From bcf6d3158c5902d92b6d62335af4422b7bf7c4e2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20T=C3=B6pel?= <bjorn@rivosinc.com>
Date: Sat, 19 Apr 2025 13:14:00 +0200
Subject: [PATCH] riscv: uprobes: Add missing fence.i after building the XOL
buffer
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[ Upstream commit 7d1d19a11cfbfd8bae1d89cc010b2cc397cd0c48 ]
The XOL (execute out-of-line) buffer is used to single-step the
replaced instruction(s) for uprobes. The RISC-V port was missing a
proper fence.i (i$ flushing) after constructing the XOL buffer, which
can result in incorrect execution of stale/broken instructions.
This was found running the BPF selftests "test_progs:
uprobe_autoattach, attach_probe" on the Spacemit K1/X60, where the
uprobes tests randomly blew up.
Reviewed-by: Guo Ren <guoren@kernel.org>
Fixes: 74784081aac8 ("riscv: Add uprobes supported")
Signed-off-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250419111402.1660267-2-bjorn@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/riscv/kernel/probes/uprobes.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
diff --git a/arch/riscv/kernel/probes/uprobes.c b/arch/riscv/kernel/probes/uprobes.c
index 4b3dc8beaf77d..cc15f7ca6cc17 100644
--- a/arch/riscv/kernel/probes/uprobes.c
+++ b/arch/riscv/kernel/probes/uprobes.c
@@ -167,6 +167,7 @@ void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
/* Initialize the slot */
void *kaddr = kmap_atomic(page);
void *dst = kaddr + (vaddr & ~PAGE_MASK);
+ unsigned long start = (unsigned long)dst;
memcpy(dst, src, len);
@@ -176,13 +177,6 @@ void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
*(uprobe_opcode_t *)dst = __BUG_INSN_32;
}
+ flush_icache_range(start, start + len);
kunmap_atomic(kaddr);
-
- /*
- * We probably need flush_icache_user_page() but it needs vma.
- * This should work on most of architectures by default. If
- * architecture needs to do something different it can define
- * its own version of the function.
- */
- flush_dcache_page(page);
}