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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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[-Werror=overflow]
Regenerating BPF target using the maintainer mode emits:
.../opcodes/bpf-opc.c:57:11: error: conversion from ‘long unsigned int’ to ‘unsigned int’ changes value from ‘18446744073709486335’ to ‘4294902015’ [-Werror=overflow]
57 | 64, 64, 0xffffffffffff00ff, { { F (F_IMM32) }, { F (F_OFFSET16) }, { F (F_SRCLE) }, { F (F_OP_CODE) }, { F (F_DSTLE) }, { F (F_OP_SRC) }, { F (F_OP_CLASS) }, { 0 } }
The use of a narrow size to handle the mask CGEN in instruction format
is causing this error. Additionally eBPF `call' instructions
constructed by expressions using symbols (BPF_PSEUDO_CALL) emits
annotations in `src' field of the instruction, used to identify BPF
target endianness.
cpu/
* bpf.cpu (define-call-insn): Remove `src' field from
instruction mask.
include/
*opcode/cge.h (CGEN_IFMT): Adjust mask bit width.
opcodes/
* bpf-opc.c: Regenerate.
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Add gas and opcodes support for two xBPF-exclusive ALU operations:
SDIV (signed division) and SMOD (signed modulo), and add tests for
them in gas.
cpu/
* bpf.cpu (insn-op-code-alu): Add SDIV and SMOD.
(define-alu-insn-bin, daib): Take ISAs as an argument.
(define-alu-instructions): Update calls to daib pmacro with
ISAs; add sdiv and smod.
gas/
* testsuite/gas/bpf/alu-xbpf.d: New file.
* testsuite/gas/bpf/alu-xbpf.s: Likewise.
* testsuite/gas/bpf/alu32-xbpf.d: Likewise.
* testsuite/gas/bpf/alu32-xbpf.d: Likewise.
* testuiste/gas/bpf/bpf.exp: Run new tests.
opcodes/
* bpf-desc.c: Regenerate.
* bpf-desc.h: Likewise.
* bpf-opc.c: Likewise.
* bpf-opc.h: Likewise.
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The div and mod eBPF instructions are unsigned, but the semantic
specification for the simulator incorrectly used signed operators.
Correct them to unsigned versions, and correct the ALU tests in
the simulator (which incorrectly assumed signed semantics).
Tested in bpf-unknown-none.
cpu/ChangeLog:
2020-09-08 David Faust <david.faust@oracle.com>
* bpf.cpu (define-alu-instructions): Correct semantic operators
for div, mod to unsigned versions.
sim/ChangeLog:
2020-09-08 David Faust <david.faust@oracle.com>
* bpf/sem-be.c: Regenerate.
* bpf/sem-le.c: Likewise.
sim/testsuite/ChangeLog:
2020-09-08 David Faust <david.faust@oracle.com>
* sim/bpf/alu.s: Correct div and mod tests.
* sim/bpf/alu32.s: Likewise.
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This patch adds support for xBPF, another ISA targetting the BPF
virtual architecture. For now, the primary difference between eBPF
and xBPF is that xBPF supports indirect calls through the
'call %reg' form of the call instruction.
bfd/
* archures.c (bfd_mach_xbpf): Define.
* bfd-in2.h: Regenerate.
* cpu-bpf.c (bfd_xbpf_arch) New.
(bfd_bpf_arch) Update next in list field to point to xbpf arch.
cpu/
* bpf.cpu (arch bpf): Add xbpf mach and isas.
(define-xbpf-isa) New pmacro.
(all-isas) Add xbpfle,xbpfbe.
(endian-isas): New pmacro.
(mach xbpf): New.
(model xbpf-def): Likewise.
(h-gpr): Add xbpf mach.
(f-dstle, f-srcle, dstle, srcle): Add xbpfle isa.
(f-dstbe, f-srcbe, dstbe, srcbe): Add xbpfbe isa.
(define-alu-insn-un): Use new endian-isas pmacro.
(define-alu-insn-bin, define-alu-insn-mov): Likewise.
(define-endian-insn, define-lddw): Likewise.
(dlind, dxli, dxsi, dsti): Likewise.
(define-cond-jump-insn, define-call-insn): Likewise.
(define-atomic-insns): Likewise.
gas/
* config/tc-bpf.c: Add option -mxbpf to select xbpf isa.
