[PATCH 3/6] x86/shadow: Use ERR_PTR infrastructure for sh_emulate_map_dest()

[Andrew Cooper <andrew.cooper3@citrix.com>]

sh_emulate_map_dest() predates the introduction of the generic ERR_PTR()
infrasturcture, but take the opportunity to avoid opencoding it.

The chosen error constants require need to be negative to work with IS_ERR(),
but no other changes.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Tim Deegan <tim@xen.org>

v2:
 * Use ~(long)X86EMUL rather than -X86EMUL so MAPPING_SILENT_FAIL is
   considered an error to IS_ERR()
---
 xen/arch/x86/mm/shadow/multi.c   | 8 ++++----
 xen/arch/x86/mm/shadow/private.h | 7 +++----
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index f65ffc6..74c3641 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -4752,8 +4752,8 @@ sh_x86_emulate_write(struct vcpu *v, unsigned long vaddr, void *src,
         return X86EMUL_UNHANDLEABLE;
 
     addr = sh_emulate_map_dest(v, vaddr, bytes, sh_ctxt);
-    if ( sh_emulate_map_dest_failed(addr) )
-        return (long)addr;
+    if ( IS_ERR(addr) )
+        return ~PTR_ERR(addr);
 
     paging_lock(v->domain);
     memcpy(addr, src, bytes);
@@ -4794,8 +4794,8 @@ sh_x86_emulate_cmpxchg(struct vcpu *v, unsigned long vaddr,
         return X86EMUL_UNHANDLEABLE;
 
     addr = sh_emulate_map_dest(v, vaddr, bytes, sh_ctxt);
-    if ( sh_emulate_map_dest_failed(addr) )
-        return (long)addr;
+    if ( IS_ERR(addr) )
+        return ~PTR_ERR(addr);
 
     paging_lock(v->domain);
     switch ( bytes )
diff --git a/xen/arch/x86/mm/shadow/private.h b/xen/arch/x86/mm/shadow/private.h
index 472676c..a59ff7a 100644
--- a/xen/arch/x86/mm/shadow/private.h
+++ b/xen/arch/x86/mm/shadow/private.h
@@ -395,10 +395,9 @@ void shadow_unhook_mappings(struct domain *d, mfn_t smfn, int user_only);
 
 /* Returns a mapped pointer to write to, or one of the following error
  * indicators. */
-#define MAPPING_UNHANDLEABLE ((void *)(unsigned long)X86EMUL_UNHANDLEABLE)
-#define MAPPING_EXCEPTION    ((void *)(unsigned long)X86EMUL_EXCEPTION)
-#define MAPPING_SILENT_FAIL  ((void *)(unsigned long)X86EMUL_OKAY)
-#define sh_emulate_map_dest_failed(rc) ((unsigned long)(rc) <= 3)
+#define MAPPING_UNHANDLEABLE ERR_PTR(~(long)X86EMUL_UNHANDLEABLE)
+#define MAPPING_EXCEPTION    ERR_PTR(~(long)X86EMUL_EXCEPTION)
+#define MAPPING_SILENT_FAIL  ERR_PTR(~(long)X86EMUL_OKAY)
 void *sh_emulate_map_dest(struct vcpu *v, unsigned long vaddr,
                           unsigned int bytes, struct sh_emulate_ctxt *sh_ctxt);
 void sh_emulate_unmap_dest(struct vcpu *v, void *addr, unsigned int bytes,
-- 
2.1.4


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