linux-toradex.git/arch/powerpc/kernel/vdso64, branch master

powerpc/vdso: Merge vdso64 and vdso32 into a single directory

2022-02-12T11:47:43+00:00

merge vdso64 into vdso32 and rename it vdso.

Reported-by: kernel test robot 
Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/4dbe05cc130f6a0858d09ac72e436c373cb08b70.1642782130.git.christophe.leroy@csgroup.eu

powerpc/vdso: Don't use r30 to avoid breaking Go lang

2021-07-29T13:13:12+00:00

The Go runtime uses r30 for some special value called 'g'. It assumes
that value will remain unchanged even when calling VDSO functions.
Although r30 is non-volatile across function calls, the callee is free
to use it, as long as the callee saves the value and restores it before
returning.

It used to be true by accident that the VDSO didn't use r30, because the
VDSO was hand-written asm. When we switched to building the VDSO from C
the compiler started using r30, at least in some builds, leading to
crashes in Go. eg:

  ~/go/src$ ./all.bash
  Building Go cmd/dist using /usr/lib/go-1.16. (go1.16.2 linux/ppc64le)
  Building Go toolchain1 using /usr/lib/go-1.16.
  go build os/exec: /usr/lib/go-1.16/pkg/tool/linux_ppc64le/compile: signal: segmentation fault
  go build reflect: /usr/lib/go-1.16/pkg/tool/linux_ppc64le/compile: signal: segmentation fault
  go tool dist: FAILED: /usr/lib/go-1.16/bin/go install -gcflags=-l -tags=math_big_pure_go compiler_bootstrap bootstrap/cmd/...: exit status 1

There are patches in flight to fix Go[1], but until they are released
and widely deployed we can workaround it in the VDSO by avoiding use of
r30.

Note this only works with GCC, clang does not support -ffixed-rN.

1: https://go-review.googlesource.com/c/go/+/328110

Fixes: ab037dd87a2f ("powerpc/vdso: Switch VDSO to generic C implementation.")
Cc: stable@vger.kernel.org # v5.11+
Reported-by: Paul Menzel 
Tested-by: Paul Menzel 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210729131244.2595519-1-mpe@ellerman.id.au

powerpc/vdso: Add support for time namespaces

2021-04-14T13:04:44+00:00

This patch adds the necessary glue to provide time namespaces.

Things are mainly copied from ARM64.

__arch_get_timens_vdso_data() calculates timens vdso data position
based on the vdso data position, knowing it is the next page in vvar.
This avoids having to redo the mflr/bcl/mflr/mtlr dance to locate
the page relative to running code position.

Signed-off-by: Christophe Leroy 
Reviewed-by: Vincenzo Frascino  # vDSO parts
Acked-by: Andrei Vagin 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/1a15495f80ec19a87b16cf874dbf7c3fa5ec40fe.1617209142.git.christophe.leroy@csgroup.eu

powerpc/64/signal: Fix regression in __kernel_sigtramp_rt64() semantics

2021-02-02T11:14:41+00:00

Commit 0138ba5783ae ("powerpc/64/signal: Balance return predictor
stack in signal trampoline") changed __kernel_sigtramp_rt64() VDSO and
trampoline code, and introduced a regression in the way glibc's
backtrace()[1] detects the signal-handler stack frame. Apart from the
practical implications, __kernel_sigtramp_rt64() was a VDSO function
with the semantics that it is a function you can call from userspace
to end a signal handling. Now this semantics are no longer valid.

I believe the aforementioned change affects all releases since 5.9.

This patch tries to fix both the semantics and practical aspect of
__kernel_sigtramp_rt64() returning it to the previous code, whilst
keeping the intended behaviour of 0138ba5783ae by adding a new symbol
to serve as the jump target from the kernel to the trampoline. Now the
trampoline has two parts, a new entry point and the old return point.

[1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2021-January/223194.html

Fixes: 0138ba5783ae ("powerpc/64/signal: Balance return predictor stack in signal trampoline")
Cc: stable@vger.kernel.org # v5.9+
Signed-off-by: Raoni Fassina Firmino 
Acked-by: Nicholas Piggin 
[mpe: Minor tweaks to change log formatting, add stable tag]
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20210201200505.iz46ubcizipnkcxe@work-tp

powerpc/vdso64: remove meaningless vgettimeofday.o build rule

2021-01-30T11:23:42+00:00

VDSO64 is only built for the 64-bit kernel, hence vgettimeofday.o is
built by the generic rule in scripts/Makefile.build.

This line does not provide anything useful.

Signed-off-by: Masahiro Yamada 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20201223171142.707053-2-masahiroy@kernel.org

powerpc/vdso: fix unnecessary rebuilds of vgettimeofday.o

2021-01-30T11:23:42+00:00

vgettimeofday.o is unnecessarily rebuilt. Adding it to 'targets' is not
enough to fix the issue. Kbuild is correctly rebuilding it because the
command line is changed.

PowerPC builds each vdso directory twice; first in vdso_prepare to
generate vdso{32,64}-offsets.h, second as part of the ordinary build
process to embed vdso{32,64}.so.dbg into the kernel.

The problem shows up when CONFIG_PPC_WERROR=y due to the following line
in arch/powerpc/Kbuild:

  subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror

In the preparation stage, Kbuild directly visits the vdso directories,
hence it does not inherit subdir-ccflags-y. In the second descend,
Kbuild adds -Werror, which results in the command line flipping
with/without -Werror.

It implies a potential danger; if a more critical flag that would impact
the resulted vdso, the offsets recorded in the headers might be different
from real offsets in the embedded vdso images.

Removing the unneeded second descend solves the problem.

Reported-by: Michael Ellerman 
Signed-off-by: Masahiro Yamada 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/linuxppc-dev/87tuslxhry.fsf@mpe.ellerman.id.au/
Link: https://lore.kernel.org/r/20201223171142.707053-1-masahiroy@kernel.org

powerpc/vdso: Block R_PPC_REL24 relocations

2020-12-21T11:06:25+00:00

Add R_PPC_REL24 relocations to the list of relocations we do NOT
support in the VDSO.

These are generated in some cases and we do not support relocating
them at runtime, so if they appear then the VDSO will not work at
runtime, therefore it's preferable to break the build if we see them.

Fixes: ab037dd87a2f ("powerpc/vdso: Switch VDSO to generic C implementation.")
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/20201218111619.1206391-1-mpe@ellerman.id.au

powerpc: Use common STABS_DEBUG and DWARF_DEBUG and ELF_DETAILS macro

2020-12-03T14:01:20+00:00

Use the common STABS_DEBUG and DWARF_DEBUG and ELF_DETAILS macro rule for
the linker script in an effort.

Signed-off-by: Youling Tang 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/1606460857-2723-1-git-send-email-tangyouling@loongson.cn

powerpc/vdso: Remove VDSO32_LBASE and VDSO64_LBASE

2020-12-03T14:01:19+00:00

VDSO32_LBASE and VDSO64_LBASE are 0. Remove them to simplify code.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/6c4d6570d886bbe1cc471e8ca01602e4b4d9beb5.1601197618.git.christophe.leroy@csgroup.eu

powerpc/vdso: Remove __kernel_datapage_offset

2020-12-03T14:01:18+00:00

__kernel_datapage_offset is not used anymore, remove it.

Signed-off-by: Christophe Leroy 
Signed-off-by: Michael Ellerman 
Link: https://lore.kernel.org/r/ddb5c746bec4e1a026d7c85243213a1876ef844f.1601197618.git.christophe.leroy@csgroup.eu