Re: [PATCHv8 bpf-next 3/9] uprobe: Add uretprobe syscall to speed up return probe

Jiri Olsa
2024-06-14T19:27:05Z

On Fri, Jun 14, 2024 at 10:48:22AM -0700, Nathan Chancellor wrote:
> Hi Jiri,
>
> On Tue, Jun 11, 2024 at 01:21:52PM +0200, Jiri Olsa wrote:
> > Adding uretprobe syscall instead of trap to speed up return probe.
> ...
> > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
> > index 2c83ba776fc7..2816e65729ac 100644
> > --- a/kernel/events/uprobes.c
> > +++ b/kernel/events/uprobes.c
> > @@ -1474,11 +1474,20 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
> > return ret;
> > }
> >
> > +void * __weak arch_uprobe_trampoline(unsigned long *psize)
> > +{
> > + static uprobe_opcode_t insn = UPROBE_SWBP_INSN;
>
> This change as commit ff474a78cef5 ("uprobe: Add uretprobe syscall to
> speed up return probe") in -next causes the following build error for
> ARCH=loongarch allmodconfig:
>
> In file included from include/linux/uprobes.h:49,
> from include/linux/mm_types.h:16,
> from include/linux/mmzone.h:22,
> from include/linux/gfp.h:7,
> from include/linux/xarray.h:16,
> from include/linux/list_lru.h:14,
> from include/linux/fs.h:13,
> from include/linux/highmem.h:5,
> from kernel/events/uprobes.c:13:
> 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;

reproduced, could you please try the change below

thanks,
jirka

---
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;
}