Re: [PATCHv5 perf/core 08/22] uprobes/x86: Add mapping for optimized uprobe trampolines

On Fri, Jul 11, 2025 at 07:46:32PM +0200, Oleg Nesterov wrote:

On 07/11, Jiri Olsa wrote:

quoted

+static unsigned long find_nearest_trampoline(unsigned long vaddr)
+{
+	struct vm_unmapped_area_info info = {
+		.length     = PAGE_SIZE,
+		.align_mask = ~PAGE_MASK,
+	};
+	unsigned long low_limit, high_limit;
+	unsigned long low_tramp, high_tramp;
+	unsigned long call_end = vaddr + 5;
+
+	if (check_add_overflow(call_end, INT_MIN, &low_limit))
+		low_limit = PAGE_SIZE;
+
+	high_limit = call_end + INT_MAX;
+
+	/* Search up from the caller address. */
+	info.low_limit = call_end;
+	info.high_limit = min(high_limit, TASK_SIZE);
+	high_tramp = vm_unmapped_area(&info);
+
+	/* Search down from the caller address. */
+	info.low_limit = max(low_limit, PAGE_SIZE);
+	info.high_limit = call_end;
+	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
+	low_tramp = vm_unmapped_area(&info);
+
+	if (IS_ERR_VALUE(high_tramp) && IS_ERR_VALUE(low_tramp))
+		return -ENOMEM;
+	if (IS_ERR_VALUE(high_tramp))
+		return low_tramp;
+	if (IS_ERR_VALUE(low_tramp))
+		return high_tramp;
+
+	/* Return address that's closest to the caller address. */
+	if (call_end - low_tramp < high_tramp - call_end)
+		return low_tramp;
+	return high_tramp;
+}

IIUC, nothing else has changed since I've acked the previous version?
Then my ack still stands,

correct, just the find_nearest_trampoline function

Acked-by: Oleg Nesterov <oleg@redhat.com>

thanks,
jirka