From c5eac6ee8bc5d32e48b3845472b547574061f49f Mon Sep 17 00:00:00 2001 From: Kalesh Singh Date: Mon, 25 Oct 2021 13:08:36 -0700 Subject: [PATCH] tracing/histogram: Simplify handling of .sym-offset in expressions The '-' in .sym-offset can confuse the hist trigger arithmetic expression parsing. Simplify the handling of this by replacing the 'sym-offset' with 'symXoffset'. This allows us to correctly evaluate expressions where the user may have inadvertently added a .sym-offset modifier to one of the operands in an expression, instead of bailing out. In this case the .sym-offset has no effect on the evaluation of the expression. The only valid use of the .sym-offset is as a hist key modifier. Link: https://lkml.kernel.org/r/20211025200852.3002369-5-kaleshsingh@google.com Signed-off-by: Kalesh Singh Suggested-by: Steven Rostedt Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events_hist.c | 43 +++++++++++++------------------- 1 file changed, 17 insertions(+), 26 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 7a50ea2ac6b1..bbaf2e16b7ae 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -68,8 +68,7 @@ C(INVALID_SORT_FIELD, "Sort field must be a key or a val"), \ C(INVALID_STR_OPERAND, "String type can not be an operand in expression"), \ C(EXPECT_NUMBER, "Expecting numeric literal"), \ - C(UNARY_MINUS_SUBEXPR, "Unary minus not supported in sub-expressions"), \ - C(SYM_OFFSET_SUBEXPR, ".sym-offset not supported in sub-expressions"), + C(UNARY_MINUS_SUBEXPR, "Unary minus not supported in sub-expressions"), #undef C #define C(a, b) HIST_ERR_##a @@ -1672,10 +1671,6 @@ static int contains_operator(char *str, char **sep) */ minus_op = strrchr(str, '-'); if (minus_op) { - /* Unfortunately, the modifier ".sym-offset" can confuse things. */ - if (minus_op - str >= 4 && !strncmp(minus_op - 4, ".sym-offset", 11)) - goto out; - /* * Unary minus is not supported in sub-expressions. If * present, it is always the next root operator. @@ -2138,7 +2133,11 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file, *flags |= HIST_FIELD_FL_HEX; else if (strcmp(modifier, "sym") == 0) *flags |= HIST_FIELD_FL_SYM; - else if (strcmp(modifier, "sym-offset") == 0) + /* + * 'sym-offset' occurrences in the trigger string are modified + * to 'symXoffset' to simplify arithmetic expression parsing. + */ + else if (strcmp(modifier, "symXoffset") == 0) *flags |= HIST_FIELD_FL_SYM_OFFSET; else if ((strcmp(modifier, "execname") == 0) && (strcmp(field_name, "common_pid") == 0)) @@ -2463,24 +2462,6 @@ static struct hist_field *parse_expr(struct hist_trigger_data *hist_data, return ERR_PTR(-EINVAL); } - /* - * ".sym-offset" in expressions has no effect on their evaluation, - * but can confuse operator parsing. - */ - if (*n_subexprs == 0) { - sep = strstr(str, ".sym-offset"); - if (sep) { - *sep = '\0'; - if (strpbrk(str, "+-/*") || strpbrk(sep + 11, "+-/*")) { - *sep = '.'; - hist_err(file->tr, HIST_ERR_SYM_OFFSET_SUBEXPR, - errpos(sep)); - return ERR_PTR(-EINVAL); - } - *sep = '.'; - } - } - field_op = contains_operator(str, &sep); if (field_op == FIELD_OP_NONE) @@ -5999,7 +5980,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops, struct synth_event *se; const char *se_name; bool remove = false; - char *trigger, *p; + char *trigger, *p, *start; int ret = 0; lockdep_assert_held(&event_mutex); @@ -6047,6 +6028,16 @@ static int event_hist_trigger_func(struct event_command *cmd_ops, trigger = strstrip(trigger); } + /* + * To simplify arithmetic expression parsing, replace occurrences of + * '.sym-offset' modifier with '.symXoffset' + */ + start = strstr(trigger, ".sym-offset"); + while (start) { + *(start + 4) = 'X'; + start = strstr(start + 11, ".sym-offset"); + }; + attrs = parse_hist_trigger_attrs(file->tr, trigger); if (IS_ERR(attrs)) return PTR_ERR(attrs);