From 28891d1127542dbb2d5ba16c575e14e741ed73ef Mon Sep 17 00:00:00 2001
From: Tao Liu <ltao@redhat.com>
Date: Thu, 4 Jan 2024 09:20:27 +0800
Subject: [PATCH 6/6] symbols: skip the module if the given address is not
within its address range
Previously, to find a module symbol and its offset by an arbitrary address,
all symbols within the module will be iterated by address ascending order
until the last symbol with a smaller address been noticed.
However if the address is not within the module address range, e.g.
the address is higher than the module's last symbol's address, then
the module can be surely skipped, because its symbol iteration is
unnecessary. This can speed up the kernel module symbols finding and improve
the overall performance.
Without the patch:
$ time echo "bt 8993" | ~/crash-dev/crash vmcore vmlinux
crash> bt 8993
PID: 8993 TASK: ffff927569cc2100 CPU: 2 COMMAND: "WriterPool0"
#0 [ffff927569cd76f0] __schedule at ffffffffb3db78d8
#1 [ffff927569cd7758] schedule_preempt_disabled at ffffffffb3db8bf9
#2 [ffff927569cd7768] __mutex_lock_slowpath at ffffffffb3db6ca7
#3 [ffff927569cd77c0] mutex_lock at ffffffffb3db602f
#4 [ffff927569cd77d8] ucache_retrieve at ffffffffc0cf4409 [secfs2]
...snip the stacktrace of the same module...
#11 [ffff927569cd7ba0] cskal_path_vfs_getattr_nosec at ffffffffc05cae76 [falcon_kal]
...snip...
#13 [ffff927569cd7c40] _ZdlPv at ffffffffc086e751 [falcon_lsm_serviceable]
...snip...
#20 [ffff927569cd7ef8] unload_network_ops_symbols at ffffffffc06f11c0 [falcon_lsm_pinned_14713]
#21 [ffff927569cd7f50] system_call_fastpath at ffffffffb3dc539a
RIP: 00007f2b28ed4023 RSP: 00007f2a45fe7f80 RFLAGS: 00000206
RAX: 0000000000000012 RBX: 00007f2a68302e00 RCX: 00007f2a682546d8
RDX: 0000000000000826 RSI: 00007eb57ea6a000 RDI: 00000000000000e3
RBP: 00007eb57ea6a000 R8: 0000000000000826 R9: 00000002670bdfd2
R10: 00000002670bdfd2 R11: 0000000000000293 R12: 00000002670bdfd2
R13: 00007f29d501a480 R14: 0000000000000826 R15: 00000002670bdfd2
ORIG_RAX: 0000000000000012 CS: 0033 SS: 002b
crash>
real 7m14.826s
user 7m12.502s
sys 0m1.091s
With the patch:
$ time echo "bt 8993" | ~/crash-dev/crash vmcore vmlinux
crash> bt 8993
PID: 8993 TASK: ffff927569cc2100 CPU: 2 COMMAND: "WriterPool0"
#0 [ffff927569cd76f0] __schedule at ffffffffb3db78d8
#1 [ffff927569cd7758] schedule_preempt_disabled at ffffffffb3db8bf9
...snip the same output...
crash>
real 0m8.827s
user 0m7.896s
sys 0m0.938s
Signed-off-by: Tao Liu <ltao@redhat.com>
Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
---
symbols.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/symbols.c b/symbols.c
index 5d919910164e..88a3fd156cb5 100644
--- a/symbols.c
+++ b/symbols.c
@@ -5561,7 +5561,7 @@ value_search_module_6_4(ulong value, ulong *offset)
sp = lm->symtable[t];
sp_end = lm->symend[t];
- if (value < sp->value)
+ if (value < sp->value || value > sp_end->value)
continue;
splast = NULL;
@@ -5646,6 +5646,9 @@ retry:
if (sp->value > value) /* invalid -- between modules */
break;
+ if (sp_end->value < value) /* not within the module */
+ continue;
+
/*
* splast will contain the last module symbol encountered.
* Note: "__insmod_"-type symbols will be set in splast only
--
2.41.0