linux-toradex.git/arch/powerpc/kernel/vdso, branch master

random: vDSO: avoid call to memset() when zeroing reserved parameter

2026-10-02T10:12:13+00:00

After a recent change in LLVM [1], builds with the random vDSO
implementation, such as PowerPC and RISC-V, fail when checking the vDSO:

  arch/powerpc/kernel/vdso/vdso32.so.dbg: dynamic relocations are not supported
  arch/riscv/kernel/vdso/vdso.so.dbg: dynamic relocations are not supported

memset() is now generated when zeroing params->reserved for some builds
because LLVM has an optimization (now run in more instances) that can
recognize at compile time when it is assigning a static value to a
contiguous area of memory and turn that into a call to memset(). Both
clang and GCC assume memset() is always available [2].

Clang has an internal fiddly hook, -max-store-memset, which we can set
to a high number, to disable generating out of line memset calls [3].
Similarly, GCC has -finline-stringops=memset to do the same [4], should
this issue ever hit future version of GCC. While these options wouldn't
make sense for normal kernel code, it is fine for the extremely limited
and intentionally compact vDSO code.

Link: https://github.com/llvm/llvm-project/commit/90cebef1411617fc3eedd359bdf00cb44b1c2439 [1]
Link: https://gcc.gnu.org/onlinedocs/gcc-16.2.0/gcc/Standards.html#index-ffreestanding [2]
Link: https://github.com/llvm/llvm-project/commit/b28eeb28bea39148738dc375e8a97072a1907e64 [3]
Link: https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-finline-stringops [4]
Closes: https://github.com/ClangBuiltLinux/linux/issues/2183
Cc: stable@vger.kernel.org # v6.12+
Signed-off-by: Nathan Chancellor 
Signed-off-by: Jason A. Donenfeld

powerpc/vdso: Respect COMPAT_32BIT_TIME

2026-07-07T21:52:53+00:00

If CONFIG_COMPAT_32BIT_TIME is disabled then the vDSO should not
provide any 32-bit time related functionality. This is the intended
effect of the kconfig option and also the fallback system calls would
also not be implemented.

Signed-off-by: Thomas Weißschuh 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Arnd Bergmann 
Link: https://patch.msgid.link/20260702-vdso-compat_32bit_time-v3-6-db9f36d8d432@linutronix.de

powerpc/vdso: Drop -DCC_USING_PATCHABLE_FUNCTION_ENTRY from 32-bit flags with clang

2026-05-06T02:15:59+00:00

After commit 73cdf24e81e4 ("powerpc64: make clang cross-build
friendly"), building 64-bit little endian + CONFIG_COMPAT=y with clang
results in many warnings along the lines of:

  $ cat arch/powerpc/configs/compat.config
  CONFIG_COMPAT=y

  $ make -skj"$(nproc)" ARCH=powerpc LLVM=1 ppc64le_defconfig compat.config arch/powerpc/kernel/vdso/
  ...
  In file included from :4:
  In file included from lib/vdso/gettimeofday.c:6:
  In file included from include/vdso/datapage.h:15:
  In file included from include/vdso/cache.h:5:
  arch/powerpc/include/asm/cache.h:77:8: warning: unknown attribute 'patchable_function_entry' ignored [-Wunknown-attributes]
     77 | static inline u32 l1_icache_bytes(void)
        |        ^~~~~~
  include/linux/compiler_types.h:235:58: note: expanded from macro 'inline'
    235 | #define inline inline __gnu_inline __inline_maybe_unused notrace
        |                                                          ^~~~~~~
  include/linux/compiler_types.h:215:34: note: expanded from macro 'notrace'
    215 | #define notrace                 __attribute__((patchable_function_entry(0, 0)))
        |                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  ...

arch/powerpc/Makefile adds -DCC_USING_PATCHABLE_FUNCTION_ENTRY to
KBUILD_CPPFLAGS, which is inherited by the 32-bit vDSO. However, the
32-bit little endian target does not support
'-fpatchable-function-entry', resulting in the warnings above.

Remove -DCC_USING_PATCHABLE_FUNCTION_ENTRY from the 32-bit vDSO flags
when building with clang to avoid the warnings.

Fixes: 73cdf24e81e4 ("powerpc64: make clang cross-build friendly")
Signed-off-by: Nathan Chancellor 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/20260311-ppc-vdso-drop-cc-using-pfe-define-clang-v1-1-66c790e22650@kernel.org

powerpc/vdso: Provide clock_getres_time64()

2026-01-14T13:57:39+00:00

For consistency with __vdso_clock_gettime64() there should also be a
64-bit variant of clock_getres(). This will allow the extension of
CONFIG_COMPAT_32BIT_TIME to the vDSO and finally the removal of 32-bit
time types from the kernel and UAPI.

Signed-off-by: Thomas Weißschuh 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Christophe Leroy (CS GROUP) 
Link: https://patch.msgid.link/20260114-vdso-powerpc-align-v1-1-acf09373d568@linutronix.de

powerpc/vdso: Fix build of VDSO32 with pcrel

2025-06-13T07:00:15+00:00

Building vdso32 on power10 with pcrel leads to following errors:

	  VDSO32A arch/powerpc/kernel/vdso/gettimeofday-32.o
	arch/powerpc/kernel/vdso/gettimeofday.S: Assembler messages:
	arch/powerpc/kernel/vdso/gettimeofday.S:40: Error: syntax error; found `@', expected `,'
	arch/powerpc/kernel/vdso/gettimeofday.S:71:  Info: macro invoked from here
	arch/powerpc/kernel/vdso/gettimeofday.S:40: Error: junk at end of line: `@notoc'
	arch/powerpc/kernel/vdso/gettimeofday.S:71:  Info: macro invoked from here
	 ...
	make[2]: *** [arch/powerpc/kernel/vdso/Makefile:85: arch/powerpc/kernel/vdso/gettimeofday-32.o] Error 1
	make[1]: *** [arch/powerpc/Makefile:388: vdso_prepare] Error 2

