Merge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/…

…git/arm64/linux

Pull arm64 fixes from Will Deacon:
 "Three arm64 fixes for -rc4.

  One of them is just a trivial documentation fix, whereas the other two
  address a warning in the kexec code and a crash in ftrace on systems
  implementing BTI.

  The latter patch has a couple of ugly ifdefs which Mark plans to clean
  up separately, but as-is the patch is straightforward for backporting
  to stable kernels.

  Summary:

   - Add missing BTI landing instructions to the ftrace*_caller
     trampolines

   - Fix kexec() WARN when DEBUG_VIRTUAL is enabled

   - Fix PAC documentation by removing stale references to compiler
     flags"

* tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux:
  arm64: ftrace: add missing BTIs
  arm64: kexec: use __pa_symbol(empty_zero_page)
  arm64: update PAC description for kernel

Documentation/arm64/pointer-authentication.rst

@@ -53,11 +53,10 @@ The number of bits that the PAC occupies in a pointer is 55 minus the
 virtual address size configured by the kernel. For example, with a
 virtual address size of 48, the PAC is 7 bits wide.
 
-Recent versions of GCC can compile code with APIAKey-based return
-address protection when passed the -msign-return-address option. This
-uses instructions in the HINT space (unless -march=armv8.3-a or higher
-is also passed), and such code can run on systems without the pointer
-authentication extension.
+When ARM64_PTR_AUTH_KERNEL is selected, the kernel will be compiled
+with HINT space pointer authentication instructions protecting
+function returns. Kernels built with this option will work on hardware
+with or without pointer authentication support.
 
 In addition to exec(), keys can also be reinitialized to random values
 using the PR_PAC_RESET_KEYS prctl. A bitmask of PR_PAC_APIAKEY,

arch/arm64/kernel/entry-ftrace.S

@@ -77,11 +77,17 @@
 	.endm
 
 SYM_CODE_START(ftrace_regs_caller)
+#ifdef BTI_C
+	BTI_C
+#endif
 	ftrace_regs_entry	1
 	b	ftrace_common
 SYM_CODE_END(ftrace_regs_caller)
 
 SYM_CODE_START(ftrace_caller)
+#ifdef BTI_C
+	BTI_C
+#endif
 	ftrace_regs_entry	0
 	b	ftrace_common
 SYM_CODE_END(ftrace_caller)

arch/arm64/kernel/machine_kexec.c

@@ -147,7 +147,7 @@ int machine_kexec_post_load(struct kimage *kimage)
 	if (rc)
 		return rc;
 	kimage->arch.ttbr1 = __pa(trans_pgd);
-	kimage->arch.zero_page = __pa(empty_zero_page);
+	kimage->arch.zero_page = __pa_symbol(empty_zero_page);
 
 	reloc_size = __relocate_new_kernel_end - __relocate_new_kernel_start;
 	memcpy(reloc_code, __relocate_new_kernel_start, reloc_size);