Merge tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 core updates from Borislav Petkov:

 - Add the call depth tracking mitigation for Retbleed which has been
   long in the making. It is a lighterweight software-only fix for
   Skylake-based cores where enabling IBRS is a big hammer and causes a
   significant performance impact.

   What it basically does is, it aligns all kernel functions to 16 bytes
   boundary and adds a 16-byte padding before the function, objtool
   collects all functions' locations and when the mitigation gets
   applied, it patches a call accounting thunk which is used to track
   the call depth of the stack at any time.

   When that call depth reaches a magical, microarchitecture-specific
   value for the Return Stack Buffer, the code stuffs that RSB and
   avoids its underflow which could otherwise lead to the Intel variant
   of Retbleed.

   This software-only solution brings a lot of the lost performance
   back, as benchmarks suggest:

       https://lore.kernel.org/all/20220915111039.092790446@infradead.org/

   That page above also contains a lot more detailed explanation of the
   whole mechanism

 - Implement a new control flow integrity scheme called FineIBT which is
   based on the software kCFI implementation and uses hardware IBT
   support where present to annotate and track indirect branches using a
   hash to validate them

 - Other misc fixes and cleanups

* tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (80 commits)
  x86/paravirt: Use common macro for creating simple asm paravirt functions
  x86/paravirt: Remove clobber bitmask from .parainstructions
  x86/debug: Include percpu.h in debugreg.h to get DECLARE_PER_CPU() et al
  x86/cpufeatures: Move X86_FEATURE_CALL_DEPTH from bit 18 to bit 19 of word 11, to leave space for WIP X86_FEATURE_SGX_EDECCSSA bit
  x86/Kconfig: Enable kernel IBT by default
  x86,pm: Force out-of-line memcpy()
  objtool: Fix weak hole vs prefix symbol
  objtool: Optimize elf_dirty_reloc_sym()
  x86/cfi: Add boot time hash randomization
  x86/cfi: Boot time selection of CFI scheme
  x86/ibt: Implement FineIBT
  objtool: Add --cfi to generate the .cfi_sites section
  x86: Add prefix symbols for function padding
  objtool: Add option to generate prefix symbols
  objtool: Avoid O(bloody terrible) behaviour -- an ode to libelf
  objtool: Slice up elf_create_section_symbol()
  kallsyms: Revert "Take callthunks into account"
  x86: Unconfuse CONFIG_ and X86_FEATURE_ namespaces
  x86/retpoline: Fix crash printing warning
  x86/paravirt: Fix a !PARAVIRT build warning
  ...

1 files changed, 20 insertions, 27 deletions

diff --git a/arch/x86/include/asm/qspinlock_paravirt.h b/arch/x86/include/asm/qspinlock_paravirt.h
index dbb38a6b4dfb..42b17cf10b10 100644
--- a/arch/x86/include/asm/qspinlock_paravirt.h
+++ b/arch/x86/include/asm/qspinlock_paravirt.h
@@ -14,8 +14,6 @@
 
 __PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock_slowpath, ".spinlock.text");
 #define __pv_queued_spin_unlock	__pv_queued_spin_unlock
-#define PV_UNLOCK		"__raw_callee_save___pv_queued_spin_unlock"
-#define PV_UNLOCK_SLOWPATH	"__raw_callee_save___pv_queued_spin_unlock_slowpath"
 
 /*
  * Optimized assembly version of __raw_callee_save___pv_queued_spin_unlock
@@ -37,32 +35,27 @@ __PV_CALLEE_SAVE_REGS_THUNK(__pv_queued_spin_unlock_slowpath, ".spinlock.text");
  *   rsi = lockval           (second argument)
  *   rdx = internal variable (set to 0)
  */
-asm    (".pushsection .spinlock.text, \"ax\";"
-	".globl " PV_UNLOCK ";"
-	".type " PV_UNLOCK ", @function;"
-	".align 4,0x90;"
-	PV_UNLOCK ": "
-	ASM_ENDBR
-	FRAME_BEGIN
-	"push  %rdx;"
-	"mov   $0x1,%eax;"
-	"xor   %edx,%edx;"
-	LOCK_PREFIX "cmpxchg %dl,(%rdi);"
-	"cmp   $0x1,%al;"
-	"jne   .slowpath;"
-	"pop   %rdx;"
+#define PV_UNLOCK_ASM							\
+	FRAME_BEGIN							\
+	"push  %rdx\n\t"						\
+	"mov   $0x1,%eax\n\t"						\
+	"xor   %edx,%edx\n\t"						\
+	LOCK_PREFIX "cmpxchg %dl,(%rdi)\n\t"				\
+	"cmp   $0x1,%al\n\t"						\
+	"jne   .slowpath\n\t"						\
+	"pop   %rdx\n\t"						\
+	FRAME_END							\
+	ASM_RET								\
+	".slowpath:\n\t"						\
+	"push   %rsi\n\t"						\
+	"movzbl %al,%esi\n\t"						\
+	"call __raw_callee_save___pv_queued_spin_unlock_slowpath\n\t"	\
+	"pop    %rsi\n\t"						\
+	"pop    %rdx\n\t"						\
 	FRAME_END
-	ASM_RET
-	".slowpath: "
-	"push   %rsi;"
-	"movzbl %al,%esi;"
-	"call " PV_UNLOCK_SLOWPATH ";"
-	"pop    %rsi;"
-	"pop    %rdx;"
-	FRAME_END
-	ASM_RET
-	".size " PV_UNLOCK ", .-" PV_UNLOCK ";"
-	".popsection");
+
+DEFINE_PARAVIRT_ASM(__raw_callee_save___pv_queued_spin_unlock,
+		    PV_UNLOCK_ASM, .spinlock.text);
 
 #else /* CONFIG_64BIT */