linux-kernel - [PATCH AUTOSEL 6.3 08/59] bpf, mips: Implement DADDI workarounds for JIT

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Message-Id: <20230504194142.3805425-8-sashal@kernel.org>
Date:   Thu,  4 May 2023 15:40:51 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Jiaxun Yang <jiaxun.yang@...goat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Philippe Mathieu-Daudé <philmd@...aro.org>,
        Johan Almbladh <johan.almbladh@...finetworks.com>,
        Sasha Levin <sashal@...nel.org>, tsbogend@...ha.franken.de,
        ast@...nel.org, andrii@...nel.org, paulburton@...nel.org,
        linux-mips@...r.kernel.org, bpf@...r.kernel.org
Subject: [PATCH AUTOSEL 6.3 08/59] bpf, mips: Implement DADDI workarounds for JIT

From: Jiaxun Yang <jiaxun.yang@...goat.com>

[ Upstream commit bbefef2f07080cd502a93cb1c529e1c8a6c4ac8e ]

For DADDI errata we just workaround by disable immediate operation
for BPF_ADD / BPF_SUB to avoid generation of DADDIU.

All other use cases in JIT won't cause overflow thus they are all safe.

Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Reviewed-by: Philippe Mathieu-Daudé <philmd@...aro.org>
Acked-by: Johan Almbladh <johan.almbladh@...finetworks.com>
Link: https://lore.kernel.org/bpf/20230228113305.83751-2-jiaxun.yang@flygoat.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/mips/Kconfig            | 1 -
 arch/mips/net/bpf_jit_comp.c | 4 ++++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index e2f3ca73f40d6..edc7d8790f1e8 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -64,7 +64,6 @@ config MIPS
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_EBPF_JIT if !CPU_MICROMIPS && \
-				!CPU_DADDI_WORKAROUNDS && \
 				!CPU_R4000_WORKAROUNDS && \
 				!CPU_R4400_WORKAROUNDS
 	select HAVE_EXIT_THREAD
diff --git a/arch/mips/net/bpf_jit_comp.c b/arch/mips/net/bpf_jit_comp.c
index b17130d510d49..a40d926b65139 100644
--- a/arch/mips/net/bpf_jit_comp.c
+++ b/arch/mips/net/bpf_jit_comp.c
@@ -218,9 +218,13 @@ bool valid_alu_i(u8 op, s32 imm)
 		/* All legal eBPF values are valid */
 		return true;
 	case BPF_ADD:
+		if (IS_ENABLED(CONFIG_CPU_DADDI_WORKAROUNDS))
+			return false;
 		/* imm must be 16 bits */
 		return imm >= -0x8000 && imm <= 0x7fff;
 	case BPF_SUB:
+		if (IS_ENABLED(CONFIG_CPU_DADDI_WORKAROUNDS))
+			return false;
 		/* -imm must be 16 bits */
 		return imm >= -0x7fff && imm <= 0x8000;
 	case BPF_AND:
-- 
2.39.2