riscv: hwprobe: do not produce frtace relocation

Such relocation causes crash of android linker similar to one
described in commit e05d57dcb8c7
("riscv: Fixup __vdso_gettimeofday broke dynamic ftrace").

Looks like this relocation is added by CONFIG_DYNAMIC_FTRACE which is
disabled in the default android kernel.

Before:

readelf -rW arch/riscv/kernel/vdso/vdso.so:

Relocation section '.rela.dyn' at offset 0xd00 contains 1 entry:
Offset Info Type
0000000000000d20 0000000000000003 R_RISCV_RELATIVE

objdump:
0000000000000c86 <__vdso_riscv_hwprobe@@LINUX_4.15>:
c86: 0001 nop
c88: 0001 nop
c8a: 0001 nop
c8c: 0001 nop
c8e: e211 bnez a2,c92 <__vdso_riscv_hwprobe...

After:
readelf -rW arch/riscv/kernel/vdso/vdso.so:

There are no relocations in this file.

objdump:
0000000000000c86 <__vdso_riscv_hwprobe@@LINUX_4.15>:
c86: e211 bnez a2,c8a <__vdso_riscv_hwprobe...
c88: c6b9 beqz a3,cd6 <__vdso_riscv_hwprobe...
c8a: e739 bnez a4,cd8 <__vdso_riscv_hwprobe...
c8c: ffffd797 auipc a5,0xffffd

Also disable SCS since it also should not be available in vdso.

Fixes: aa5af0aa90ba ("RISC-V: Add hwprobe vDSO function and data")
Signed-off-by: Roman Artemev <roman.artemev@syntacore.com>
Signed-off-by: Vladimir Isaev <vladimir.isaev@syntacore.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Link: https://lore.kernel.org/r/20240313085843.17661-1-vladimir.isaev@syntacore.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

riscv: Implement Shadow Call Stack

Implement CONFIG_SHADOW_CALL_STACK for RISC-V. When enabled, the
compiler injects instructions to all non-leaf C functions to
store the return address to the shadow stack and unconditionally
load it again before returning, which makes it harder to corrupt
the return address through a stack overflow, for example.

The active shadow call stack pointer is stored in the gp
register, which makes SCS incompatible with gp relaxation. Use
--no-relax-gp to ensure gp relaxation is disabled and disable
global pointer loading. Add SCS pointers to struct thread_info,
implement SCS initialization, and task switching

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/20230927224757.1154247-12-samitolvanen@google.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

kbuild: unify vdso_install rules

Currently, there is no standard implementation for vdso_install,
leading to various issues:

1. Code duplication

Many architectures duplicate similar code just for copying files
to the install destination.

Some architectures (arm, sparc, x86) create build-id symlinks,
introducing more code duplication.

2. Unintended updates of in-tree build artifacts

The vdso_install rule depends on the vdso files to install.
It may update in-tree build artifacts. This can be problematic,
as explained in commit 19514fc665ff ("arm, kbuild: make
"make install" not depend on vmlinux").

3. Broken code in some architectures

Makefile code is often copied from one architecture to another
without proper adaptation.

'make vdso_install' for parisc does not work.

'make vdso_install' for s390 installs vdso64, but not vdso32.

To address these problems, this commit introduces a generic vdso_install
rule.

Architectures that support vdso_install need to define vdso-install-y
in arch/*/Makefile. vdso-install-y lists the files to install.

For example, arch/x86/Makefile looks like this:

vdso-install-$(CONFIG_X86_64) += arch/x86/entry/vdso/vdso64.so.dbg
vdso-install-$(CONFIG_X86_X32_ABI) += arch/x86/entry/vdso/vdsox32.so.dbg
vdso-install-$(CONFIG_X86_32) += arch/x86/entry/vdso/vdso32.so.dbg
vdso-install-$(CONFIG_IA32_EMULATION) += arch/x86/entry/vdso/vdso32.so.dbg

These files will be installed to $(MODLIB)/vdso/ with the .dbg suffix,
if exists, stripped away.

vdso-install-y can optionally take the second field after the colon
separator. This is needed because some architectures install a vdso
file as a different base name.

