Re: [PATCH 2/5] tracing: Add division and multiplication support for hist triggers

On Wed, 15 Sep 2021 19:52:46 +0000 Kalesh Singh kaleshsingh@google.com wrote:

+static u64 hist_field_div(struct hist_field *hist_field,

• 	   struct tracing_map_elt *elt,
  

• 	   struct trace_buffer *buffer,
  

• 	   struct ring_buffer_event *rbe,
  

• 	   void *event)
  

+{

• struct hist_field *operand1 = hist_field->operands[0];
• struct hist_field *operand2 = hist_field->operands[1];
• u64 val1 = operand1->fn(operand1, elt, buffer, rbe, event);
• u64 val2 = operand2->fn(operand2, elt, buffer, rbe, event);
• /* Return -1 for the undefined case */
• if (!val2)

• return -1;
  

• return val1 / val2;

This wont work on x86 32 bit machines, as u64 division will trigger floating point arithmetic by the compiler, and cause a fault.

You'll need to use one of the div64() helpers.

-- Steve

+}