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2fb761823e
Implement the arch_bpf_timed_may_goto function using inline assembly to have control over which registers are spilled, and use our special protocol of using BPF_REG_AX as an argument into the function, and as the return value when going back. Emit call depth accounting for the call made from this stub, and ensure we don't have naked returns (when rethunk mitigations are enabled) by falling back to the RET macro (instead of retq). After popping all saved registers, the return address into the BPF program should be on top of the stack. Since the JIT support is now enabled, ensure selftests which are checking the produced may_goto sequences do not break by adjusting them. Make sure we still test the old may_goto sequence on other architectures, while testing the new sequence on x86_64. Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> Link: https://lore.kernel.org/r/20250304003239.2390751-3-memxor@gmail.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
128 lines
3.0 KiB
C
128 lines
3.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */
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#include <linux/bpf.h>
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#include <bpf/bpf_helpers.h>
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#include "../../../include/linux/filter.h"
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#include "bpf_misc.h"
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SEC("raw_tp")
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__description("may_goto 0")
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__arch_x86_64
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__xlated("0: r0 = 1")
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__xlated("1: exit")
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__success
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__naked void may_goto_simple(void)
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{
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asm volatile (
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".8byte %[may_goto];"
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"r0 = 1;"
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".8byte %[may_goto];"
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"exit;"
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:
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: __imm_insn(may_goto, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 0 /* offset */, 0))
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: __clobber_all);
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}
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SEC("raw_tp")
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__description("batch 2 of may_goto 0")
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__arch_x86_64
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__xlated("0: r0 = 1")
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__xlated("1: exit")
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__success
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__naked void may_goto_batch_0(void)
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{
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asm volatile (
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".8byte %[may_goto1];"
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".8byte %[may_goto1];"
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"r0 = 1;"
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".8byte %[may_goto1];"
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".8byte %[may_goto1];"
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"exit;"
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:
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: __imm_insn(may_goto1, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 0 /* offset */, 0))
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: __clobber_all);
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}
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SEC("raw_tp")
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__description("may_goto batch with offsets 2/1/0")
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__arch_x86_64
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__xlated("0: r0 = 1")
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__xlated("1: exit")
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__success
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__naked void may_goto_batch_1(void)
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{
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asm volatile (
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".8byte %[may_goto1];"
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".8byte %[may_goto2];"
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".8byte %[may_goto3];"
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"r0 = 1;"
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".8byte %[may_goto1];"
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".8byte %[may_goto2];"
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".8byte %[may_goto3];"
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"exit;"
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:
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: __imm_insn(may_goto1, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 2 /* offset */, 0)),
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__imm_insn(may_goto2, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 1 /* offset */, 0)),
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__imm_insn(may_goto3, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 0 /* offset */, 0))
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: __clobber_all);
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}
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SEC("raw_tp")
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__description("may_goto batch with offsets 2/0 - x86_64")
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__arch_x86_64
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__xlated("0: *(u64 *)(r10 -16) = 65535")
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__xlated("1: *(u64 *)(r10 -8) = 0")
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__xlated("2: r11 = *(u64 *)(r10 -16)")
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__xlated("3: if r11 == 0x0 goto pc+6")
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__xlated("4: r11 -= 1")
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__xlated("5: if r11 != 0x0 goto pc+2")
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__xlated("6: r11 = -16")
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__xlated("7: call unknown")
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__xlated("8: *(u64 *)(r10 -16) = r11")
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__xlated("9: r0 = 1")
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__xlated("10: r0 = 2")
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__xlated("11: exit")
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__success
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__naked void may_goto_batch_2_x86_64(void)
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{
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asm volatile (
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".8byte %[may_goto1];"
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".8byte %[may_goto3];"
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"r0 = 1;"
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"r0 = 2;"
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"exit;"
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:
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: __imm_insn(may_goto1, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 2 /* offset */, 0)),
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__imm_insn(may_goto3, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 0 /* offset */, 0))
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: __clobber_all);
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}
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SEC("raw_tp")
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__description("may_goto batch with offsets 2/0 - arm64")
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__arch_arm64
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__xlated("0: *(u64 *)(r10 -8) = 8388608")
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__xlated("1: r11 = *(u64 *)(r10 -8)")
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__xlated("2: if r11 == 0x0 goto pc+3")
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__xlated("3: r11 -= 1")
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__xlated("4: *(u64 *)(r10 -8) = r11")
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__xlated("5: r0 = 1")
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__xlated("6: r0 = 2")
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__xlated("7: exit")
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__success
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__naked void may_goto_batch_2_arm64(void)
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{
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asm volatile (
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".8byte %[may_goto1];"
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".8byte %[may_goto3];"
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"r0 = 1;"
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"r0 = 2;"
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"exit;"
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:
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: __imm_insn(may_goto1, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 2 /* offset */, 0)),
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__imm_insn(may_goto3, BPF_RAW_INSN(BPF_JMP | BPF_JCOND, 0, 0, 0 /* offset */, 0))
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: __clobber_all);
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}
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char _license[] SEC("license") = "GPL";
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