The following is a snippet from arch/arm64/Makefile.

vdso-install-$(CONFIG_COMPAT_VDSO) += arch/arm64/kernel/vdso32/vdso.so.dbg:vdso32.so

This will rename vdso.so.dbg to vdso32.so during installation. If such
architectures change their implementation so that the base names match,
this workaround will go away.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Acked-by: Sven Schnelle <svens@linux.ibm.com> # s390
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>
Reviewed-by: Guo Ren <guoren@kernel.org>
Acked-by: Helge Deller <deller@gmx.de> # parisc
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

RISC-V: Add hwprobe vDSO function and data

Add a vDSO function __vdso_riscv_hwprobe, which can sit in front of the
riscv_hwprobe syscall and answer common queries. We stash a copy of
static answers for the "all CPUs" case in the vDSO data page. This data
is private to the vDSO, so we can decide later to change what's stored
there or under what conditions we defer to the syscall. Currently all
data can be discovered at boot, so the vDSO function answers all queries
when the cpumask is set to the "all CPUs" hint.

There's also a boolean in the data that lets the vDSO function know that
all CPUs are the same. In that case, the vDSO will also answer queries
for arbitrary CPU masks in addition to the "all CPUs" hint.

Signed-off-by: Evan Green <evan@rivosinc.com>
Link: https://lore.kernel.org/r/20230407231103.2622178-7-evan@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

vdso: Improve cmd_vdso_check to check all dynamic relocations

The actual intention is that no dynamic relocation exists in the VDSO. For
this the VDSO build validates that the resulting .so file does not have any
relocations which are specified via $(ARCH_REL_TYPE_ABS) per architecture,
which is fragile as e.g. ARM64 lacks an entry for R_AARCH64_RELATIVE. Aside
of that ARCH_REL_TYPE_ABS is a misnomer as it checks for relative
relocations too.

However, some GNU ld ports produce unneeded R_*_NONE relocation entries. If
a port fails to determine the exact .rel[a].dyn size, the trailing zeros
become R_*_NONE relocations. E.g. ld's powerpc port recently fixed
https://sourceware.org/bugzilla/show_bug.cgi?id=29540). R_*_NONE are
generally a no-op in the dynamic loaders. So just ignore them.

Remove the ARCH_REL_TYPE_ABS defines and just validate that the resulting
.so file does not contain any R_* relocation entries except R_*_NONE.

Signed-off-by: Fangrui Song <maskray@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # for aarch64
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> # for vDSO, aarch64
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
Link: https://lore.kernel.org/r/20230310190750.3323802-1-maskray@google.com

riscv: vdso: fix section overlapping under some conditions

lkp reported a build error, I tried the config and can reproduce
build error as below:

VDSOLD arch/riscv/kernel/vdso/vdso.so.dbg
ld.lld: error: section .note file range overlaps with .text
>>> .note range is [0x7C8, 0x803]
>>> .text range is [0x800, 0x1993]

ld.lld: error: section .text file range overlaps with .dynamic
>>> .text range is [0x800, 0x1993]
>>> .dynamic range is [0x808, 0x937]

ld.lld: error: section .note virtual address range overlaps with .text
>>> .note range is [0x7C8, 0x803]
>>> .text range is [0x800, 0x1993]

Fix it by setting DISABLE_BRANCH_PROFILING which will disable branch
tracing for vdso, thus avoid useless _ftrace_annotated_branch section
and _ftrace_branch section. Although we can also fix it by removing
the hardcoded .text begin address, but I think that's another story
and should be put into another patch.

