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CGEN is cool, but the BPF architecture is simply too bizarre for it.
The weird way of BPF to handle endianness in instruction encoding, the
weird C-like alternative assembly syntax, the weird abuse of
multi-byte (or infra-byte) instruction fields as opcodes, the unusual
presence of opcodes beyond the first 32-bits of some instructions, are
all examples of what makes it a PITA to continue using CGEN for this
port. The bpf.cpu file is becoming so complex and so nested with
p-macros that it is very difficult to read, and quite challenging to
update. Also, every time we are forced to change something in CGEN to
accommodate BPF requirements (which is often) we have to do extensive
testing to make sure we do not break any other target using CGEN.
This is getting un-maintenable.
So I have decided to bite the bullet and revamp/rewrite the port so it
no longer uses CGEN. Overall, this involved:
* To remove the cpu/bpf.{cpu,opc} descriptions.
* To remove the CGEN generated files.
* To replace the CGEN generated opcodes table with a new hand-written
opcodes table for BPF.
* To replace the CGEN generated disassembler wih a new disassembler
that uses the new opcodes.
* To replace the CGEN generated assembler with a new assembler that uses the
new opcodes.
* To replace the CGEN generated simulator with a new simulator that uses the
new opcodes. [This is pushed in GDB in another patch.]
* To adapt the build systems to the new situation.
Additionally, this patch introduces some extensions and improvements:
* A new BPF relocation BPF_RELOC_BPF_DISP16 plus corresponding ELF
relocation R_BPF_GNU_64_16 are added to the BPF BFD port. These
relocations are used for section-relative 16-bit offsets used in
load/store instructions.
* The disassembler now has support for the "pseudo-c" assembly syntax of
BPF. What dialect to use when disassembling is controlled by a command
line option.
* The disassembler now has support for dumping instruction immediates in
either octal, hexadecimal or decimal. The used output base is controlled
by a new command-line option.
* The GAS BPF test suite has been re-structured and expanded in order to
test the disassembler pseudoc syntax support. Minor bugs have been also
fixed there. The assembler generic tests that were disabled for bpf-*-*
targets due to the previous implementation of pseudoc syntax are now
re-enabled. Additional tests have been added to test the new features of
the assembler. .dump files are no longer used.
* The linker BPF test suite has been adapted to the command line options
used by the new disassembler.
The result is very satisfactory. This patchs adds 3448 lines of code
and removes 10542 lines of code.
Tested in:
* Target bpf-unknown-none with 64-bit little-endian host and 32-bit
little-endian host.
* Target x86-64-linux-gnu with --enable-targets=all
Note that I have not tested in a big-endian host yet. I will do so
once this lands upstream so I can use the GCC compiler farm.
I have not included ChangeLog entries in this patch: these would be
massive and not very useful, considering this is pretty much a rewrite
of the port. I beg the indulgence of the global maintainers.
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The newer update-copyright.py fixes file encoding too, removing cr/lf
on binutils/bfdtest2.c and ld/testsuite/ld-cygwin/exe-export.exp, and
embedded cr in binutils/testsuite/binutils-all/ar.exp string match.
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The result of running etc/update-copyright.py --this-year, fixing all
the files whose mode is changed by the script, plus a build with
--enable-maintainer-mode --enable-cgen-maint=yes, then checking
out */po/*.pot which we don't update frequently.
The copy of cgen was with commit d1dd5fcc38ead reverted as that commit
breaks building of bfp opcodes files.
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bfin-dis.c:160 shift exponent 32 is too large for 32-bit type 'long unsigned int'
bpf-ibld.c:196 left shift of 1 by 31 places cannot be represented in type 'long int'
bpf-ibld.c:196 negation of -2147483648 cannot be represented in type 'long int'; cast to an unsigned type to negate this
itself
bpf-ibld.c:197 left shift of 1 by 31 places cannot be represented in type 'long int'
bpf-ibld.c:197 signed integer overflow: -2147483648 - 1 cannot be represented in type 'long int'
bpf-ibld.c:501 left shift of 1 by 31 places cannot be represented in type 'long int'
* cgen-ibld.in (insert_normal, extract_normal): Use 1UL in left shift.