* testsuite/gas/bpf/indcall-1.d: New file.
* testsuite/gas/bpf/indcall-1.s: Likewise.
* testsuite/gas/bpf/indcall-bad-1.l: Likewise.
* testsuite/gas/bpf/indcall-bad-1.s: Likewise.
* testsuite/gas/bpf/bpf.exp: Run new tests.
opcodes/
* bpf-desc.c: Regenerate.
* bpf-desc.h: Likewise.
* bpf-opc.c: Likewise.
* bpf-opc.h: Likewise.
* disassemble.c (disassemble_init_for_target): Set bits for xBPF
ISA when appropriate.
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Correct the type of the offset16 field to HI, and simplify memory
accesses which use it. Also update c-calls in semantics for a
few instructions.
cpu/ChangeLog:
2020-06-25 David Faust <david.faust@oracle.com>
* bpf.cpu (f-offset16): Change type from INT to HI.
(dxli): Simplify memory access.
(dxsi): Likewise.
(define-endian-insn): Update c-call in semantics.
(dlabs) Likewise.
(dlind) Likewise.
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cpu/ChangeLog:
2020-06-02 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf.cpu (define-bpf-isa): Set base-insn-bitsize to 64.
* bpf.opc (bpf_print_insn): Do not set endian_code here.
gas/ChangeLog:
2020-06-04 Jose E. Marchesi <jose.marchesi@oracle.com>
* config/tc-bpf.c (md_begin): Pass CGEN_CPU_OPEN_INSN_ENDIAN to
bpf_cgen_cpu_open.
(md_assemble): Remove no longer needed hack.
opcodes/ChangeLog:
2020-06-04 Jose E. Marchesi <jose.marchesi@oracle.com>
* disassemble.c (disassemble_init_for_target): Set endian_code for
bpf targets.
* bpf-desc.c: Regenerate.
* bpf-opc.c: Likewise.
* bpf-dis.c: Likewise.
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This patch adds semantic RTL descriptions to the eBPF instructions
defined in cpu/bpf.cpu. It also contains a couple of minor
improvements.
Tested in bpf-unknown-none targets.
No regressions.
cpu/ChangeLog:
2020-05-28 Jose E. Marchesi <jose.marchesi@oracle.com>
David Faust <david.faust@oracle.com>
* bpf.cpu (define-alu-insn-un): Add definitions of semantics.
(define-alu-insn-mov): Likewise.
(daib): Likewise.
(define-alu-instructions): Likewise.
(define-endian-insn): Likewise.
(define-lddw): Likewise.
(dlabs): Likewise.
(dlind): Likewise.
(dxli): Likewise.
(dxsi): Likewise.
(dsti): Likewise.
(define-ldstx-insns): Likewise.
(define-st-insns): Likewise.
(define-cond-jump-insn): Likewise.
(dcji): Likewise.
(define-condjump-insns): Likewise.
(define-call-insn): Likewise.
(ja): Likewise.
("exit"): Likewise.
(define-atomic-insns): Likewise.
(sem-exchange-and-add): New macro.
* bpf.cpu ("brkpt"): New instruction.
(bpfbf): Set word-bitsize to 32 and insn-endian big.
(h-gpr): Prefer r0 to `a' and r6 to `ctx'.
(h-pc): Expand definition.
* bpf.opc (bpf_print_insn): Set endian_code to BIG.
opcodes/ChangeLog:
2020-05-28 Jose E. Marchesi <jose.marchesi@oracle.com>
David Faust <david.faust@oracle.com>
* bpf-desc.c: Regenerate.
* bpf-opc.h: Likewise.
* bpf-opc.c: Likewise.
* bpf-dis.c: Likewise.
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Add support for the JMP32 class of eBPF instructions.
cpu/ChangeLog
* bpf.cpu (define-cond-jump-insn): Renamed from djci.
(dcji) New version with support for JMP32
gas/ChangeLog
* testsuite/gas/bpf/bpf.exp: Run jump32 tests.
* testsuite/gas/bpf/jump32.s: New file.
* testsuite/gas/bpf/jump32.d: Likewise.
opcodes/ChangeLog
* bpf-desc.c: Regenerate.
* bpf-desc.h: Likewise.
* bpf-opc.c: Regenerate.
* bpf-opc.h: Likewise.