Link: https://lore.kernel.org/lkml/202210122123.Cc4FPShJ-lkp@intel.com/#r
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Link: https://lore.kernel.org/r/20221102170254.1925-1-jszhang@kernel.org
Fixes: ad5d1122b82f ("riscv: use vDSO common flow to reduce the latency of the time-related functions")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

RISC-V: vdso: Do not add missing symbols to version section in linker script

Recently, ld.lld moved from '--undefined-version' to
'--no-undefined-version' as the default, which breaks the compat vDSO
build:

ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_gettimeofday' failed: symbol not defined
ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_clock_gettime' failed: symbol not defined
ld.lld: error: version script assignment of 'LINUX_4.15' to symbol '__vdso_clock_getres' failed: symbol not defined

These symbols are not present in the compat vDSO or the regular vDSO for
32-bit but they are unconditionally included in the version section of
the linker script, which is prohibited with '--no-undefined-version'.

Fix this issue by only including the symbols that are actually exported
in the version section of the linker script.

Link: https://github.com/ClangBuiltLinux/linux/issues/1756
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20221108171324.3377226-1-nathan@kernel.org/
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

riscv: vdso: fix build with llvm

Even after commit 89fd4a1df829 ("riscv: jump_label: mark arguments as
const to satisfy asm constraints"), building with CC_OPTIMIZE_FOR_SIZE
+ LLVM=1 can reproduce below build error:

CC arch/riscv/kernel/vdso/vgettimeofday.o
In file included from <built-in>:4:
In file included from lib/vdso/gettimeofday.c:5:
In file included from include/vdso/datapage.h:17:
In file included from include/vdso/processor.h:10:
In file included from arch/riscv/include/asm/vdso/processor.h:7:
In file included from include/linux/jump_label.h:112:
arch/riscv/include/asm/jump_label.h:42:3: error:
invalid operand for inline asm constraint 'i'
" .option push \n\t"
^
1 error generated.

I think the problem is when "-Os" is passed as CFLAGS, it's removed by
"CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os" which is
introduced in commit e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday
broke dynamic ftrace"), thus no optimization at all for vgettimeofday.c
arm64 does remove "-Os" as well, but it forces "-O2" after removing
"-Os".

I compared the generated vgettimeofday.o with "-O2" and "-Os",
I think no big performance difference. So let's tell the kbuild not
to remove "-Os" rather than follow arm64 style.

vdso related performance can be improved a lot when building kernel with
CC_OPTIMIZE_FOR_SIZE after this commit, ("-Os" VS no optimization)

Fixes: e05d57dcb8c7 ("riscv: Fixup __vdso_gettimeofday broke dynamic ftrace")
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20221031182943.2453-1-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

riscv: explicitly use symbol offsets for VDSO

The current implementation of the `__rt_sigaction` reference computed an
absolute offset relative to the mapped base of the VDSO. While this can
be handled in the medlow model, the medany model cannot handle this as
it is meant to be position independent. The current implementation
relied on the BFD linker relaxing the PC-relative relocation into an
absolute relocation as it was a near-zero address allowing it to be
referenced relative to `zero`.

We now extract the offsets and create a generated header allowing the
build with LLVM and lld to succeed as we no longer depend on the linker
rewriting address references near zero. This change was largely
modelled after the ARM64 target which does something similar.

Signed-off-by: Saleem Abdulrasool <abdulras@google.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: Enable Undefined Behavior Sanitizer UBSAN

Select ARCH_HAS_UBSAN_SANITIZE_ALL in order to allow the user to
enable CONFIG_UBSAN_SANITIZE_ALL and instrument the entire kernel for
ubsan checks.

VDSO is excluded because its build doesn't include the
__ubsan_handle_*() functions from lib/ubsan.c, and the VDSO has no
sane way to report errors even if it has definitions of these functions.

Passed lib/test_ubsan.c test.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: vdso: fix and clean-up Makefile

Running "make" on an already compiled kernel tree will rebuild the
kernel even without any modifications:

CALL linux/scripts/checksyscalls.sh
CALL linux/scripts/atomic/check-atomics.sh
CHK include/generated/compile.h
SO2S arch/riscv/kernel/vdso/vdso-syms.S
AS arch/riscv/kernel/vdso/vdso-syms.o
AR arch/riscv/kernel/vdso/built-in.a
AR arch/riscv/kernel/built-in.a
AR arch/riscv/built-in.a
GEN .version
CHK include/generated/compile.h
UPD include/generated/compile.h
CC init/version.o
AR init/built-in.a
LD vmlinux.o

The reason is "Any target that utilizes if_changed must be listed in
$(targets), otherwise the command line check will fail, and the target
will always be built" as explained by Documentation/kbuild/makefiles.rst

Fix this build bug by adding vdso-syms.S to $(targets)

At the same time, there are two trivial clean up modifications:

- the vdso-dummy.o is not needed any more after so remove it.

