Re: [Qemu-devel] [PATCH 01/10] target/riscv: avoid integer overflow in next_page PC check

[Michael Clark]

On Wed, Apr 11, 2018 at 4:19 AM, Emilio G. Cota <address@hidden> wrote:

> If the PC is in the last page of the address space, next_page_start
> overflows to 0. Fix it.
>
> Reported-by: Richard Henderson <address@hidden>
> Suggested-by: Richard Henderson <address@hidden>
> Cc: Michael Clark <address@hidden>
> Cc: Palmer Dabbelt <address@hidden>
> Cc: Sagar Karandikar <address@hidden>
> Cc: Bastian Koppelmann <address@hidden>
> Signed-off-by: Emilio G. Cota <address@hidden>
>

Reviewed-by: Michael Clark <address@hidden>


> ---
>  target/riscv/translate.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/target/riscv/translate.c b/target/riscv/translate.c
> index 808eab7..d2d2e5e 100644
> --- a/target/riscv/translate.c
> +++ b/target/riscv/translate.c
> @@ -1849,11 +1849,11 @@ void gen_intermediate_code(CPUState *cs,
> TranslationBlock *tb)
>      CPURISCVState *env = cs->env_ptr;
>      DisasContext ctx;
>      target_ulong pc_start;
> -    target_ulong next_page_start;
> +    target_ulong page_start;
>      int num_insns;
>      int max_insns;
>      pc_start = tb->pc;
> -    next_page_start = (pc_start & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
> +    page_start = pc_start & TARGET_PAGE_MASK;
>      ctx.pc = pc_start;
>
>      /* once we have GDB, the rest of the translate.c implementation
> should be
> @@ -1903,7 +1903,7 @@ void gen_intermediate_code(CPUState *cs,
> TranslationBlock *tb)
>          if (cs->singlestep_enabled) {
>              break;
>          }
> -        if (ctx.pc >= next_page_start) {
> +        if (ctx.pc - page_start >= TARGET_PAGE_SIZE) {
>              break;
>          }
>          if (tcg_op_buf_full()) {
> --
> 2.7.4
>
>