Messages in this thread | | | Date | Fri, 11 Dec 2009 10:41:54 +0800 | From | Lai Jiangshan <> | Subject | Re: [PATCH 07/10] trace_syscalls: init print_fmt |
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Steven Rostedt wrote: > On Wed, 2009-12-09 at 15:15 +0800, Lai Jiangshan wrote: >> Init print_fmt for trace_syscalls. >> It will be used for replacing ->show_format(). > > This needs more explanation too. > >> Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> >> --- >> diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c >> index 75289f3..dcd8699 100644 >> --- a/kernel/trace/trace_syscalls.c >> +++ b/kernel/trace/trace_syscalls.c >> @@ -191,6 +191,61 @@ int syscall_enter_format(struct ftrace_event_call *call, struct trace_seq *s) >> return trace_seq_putc(s, '\n'); >> } >> >> +static >> +int __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len) >> +{ >> + int i; >> + int pos = 0; >> + >> + pos += snprintf(buf + pos, len > pos ? len - pos : 0, "\""); >> + for (i = 0; i < entry->nb_args; i++) { >> + pos += snprintf(buf + pos, len > pos ? len - pos : 0, >> + "%s: 0x%%0%zulx%s", entry->args[i], >> + sizeof(unsigned long), >> + i == entry->nb_args - 1 ? "" : ", "); >> + } >> + pos += snprintf(buf + pos, len > pos ? len - pos : 0, "\""); >> + >> + for (i = 0; i < entry->nb_args; i++) { >> + pos += snprintf(buf + pos, len > pos ? len - pos : 0, >> + ", ((unsigned long)(REC->%s))", entry->args[i]); > > Yuck! 4 snprintf(buf + pos, len > pos ? len - pos: 0 ... > > Please make a wrapper for that.
Do you mind if I use a macro? Readability are still the same...
static int __set_enter_print_fmt(struct syscall_metadata *entry, char *buf, int len) { int i; int pos = 0;
#define BUF_PRINTF(fmt...) \ do { \ pos += snprintf(buf + pos, len > pos ? len - pos : 0, fmt); \ } while (0)
BUF_PRINTF("\""); for (i = 0; i < entry->nb_args; i++) { BUF_PRINTF("%s: 0x%%0%zulx%s", entry->args[i], sizeof(unsigned long), i == entry->nb_args - 1 ? "\"" : ", "); }
for (i = 0; i < entry->nb_args; i++) BUF_PRINTF(", ((unsigned long)(REC->%s))", entry->args[i]);
#under BUF_PRINTF
/* return the length of print_fmt */ return pos; }
> > Actually, this could use the new trace_seq code if I separate the > buffer. You would just need to do: > > struct trace_seq s;
I think trace_seq can not help. __set_enter_print_fmt() is called twice. We calculate the length at the first time(don't write any thing), then allocate memory and then really "snprintf" string into the buffer.
-- Lai
> > trace_seq_init(&s, buf, len); > > trace_seq_putc(&s, '"'); > for (i = 0; i < entry->nb_args; i++) > trace_seq_printf(&s, "%s: 0x%%0%zulx%s", entry->args[i], > sizeof(unsigned long), > i == entry->nb_args - 1 ? "" : ", "); > > trace_seq_putc(&s, '"'); > > for (i = 0; i < entry->nb_args; i++) > trace_seq_printf(&s, ", ((unsigned long)(REC->%s)", > entry->args[i]); > > return s.len; > > > Looks much better, and less error prone. > > -- Steve >
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