- vdso.lds is a generated file, so it should be prefixed with
$(obj)/ instead of $(src)/

Fixes: c2c81bb2f691 ("RISC-V: Fix the VDSO symbol generaton for binutils-2.35+")
Cc: stable@vger.kernel.org
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: Use $(LD) instead of $(CC) to link vDSO

Currently, the VDSO is being linked through $(CC). This does not match
how the rest of the kernel links objects, which is through the $(LD)
variable.

When linking with clang, there are a couple of warnings about flags that
will not be used during the link:

clang-12: warning: argument unused during compilation: '-no-pie' [-Wunused-command-line-argument]
clang-12: warning: argument unused during compilation: '-pg' [-Wunused-command-line-argument]

'-no-pie' was added in commit 85602bea297f ("RISC-V: build vdso-dummy.o
with -no-pie") to override '-pie' getting added to the ld command from
distribution versions of GCC that enable PIE by default. It is
technically no longer needed after commit c2c81bb2f691 ("RISC-V: Fix the
VDSO symbol generaton for binutils-2.35+"), which removed vdso-dummy.o
in favor of generating vdso-syms.S from vdso.so with $(NM) but this also
resolves the issue in case it ever comes back due to having full control
over the $(LD) command. '-pg' is for function tracing, it is not used
during linking as clang states.

These flags could be removed/filtered to fix the warnings but it is
easier to just match the rest of the kernel and use $(LD) directly for
linking. See commits

fe00e50b2db8 ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to link VDSO")
691efbedc60d ("arm64: vdso: use $(LD) instead of $(CC) to link VDSO")
2ff906994b6c ("MIPS: VDSO: Use $(LD) instead of $(CC) to link VDSO")
2b2a25845d53 ("s390/vdso: Use $(LD) instead of $(CC) to link vDSO")

for more information.

The flags are converted to linker flags and '--eh-frame-hdr' is added to
match what is added by GCC implicitly, which can be seen by adding '-v'
to GCC's invocation.

Additionally, since this area is being modified, use the $(OBJCOPY)
variable instead of an open coded $(CROSS_COMPILE)objcopy so that the
user's choice of objcopy binary is respected.

Link: https://github.com/ClangBuiltLinux/linux/issues/803
Link: https://github.com/ClangBuiltLinux/linux/issues/970
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Fangrui Song <maskray@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: Disable KSAN_SANITIZE for vDSO

We use the generic C VDSO implementations of a handful of clock-related
functions. When kasan is enabled this results in asan stub calls that
are unlikely to be resolved by userspace, this just disables KASAN
when building the VDSO.

Verified the fix on a kernel with KASAN enabled using vDSO selftests.

Link: https://lore.kernel.org/lkml/CACT4Y+ZNJBnkKHXUf=tm_yuowvZvHwN=0rmJ=7J+xFd+9r_6pQ@mail.gmail.com/
Tested-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
[Palmer: commit text]
Fixes: ad5d1122b82f ("riscv: use vDSO common flow to reduce the latency of the time-related functions")
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: Explicitly specify the build id style in vDSO Makefile again

Commit a96843372331 ("kbuild: explicitly specify the build id style")
explicitly set the build ID style to SHA1. Commit c2c81bb2f691 ("RISC-V:
Fix the VDSO symbol generaton for binutils-2.35+") undid this change,
likely unintentionally.

Restore it so that the build ID style stays consistent across the tree
regardless of linker.