* bpf-ibld.c: Regenerate.
* epiphany-ibld.c: Regenerate.
* fr30-ibld.c: Regenerate.
* frv-ibld.c: Regenerate.
* ip2k-ibld.c: Regenerate.
* iq2000-ibld.c: Regenerate.
* lm32-ibld.c: Regenerate.
* m32c-ibld.c: Regenerate.
* m32r-ibld.c: Regenerate.
* mep-ibld.c: Regenerate.
* mt-ibld.c: Regenerate.
* or1k-ibld.c: Regenerate.
* xc16x-ibld.c: Regenerate.
* xstormy16-ibld.c: Regenerate.
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Eh well, I guess the code didn't quite live up to the comment.
PR 26449
PR 26450
* cgen-ibld.in (insert_1): Use 1UL in forming mask.
(extract_normal): Likewise.
(insert_normal): Likewise, and move past zero length test.
(put_insn_int_value): Handle mask for zero length, use 1UL.
* bpf-ibld.c, * epiphany-ibld.c, * fr30-ibld.c, * frv-ibld.c,
* ip2k-ibld.c, * iq2000-ibld.c, * lm32-ibld.c, * m32c-ibld.c,
* m32r-ibld.c, * mep-ibld.c, * mt-ibld.c, * or1k-ibld.c,
* xc16x-ibld.c, * xstormy16-ibld.c: Regenerate.
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The CGEN support code in opcodes accesses instruction contents using a
couple of functions defined in cgen-opc.c: cgen_get_insn_value and
cgen_put_insn_value. These functions use the "instruction endianness"
in the CPU description to order the read/written bytes.
The process of writing an instruction to the object file is:
a) cgen_put_insn_value ;; Writes out the opcodes.
b) ARCH_cgen_insert_operand
insert_normal
insert_1
cgen_put_insn_value ;; Writes out the bytes of the
;; operand.
Likewise, the process of reading an instruction from the object file
is:
a) cgen_get_insn_value ;; Reads the opcodes.
b) ARCH_cgen_extract_operand
extract_normal
extract_1
cgen_get_insn_value ;; Reads in the bytes of the
;; operand.
As can be seen above, cgen_{get,put}_insn_value are used to both
process the instruction opcodes (the constant fields conforming the
base instruction) and also the values of the instruction operands,
such as immediates.
This is problematic for architectures in which the endianness of
instructions is different to the endianness of data. An example is
BPF, where instructions are always encoded big-endian but the data may
be either big or little.
This patch changes the cgen_{get,put}_insn_value functions in order to
get an extra argument with the endianness to use, and adapts the
existin callers to these functions in order to provide cd->endian or
cd->insn_endian, whatever appropriate. Callers like extract_1 and
insert_1 pass cd->endian (since they are reading/writing operand
values) while callers reading/writing the base instruction pass
cd->insn_endian instead.
A few little adjustments have been needed in some existing CGEN based
ports:
* The BPF assembler uses cgen_put_insn_value. It has been adapted to
pass the new endian argument.
* The mep port has code in mep.opc that uses cgen_{get,put}_insn_value.
It has been adapted to pass the new endianargument. Ditto for a
call in the assembler.
Tested with --enable-targets=all.
Regested in all supported targets.
No regressions.
include/ChangeLog:
2020-06-04 Jose E. Marchesi <jose.marchesi@oracle.com>
* opcode/cgen.h: Get an `endian' argument in both
cgen_get_insn_value and cgen_put_insn_value.
opcodes/ChangeLog:
2020-06-04 Jose E. Marchesi <jose.marchesi@oracle.com>
* cgen-opc.c (cgen_get_insn_value): Get an `endian' argument.
(cgen_put_insn_value): Likewise.
(cgen_lookup_insn): Pass endianness to cgen_{get,put}_insn_value.
* cgen-dis.in (print_insn): Likewise.
* cgen-ibld.in (insert_1): Likewise.
(insert_1): Likewise.
(insert_insn_normal): Likewise.