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This patch fixes the neg/neg32 BPF instructions, which have K (=0)
instead of X (=1) in their header source bit, despite operating on
registes.
cpu/ChangeLog:
2020-01-30 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf.cpu (define-alu-insn-un): The unary BPF instructions
(neg and neg32) use OP_SRC_K even if they operate only in
registers.
opcodes/ChangeLog:
2020-01-30 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf-opc.c: Regenerate.
gas/ChangeLog:
2020-01-30 Jose E. Marchesi <jose.marchesi@oracle.com>
* testsuite/gas/bpf/alu.d: Update expected opcode for `neg'.
* testsuite/gas/bpf/alu-be.d: Likewise.
* testsuite/gas/bpf/alu32.d: Likewise for `neg32'.
* testsuite/gas/bpf/alu32-be.d: Likewise.
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cpu/
* bpf.cpu (f-imm64): Avoid signed overflow.
opcodes/
* bpf-ibld.c: Regenerate.
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2019-11-20 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf.cpu: Fix comment describing the 128-bit instruction format.
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This patch changes the eBPF CPU description to prefer the register
names %r0 and %r6 instead of %a and %ctx when disassembling. This
matches better with the current practice, vs. cBPF.
It also updates the GAS tests in order to reflect this change.
Tested in a x86_64 host.
cpu/ChangeLog:
2019-07-19 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf.cpu (h-gpr): when disassembling, use %r0 and %r6 instead of
%a and %ctx.
opcodes/ChangeLog:
2019-07-19 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf-desc.c: Regenerated.
gas/ChangeLog:
2019-07-19 Jose E. Marchesi <jose.marchesi@oracle.com>
* testsuite/gas/bpf/alu.d: Use %r6 instead of %ctx.
* testsuite/gas/bpf/lddw-be.d: Likewise.
* testsuite/gas/bpf/lddw.d: Likewise.
* testsuite/gas/bpf/alu-be.d: Likewise.
* testsuite/gas/bpf/alu32.d: Likewise.
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This patch fixes the eBPF CPU description in order to reflect the
right explicit arguments passed to the ldabs{b,h,w,dw} instructions,
updates the corresponding GAS tests, and updates the BPF section of
the GAS manual.
cpu/ChangeLog:
2019-07-15 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf.cpu (dlabs): New pmacro.
(dlind): Likewise.
opcodes/ChangeLog:
2019-07-15 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf-desc.c: Regenerate.
* bpf-opc.c: Likewise.
* bpf-opc.h: Likewise.
gas/ChangeLog:
2019-07-15 Jose E. Marchesi <jose.marchesi@oracle.com>
* testsuite/gas/bpf/mem.s: ldabs instructions do not take a `src'
register as an argument.
* testsuite/gas/bpf/mem.d: Updated accordingly.
* testsuite/gas/bpf/mem-be.d: Likewise.
* doc/c-bpf.texi (BPF Opcodes): Update to reflect the correct
explicit arguments to ldabs and ldind instructions.
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The eBPF non-generic load instructions ldind{b,h,w,dw} and
ldabs{b,h,w,dw} do not take an explicit destination register as an
argument. Instead, they put the loaded value in %r0, implicitly.
This patch fixes the CPU BPF description to not expect a 'dst'
argument in these arguments, regenerates the corresponding files in
opcodes, and updates the impacted GAS tests.
Tested in a x86-64 host.
cpu/ChangeLog:
2019-07-14 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf.cpu (dlsi): ldabs and ldind instructions do not take an
explicit 'dst' argument.
opcodes/ChangeLog:
2019-07-14 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf-desc.c: Regenerate.
* bpf-opc.c: Likewise.
gas/ChangeLog:
2019-07-14 Jose E. Marchesi <jose.marchesi@oracle.com>
* testsuite/gas/bpf/mem.s: Do not use explicit arguments for
ldabs and ldind instructions.
* testsuite/gas/bpf/mem.d: Updated accordingly.
* testsuite/gas/bpf/mem-be.d: Likewise.
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This patch adds a CPU description for the Linux kernel eBPF virtual
machine, plus supporting code for disassembler and assembler.
cpu/ChangeLog:
2019-05-23 Jose E. Marchesi <jose.marchesi@oracle.com>
* bpf.cpu: New file.
* bpf.opc: Likewise.
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