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Mark Rutland 9df3f5082f arm64: avoid redundant PAC stripping in __builtin_return_address() 
In old versions of GCC and Clang, __builtin_return_address() did not
strip the PAC. This was not the behaviour we desired, and so we wrapped
this with code to strip the PAC in commit:

  689eae42af ("arm64: mask PAC bits of __builtin_return_address")

Since then, both GCC and Clang decided that __builtin_return_address()
*should* strip the PAC, and the existing behaviour was a bug.

GCC was fixed in 11.1.0, with those fixes backported to 10.2.0, 9.4.0,
8.5.0, but not earlier:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94891

Clang was fixed in 12.0.0, though this was not backported:

  https://reviews.llvm.org/D75044

When using a compiler whose __builtin_return_address() strips the PAC,
our wrapper to strip the PAC is redundant. Similarly, when pointer
authentication is not in use within the kernel pointers will not have a
PAC, and so there's no point stripping those pointers.

To avoid this redundant work, this patch updates the
__builtin_return_address() wrapper to only be used when in-kernel
pointer authentication is configured and the compiler's
__builtin_return_address() does not strip the PAC.

This is a cleanup/optimization, and not a fix that requires backporting.
Stripping a PAC should be an idempotent operation, and so redundantly
stripping the PAC is not harmful.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Kristina Martsenko <kristina.martsenko@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20230412160134.306148-2-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
2023-04-13 12:27:11 +01:00
..
boot We have one small patch to the clk core this time around. It fixes a corner 2023-02-25 15:16:23 -08:00
configs ARM: SoC fixes for 6.3, part 1 2023-02-27 10:09:40 -08:00
crypto crypto: arm64/sm4-gcm - Fix possible crash in GCM cryption 2023-02-10 17:20:19 +08:00
hyperv hyperv: simplify and rename generate_guest_id 2022-09-28 13:36:56 +00:00
include arm64: avoid redundant PAC stripping in __builtin_return_address() 2023-04-13 12:27:11 +01:00
kernel arm64: stacktrace: always inline core stacktrace functions 2023-04-11 18:34:59 +01:00
kvm KVM: arm64: timers: Convert per-vcpu virtual offset to a global value 2023-03-11 02:00:40 -08:00
lib Merge branch 'for-next/sysregs' into for-next/core 2022-12-06 11:32:25 +00:00
mm arm64 fixes: 2023-03-02 14:57:53 -08:00
net bpf: Remove prog->active check for bpf_lsm and bpf_iter 2022-10-25 23:11:46 -07:00
tools ARM: 2023-02-25 11:30:21 -08:00
xen
Kbuild
Kconfig arm64: avoid redundant PAC stripping in __builtin_return_address() 2023-04-13 12:27:11 +01:00
Kconfig.debug
Kconfig.platforms arm64 updates for 6.3: 2023-02-21 15:27:48 -08:00
Makefile arm64 updates for 6.3: 2023-02-21 15:27:48 -08:00