LoongArch has supported PREEMPT_RT now. It uses GENERIC_ENTRY, so just
add the TIF bit (TIF_NEED_RESCHED_LAZY) related definitions and select
the Kconfig symbol (ARCH_HAS_PREEMPT_LAZY) is enough to make it go.
Signed-off-by: Xi Ruoyao <xry111@xry111.site>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
Now the min_delta is 0x600 (1536) for LoongArch's constant clockevent
device. For a 100MHz hardware timer this means ~15us. This is a little
big, especially for PREEMPT_RT enabled kernels. So reduce it to 100 for
PREEMPT_RT kernel, and 1000 for others (we don't want too small values
to affect performance).
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
(1) Description of Problem:
When testing BPF JIT with the latest compiler toolchains on LoongArch,
there exist some strange failed test cases, dmesg shows something like
this:
# dmesg -t | grep FAIL | head -1
... ret -3 != -3 (0xfffffffd != 0xfffffffd)FAIL ...
(2) Steps to Reproduce:
# echo 1 > /proc/sys/net/core/bpf_jit_enable
# modprobe test_bpf
(3) Additional Info:
There are no failed test cases compiled with the lower version of GCC
such as 13.3.0, while the problems only appear with higher version of
GCC such as 14.2.0.
This is because the problems were hidden by the lower version of GCC due
to redundant sign extension instructions generated by compiler, but with
optimization of higher version of GCC, the sign extension instructions
have been removed.
(4) Root Cause Analysis:
The LoongArch architecture does not expose sub-registers, and hold all
32-bit values in a sign-extended format. While BPF, on the other hand,
exposes sub-registers, and use zero-extension (similar to arm64/x86).
This has led to some subtle bugs, where a BPF JITted program has not
sign-extended the a0 register (return value in LoongArch land), passed
the return value up the kernel, for example:
| int from_bpf(void);
|
| long foo(void)
| {
| return from_bpf();
| }
Here, a0 would be 0xffffffff instead of the expected 0xffffffffffffffff.
Internally, the LoongArch JIT uses a5 as a dedicated register for BPF
return values. That is to say, the LoongArch BPF uses a5 for BPF return
values, which are zero-extended, whereas the LoongArch ABI uses a0 which
is sign-extended.
(5) Final Solution:
Keep a5 zero-extended, but explicitly sign-extend a0 (which is used
outside BPF land). Because libbpf currently defines the return value
of an ebpf program as a 32-bit unsigned integer, just use addi.w to
extend bit 31 into bits 63 through 32 of a5 to a0. This is similar to
commit 2f1b0d3d7331 ("riscv, bpf: Sign-extend return values").
Fixes: 5dc615520c4d ("LoongArch: Add BPF JIT support")
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
Whenever I try to build the kernel with upcoming GCC 15 which defaults
to -std=gnu23 I get a build failure:
CC arch/loongarch/vdso/vgetcpu.o
In file included from ./include/uapi/linux/posix_types.h:5,
from ./include/uapi/linux/types.h:14,
from ./include/linux/types.h:6,
from ./include/linux/kasan-checks.h:5,
from ./include/asm-generic/rwonce.h:26,
from ./arch/loongarch/include/generated/asm/rwonce.h:1,
from ./include/linux/compiler.h:317,
from ./include/asm-generic/bug.h:5,
from ./arch/loongarch/include/asm/bug.h:60,
from ./include/linux/bug.h:5,
from ./include/linux/mmdebug.h:5,
from ./include/linux/mm.h:6,
from ./arch/loongarch/include/asm/vdso.h:10,
from arch/loongarch/vdso/vgetcpu.c:6:
./include/linux/stddef.h:11:9: error: expected identifier before 'false'
11 | false = 0,
| ^~~~~
./include/linux/types.h:35:33: error: two or more data types in declaration specifiers
35 | typedef _Bool bool;
| ^~~~
./include/linux/types.h:35:1: warning: useless type name in empty declaration
35 | typedef _Bool bool;
| ^~~~~~~
The kernel builds explicitly with -std=gnu11 in top Makefile, but
arch/loongarch/vdso does not use KBUILD_CFLAGS from the rest of the
kernel, just add -std=gnu11 flag to arch/loongarch/vdso/Makefile.
By the way, commit e8c07082a810 ("Kbuild: move to -std=gnu11") did a
similar change for arch/arm64/kernel/vdso32/Makefile.
Fixes: c6b99bed6b8f ("LoongArch: Add VDSO and VSYSCALL support")
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
LoongArch's toolchain may change the default code model from normal to
medium. This is unnecessary for kernel, and generates some relocations
which cannot be handled by the module loader. So explicitly specify the
code model to normal in Makefile (for Rust 'normal' is 'small').
Cc: stable@vger.kernel.org
Tested-by: Haiyong Sun <sunhaiyong@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
For now, it is time to remove -fno-jump-tables to enable jump table for
objtool if the compiler has -mannotate-tablejump, otherwise it is better
to remain -fno-jump-tables to keep compatibility with older compilers.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
The objtool program need to analysis the control flow of each object file
generated by compiler toolchain, it needs to know all the locations that
a branch instruction may jump into, if a jump table is used, objtool has
to correlate the jump instruction with the table.
