[Crash-utility] [PATCH v2] struct: Fix handing of percpu symbols (when symbolic argument only)
Hi Dave,
Sorry about the delay. I completely forgot about this one!
Please note I have only addressed the case when the argument to the
'struct' command is not an address:
When a percpu symbol is of type pointer, the 'struct' command does
not generate the expected output. For example:
Note: The correct value of 'exec_start' should be
0x15b070b28b0c27 not 0x0
crash> struct task_struct.se.exec_start softlockup_watchdog:0
[0]: ffff880214e55a00
se.exec_start = 0x0,
crash> px softlockup_watchdog:0-1
per_cpu(softlockup_watchdog, 0) = $1 = (struct task_struct *) 0xffff880fe97e2e00
crash> px ((struct task_struct *)0xffff880fe97e2e00)->se.exec_start
$2 = 0x15b070b28b0c27
Currently, the 'struct' and 'p' command simply calculates
'cpuaddr' as
follows -- where 'addr' is a percpu's value:
cpuaddr = addr + __per_cpu_offset
This is correct if the percpu symbol or offset
(i.e. [percpu symbol:cpu-specifier] or [percpu value:cpu-specifier])
is not of type pointer. If a given percpu symbol is of type pointer such as
in 'static DEFINE_PER_CPU(struct task_struct *, softlockup_watchdog)', we
need to dereference the pointer to obtain the above correct kernel virtual
address.
For instance, using the above example, we need to pass the following to gdb
to resolve appropriately:
kernel virtual addresses for the cpus specified.
crash> set gdb on
gdb: on
gdb> p *(struct task_struct **) 0xffff880fffc0ddc0
$1 = (struct task_struct *) 0xffff880fe97e2e00
gdb>
With this patch, we now obtain the expected output:
crash> struct task_struct.se.exec_start softlockup_watchdog:0
[0]: ffff880214e55a00
se.exec_start = 0x15b070b28b0c27,
Signed-off-by: Aaron Tomlin <atomlin(a)redhat.com>
---
symbols.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)
diff --git a/symbols.c b/symbols.c
index 8b0d8b9..b68d0d3 100644
--- a/symbols.c
+++ b/symbols.c
@@ -81,6 +81,7 @@ static void cmd_datatype_common(ulong);
static void do_datatype_addr(struct datatype_member *, ulong, int,
ulong, char **, int);
static void process_gdb_output(char *, unsigned, const char *, int);
+static char *expr_type_name(const char *);
static int display_per_cpu_info(struct syment *, int, char *);
static struct load_module *get_module_percpu_sym_owner(struct syment *);
static int is_percpu_symbol(struct syment *);
@@ -6112,6 +6113,11 @@ cmd_datatype_common(ulong flags)
char *separator;
char *structname, *members;
char *memberlist[MAXARGS];
+ char *typename;
+ char buf[BUFSIZE];
+ char *argv[MAXARGS];
+ FILE *tmpfp;
+ ushort ptype;
dm = &datatype_member;
count = 0xdeadbeef;
@@ -6122,6 +6128,7 @@ cmd_datatype_common(ulong flags)
separator = members = NULL;
cpuspec = NULL;
cpus = NULL;
+ ptype = 0;
while ((c = getopt(argcnt, args, "pxdhfuc:rvol:")) != EOF) {
switch (c)
@@ -6262,6 +6269,12 @@ cmd_datatype_common(ulong flags)
SET_BIT(cpus, CURRENT_CONTEXT()->processor);
else
make_cpumask(cpuspec, cpus, FAULT_ON_ERROR, NULL);
+
+ if (sp) {
+ typename = expr_type_name(sp->name);
+ ptype = typename &&
+ LASTCHAR(typename) == '*' ? 1 : 0;
+ }
}
optind = optind_save;
@@ -6346,6 +6359,19 @@ cmd_datatype_common(ulong flags)
continue;
}
+ if (ptype) {
+ open_tmpfile();
+ snprintf(buf, sizeof buf, "p *(%s*) 0x%lx",
+ typename, cpuaddr);
+ gdb_pass_through(buf, pc->tmpfile, GNU_RETURN_ON_ERROR);
+
+ rewind(pc->tmpfile);
+ fgets(buf, BUFSIZE, pc->tmpfile);
+ parse_line(buf, argv);
+ cpuaddr = htol(argv[3], FAULT_ON_ERROR, NULL);
+ close_tmpfile();
+ }
+
fprintf(fp, "%lx\n", cpuaddr);
do_datatype_addr(dm, cpuaddr , count,
flags, memberlist, argc_members);
@@ -6364,6 +6390,9 @@ freebuf:
if (cpus)
FREEBUF(cpus);
+
+ if (typename)
+ FREEBUF(typename);
}
static void
--
2.5.5