From: Jim Cromie <jim.cromie@gmail.com>
To: Jason Baron <jbaron@akamai.com>, linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, Jim Cromie <jim.cromie@gmail.com>
Subject: [RFC PATCH v5 21/28] dyndbg: validate ddebug_site_get invariants
Date: Tue, 11 May 2021 12:50:50 -0600 [thread overview]
Message-ID: <20210511185057.3815777-22-jim.cromie@gmail.com> (raw)
In-Reply-To: <20210511185057.3815777-1-jim.cromie@gmail.com>
This commit adds several BUG_ONs to assert all the invariants needed
to support the reliance on the "back-N-to-header-overto-site-out-N"
use of the 2 __dyndbg* vectors (with their included headers).
RFC: I don't think we want this permanently; BUG_ON/panic seems kinda
overkill, but its useful to know if it survives lkp auto-testing.
- dp is (struct _ddebug*) to the callsite, passed in.
- dh is (struct _ddebug*) to the header. derived from dp & _index.
known by BUG_ON(!is_dyndbg_header(dh))
this is the "up-N-to-header" from dp.
- dh has good site pointer, to __dyndbg_sites[]
by BUG_ON(!is_dyndbg_header_pair())
There are 2 main cases to validate: builtin and loadable modules.
For loadable modules, we will depend upon the headers presence, and
its site pointer to the vector of _ddebug_sites[], expressed as:
BUG_ON(&dh->site[dp->_index] != dp->site);
Builtin pr-debugs have the additional property:
!!(&__start___dyndbg <= dp < __stop___dyndbg),
We could use this property directly to return site, but since builtin
modules also have a header record, we can use that instead. So the
1st BUG_ON is hoisted out of the !builtin branch, and asserted just
before return. Also hoist dh derivation, making it a declaration +
initialization + BUG_ON instead.
NB: grep -- '->site' will confirm that site is now used just for
BUG_ON assertions, so we are close to the drop.
NEXT
To drop site pointer from struct _ddebug, we need:
- recast header as a different struct, unionized with _ddebug.
- preserve site pointer there.
- drop from struct _ddebug.
- fix and fold back any fallout from size reduction.
OR defer that, and proceed with compressing __dyndbg_sites[], then
replacing ddebug_site_get's guts (with all the BUG_ONs) with a
decompress and _index.
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
lib/dynamic_debug.c | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 462d364fc788..af9791258f8f 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -123,6 +123,8 @@ do { \
#define vpr_info(fmt, ...) vnpr_info(1, fmt, ##__VA_ARGS__)
#define v2pr_info(fmt, ...) vnpr_info(2, fmt, ##__VA_ARGS__)
#define v3pr_info(fmt, ...) vnpr_info(3, fmt, ##__VA_ARGS__)
+#define v4pr_info(fmt, ...) vnpr_info(4, fmt, ##__VA_ARGS__)
+#define v5pr_info(fmt, ...) vnpr_info(5, fmt, ##__VA_ARGS__)
static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
{
@@ -146,7 +148,34 @@ static void vpr_info_dq(const struct ddebug_query *query, const char *msg)
static struct _ddebug_site *ddebug_site_get(struct _ddebug *dp)
{
- return dp->site; /* passthru abstraction */
+ struct _ddebug *dh = dp - (dp->_index);
+
+ WARN_ON(!is_dyndbg_header_pair(dh, dh->site));
+
+ if (dp >= __start___dyndbg && dp < __stop___dyndbg) {
+
+ v5pr_info("get: %s is builtin: %d %d %s:%s:%d\n",
+ dp->site->modname, dp->_index, (int)(dp - dh),
+ dh->site[dp->_index].filename,
+ dh->site[dp->_index].function, dp->lineno);
+
+ WARN_ON(dp != &__start___dyndbg[dp->_index]);
+
+ WARN_ON(!(dp->_index == (dp - dh) &&
+ dp->_index == (dp - __start___dyndbg) &&
+ dp->_index == (&__start___dyndbg_sites[dp->_index]
+ - &__start___dyndbg_sites[0])));
+
+ WARN_ON(&__start___dyndbg_sites[dp->_index] != dp->site);
+ } else {
+ v4pr_info("get: %s is loaded: %d %s:%s:%d\n",
+ dp->site->modname, dp->_index,
+ dh->site[dp->_index].filename,
+ dh->site[dp->_index].function, dp->lineno);
+ }
+ WARN_ON(&dh->site[dp->_index] != dp->site);
+
+ return dp->site;
}
static inline void ddebug_site_put(struct _ddebug *dp)
{
--
2.31.1
next prev parent reply other threads:[~2021-05-11 18:52 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20210511185057.3815777-1-jim.cromie@gmail.com>
2021-05-11 18:50 ` [RFC PATCH v5 01/28] dyndbg: avoid calling dyndbg_emit_prefix when it has no work Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 02/28] dyndbg: drop uninformative vpr_info Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 03/28] dyndbg: split struct _ddebug's display fields to new _ddebug_site Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 04/28] dyndbg: __init iterate over __dyndbg & __dyndbg_site in parallel Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 05/28] dyndbg: refactor part of ddebug_change to ddebug_match_site Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 06/28] dyndbg: accept null site in ddebug_match_site Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 07/28] dyndbg: hoist ->site out of ddebug_match_site Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 08/28] dyndbg: accept null site in ddebug_change Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 09/28] dyndbg: accept null site in dynamic_emit_prefix Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 10/28] dyndbg: accept null site in ddebug_proc_show Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 11/28] dyndbg: refactor ddebug_alter_site out of ddebug_change Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 12/28] dyndbg: allow deleting site info via control interface Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 13/28] dyndbg+module: expose ddebug_sites to modules Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 14/28] dyndbg: add ddebug_site(_get|_put) abstraction Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 15/28] dyndbg: ddebug_add_module avoid adding empty modules Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 16/28] dyndbg: add _index to struct _ddebug Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 17/28] dyndbg: prevent build bugs via -DNO_DYNAMIC_DEBUG_TABLE Jim Cromie
2021-05-12 14:55 ` Ard Biesheuvel
2021-05-12 18:03 ` jim.cromie
2021-05-11 18:50 ` [RFC PATCH v5 18/28] dyndbg: RFC - DEFINE_DYNAMIC_DEBUG_TABLE Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 19/28] dyndbg: RFC handle __dyndbg* sections in module.lds.h Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 20/28] dyndbg: ddebug_add_module() handle headers Jim Cromie
2021-05-11 18:50 ` Jim Cromie [this message]
2021-05-11 18:50 ` [RFC PATCH v5 22/28] dyndbg: fix NULL deref after deleting sites Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 23/28] dyndbg: dont show header records in control Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 24/28] dyndbg: make site pointer and checks on it optional (not quite) Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 25/28] dyndbg: swap WARN_ON for BUG_ON see what 0-day says Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 26/28] dyndbg: fixup protect header when deleting site Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 27/28] dyndbg: unionize _ddebug*_headers with struct _ddebug* Jim Cromie
2021-05-11 18:50 ` [RFC PATCH v5 28/28] dyndbg: RFC drop _ddebug.site pointer Jim Cromie
2021-05-12 22:08 ` Fwd: [RFC PATCH v5 00/28] dynamic debug diet plan jim.cromie
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