Unverified Commit 7d1d19a1 authored by Björn Töpel's avatar Björn Töpel Committed by Palmer Dabbelt
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riscv: uprobes: Add missing fence.i after building the XOL buffer 



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: default avatarGuo Ren <guoren@kernel.org>
Fixes: 74784081 ("riscv: Add uprobes supported")
Signed-off-by: default avatarBjörn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20250419111402.1660267-2-bjorn@kernel.org


Signed-off-by: default avatarPalmer Dabbelt <palmer@rivosinc.com>
parent 121f3434

arch/riscv/kernel/probes/uprobes.c

+2 −8
Original line number Diff line number Diff line
@@ -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);

}