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SubjectRe: [PATCH v3 5/5] tracing/probe: Support user-space dereference
On Wed, 27 Feb 2019 21:42:45 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Wed, 27 Feb 2019 23:44:42 +0900
> Masami Hiramatsu <mhiramat@kernel.org> wrote:
>
> > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> > index a7012de37a00..0efef172db17 100644
> > --- a/kernel/trace/trace_probe.c
> > +++ b/kernel/trace/trace_probe.c
> > @@ -239,6 +239,7 @@ parse_probe_arg(char *arg, const struct fetch_type *type,
> > {
> > struct fetch_insn *code = *pcode;
> > unsigned long param;
> > + int deref = FETCH_OP_DEREF;
> > long offset = 0;
> > char *tmp;
> > int ret = 0;
> > @@ -301,8 +302,17 @@ parse_probe_arg(char *arg, const struct fetch_type *type,
> > break;
> >
> > case '+': /* deref memory */
> > - arg++; /* Skip '+', because kstrtol() rejects it. */
> > case '-':
> > + if (arg[0] == '+') {
> > + arg++; /* Skip '+', because kstrtol() rejects it. */
> > + if (arg[0] == 'u') {
> > + deref = FETCH_OP_UDEREF;
> > + arg++;
> > + }
> > + } else if (arg[1] == 'u') { /* Start with "-u" */
> > + deref = FETCH_OP_UDEREF;
> > + *(++arg) = '-';
> > + }
>
> What about:
>
> if (arg[1] == 'u') {
> deref = FETCH_OP_UDEREF;
> arg[1] = arg[0];
> arg++;
> }
> if (arg[0] == '+')
> arg++; /* Skip '+', because kstrtol() rejects it. */
>
> A bit less messy.

Ah, thanks! I'll take it.

>
>
> > tmp = strchr(arg, '(');
> > if (!tmp)
> > return -EINVAL;
> > @@ -328,7 +338,7 @@ parse_probe_arg(char *arg, const struct fetch_type *type,
> > return -E2BIG;
> > *pcode = code;
> >
> > - code->op = FETCH_OP_DEREF;
> > + code->op = deref;
> > code->offset = offset;
> > }
> > break;
> > @@ -444,13 +454,14 @@ static int traceprobe_parse_probe_arg_body(char *arg, ssize_t *size,
> > /* Store operation */
> > if (!strcmp(parg->type->name, "string") ||
> > !strcmp(parg->type->name, "ustring")) {
> > - if (code->op != FETCH_OP_DEREF && code->op != FETCH_OP_IMM &&
> > - code->op != FETCH_OP_COMM) {
> > + if (code->op != FETCH_OP_DEREF && code->op != FETCH_OP_UDEREF
> > + && code->op != FETCH_OP_IMM && code->op != FETCH_OP_COMM) {
> > pr_info("string only accepts memory or address.\n");
> > ret = -EINVAL;
> > goto fail;
> > }
> > - if (code->op != FETCH_OP_DEREF || parg->count) {
> > + if ((code->op == FETCH_OP_IMM && code->op == FETCH_OP_COMM)
> > + || parg->count) {
>
> How would "code->op == FETCH_OP_IMM && code->op == FETCH_OP_COMM" ever be true?
>
> Did you mean || ?

Oops, yes. It is a simple mistake...

Thank you!

>
> -- Steve
>
> > /*
> > * IMM and COMM is pointing actual address, those must
> > * be kept, and if parg->count != 0, this is an array
> > @@ -463,7 +474,8 @@ static int traceprobe_parse_probe_arg_body(char *arg, ssize_t *size,
> > }
> > }
> > /* If op == DEREF, replace it with STRING */
> > - if (!strcmp(parg->type->name, "ustring"))
> > + if (!strcmp(parg->type->name, "ustring") ||
> > + code->op == FETCH_OP_UDEREF)
> > code->op = FETCH_OP_ST_USTRING;
> > else
> > code->op = FETCH_OP_ST_STRING;


--
Masami Hiramatsu <mhiramat@kernel.org>

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