On x86 (which is the only port supported by objtool before LoongArch),
there is a relocation type on the jump instruction and directly points
to the table. But on LoongArch, the relocation is on another kind of
instruction prior to the jump instruction, and also with scheduling it
is not very easy to tell the offset of that instruction from the jump
instruction. Furthermore, because LoongArch has -fsection-anchors (often
enabled at -O1 or above) the relocation may actually points to a section
anchor instead of the table itself.
For the jump table of switch cases, a GCC patch "LoongArch: Add support
to annotate tablejump" and a Clang patch "[LoongArch] Add options for
annotate tablejump" have been merged into the upstream mainline, it can
parse the additional section ".discard.tablejump_annotate" which stores
the jump info as pairs of addresses, each pair contains the address of
jump instruction and the address of jump table.
For the jump table of computed gotos, it is indeed not easy to implement
in the compiler, especially if there is more than one computed goto in a
function such as ___bpf_prog_run(). objdump kernel/bpf/core.o shows that
there are many table jump instructions in ___bpf_prog_run(), but there are
no relocations on the table jump instructions and to the table directly on
LoongArch.
Without the help of compiler, in order to figure out the address of goto
table for the special case of ___bpf_prog_run(), since the instruction
sequence is relatively single and stable, it makes sense to add a helper
find_reloc_of_rodata_c_jump_table() to find the relocation which points
to the section ".rodata..c_jump_table".
If find_reloc_by_table_annotate() failed, it means there is no relocation
info of switch table address in ".rela.discard.tablejump_annotate", then
objtool may find the relocation info of goto table ".rodata..c_jump_table"
with find_reloc_of_rodata_c_jump_table().
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
The objtool program need to analysis the control flow of each object file
generated by compiler toolchain, it needs to know all the locations that
a branch instruction may jump into, if a jump table is used, objtool has
to correlate the jump instruction with the table.
On x86 (which is the only port supported by objtool before LoongArch),
there is a relocation type on the jump instruction and directly points
to the table. But on LoongArch, the relocation is on another kind of
instruction prior to the jump instruction, and also with scheduling it
is not very easy to tell the offset of that instruction from the jump
instruction. Furthermore, because LoongArch has -fsection-anchors (often
enabled at -O1 or above) the relocation may actually points to a section
anchor instead of the table itself.
The good news is that after continuous analysis and discussion, at last
a GCC patch "LoongArch: Add support to annotate tablejump" and a Clang
patch "[LoongArch] Add options for annotate tablejump" have been merged
into the upstream mainline, the compiler changes make life much easier
for switch table support of objtool on LoongArch.
By now, there is an additional section ".discard.tablejump_annotate" to
store the jump info as pairs of addresses, each pair contains the address
of jump instruction and the address of jump table.
In order to find switch table, it is easy to parse the relocation section
".rela.discard.tablejump_annotate" to get table_sec and table_offset, the
rest process is somehow like x86.
Link: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=0ee028f55640
Link: https://github.com/llvm/llvm-project/commit/4c2c17756739
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
When compiling with Clang on LoongArch, there are unsorted table offset
of rodata if there exist many jump tables, it will get the wrong table
end and find the wrong jump destination instructions in add_jump_table().
Sort the rodata table offset by parsing ".rela.discard.tablejump_annotate"
and then get each table size of rodata corresponded with each table jump
instruction, it is used to check the table end and will break the process
when parsing ".rela.rodata" to avoid getting the wrong jump destination
instructions.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
When compiling with Clang on LoongArch, there are unsorted table offset
of rodata if there exist many jump tables, it will get the wrong table
end and find the wrong jump destination instructions in add_jump_table(),
so it needs to check the table size of rodata to break the process when
parsing the relocation section of rodata.
This is preparation for later patch on LoongArch, there is no effect for
the other archs with this patch.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
When compiling with Clang on LoongArch, there exists unreachable entry of
rodata which points to a position after the function return instruction,
this is generated by compiler to fill the non-existent switch case, just
skip the entry when parsing the relocation section of rodata.
This is preparation for later patch on LoongArch, there is no effect for
the other archs with this patch.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
In the most cases, the entry size of rodata is 8 bytes because the
relocation type is 64 bit, but when compiling with Clang on LoongArch,
there exists 32 bit relocation type, the entry size of rodata should
be 4 bytes in this case.
This is preparation for later patch on LoongArch, there is no effect
for the other archs with this patch.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
There are some "unreachable instruction" objtool warnings when compiling
with Clang on LoongArch, this is because the "break" instruction is set
as dead end due to its type is INSN_BUG in decode_instructions() at the
beginning, and it does not set insn->dead_end of the "break" instruction
as false after checking ".rela.discard.reachable" in add_dead_ends(), so
the next instruction of "break" is marked as unreachable.
Actually, it can find the reachable instruction after parsing the section
".rela.discard.reachable", in some cases, the "break" instruction may not
be the first previous instruction with scheduling by Machine Instruction
Scheduler of LLVM, it should find more times and then set insn->dead_end
of the "break" instruction as false.
This is preparation for later patch on LoongArch, there is no effect for
the other archs with this patch.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
In the relocation section ".rela.rodata" of each .o file compiled with
LoongArch toolchain, there are various symbol types such as STT_NOTYPE,
STT_OBJECT, STT_FUNC in addition to the usual STT_SECTION, it needs to
use reloc symbol offset instead of reloc addend to find the destination
instruction in find_jump_table() and add_jump_table().
This is preparation for later patch on LoongArch, there is no effect for
the other archs with this patch.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: michael <michael5hzg@gmail.com>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
Huacai Chen