {
>      ptrdiff_t offset = (tcg_ptr_byte_diff(target, code_ptr) - 8) >> 2;
> -    *code_ptr = (*code_ptr & ~0xffffff) | (offset & 0xffffff);
> +    if (offset == sextract32(offset, 0, 24)) {
> +        *code_ptr = (*code_ptr & ~0xffffff) | (offset & 0xffffff);
> +        return true;
> +    }
> +    return false;
>  }
>
>  static bool patch_reloc(tcg_insn_unit *code_ptr, int type,
> @@ -199,7 +203,7 @@ static bool patch_reloc(tcg_insn_unit *code_ptr, int type,
>      tcg_debug_assert(addend == 0);
>
>      if (type == R_ARM_PC24) {
> -        reloc_pc24(code_ptr, (tcg_insn_unit *)value);
> +        return reloc_pc24(code_ptr, (tcg_insn_unit *)value);
>      } else if (type == R_ARM_PC13) {
>          intptr_t diff = value - (uintptr_t)(code_ptr + 2);
>          tcg_insn_unit insn = *code_ptr;
> @@ -213,7 +217,11 @@ static bool patch_reloc(tcg_insn_unit *code_ptr, int type,
>          } else {
>              int rd = extract32(insn, 12, 4);
>              int rt = rd == TCG_REG_PC ? TCG_REG_TMP : rd;
> -            assert(diff >= 0x1000 && diff < 0x100000);
> +
> +            if (diff < 0x1000 || diff >= 0x100000) {
> +                return false;
> +            }
> +
>              /* add rt, pc, #high */
>              *code_ptr++ = ((insn & 0xf0000000) | (1 << 25) | ARITH_ADD
>                             | (TCG_REG_PC << 16) | (rt << 12)
> @@ -1372,7 +1380,8 @@ static void tcg_out_qemu_ld_slow_path(TCGContext *s, TCGLabelQemuLdst *lb)
>      TCGMemOp opc = get_memop(oi);
>      void *func;
>
> -    reloc_pc24(lb->label_ptr[0], s->code_ptr);
> +    bool ok = reloc_pc24(lb->label_ptr[0], s->code_ptr);
> +    tcg_debug_assert(ok);
>
>      argreg = tcg_out_arg_reg32(s, TCG_REG_R0, TCG_AREG0);
>      if (TARGET_LONG_BITS == 64) {
> @@ -1432,7 +1441,8 @@ static void tcg_out_qemu_st_slow_path(TCGContext *s, TCGLabelQemuLdst *lb)
>      TCGMemOpIdx oi = lb->oi;
>      TCGMemOp opc = get_memop(oi);
>
> -    reloc_pc24(lb->label_ptr[0], s->code_ptr);
> +    bool ok = reloc_pc24(lb->label_ptr[0], s->code_ptr);
> +    tcg_debug_assert(ok);
>
>      argreg = TCG_REG_R0;
>      argreg = tcg_out_arg_reg32(s, argreg, TCG_AREG0);


--
Alex Bennée