[xen master] x86: rework hypercall argument count table instantiation & use

[patchbot@xxxxxxx]

commit 6c987150cf71976b5dd16b5f736dd5b0c6f6aee8
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Aug 18 09:30:41 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Aug 18 09:30:41 2022 +0200

    x86: rework hypercall argument count table instantiation & use
    
    The initial observation were duplicate symbols that our checking warns
    about. Instead of merely renaming one or both pair(s) of symbols,
    reduce #ifdef-ary at the same time by moving the instantiation of the
    arrays into a macro. While doing the conversion also stop open-coding
    array_access_nospec().
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/hvm/hypercall.c         |  9 ++-------
 xen/arch/x86/include/asm/hypercall.h | 19 +++++++------------
 xen/arch/x86/pv/hypercall.c          | 11 ++---------
 3 files changed, 11 insertions(+), 28 deletions(-)

diff --git a/xen/arch/x86/hvm/hypercall.c b/xen/arch/x86/hvm/hypercall.c
index 29d1ca7a13..405d0a95af 100644
--- a/xen/arch/x86/hvm/hypercall.c
+++ b/xen/arch/x86/hvm/hypercall.c
@@ -111,11 +111,6 @@ long hvm_physdev_op(int cmd, XEN_GUEST_HANDLE_PARAM(void) 
arg)
         return compat_physdev_op(cmd, arg);
 }
 
-#ifndef NDEBUG
-static const unsigned char hypercall_args_64[] = hypercall_args_hvm64;
-static const unsigned char hypercall_args_32[] = hypercall_args_hvm32;
-#endif
-
 int hvm_hypercall(struct cpu_user_regs *regs)
 {
     struct vcpu *curr = current;
@@ -177,7 +172,7 @@ int hvm_hypercall(struct cpu_user_regs *regs)
                             regs->r10, regs->r8);
 
         if ( !curr->hcall_preempted && regs->rax != -ENOSYS )
-            clobber_regs(regs, get_nargs(hypercall_args_64, eax));
+            clobber_regs(regs, eax, hvm, 64);
     }
     else
     {
@@ -190,7 +185,7 @@ int hvm_hypercall(struct cpu_user_regs *regs)
         curr->hcall_compat = false;
 
         if ( !curr->hcall_preempted && regs->eax != -ENOSYS )
-            clobber_regs32(regs, get_nargs(hypercall_args_32, eax));
+            clobber_regs(regs, eax, hvm, 32);
     }
 
     hvmemul_cache_restore(curr, token);
diff --git a/xen/arch/x86/include/asm/hypercall.h 
b/xen/arch/x86/include/asm/hypercall.h
index ab8bd12e60..ec2edc771e 100644
--- a/xen/arch/x86/include/asm/hypercall.h
+++ b/xen/arch/x86/include/asm/hypercall.h
@@ -43,18 +43,8 @@ compat_common_vcpu_op(
 
 #endif /* CONFIG_COMPAT */
 
-#ifndef NDEBUG
-static inline unsigned int _get_nargs(const unsigned char *tbl, unsigned int c)
-{
-    return tbl[c];
-}
-#define get_nargs(t, c) _get_nargs(t, array_index_nospec(c, ARRAY_SIZE(t)))
-#else
-#define get_nargs(tbl, c) 0
-#endif
-
-static inline void clobber_regs(struct cpu_user_regs *regs,
-                                unsigned int nargs)
+static inline void clobber_regs64(struct cpu_user_regs *regs,
+                                  unsigned int nargs)
 {
 #ifndef NDEBUG
     /* Deliberately corrupt used parameter regs. */
@@ -85,4 +75,9 @@ static inline void clobber_regs32(struct cpu_user_regs *regs,
 #endif
 }
 
+#define clobber_regs(r, n, t, b) ({ \
+    static const unsigned char t ## b[] = hypercall_args_ ## t ## b; \
+    clobber_regs ## b(r, array_access_nospec(t ## b, n)); \
+})
+
 #endif /* __ASM_X86_HYPERCALL_H__ */
diff --git a/xen/arch/x86/pv/hypercall.c b/xen/arch/x86/pv/hypercall.c
index bf64bb41bb..2eedfbfae8 100644
--- a/xen/arch/x86/pv/hypercall.c
+++ b/xen/arch/x86/pv/hypercall.c
@@ -27,13 +27,6 @@
 #include <asm/multicall.h>
 #include <irq_vectors.h>
 
-#ifndef NDEBUG
-static const unsigned char hypercall_args_64[] = hypercall_args_pv64;
-#ifdef CONFIG_PV32
-static const unsigned char hypercall_args_32[] = hypercall_args_pv32;
-#endif
-#endif
-
 /* Forced inline to cause 'compat' to be evaluated at compile time. */
 static void always_inline
 _pv_hypercall(struct cpu_user_regs *regs, bool compat)
@@ -65,7 +58,7 @@ _pv_hypercall(struct cpu_user_regs *regs, bool compat)
         call_handlers_pv64(eax, regs->rax, rdi, rsi, rdx, r10, r8);
 
         if ( !curr->hcall_preempted && regs->rax != -ENOSYS )
-            clobber_regs(regs, get_nargs(hypercall_args_64, eax));
+            clobber_regs(regs, eax, pv, 64);
     }
 #ifdef CONFIG_PV32
     else
@@ -90,7 +83,7 @@ _pv_hypercall(struct cpu_user_regs *regs, bool compat)
         curr->hcall_compat = false;
 
         if ( !curr->hcall_preempted && regs->eax != -ENOSYS )
-            clobber_regs32(regs, get_nargs(hypercall_args_32, eax));
+            clobber_regs(regs, eax, pv, 32);
     }
 #endif /* CONFIG_PV32 */
 
--
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