Fixes: c2c81bb2f691 ("RISC-V: Fix the VDSO symbol generaton for binutils-2.35+")
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Bill Wendling <morbo@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

RISC-V: Fix the VDSO symbol generaton for binutils-2.35+

We were relying on GNU ld's ability to re-link executable files in order
to extract our VDSO symbols. This behavior was deemed a bug as of
binutils-2.35 (specifically the binutils-gdb commit a87e1817a4 ("Have
the linker fail if any attempt to link in an executable is made."), but
as that has been backported to at least Debian's binutils-2.34 in may
manifest in other places.

The previous version of this was a bit of a mess: we were linking a
static executable version of the VDSO, containing only a subset of the
input symbols, which we then linked into the kernel. This worked, but
certainly wasn't a supported path through the toolchain. Instead this
new version parses the textual output of nm to produce a symbol table.
Both rely on near-zero addresses being linkable, but as we rely on weak
undefined symbols being linkable elsewhere I don't view this as a major
issue.

Fixes: e2c0cdfba7f6 ("RISC-V: User-facing API")
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

kbuild: explicitly specify the build id style

ld's --build-id defaults to "sha1" style, while lld defaults to "fast".
The build IDs are very different between the two, which may confuse
programs that reference them.

Signed-off-by: Bill Wendling <morbo@google.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

riscv: disable stack-protector for vDSO

Currently, building the vDSO with clang leads assembler errors like the
following:

/tmp/vgettimeofday-1ae0d2.s: Assembler messages:
/tmp/vgettimeofday-1ae0d2.s:28: Error: bad expression
/tmp/vgettimeofday-1ae0d2.s:28: Error: illegal operands `auipc a2,%got_pcrel_hi(__stack_chk_guard)'

Disable the stack-protector for vDSO to fix these.

Link: https://github.com/ClangBuiltLinux/linux/issues/1112
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: Allow building with kcov coverage

Add ARCH_HAS_KCOV and HAVE_GCC_PLUGINS to the riscv Kconfig.
Also disable instrumentation of some early boot code and vdso.

Boot-tested on QEMU's riscv64 virt machine.

Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: Fixup __vdso_gettimeofday broke dynamic ftrace

For linux-5.8-rc1, enable ftrace of riscv will cause boot panic:

[ 2.388980] Run /sbin/init as init process
[ 2.529938] init[39]: unhandled signal 4 code 0x1 at 0x0000003ff449e000
[ 2.531078] CPU: 0 PID: 39 Comm: init Not tainted 5.8.0-rc1-dirty #13
[ 2.532719] epc: 0000003ff449e000 ra : 0000003ff449e954 sp : 0000003fffedb900
[ 2.534005] gp : 00000000000e8528 tp : 0000003ff449d800 t0 : 000000000000001e
[ 2.534965] t1 : 000000000000000a t2 : 0000003fffedb89e s0 : 0000003fffedb920
[ 2.536279] s1 : 0000003fffedb940 a0 : 0000003ff43d4b2c a1 : 0000000000000000
[ 2.537334] a2 : 0000000000000001 a3 : 0000000000000000 a4 : fffffffffbad8000
[ 2.538466] a5 : 0000003ff449e93a a6 : 0000000000000000 a7 : 0000000000000000
[ 2.539511] s2 : 0000000000000000 s3 : 0000003ff448412c s4 : 0000000000000010
[ 2.541260] s5 : 0000000000000016 s6 : 00000000000d0a30 s7 : 0000003fffedba70
[ 2.542152] s8 : 0000000000000000 s9 : 0000000000000000 s10: 0000003fffedb960
[ 2.543335] s11: 0000000000000000 t3 : 0000000000000000 t4 : 0000003fffedb8a0
[ 2.544471] t5 : 0000000000000000 t6 : 0000000000000000
[ 2.545730] status: 0000000000004020 badaddr: 00000000464c457f cause: 0000000000000002
[ 2.549867] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000004
[ 2.551267] CPU: 0 PID: 1 Comm: init Not tainted 5.8.0-rc1-dirty #13
[ 2.552061] Call Trace:
[ 2.552626] [<ffffffe00020374a>] walk_stackframe+0x0/0xc4
[ 2.553486] [<ffffffe0002039f4>] show_stack+0x40/0x4c
[ 2.553995] [<ffffffe00054a6ae>] dump_stack+0x7a/0x98
[ 2.554615] [<ffffffe00020b9b8>] panic+0x114/0x2f4
[ 2.555395] [<ffffffe00020ebd6>] do_exit+0x89c/0x8c2
[ 2.555949] [<ffffffe00020f930>] do_group_exit+0x3a/0x90
[ 2.556715] [<ffffffe000219e08>] get_signal+0xe2/0x6e6
[ 2.557388] [<ffffffe000202d72>] do_notify_resume+0x6a/0x37a
[ 2.558089] [<ffffffe000201c16>] ret_from_exception+0x0/0xc

