Re: [Xen-devel] [PATCH 3/3] xen/arm: Don't crash the domain on invalid HVC immediate

[Julien Grall]

On 30/01/18 18:24, Stefano Stabellini wrote:
On Tue, 30 Jan 2018, Julien Grall wrote:
domain_crash_synchronous() should only be used when something went wrong
in Xen. It is better to inject to the guest as it will be in better
                                                               ^ a better


position to provide helpful information (stack trace...).

Signed-off-by: Julien Grall <julien.gr...@arm.com>

---

     We potentially want to return -1 instead. This would make Xen more
     future-proof if we decide to implement the other HVC immediate.
---
  xen/arch/arm/traps.c | 13 ++++++++-----
  1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 843adf4959..18da45dff3 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1473,14 +1473,17 @@ static void do_debug_trap(struct cpu_user_regs *regs, 
unsigned int code)
  #endif
  
  static void do_trap_hypercall(struct cpu_user_regs *regs, register_t *nr,
-                              unsigned long iss)
+                              const union hsr hsr)
  {
      arm_hypercall_fn_t call = NULL;
  
      BUILD_BUG_ON(NR_hypercalls < ARRAY_SIZE(arm_hypercall_table) );
  
-    if ( iss != XEN_HYPERCALL_TAG )
-        domain_crash_synchronous();
+    if ( hsr.iss != XEN_HYPERCALL_TAG )
+    {
+        gprintk(XENLOG_WARNING, "Invalid HVC imm 0x%x\n", hsr.iss);
+        return inject_undef_exception(regs, hsr);

It looks a bit weird, given that inject_undef_exception doesn't return
anything. This is just code style so anyway:

I followed coding style in other part of the emulation (see do_sysreg 
for instance). I am happy to change that though.

Cheers,


Reviewed-by: Stefano Stabellini <sstabell...@kernel.org>


+    }
  
      if ( *nr >= ARRAY_SIZE(arm_hypercall_table) )
      {
@@ -2150,7 +2153,7 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
          if ( hsr.iss == 0 )
              return do_trap_hvc_smccc(regs);
          nr = regs->r12;
-        do_trap_hypercall(regs, &nr, hsr.iss);
+        do_trap_hypercall(regs, &nr, hsr);
          regs->r12 = (uint32_t)nr;
          break;
      }
@@ -2164,7 +2167,7 @@ void do_trap_guest_sync(struct cpu_user_regs *regs)
  #endif
          if ( hsr.iss == 0 )
              return do_trap_hvc_smccc(regs);
-        do_trap_hypercall(regs, &regs->x16, hsr.iss);
+        do_trap_hypercall(regs, &regs->x16, hsr);
          break;
      case HSR_EC_SMC64:
          /*
--
2.11.0


--
Julien Grall

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