(extract_1): Likewise.
* bpf-dis.c: Regenerate.
* bpf-ibld.c: Likewise.
* bpf-ibld.c: Likewise.
* cgen-dis.in: Likewise.
* cgen-ibld.in: Likewise.
* cgen-opc.c: Likewise.
* epiphany-dis.c: Likewise.
* epiphany-ibld.c: Likewise.
* fr30-dis.c: Likewise.
* fr30-ibld.c: Likewise.
* frv-dis.c: Likewise.
* frv-ibld.c: Likewise.
* ip2k-dis.c: Likewise.
* ip2k-ibld.c: Likewise.
* iq2000-dis.c: Likewise.
* iq2000-ibld.c: Likewise.
* lm32-dis.c: Likewise.
* lm32-ibld.c: Likewise.
* m32c-dis.c: Likewise.
* m32c-ibld.c: Likewise.
* m32r-dis.c: Likewise.
* m32r-ibld.c: Likewise.
* mep-dis.c: Likewise.
* mep-ibld.c: Likewise.
* mt-dis.c: Likewise.
* mt-ibld.c: Likewise.
* or1k-dis.c: Likewise.
* or1k-ibld.c: Likewise.
* xc16x-dis.c: Likewise.
* xc16x-ibld.c: Likewise.
* xstormy16-dis.c: Likewise.
* xstormy16-ibld.c: Likewise.
gas/ChangeLog:
2020-06-04 Jose E. Marchesi <jose.marchesi@oracle.com>
* cgen.c (gas_cgen_finish_insn): Pass the endianness to
cgen_put_insn_value.
(gas_cgen_md_apply_fix): Likewise.
(gas_cgen_md_apply_fix): Likewise.
* config/tc-bpf.c (md_apply_fix): Pass data endianness to
cgen_put_insn_value.
* config/tc-mep.c (mep_check_ivc2_scheduling): Pass endianness to
cgen_put_insn_value.
cpu/ChangeLog:
2020-06-02 Jose E. Marchesi <jose.marchesi@oracle.com>
* mep.opc (print_slot_insn): Pass the insn endianness to
cgen_get_insn_value.
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* cgen-ibld.in (extract_normal): Set *valuep on all return paths.
* bpf-ibld.c, * epiphany-ibld.c, * fr30-ibld.c, * frv-ibld.c,
* ip2k-ibld.c, * iq2000-ibld.c, * lm32-ibld.c, * m32c-ibld.c,
* m32r-ibld.c, * mep-ibld.c, * mt-ibld.c, * or1k-ibld.c,
* xc16x-ibld.c, * xstormy16-ibld.c: Regenerate.
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cpu/
* bpf.cpu (f-imm64): Avoid signed overflow.
opcodes/
* bpf-ibld.c: Regenerate.
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This patch adds support for the Linux kernel eBPF architecture to the
opcodes. The port is based on CGEN.
opcodes/ChangeLog:
2019-05-23 Jose E. Marchesi <jose.marchesi@oracle.com>
* configure.ac (SHARED_DEPENDENCIES): Add case for bfd_bpf_arch.
* configure: Regenerated.
* Makefile.am: Add rules for the files generated from cpu/bpf.cpu
and cpu/bpf.opc.
(HFILES): Add bpf-desc.h and bpf-opc.h.
(TARGET_LIBOPCODES_CFILES): Add bpf-asm.c, bpf-desc.c, bpf-dis.c,
bpf-ibld.c and bpf-opc.c.
(BPF_DEPS): Define.
* Makefile.in: Regenerated.
* disassemble.c (ARCH_bpf): Define.
(disassembler): Add case for bfd_arch_bpf.
(disassemble_init_for_target): Likewise.
(enum epbf_isa_attr): Define.
* disassemble.h: extern print_insn_bpf.
* bpf-asm.c: Generated.
* bpf-opc.h: Likewise.
* bpf-opc.c: Likewise.
* bpf-ibld.c: Likewise.
* bpf-dis.c: Likewise.
* bpf-desc.h: Likewise.
* bpf-desc.c: Likewise.
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