"ra:0x3ff449e954" is the return address of "call _mcount" in the
prologue of __vdso_gettimeofday(). Without proper relocate, pc jmp
to 0x0000003ff449e000 (vdso map base) with a illegal instruction
trap.

The solution comes from arch/arm64/kernel/vdso/Makefile:

CFLAGS_REMOVE_vgettimeofday.o = $(CC_FLAGS_FTRACE) -Os $(CC_FLAGS_SCS)

- CC_FLAGS_SCS is ShadowCallStack feature in Clang and only
implemented for arm64, no use for riscv.

Fixes: ad5d1122b82f ("riscv: use vDSO common flow to reduce the latency of the time-related functions")
Cc: stable@vger.kernel.org
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Reviewed-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: Add -fPIC option to CFLAGS_vgettimeofday.o

The time related vDSO functions use a variable, vdso_data, to access the
vDSO data page to get the system time information. Because the vdso_data
for CFLAGS_vgettimeofday.o is an external variable defined in vdso.o,
the CFLAGS_vgettimeofday.o should be compiled with -fPIC to ensure
that vdso_data is addressable.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: use vDSO common flow to reduce the latency of the time-related functions

Even if RISC-V has supported the vDSO feature, the latency of the functions
for obtaining the system time is still expensive. It is because these
functions still trigger a corresponding system call in the process, which
slows down the response time. If we want to remove the system call to
reduce the latency, the kernel should have the ability to output the system
clock information to userspace. This patch introduces the vDSO common flow
to enable the kernel to achieve the above feature and uses "rdtime"
instruction to obtain the current time in the user space. Under this
condition, the latency cost by the ecall from U-mode to S-mode can be
eliminated. After applying this patch, the latency of gettimeofday()
measured on the HiFive unleashed board can be reduced by %61.

Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: add Linux note to vdso

The Linux note in the vdso allows glibc to check the running kernel
version without having to issue the uname syscall.

Signed-off-by: Andreas Schwab <schwab@suse.de>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: fix vdso build with lld

When building with the LLVM linker this error occurrs:
LD arch/riscv/kernel/vdso/vdso-syms.o
ld.lld: error: no input files

This happens because the lld treats -R as an alias to -rpath, as opposed
to ld where -R means --just-symbols.

Use the long option name for compatibility between the two.

Link: https://github.com/ClangBuiltLinux/linux/issues/805
Reported-by: Dmitry Golovin <dima@golovin.in>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Ilie Halip <ilie.halip@gmail.com>
Reviewed-by: Fangrui Song <maskray@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

riscv: delete temporary files

Temporary files used in the VDSO build process linger on even after make
mrproper: vdso-dummy.o.tmp, vdso.so.dbg.tmp.

Delete them once they're no longer needed.

Signed-off-by: Ilie Halip <ilie.halip@gmail.com>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

riscv: Fix perf record without libelf support

This patch fix following perf record error by linking vdso.so with
build id.

perf.data perf.data.old
[ perf record: Woken up 1 times to write data ]
free(): double free detected in tcache 2
Aborted

perf record use filename__read_build_id(util/symbol-minimal.c) to get
build id when libelf is not supported. When vdso.so is linked without
build id, the section size of PT_NOTE will be zero, buf size will
realloc to zero and cause memory corruption.

