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tracing: Clean up and document pred_funcs_##type creation and use
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The pred_funcs_##type arrays consist of five functions that are assigned
based on the ops. The array must be in the same order of the ops each
function represents. The PRED_FUNC_START macro denotes the op enum that
starts the op that maps to the pred_funcs_##type arrays. This is all very
subtle and prone to bugs if the code is changed.

Add comments describing how PRED_FUNC_START and pred_funcs_##type array is
used, and also a PRED_FUNC_MAX that is the maximum number of functions in
the arrays.

Clean up select_comparison_fn() that assigns the predicates to the
pred_funcs_##type array function as well as add protection in case an op is
passed in that does not map correctly to the array.

Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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rostedt committed Mar 14, 2018
1 parent e9baef0 commit 478325f
Showing 1 changed file with 32 additions and 14 deletions.
46 changes: 32 additions & 14 deletions kernel/trace/trace_events_filter.c
Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,13 @@ struct filter_op {

static struct filter_op filter_ops[] = { OPS };

/*
* pred functions are OP_LT, OP_LE, OP_GT, OP_GE, and OP_BAND
* pred_funcs_##type below must match the order of them above.
*/
#define PRED_FUNC_START OP_LT
#define PRED_FUNC_MAX (OP_BAND - PRED_FUNC_START)

#define ERRORS \
C( NONE, "No error"), \
C( INVALID_OP, "Invalid operator"), \
Expand Down Expand Up @@ -172,8 +179,6 @@ static const filter_pred_fn_t pred_funcs_##type[] = { \
filter_pred_BAND_##type, \
};

#define PRED_FUNC_START OP_LT

#define DEFINE_EQUALITY_PRED(size) \
static int filter_pred_##size(struct filter_pred *pred, void *event) \
{ \
Expand Down Expand Up @@ -946,39 +951,52 @@ static filter_pred_fn_t select_comparison_fn(enum filter_op_ids op,
int field_size, int field_is_signed)
{
filter_pred_fn_t fn = NULL;
int pred_func_index = -1;

switch (op) {
case OP_EQ:
case OP_NE:
break;
default:
if (WARN_ON_ONCE(op < PRED_FUNC_START))
return NULL;
pred_func_index = op - PRED_FUNC_START;
if (WARN_ON_ONCE(pred_func_index > PRED_FUNC_MAX))
return NULL;
}

switch (field_size) {
case 8:
if (op == OP_EQ || op == OP_NE)
if (pred_func_index < 0)
fn = filter_pred_64;
else if (field_is_signed)
fn = pred_funcs_s64[op - PRED_FUNC_START];
fn = pred_funcs_s64[pred_func_index];
else
fn = pred_funcs_u64[op - PRED_FUNC_START];
fn = pred_funcs_u64[pred_func_index];
break;
case 4:
if (op == OP_EQ || op == OP_NE)
if (pred_func_index < 0)
fn = filter_pred_32;
else if (field_is_signed)
fn = pred_funcs_s32[op - PRED_FUNC_START];
fn = pred_funcs_s32[pred_func_index];
else
fn = pred_funcs_u32[op - PRED_FUNC_START];
fn = pred_funcs_u32[pred_func_index];
break;
case 2:
if (op == OP_EQ || op == OP_NE)
if (pred_func_index < 0)
fn = filter_pred_16;
else if (field_is_signed)
fn = pred_funcs_s16[op - PRED_FUNC_START];
fn = pred_funcs_s16[pred_func_index];
else
fn = pred_funcs_u16[op - PRED_FUNC_START];
fn = pred_funcs_u16[pred_func_index];
break;
case 1:
if (op == OP_EQ || op == OP_NE)
if (pred_func_index < 0)
fn = filter_pred_8;
else if (field_is_signed)
fn = pred_funcs_s8[op - PRED_FUNC_START];
fn = pred_funcs_s8[pred_func_index];
else
fn = pred_funcs_u8[op - PRED_FUNC_START];
fn = pred_funcs_u8[pred_func_index];
break;
}

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