[xen staging-4.18] x86: Drop INDIRECT_JMP

[patchbot@xxxxxxx]

commit 62844c4415f50e01ab46fa8bedc127cc098aa77b
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Dec 22 18:01:37 2023 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Tue Apr 9 16:45:01 2024 +0100

    x86: Drop INDIRECT_JMP
    
    Indirect JMPs which are not tailcalls can lead to an unwelcome form of
    speculative type confusion, and we've removed the uses of INDIRECT_JMP to
    compensate.  Remove the temptation to reintroduce new instances.
    
    This is part of XSA-456 / CVE-2024-2201.
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    (cherry picked from commit 0b66d7ce3c0290eaad28bdafb35200052d012b14)
---
 xen/arch/x86/include/asm/asm-defns.h | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/xen/arch/x86/include/asm/asm-defns.h 
b/xen/arch/x86/include/asm/asm-defns.h
index 9a7073ced5..d55dd3bbc3 100644
--- a/xen/arch/x86/include/asm/asm-defns.h
+++ b/xen/arch/x86/include/asm/asm-defns.h
@@ -29,10 +29,9 @@
     BUG   /* Shouldn't return */
 .endm
 
-.macro INDIRECT_BRANCH insn:req arg:req
+.macro INDIRECT_CALL arg:req
 /*
- * Create an indirect branch.  insn is one of call/jmp, arg is a single
- * register.
+ * Create an indirect call.  arg is a single register.
  *
  * With no compiler support, this degrades into a plain indirect call/jmp.
  * With compiler support, dispatch to the correct __x86_indirect_thunk_*
@@ -42,7 +41,7 @@
         $done = 0
         .irp reg, ax, cx, dx, bx, bp, si, di, 8, 9, 10, 11, 12, 13, 14, 15
         .ifeqs "\arg", "%r\reg"
-            \insn __x86_indirect_thunk_r\reg
+            call __x86_indirect_thunk_r\reg
             $done = 1
            .exitm
         .endif
@@ -53,19 +52,10 @@
         .endif
 
     .else
-        \insn *\arg
+        call *\arg
     .endif
 .endm
 
-/* Convenience wrappers. */
-.macro INDIRECT_CALL arg:req
-    INDIRECT_BRANCH call \arg
-.endm
-
-.macro INDIRECT_JMP arg:req
-    INDIRECT_BRANCH jmp \arg
-.endm
-
 #ifdef CONFIG_XEN_IBT
 # define ENDBR64 endbr64
 #else
--
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