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arm64 fixes for -rc4

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- 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
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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
This commit is contained in:
Linus Torvalds 2021-12-03 10:50:14 -08:00
commit a2aeaeabbc
3 changed files with 11 additions and 6 deletions
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9
Documentation/arm64/pointer-authentication.rst
View File

@ -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,

6
arch/arm64/kernel/entry-ftrace.S
View File

@ -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)

2
arch/arm64/kernel/machine_kexec.c
View File

@ -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);