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[PW_SID:1127043] bpf, riscv: add timed may_goto support #2276

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[PW_SID:1127043] bpf, riscv: add timed may_goto support #2276

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d670210
bpf, riscv: add support for timed may_goto
flynnjiang Jul 14, 2026
d68baa4
selftests/bpf: enable timed may_goto tests for riscv64
flynnjiang Jul 14, 2026
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2 changes: 1 addition & 1 deletion arch/riscv/net/Makefile
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,7 @@
obj-$(CONFIG_BPF_JIT) += bpf_jit_core.o

ifeq ($(CONFIG_ARCH_RV64I),y)
obj-$(CONFIG_BPF_JIT) += bpf_jit_comp64.o
obj-$(CONFIG_BPF_JIT) += bpf_jit_comp64.o bpf_timed_may_goto.o
else
obj-$(CONFIG_BPF_JIT) += bpf_jit_comp32.o
endif
5 changes: 5 additions & 0 deletions arch/riscv/net/bpf_jit_comp64.c
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Expand Up @@ -2157,3 +2157,8 @@ bool bpf_jit_supports_fsession(void)
{
return true;
}

bool bpf_jit_supports_timed_may_goto(void)
{
return true;
}
44 changes: 44 additions & 0 deletions arch/riscv/net/bpf_timed_may_goto.S
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@@ -0,0 +1,44 @@
/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (c) 2026 Feng Jiang <jiangfeng@kylinos.cn> */

#include <linux/linkage.h>
#include <asm/asm.h>

/*
* Trampoline for the BPF timed may_goto loop bound. Custom calling convention:
* - input: stack offset in BPF_REG_AX (t0)
* - output: updated count in BPF_REG_AX (t0)
*
* Calls bpf_check_timed_may_goto(ptr) with the standard RISC-V ABI, where
* ptr = BPF_REG_FP (s5) + BPF_REG_AX (t0). BPF R0-R5 (a5, a0-a4) are saved
* across the call; BPF_REG_FP (s5) is callee-saved and needs no saving.
*/

SYM_FUNC_START(arch_bpf_timed_may_goto)
addi sp, sp, -64
sd ra, 56(sp)

/* Save BPF registers R0-R5 (a5, a0-a4) */
sd a5, 48(sp)
sd a0, 40(sp)
sd a1, 32(sp)
sd a2, 24(sp)
sd a3, 16(sp)
sd a4, 8(sp)

add a0, t0, s5
call bpf_check_timed_may_goto
mv t0, a0

/* Restore BPF registers R0-R5 */
ld a4, 8(sp)
ld a3, 16(sp)
ld a2, 24(sp)
ld a1, 32(sp)
ld a0, 40(sp)
ld a5, 48(sp)

ld ra, 56(sp)
addi sp, sp, 64
ret
SYM_FUNC_END(arch_bpf_timed_may_goto)
1 change: 1 addition & 0 deletions tools/testing/selftests/bpf/progs/stream.c
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Expand Up @@ -64,6 +64,7 @@ SEC("syscall")
__arch_x86_64
__arch_arm64
__arch_s390x
__arch_riscv64
__success __retval(0)
__stderr("ERROR: Timeout detected for may_goto instruction")
__stderr("CPU: {{[0-9]+}} UID: 0 PID: {{[0-9]+}} Comm: {{.*}}")
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4 changes: 4 additions & 0 deletions tools/testing/selftests/bpf/progs/verifier_may_goto_1.c
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Expand Up @@ -11,6 +11,7 @@ __description("may_goto 0")
__arch_x86_64
__arch_s390x
__arch_arm64
__arch_riscv64
__xlated("0: r0 = 1")
__xlated("1: exit")
__success
Expand All @@ -31,6 +32,7 @@ __description("batch 2 of may_goto 0")
__arch_x86_64
__arch_s390x
__arch_arm64
__arch_riscv64
__xlated("0: r0 = 1")
__xlated("1: exit")
__success
Expand All @@ -53,6 +55,7 @@ __description("may_goto batch with offsets 2/1/0")
__arch_x86_64
__arch_s390x
__arch_arm64
__arch_riscv64
__xlated("0: r0 = 1")
__xlated("1: exit")
__success
Expand All @@ -79,6 +82,7 @@ __description("may_goto batch with offsets 2/0")
__arch_x86_64
__arch_s390x
__arch_arm64
__arch_riscv64
__xlated("0: *(u64 *)(r10 -16) = 65535")
__xlated("1: *(u64 *)(r10 -8) = 0")
__xlated("2: r12 = *(u64 *)(r10 -16)")
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