Re: [PATCH v4 33/36] bsd-user/arm/target_arch_signal.c: arm set_mcontext

[Richard Henderson <richard.henderson@linaro.org>]

On 11/4/21 11:19 PM, Warner Losh wrote:
> +/* Compare to arm/arm/exec_machdep.c set_mcontext() */
> +abi_long set_mcontext(CPUARMState *env, target_mcontext_t *mcp, int srflag)
> +{
> +    int err = 0;
> +    const uint32_t *gr = mcp->__gregs;
> +    uint32_t cpsr, ccpsr = cpsr_read(env);
> +    uint32_t fpscr, mask;
> +
> +    cpsr = tswap32(gr[TARGET_REG_CPSR]);
> +    /*
> +     * Only allow certain bits to change, reject attempted changes to non-user
> +     * bits. In addition, make sure we're headed for user mode and none of the
> +     * interrupt bits are set.
> +     */
> +    if ((ccpsr & ~CPSR_USER) != (cpsr & ~CPSR_USER)) {
> +        return -TARGET_EINVAL;
> +    }
> +    if ((cpsr & CPSR_M) != ARM_CPU_MODE_USR ||
> +        (cpsr & (CPSR_I | CPSR_F)) != 0) {
> +        return -TARGET_EINVAL;
> +    }
> +    mask = cpsr & CPSR_T ? 0x1 : 0x3;

Should add a sentence or so here, pointing to the exception return instruction used by the 
freebsd kernel, which does this masking.

> +    /*
> +     * Make sure T mode matches the PC's notion of thumb mode, although
> +     * FreeBSD lets the processor sort this out, so we may need remove
> +     * this check, or generate a signal...
> +     */
> +    if (!!(tswap32(gr[TARGET_REG_PC]) & 1) != !!(cpsr & CPSR_T)) {
> +        return -TARGET_EINVAL;
> +    }

Remove this.

> +    env->regs[15] = tswap32(gr[TARGET_REG_PC] & mask);

You wanted ~mask.


r~