Signed-off-by: Mao Han <han_mao@c-sky.com>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

treewide: Add SPDX license identifier - Makefile/Kconfig

Add SPDX license identifiers to all Make/Kconfig files which:

- Have no license information of any form

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

GPL-2.0-only

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

riscv: vdso: drop unnecessary cc-ldoption

Towards the goal of removing cc-ldoption, it seems that --hash-style=
was added to binutils 2.17.50.0.2 in 2006. The minimal required version
of binutils for the kernel according to
Documentation/process/changes.rst is 2.20.

Link: https://gcc.gnu.org/ml/gcc/2007-01/msg01141.html
Cc: clang-built-linux@googlegroups.com
Suggested-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

riscv: Use latest system call ABI

We don't yet have an upstream glibc port for riscv, so there is no user
space for the existing ABI, and we can remove the definitions for 32-bit
time_t, off_t and struct resource and system calls based on them,
including the vdso.

Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

RISC-V: Use KBUILD_CFLAGS instead of KCFLAGS when building the vDSO

If you use a 64-bit compiler to build a 32-bit kernel then you'll get an
error when building the vDSO due to a library mismatch. The happens
because the relevant "-march" argument isn't supplied to the GCC run
that generates one of the vDSO intermediate files.

I'm not actually sure what the right thing to do here is as I'm not
particularly familiar with the kernel build system. I poked the
documentation and it appears that KCFLAGS is the correct thing to do
(it's suggested that should be used when building modules), but we set
KBUILD_CFLAGS in arch/riscv/Makefile.

This does at least fix the build error.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

RISC-V: build vdso-dummy.o with -no-pie

Debian toolcahin defaults to PIE, and I guess that will also be the case
of most distributions. This causes the following build failure:

AS arch/riscv/kernel/vdso/getcpu.o
AS arch/riscv/kernel/vdso/flush_icache.o
VDSOLD arch/riscv/kernel/vdso/vdso.so.dbg
OBJCOPY arch/riscv/kernel/vdso/vdso.so
AS arch/riscv/kernel/vdso/vdso.o
VDSOLD arch/riscv/kernel/vdso/vdso-dummy.o
LD arch/riscv/kernel/vdso/vdso-syms.o
riscv64-linux-gnu-ld: attempted static link of dynamic object `arch/riscv/kernel/vdso/vdso-dummy.o'
make[2]: *** [arch/riscv/kernel/vdso/Makefile:43: arch/riscv/kernel/vdso/vdso-syms.o] Error 1
make[1]: *** [scripts/Makefile.build:575: arch/riscv/kernel/vdso] Error 2
make: *** [Makefile:1018: arch/riscv/kernel] Error 2

While the root Makefile correctly passes "-fno-PIE" to build individual
object files, the RISC-V kernel also builds vdso-dummy.o as an
executable, which is therefore linked as PIE. Fix that by updating this
specific link rule to also include "-no-pie".

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

RISC-V: Allow userspace to flush the instruction cache

Despite RISC-V having a direct 'fence.i' instruction available to
userspace (which we can't trap!), that's not actually viable when
running on Linux because the kernel might schedule a process on another
hart. There is no way for userspace to handle this without invoking the
kernel (as it doesn't know the thread->hart mappings), so we've defined
a RISC-V specific system call to flush the instruction cache.

This patch adds both a system call and a VDSO entry. If possible, we'd
like to avoid having the system call be considered part of the
user-facing ABI and instead restrict that to the VDSO entry -- both just
in general to avoid having additional user-visible ABI to maintain, and
because we'd prefer that users just call the VDSO entry because there
might be a better way to do this in the future (ie, one that doesn't
require entering the kernel).

Signed-off-by: Andrew Waterman <andrew@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

RISC-V: Add VDSO entries for clock_get/gettimeofday/getcpu

For now these are just placeholders that execute the syscall. We will
later optimize them to avoid kernel crossings, but we'd like to have the
VDSO entries from the first released kernel version to make the ABI
simpler.

Signed-off-by: Andrew Waterman <andrew@sifive.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

RISC-V: User-facing API

This patch contains code that is in some way visible to the user:
including via system calls, the VDSO, module loading and signal
handling. It also contains some generic code that is ABI visible.

Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>