[v2,24/30] bsd-user/arm/target_arch_signal.h: arm set_mcontext

Commit Message

Warner Losh Nov. 2, 2021, 10:52 p.m. UTC

Move the machine context to the CPU state.

Signed-off-by: Stacey Son <[e-mail]>
Signed-off-by: Kyle Evans <[e-mail]>
Signed-off-by: Warner Losh <[e-mail]>
---
 bsd-user/arm/target_arch_signal.h | 75 +++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)

Comments

Richard Henderson Nov. 3, 2021, 3:40 a.m. UTC | #1

On 11/2/21 6:52 PM, Warner Losh wrote:
> +    env->regs[15] = tswap32(gr[TARGET_REG_PC]);

This will be able to crash qemu with an odd pc in thumb mode.
You'd have to artificially create this mcontext of course.

Otherwise,
Reviewed-by: Richard Henderson <[e-mail]>


r~

Warner Losh Nov. 3, 2021, 7:19 p.m. UTC | #2

On Tue, Nov 2, 2021 at 9:40 PM Richard Henderson <
[e-mail]> wrote:

> On 11/2/21 6:52 PM, Warner Losh wrote:
> > +    env->regs[15] = tswap32(gr[TARGET_REG_PC]);
>
> This will be able to crash qemu with an odd pc in thumb mode.
> You'd have to artificially create this mcontext of course.
>

Sure. And if you did this natively, you'd also get SIGILL or something
similar and the process would die and/or coredump.
Is there something different about qemu-user that I'm missing in this
context?

Warner


> Otherwise,
> Reviewed-by: Richard Henderson <[e-mail]>
>
>
> r~
>

Patch

diff --git a/bsd-user/arm/target_arch_signal.h b/bsd-user/arm/target_arch_signal.h
index b42d08402f..3b2f56ffab 100644
--- a/bsd-user/arm/target_arch_signal.h
+++ b/bsd-user/arm/target_arch_signal.h
@@ -179,4 +179,79 @@  static inline abi_long get_mcontext(CPUARMState *env, target_mcontext_t *mcp,
     return err;
 }
 
+/* Compare to arm/arm/exec_machdep.c set_mcontext() */
+static inline 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;
+
+    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;
+    }
+
+    /*
+     * Make sure that we either have no vfp, or it's the correct size.
+     * FreeBSD just ignores it, though, so maybe we'll need to adjust
+     * things below instead.
+     */
+    if (mcp->mc_vfp_size != 0 && mcp->mc_vfp_size != sizeof(target_mcontext_vfp_t)) {
+        return -TARGET_EINVAL;
+    }
+    /*
+     * 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;
+    }
+
+    env->regs[0] = tswap32(gr[TARGET_REG_R0]);
+    env->regs[1] = tswap32(gr[TARGET_REG_R1]);
+    env->regs[2] = tswap32(gr[TARGET_REG_R2]);
+    env->regs[3] = tswap32(gr[TARGET_REG_R3]);
+    env->regs[4] = tswap32(gr[TARGET_REG_R4]);
+    env->regs[5] = tswap32(gr[TARGET_REG_R5]);
+    env->regs[6] = tswap32(gr[TARGET_REG_R6]);
+    env->regs[7] = tswap32(gr[TARGET_REG_R7]);
+    env->regs[8] = tswap32(gr[TARGET_REG_R8]);
+    env->regs[9] = tswap32(gr[TARGET_REG_R9]);
+    env->regs[10] = tswap32(gr[TARGET_REG_R10]);
+    env->regs[11] = tswap32(gr[TARGET_REG_R11]);
+    env->regs[12] = tswap32(gr[TARGET_REG_R12]);
+
+    env->regs[13] = tswap32(gr[TARGET_REG_SP]);
+    env->regs[14] = tswap32(gr[TARGET_REG_LR]);
+    env->regs[15] = tswap32(gr[TARGET_REG_PC]);
+    if (mcp->mc_vfp_size != 0 && mcp->mc_vfp_ptr != NULL) {
+        /* see set_vfpcontext in sys/arm/arm/exec_machdep.c */
+        target_mcontext_vfp_t *vfp = (target_mcontext_vfp_t *)mcp->mc_vfp_ptr;
+        for (int i = 0; i < 32; i++) {
+            *aa32_vfp_dreg(env, i) = tswap64(vfp->mcv_reg[i]);
+        }
+        fpscr =  tswap32(vfp->mcv_fpscr);
+        vfp_set_fpscr(env, fpscr);
+        /*
+         * linux-user sets fpexc, fpinst and fpinst2, but these aren't in
+         * FreeBSD's mcontext, what to do?
+         */
+    }
+    cpsr_write(env, cpsr, CPSR_USER | CPSR_EXEC, CPSRWriteByInstr);
+
+    return err;
+}
+
 #endif /* !_TARGET_ARCH_SIGNAL_H_ */