On 7/25/15, Dmitry V. Levin <l...@altlinux.org> wrote:
> On Fri, Jul 24, 2015 at 09:17:59PM -0700, enh wrote:
>> Android kernels have an extra prctl that lets us set a name for an
>> anonymous VMA, which is useful for debugging. at the moment strace
>> shows it like this:
>>
>> prctl(0x53564d41 /* PR_??? */, 0, 0x7f7ab0e000, 0x2000, 0x7f7aaf76d0) = 0
>> prctl(0x53564d41 /* PR_??? */, 0, 0x7f7ab0d000, 0x1000, 0x7f7aaf76e8) = 0
>>
>> with this patch:
>>
>> diff --git a/prctl.c b/prctl.c
>> index 4a6bd25..e43569c 100644
>> --- a/prctl.c
>> +++ b/prctl.c
>> @@ -94,6 +94,22 @@ prctl_enter(struct tcb *tcp)
>> printstr(tcp, tcp->u_arg[1], TASK_COMM_LEN);
>> break;
>>
>> +#define PR_SET_VMA 0x53564d41
>> +#define PR_SET_VMA_ANON_NAME 0
>
> If there is a chance of these constants being defined in system headers
> some day, please wrap these definitions in ifdefs.
i'm told not, but never is a long time. sounds like a good idea to me.
i've wrapped the whole thing in an #ifdef __ANDROID__ too.
>> + case PR_SET_VMA:
>> + if (tcp->u_arg[1] == PR_SET_VMA_ANON_NAME) {
>> + tprintf(", %lu", tcp->u_arg[1]);
>> + tprintf(", %#lx", tcp->u_arg[2]);
>> + tprintf(", %lu, ", tcp->u_arg[3]);
>> + printstr(tcp, tcp->u_arg[4], -1);
>> + } else {
>> + // There are no other sub-options now, but there
>> + // might be in future...
>> + for (i = 1; i < tcp->s_ent->nargs; i++)
>> + tprintf(", %#lx", tcp->u_arg[i]);
>
> Starting with commit v4.10-259-g3691562, this loop should be replaced with
>
> print_prctl_args(tcp, 1);
done.
>> + }
>> + break;
>> +
>> case PR_SET_MM:
>> tprints(", ");
>> printxval(pr_set_mm, tcp->u_arg[1], "PR_SET_MM_???");
>>
>> we get this instead:
>>
>> prctl(0x53564d41 /* PR_??? */, 0, 0x7f7ffe0000, 8192, "thread signal
>> stack") = 0
>> prctl(0x53564d41 /* PR_??? */, 0, 0x7f7ffdf000, 4096, "thread signal
>> stack guard page") = 0
>>
>> obviously i could change the xlat prctl_options.in file to add
>> PR_SET_VMA, but this isn't in upstream kernels so that seems wrong.
>
> Agreed.
>
>> i can easily keep the patch above and/or the one that touches the xlat
>> file in our tree, but i thought i'd ask what -- if anything -- of this
>> you'd be interested in having in upstream strace.
>
> I think this change would be OK for upstream strace.
cool. here's a cleaned up patch then:
diff --git a/prctl.c b/prctl.c
index 4c12bac..f5f655c 100644
--- a/prctl.c
+++ b/prctl.c
@@ -168,6 +168,27 @@ SYS_FUNC(prctl)
printstr(tcp, tcp->u_arg[1], TASK_COMM_LEN);
return RVAL_DECODED;
+#ifdef __ANDROID__
+# ifndef PR_SET_VMA
+# define PR_SET_VMA 0x53564d41
+# endif
+# ifndef PR_SET_VMA_ANON_NAME
+# define PR_SET_VMA_ANON_NAME 0
+# endif
+ case PR_SET_VMA:
+ if (tcp->u_arg[1] == PR_SET_VMA_ANON_NAME) {
+ tprintf(", %lu", tcp->u_arg[1]);
+ tprintf(", %#lx", tcp->u_arg[2]);
+ tprintf(", %lu, ", tcp->u_arg[3]);
+ printstr(tcp, tcp->u_arg[4], -1);
+ } else {
+ // There are no other sub-options now, but there
+ // might be in future...
+ print_prctl_args(tcp, 1);
+ }
+ break;
+#endif
+
case PR_SET_MM:
tprints(", ");
printxval(pr_set_mm, tcp->u_arg[1], "PR_SET_MM_???");
>
> --
> ldv
>
--
Elliott Hughes - http://who/enh - http://jessies.org/~enh/
Android native code/tools questions? Mail me/drop by/add me as a reviewer.
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