powerpc64: make clang cross-build friendly

ARCH_USING_PATCHABLE_FUNCTION_ENTRY depends on toolchain support for
-fpatchable-function-entry option. The current script that checks
for this support onl

powerpc64: make clang cross-build friendly

ARCH_USING_PATCHABLE_FUNCTION_ENTRY depends on toolchain support for
-fpatchable-function-entry option. The current script that checks
for this support only handles GCC. Rename the script and extend it
to detect support for -fpatchable-function-entry with Clang as well,
allowing clean cross-compilation with Clang toolchains.

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20260127084926.34497-2-hbathini@linux.ibm.com

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powerpc/tools: drop `-o pipefail` in gcc check scripts

Fixes: 0f71dcfb4aef ("powerpc/ftrace: Add support for -fpatchable-function-entry")
Fixes: b71c9ffb1405 ("powerpc: Add arch/powerpc/tools direct

powerpc/tools: drop `-o pipefail` in gcc check scripts

Fixes: 0f71dcfb4aef ("powerpc/ftrace: Add support for -fpatchable-function-entry")
Fixes: b71c9ffb1405 ("powerpc: Add arch/powerpc/tools directory")
Reported-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Jan Stancek <jstancek@redhat.com>
Fixes: 8c50b72a3b4f ("powerpc/ftrace: Add Kconfig & Make glue for mprofile-kernel")
Fixes: abba759796f9 ("powerpc/kbuild: move -mprofile-kernel check to Kconfig")
Tested-by: Justin M. Forbes <jforbes@fedoraproject.org>
Reviewed-by: Naveen N Rao (AMD) <naveen@kernel.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/cc6cdd116c3ad9d990df21f13c6d8e8a83815bbd.1758641374.git.jstancek@redhat.com

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powerpc/ftrace: Add support for -fpatchable-function-entry

GCC v13.1 updated support for -fpatchable-function-entry on ppc64le to
emit nops after the local entry point, rather than before it. This
a

powerpc/ftrace: Add support for -fpatchable-function-entry

GCC v13.1 updated support for -fpatchable-function-entry on ppc64le to
emit nops after the local entry point, rather than before it. This
allows us to use this in the kernel for ftrace purposes. A new script is
added under arch/powerpc/tools/ to help detect if nops are emitted after
the function local entry point, or before the global entry point.

With -fpatchable-function-entry, we no longer have the profiling
instructions generated at function entry, so we only need to validate
the presence of two nops at the ftrace location in ftrace_init_nop(). We
patch the preceding instruction with 'mflr r0' to match the
-mprofile-kernel ABI for subsequent ftrace use.

This changes the profiling instructions used on ppc32. The default -pg
option emits an additional 'stw' instruction after 'mflr r0' and before
the branch to _mcount 'bl _mcount'. This is very similar to the original
-mprofile-kernel implementation on ppc64le, where an additional 'std'
instruction was used to save LR to its save location in the caller's
stackframe. Subsequently, this additional store was removed in later
compiler versions for performance reasons. The same reasons apply for
ppc32 so we only patch in a 'mflr r0'.

Signed-off-by: Naveen N Rao <naveen@kernel.org>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/68586d22981a2c3bb45f27a2b621173d10a7d092.1687166935.git.naveen@kernel.org

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