On 10/06/2024 15:04, Torbjörn SVENSSON wrote:
> Properly handle zero and sign extension for Armv8-M.baseline as
> Cortex-M23 can have the security extension active.
> Currently, there is an internal compiler error on Cortex-M23 for the
> epilog processing of sign extension.
>
> This patch addresses the following CVE-2024-0151 for Armv8-M.baseline.
>
> gcc/ChangeLog:
>
> PR target/115253
> * config/arm/arm.cc (cmse_nonsecure_call_inline_register_clear):
> Sign extend for Thumb1.
> (thumb1_expand_prologue): Add zero/sign extend.
>
> Signed-off-by: Torbjörn SVENSSON <torbjorn.svens...@foss.st.com>
> Co-authored-by: Yvan ROUX <yvan.r...@foss.st.com>
> ---
> gcc/config/arm/arm.cc | 71 ++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 63 insertions(+), 8 deletions(-)
>
> diff --git a/gcc/config/arm/arm.cc b/gcc/config/arm/arm.cc
> index ea0c963a4d6..e7b4caf1083 100644
> --- a/gcc/config/arm/arm.cc
> +++ b/gcc/config/arm/arm.cc
> @@ -19220,17 +19220,22 @@ cmse_nonsecure_call_inline_register_clear (void)
> || TREE_CODE (ret_type) == BOOLEAN_TYPE)
> && known_lt (GET_MODE_SIZE (TYPE_MODE (ret_type)), 4))
> {
> - machine_mode ret_mode = TYPE_MODE (ret_type);
> + rtx ret_reg = gen_rtx_REG (TYPE_MODE (ret_type), R0_REGNUM);
> + rtx si_reg = gen_rtx_REG (SImode, R0_REGNUM);
> rtx extend;
> if (TYPE_UNSIGNED (ret_type))
> - extend = gen_rtx_ZERO_EXTEND (SImode,
> - gen_rtx_REG (ret_mode,
> R0_REGNUM));
> + extend = gen_rtx_SET (si_reg, gen_rtx_ZERO_EXTEND (SImode,
> + ret_reg));
> else
> - extend = gen_rtx_SIGN_EXTEND (SImode,
> - gen_rtx_REG (ret_mode,
> R0_REGNUM));
> - emit_insn_after (gen_rtx_SET (gen_rtx_REG (SImode, R0_REGNUM),
> - extend), insn);
> -
> + /* Signed-extension is a special case because of
> + thumb1_extendhisi2. */
> + if (TARGET_THUMB1
You effectively have an 'else if' split across a comment here, and the
indentation looks weird. Either write 'else if' on one line (and re-indent
accordingly) or put this entire block inside braces.
> + && known_ge (GET_MODE_SIZE (TYPE_MODE (ret_type)), 2))
You can use known_eq here. We'll never have any value other than 2, given the
known_le (4) above and anyway it doesn't make sense to call extendhisi with any
other size.
> + extend = gen_thumb1_extendhisi2 (si_reg, ret_reg);
> + else
> + extend = gen_rtx_SET (si_reg, gen_rtx_SIGN_EXTEND (SImode,
> + ret_reg));
> + emit_insn_after (extend, insn);
> }
>
>
> @@ -27250,6 +27255,56 @@ thumb1_expand_prologue (void)
> live_regs_mask = offsets->saved_regs_mask;
> lr_needs_saving = live_regs_mask & (1 << LR_REGNUM);
>
Similar comments to above apply to the hunk below.
> + /* The AAPCS requires the callee to widen integral types narrower
> + than 32 bits to the full width of the register; but when handling
> + calls to non-secure space, we cannot trust the callee to have
> + correctly done so. So forcibly re-widen the result here. */
> + if (IS_CMSE_ENTRY (func_type))
> + {
> + function_args_iterator args_iter;
> + CUMULATIVE_ARGS args_so_far_v;
> + cumulative_args_t args_so_far;
> + bool first_param = true;
> + tree arg_type;
> + tree fndecl = current_function_decl;
> + tree fntype = TREE_TYPE (fndecl);
> + arm_init_cumulative_args (&args_so_far_v, fntype, NULL_RTX, fndecl);
> + args_so_far = pack_cumulative_args (&args_so_far_v);
> + FOREACH_FUNCTION_ARGS (fntype, arg_type, args_iter)
> + {
> + rtx arg_rtx;
> +
> + if (VOID_TYPE_P (arg_type))
> + break;
> +
> + function_arg_info arg (arg_type, /*named=*/true);
> + if (!first_param)
> + /* We should advance after processing the argument and pass
> + the argument we're advancing past. */
> + arm_function_arg_advance (args_so_far, arg);
> + first_param = false;
> + arg_rtx = arm_function_arg (args_so_far, arg);
> + gcc_assert (REG_P (arg_rtx));
> + if ((TREE_CODE (arg_type) == INTEGER_TYPE
> + || TREE_CODE (arg_type) == ENUMERAL_TYPE
> + || TREE_CODE (arg_type) == BOOLEAN_TYPE)
> + && known_lt (GET_MODE_SIZE (GET_MODE (arg_rtx)), 4))
> + {
> + rtx res_reg = gen_rtx_REG (SImode, REGNO (arg_rtx));
> + if (TYPE_UNSIGNED (arg_type))
> + emit_set_insn (res_reg, gen_rtx_ZERO_EXTEND (SImode, arg_rtx));
> + else
> + /* Signed-extension is a special case because of
> + thumb1_extendhisi2. */
> + if (known_ge (GET_MODE_SIZE (GET_MODE (arg_rtx)), 2))
> + emit_insn (gen_thumb1_extendhisi2 (res_reg, arg_rtx));
> + else
> + emit_set_insn (res_reg,
> + gen_rtx_SIGN_EXTEND (SImode, arg_rtx));
> + }
> + }
> + }
> +
> /* Extract a mask of the ones we can give to the Thumb's push instruction.
> */
> l_mask = live_regs_mask & 0x40ff;
> /* Then count how many other high registers will need to be pushed. */
OK with those changes.
R.
