riscv: uprobes: Add missing fence.i after building the XOL buffer

[ 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>

diff --git a/arch/riscv/kernel/probes/uprobes.c b/arch/riscv/kernel/probes/uprobes.c
index 4b3dc8beaf77d31d0c828a7a04cc81e2d78ef2e0..cc15f7ca6cc17b809de60be5dca7653c8f596503 100644 (file)
--- 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);
 }