Once the above is fixed, the following happens:

	  VDSO32C arch/powerpc/kernel/vdso/vgettimeofday-32.o
	cc1: error: '-mpcrel' requires '-mcmodel=medium'
	make[2]: *** [arch/powerpc/kernel/vdso/Makefile:89: arch/powerpc/kernel/vdso/vgettimeofday-32.o] Error 1
	make[1]: *** [arch/powerpc/Makefile:388: vdso_prepare] Error 2
	make: *** [Makefile:251: __sub-make] Error 2

Make sure pcrel version of CFUNC() macro is used only for powerpc64
builds and remove -mpcrel for powerpc32 builds.

Fixes: 7e3a68be42e1 ("powerpc/64: vmlinux support building with PCREL addresing")
Signed-off-by: Christophe Leroy 
Signed-off-by: Madhavan Srinivasan 
Link: https://patch.msgid.link/1fa3453f07d42a50a70114da9905bf7b73304fca.1747073669.git.christophe.leroy@csgroup.eu

powerpc/vdso: Switch to generic storage implementation

2025-02-21T08:54:02+00:00

The generic storage implementation provides the same features as the
custom one. However it can be shared between architectures, making
maintenance easier.

Co-developed-by: Nam Cao 
Signed-off-by: Nam Cao 
Signed-off-by: Thomas Weißschuh 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Christophe Leroy 
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-14-13a4669dfc8c@linutronix.de

vdso: Rename included Makefile

2025-02-21T08:54:01+00:00

As the Makefile is included into other Makefiles it can not be used to
define objects to be built from the current source directory.
However the generic datastore will introduce such a local source file.
Rename the included Makefile so it is clear how it is to be used and to
make room for a regular Makefile in lib/vdso/.

Signed-off-by: Thomas Weißschuh 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20250204-vdso-store-rng-v3-4-13a4669dfc8c@linutronix.de

powerpc/Makefile: Allow overriding CPP

2024-11-15T00:59:55+00:00

Unlike all other arches, powerpc doesn't allow the user to override CPP,
because it sets it unconditionally in the arch Makefile. This can lead
to strange build failures.

Instead add the required flags to KBUILD_CPPFLAGS, which are passed
to CPP, CC and AS invocations by the generic Makefile logic.

Reported-by: Arnd Bergmann 
Tested-by: Nathan Chancellor 
Reviewed-by: Nathan Chancellor 
Closes: https://lore.kernel.org/all/20240607061629.530301-1-arnd@kernel.org
Signed-off-by: Arnd Bergmann 
[mpe: Rebase, write change log, add Arnd's SoB as communicated privately]
Signed-off-by: Michael Ellerman 
Link: https://patch.msgid.link/20241107112646.32401-1-mpe@ellerman.id.au

powerpc/vdso: Drop -mstack-protector-guard flags in 32-bit files with clang

2024-11-04T06:03:10+00:00

Under certain conditions, the 64-bit '-mstack-protector-guard' flags may
end up in the 32-bit vDSO flags, resulting in build failures due to the
structure of clang's argument parsing of the stack protector options,
which validates the arguments of the stack protector guard flags
unconditionally in the frontend, choking on the 64-bit values when
targeting 32-bit:

  clang: error: invalid value 'r13' in 'mstack-protector-guard-reg=', expected one of: r2
  clang: error: invalid value 'r13' in 'mstack-protector-guard-reg=', expected one of: r2
  make[3]: *** [arch/powerpc/kernel/vdso/Makefile:85: arch/powerpc/kernel/vdso/vgettimeofday-32.o] Error 1
  make[3]: *** [arch/powerpc/kernel/vdso/Makefile:87: arch/powerpc/kernel/vdso/vgetrandom-32.o] Error 1

Remove these flags by adding them to the CC32FLAGSREMOVE variable, which
already handles situations similar to this. Additionally, reformat and
align a comment better for the expanding CONFIG_CC_IS_CLANG block.

Cc: stable@vger.kernel.org # v6.1+
Signed-off-by: Nathan Chancellor 
Signed-off-by: Michael Ellerman 
Link: https://patch.msgid.link/20241030-powerpc-vdso-drop-stackp-flags-clang-v1-1-d95e7376d29c@kernel.org

powerpc/vdso: Implement __arch_get_vdso_rng_data()

2024-10-16T00:14:40+00:00

VDSO time functions do not call any other function, so they don't
need to save/restore LR. However, retrieving the address of VDSO data
page requires using LR hence saving then restoring it, which can be
heavy on some CPUs. On the other hand, VDSO functions on powerpc are
not standard functions and require a wrapper function to call C VDSO
functions. And that wrapper has to save and restore LR in order to
call the C VDSO function, so retrieving VDSO data page address in that
wrapper doesn't require additional save/restore of LR.

For random VDSO functions it is a bit different. Because the function
calls __arch_chacha20_blocks_nostack(), it saves and restores LR.
Retrieving VDSO data page address can then be done there without
additional save/restore of LR.

So lets implement __arch_get_vdso_rng_data() and simplify the wrapper.

It starts paving the way for the day powerpc will implement a more
standard ABI for VDSO functions.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://patch.msgid.link/a1a9bd0df508f1b5c04684b7366940577dfc6262.1727858295.git.christophe.leroy@csgroup.eu