Avoid integer overflow in next_page_start

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

Posted by Emilio G. Cota 7 years, 10 months ago

If the PC is in the last page of the address space, next_page_start
overflows to 0. Fix it.

Reported-by: Richard Henderson <richard.henderson@linaro.org>
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Cc: Michael Clark <mjc@sifive.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Signed-off-by: Emilio G. Cota <cota@braap.org>
---
 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

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

Posted by Bastian Koppelmann 7 years, 10 months ago

On 04/10/2018 06:19 PM, Emilio G. Cota 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 <richard.henderson@linaro.org>
> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
> Cc: Michael Clark <mjc@sifive.com>
> Cc: Palmer Dabbelt <palmer@sifive.com>
> Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
> Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
> Signed-off-by: Emilio G. Cota <cota@braap.org>
> ---

Acked-by: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>

Cheers,
Bastian

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

Posted by Michael Clark 7 years, 10 months ago

On Wed, Apr 11, 2018 at 4:19 AM, Emilio G. Cota <cota@braap.org> 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 <richard.henderson@linaro.org>
> Suggested-by: Richard Henderson <richard.henderson@linaro.org>
> Cc: Michael Clark <mjc@sifive.com>
> Cc: Palmer Dabbelt <palmer@sifive.com>
> Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
> Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
> Signed-off-by: Emilio G. Cota <cota@braap.org>
>

Reviewed-by: Michael Clark <mjc@sifive.com>


> ---
>  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
>
>