| 539d7344 | 18-Sep-2025 |
Tiezhu Yang <yangtiezhu@loongson.cn> |
objtool/LoongArch: Mark special atomic instruction as INSN_BUG type
When compiling with LLVM and CONFIG_RUST is set, there exists the
following objtool warning:
rust/compiler_builtins.o: warning:
objtool/LoongArch: Mark special atomic instruction as INSN_BUG type
When compiling with LLVM and CONFIG_RUST is set, there exists the
following objtool warning:
rust/compiler_builtins.o: warning: objtool: __rust__unordsf2(): unexpected end of section .text.unlikely.
objdump shows that the end of section .text.unlikely is an atomic
instruction:
amswap.w $zero, $ra, $zero
According to the LoongArch Reference Manual, if the amswap.w atomic
memory access instruction has the same register number as rd and rj,
the execution will trigger an Instruction Non-defined Exception, so
mark the above instruction as INSN_BUG type to fix the warning.
Cc: stable@vger.kernel.org
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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| 88cbb468 | 11-Feb-2025 |
Tiezhu Yang <yangtiezhu@loongson.cn> |
objtool/LoongArch: Add support for goto table
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 bra
objtool/LoongArch: Add support for goto table
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>
Link: https://lore.kernel.org/r/20250211115016.26913-6-yangtiezhu@loongson.cn
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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| b95f852d | 11-Feb-2025 |
Tiezhu Yang <yangtiezhu@loongson.cn> |
objtool/LoongArch: Add support for switch table
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 b
objtool/LoongArch: Add support for switch table
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.
Additionally, it needs to get each table size. When compiling on LoongArch,
there are unsorted table offsets of rodata if there exist many jump tables,
it will get the wrong table end and find the wrong table 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.
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>
Link: https://lore.kernel.org/r/20250211115016.26913-5-yangtiezhu@loongson.cn
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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| c4b93b06 | 11-Feb-2025 |
Tiezhu Yang <yangtiezhu@loongson.cn> |
objtool: Handle PC relative relocation type
For the most part, an absolute relocation type is used for rodata.
In the case of STT_SECTION, reloc->sym->offset is always zero, for
the other symbol typ
objtool: Handle PC relative relocation type
For the most part, an absolute relocation type is used for rodata.
In the case of STT_SECTION, reloc->sym->offset is always zero, for
the other symbol types, reloc_addend(reloc) is always zero, thus it
can use a simple statement "reloc->sym->offset + reloc_addend(reloc)"
to obtain the symbol offset for various symbol types.
When compiling on LoongArch, there exist PC relative relocation types
for rodata, it needs to calculate the symbol offset with "S + A - PC"
according to the spec of "ELF for the LoongArch Architecture".
If there is only one jump table in the rodata, the "PC" is the entry
address which is equal with the value of reloc_offset(reloc), at this
time, reloc_offset(table) is 0.
If there are many jump tables in the rodata, the "PC" is the offset
of the jump table's base address which is equal with the value of
reloc_offset(reloc) - reloc_offset(table).
So for LoongArch, if the relocation type is PC relative, it can use a
statement "reloc_offset(reloc) - reloc_offset(table)" to get the "PC"
value when calculating the symbol offset with "S + A - PC" for one or
many jump tables in the rodata.
Add an arch-specific function arch_jump_table_sym_offset() to assign
the symbol offset, for the most part that is an absolute relocation,
the default value is "reloc->sym->offset + reloc_addend(reloc)" in
the weak definition, it can be overridden by each architecture that
has different requirements.
Link: https://github.com/loongson/la-abi-specs/blob/release/laelf.adoc
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Link: https://lore.kernel.org/r/20250211115016.26913-4-yangtiezhu@loongson.cn
Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
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| 3c7266cd | 11-Mar-2024 |
Tiezhu Yang <yangtiezhu@loongson.cn> |
objtool/LoongArch: Enable orc to be built
Implement arch-specific init_orc_entry(), write_orc_entry(), reg_name(),
orc_type_name(), print_reg() and orc_print_dump(), then set BUILD_ORC as
y to build
objtool/LoongArch: Enable orc to be built
Implement arch-specific init_orc_entry(), write_orc_entry(), reg_name(),
orc_type_name(), print_reg() and orc_print_dump(), then set BUILD_ORC as
y to build the orc related files.
Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Co-developed-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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| b2d23158 | 11-Mar-2024 |
Tiezhu Yang <yangtiezhu@loongson.cn> |
objtool/LoongArch: Implement instruction decoder
Only copy the minimal definitions of instruction opcodes and formats
in inst.h from arch/loongarch to tools/arch/loongarch, and also copy
the definit
objtool/LoongArch: Implement instruction decoder
Only copy the minimal definitions of instruction opcodes and formats
in inst.h from arch/loongarch to tools/arch/loongarch, and also copy
the definition of sign_extend64() to tools/include/linux/bitops.h to
decode the following kinds of instructions:
(1) stack pointer related instructions
addi.d, ld.d, st.d, ldptr.d and stptr.d
(2) branch and jump related instructions
beq, bne, blt, bge, bltu, bgeu, beqz, bnez, bceqz, bcnez, b, bl and jirl
(3) other instructions
break, nop and ertn
See more info about instructions in LoongArch Reference Manual:
https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html
Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Co-developed-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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