[Xen-devel] [PATCH v3 4/4] xen/arm: Don't crash the domain on invalid HVC immediate

[Julien Grall <julien.grall@xxxxxxx>]

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

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

---

    We potentially want to return -1 instead. This would make Xen more
    future-proof if we decide to implement the other HVC immediate.

    Changes in v2:
        - Add Stefano's reviewed-by
---
 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 1e85f99ec1..1cba7e584d 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -1471,14 +1471,17 @@ 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);
+    }
 
     if ( *nr >= ARRAY_SIZE(arm_hypercall_table) )
     {
@@ -2109,7 +2112,7 @@ 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;
     }
@@ -2123,7 +2126,7 @@ 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


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