linux.git/arch/riscv/kernel/vdso, branch v5.11

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

2020-11-25T17:44:14+00:00

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 
Reviewed-by: Nick Desaulniers 
Reviewed-by: Bill Wendling 
Signed-off-by: Palmer Dabbelt

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

2020-11-06T08:03:48+00:00

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

kbuild: explicitly specify the build id style

2020-10-09T14:57:30+00:00

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 
Acked-by: David S. Miller 
Signed-off-by: Masahiro Yamada

riscv: disable stack-protector for vDSO

2020-08-04T22:02:49+00:00

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 
Signed-off-by: Palmer Dabbelt

riscv: Allow building with kcov coverage

2020-07-30T18:37:35+00:00

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 
Acked-by: Dmitry Vyukov 
Signed-off-by: Palmer Dabbelt

riscv: Fixup __vdso_gettimeofday broke dynamic ftrace

2020-06-25T22:38:39+00:00

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] [] walk_stackframe+0x0/0xc4
[    2.553486] [] show_stack+0x40/0x4c
[    2.553995] [] dump_stack+0x7a/0x98
[    2.554615] [] panic+0x114/0x2f4
[    2.555395] [] do_exit+0x89c/0x8c2
[    2.555949] [] do_group_exit+0x3a/0x90
[    2.556715] [] get_signal+0xe2/0x6e6
[    2.557388] [] do_notify_resume+0x6a/0x37a
[    2.558089] [] 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 
Reviewed-by: Vincent Chen 
Signed-off-by: Palmer Dabbelt

riscv: Add extern declarations for vDSO time-related functions

2020-06-25T22:15:51+00:00

Add extern declarations for vDSO time-related functions to notify the
compiler these functions will be used in somewhere to avoid
"no previous prototype" compile warning.

Reported-by: kernel test robot 
Signed-off-by: Vincent Chen 
Signed-off-by: Palmer Dabbelt

riscv: Add -fPIC option to CFLAGS_vgettimeofday.o

2020-06-25T21:58:59+00:00

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 
Signed-off-by: Vincent Chen 
Signed-off-by: Palmer Dabbelt

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

2020-06-11T02:47:16+00:00

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 
Reviewed-by: Atish Patra 
Signed-off-by: Palmer Dabbelt

riscv: add Linux note to vdso

2020-05-04T21:22:34+00:00

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 
Signed-off-by: Palmer Dabbelt