Re: [PATCH] uprobe: Do not use UPROBE_SWBP_INSN as static initializer
From: Andrii Nakryiko <hidden>
Date: 2024-06-20 19:01:08
Also in:
bpf, lkml
On Tue, Jun 18, 2024 at 12:43 PM Jiri Olsa [off-list ref] wrote:
Nathan reported compilation fail for loongarch arch:
kernel/events/uprobes.c: In function 'arch_uprobe_trampoline':
arch/loongarch/include/asm/uprobes.h:12:33: error: initializer element is not constant
12 | #define UPROBE_SWBP_INSN larch_insn_gen_break(BRK_UPROBE_BP)
| ^~~~~~~~~~~~~~~~~~~~
kernel/events/uprobes.c:1479:39: note: in expansion of macro 'UPROBE_SWBP_INSN'
1479 | static uprobe_opcode_t insn = UPROBE_SWBP_INSN;
Loongarch defines UPROBE_SWBP_INSN as function call, so we can't
use it to initialize static variable.
Cc: Oleg Nesterov <oleg@redhat.com>
Fixes: ff474a78cef5 ("uprobe: Add uretprobe syscall to speed up return probe")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
kernel/events/uprobes.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)Can we instead ask loongarch folks to rewrite it to be a constant? Having this as a function call is both an inconvenience and potential performance problem (a minor one, but still). I would imagine it's not hard to hard-code an instruction as a constant here.
quoted hunk ↗ jump to hunk
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index 2816e65729ac..6986bd993702 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c@@ -1476,8 +1476,9 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area) void * __weak arch_uprobe_trampoline(unsigned long *psize) { - static uprobe_opcode_t insn = UPROBE_SWBP_INSN; + static uprobe_opcode_t insn; + insn = insn ?: UPROBE_SWBP_INSN; *psize = UPROBE_SWBP_INSN_SIZE; return &insn; } --2.45.1