From: Jan Beulich <jbeulich@suse.com>
Date: Fri, 9 Jul 2021 06:32:07 +0000 (+0200)
Subject: x86: mark hypercall argument regs clobbering for intended fall-through
X-Git-Tag: archive/raspbian/4.16.0+51-g0941d6cb-1+rpi1~2^2~42^2~338
X-Git-Url: https://dgit.raspbian.org/%22http://www.example.com/cgi/success/%22http:/www.example.com/cgi/success?a=commitdiff_plain;h=140931aa2894991d9d6f1b2ba6ca275e1bc56259;p=xen.git

x86: mark hypercall argument regs clobbering for intended fall-through

The CIDs below are all for the PV side of things, yet while at it take
care of the HVM side as well.

Coverity-ID: 1485896, 1485901, 1485906, 1485910, 1485911,
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 9e1f7249f3..263d5407ea 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/xen/arch/x86/hvm/hypercall.c
@@ -248,11 +248,11 @@ int hvm_hypercall(struct cpu_user_regs *regs)
         /* Deliberately corrupt parameter regs not used by this hypercall. */
         switch ( hypercall_args_table[eax].native )
         {
-        case 0: rdi = 0xdeadbeefdeadf00dUL;
-        case 1: rsi = 0xdeadbeefdeadf00dUL;
-        case 2: rdx = 0xdeadbeefdeadf00dUL;
-        case 3: r10 = 0xdeadbeefdeadf00dUL;
-        case 4: r8 = 0xdeadbeefdeadf00dUL;
+        case 0: rdi = 0xdeadbeefdeadf00dUL; fallthrough;
+        case 1: rsi = 0xdeadbeefdeadf00dUL; fallthrough;
+        case 2: rdx = 0xdeadbeefdeadf00dUL; fallthrough;
+        case 3: r10 = 0xdeadbeefdeadf00dUL; fallthrough;
+        case 4: r8 = 0xdeadbeefdeadf00dUL; fallthrough;
         case 5: r9 = 0xdeadbeefdeadf00dUL;
         }
 #endif
@@ -266,11 +266,11 @@ int hvm_hypercall(struct cpu_user_regs *regs)
             /* Deliberately corrupt parameter regs used by this hypercall. */
             switch ( hypercall_args_table[eax].native )
             {
-            case 6: regs->r9  = 0xdeadbeefdeadf00dUL;
-            case 5: regs->r8  = 0xdeadbeefdeadf00dUL;
-            case 4: regs->r10 = 0xdeadbeefdeadf00dUL;
-            case 3: regs->rdx = 0xdeadbeefdeadf00dUL;
-            case 2: regs->rsi = 0xdeadbeefdeadf00dUL;
+            case 6: regs->r9  = 0xdeadbeefdeadf00dUL; fallthrough;
+            case 5: regs->r8  = 0xdeadbeefdeadf00dUL; fallthrough;
+            case 4: regs->r10 = 0xdeadbeefdeadf00dUL; fallthrough;
+            case 3: regs->rdx = 0xdeadbeefdeadf00dUL; fallthrough;
+            case 2: regs->rsi = 0xdeadbeefdeadf00dUL; fallthrough;
             case 1: regs->rdi = 0xdeadbeefdeadf00dUL;
             }
         }
diff --git a/xen/arch/x86/pv/hypercall.c b/xen/arch/x86/pv/hypercall.c
index 200b8a05b0..03939bdfcf 100644
--- a/xen/arch/x86/pv/hypercall.c
+++ b/xen/arch/x86/pv/hypercall.c
@@ -150,11 +150,11 @@ void pv_hypercall(struct cpu_user_regs *regs)
         /* Deliberately corrupt parameter regs not used by this hypercall. */
         switch ( hypercall_args_table[eax].native )
         {
-        case 0: rdi = 0xdeadbeefdeadf00dUL;
-        case 1: rsi = 0xdeadbeefdeadf00dUL;
-        case 2: rdx = 0xdeadbeefdeadf00dUL;
-        case 3: r10 = 0xdeadbeefdeadf00dUL;
-        case 4: r8 = 0xdeadbeefdeadf00dUL;
+        case 0: rdi = 0xdeadbeefdeadf00dUL; fallthrough;
+        case 1: rsi = 0xdeadbeefdeadf00dUL; fallthrough;
+        case 2: rdx = 0xdeadbeefdeadf00dUL; fallthrough;
+        case 3: r10 = 0xdeadbeefdeadf00dUL; fallthrough;
+        case 4: r8 = 0xdeadbeefdeadf00dUL; fallthrough;
         case 5: r9 = 0xdeadbeefdeadf00dUL;
         }
 #endif
@@ -173,11 +173,11 @@ void pv_hypercall(struct cpu_user_regs *regs)
             /* Deliberately corrupt parameter regs used by this hypercall. */
             switch ( hypercall_args_table[eax].native )
             {
-            case 6: regs->r9  = 0xdeadbeefdeadf00dUL;
-            case 5: regs->r8  = 0xdeadbeefdeadf00dUL;
-            case 4: regs->r10 = 0xdeadbeefdeadf00dUL;
-            case 3: regs->rdx = 0xdeadbeefdeadf00dUL;
-            case 2: regs->rsi = 0xdeadbeefdeadf00dUL;
+            case 6: regs->r9  = 0xdeadbeefdeadf00dUL; fallthrough;
+            case 5: regs->r8  = 0xdeadbeefdeadf00dUL; fallthrough;
+            case 4: regs->r10 = 0xdeadbeefdeadf00dUL; fallthrough;
+            case 3: regs->rdx = 0xdeadbeefdeadf00dUL; fallthrough;
+            case 2: regs->rsi = 0xdeadbeefdeadf00dUL; fallthrough;
             case 1: regs->rdi = 0xdeadbeefdeadf00dUL;
             }
         }