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kerneldump: Inline dump_savectx() into its callers

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The callers of dump_savectx() (i.e., doadump() and livedump_start())
subsequently call dumpsys()/minidumpsys(), which dump the calling
thread's stack when writing the dump.  If dump_savectx() gets its own
stack frame, that frame might be clobbered when its caller later calls
dumpsys()/minidumpsys(), making it difficult for debuggers to unwind the
stack.

Fix this by making dump_savectx() a macro, so that savectx() is always
called directly by the function which subsequently calls
dumpsys()/minidumpsys().

This fixes stack unwinding for the panicking thread from arm64
minidumps.  The same happened to work on amd64, but kgdb reports the
dump_savectx() calls as coming from dumpsys(), so in that case it
appears to work by accident.

Fixes:	c9114f9f86 ("Add new vnode dumper to support live minidumps")
Reviewed by:	mhorne, jhb
MFC after:	3 days
Differential Revision:	https://reviews.freebsd.org/D39151
This commit is contained in:
Mark Johnston 2023-03-20 14:16:00 -04:00
parent 3ce64010f8
commit c3179891f8
3 changed files with 18 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
sys/kern/kern_shutdown.c
View File

@ -244,8 +244,8 @@ MTX_SYSINIT(dumper_configs, &dumpconf_list_lk, "dumper config list", MTX_DEF);
static TAILQ_HEAD(dumpconflist, dumperinfo) dumper_configs =
TAILQ_HEAD_INITIALIZER(dumper_configs);
/* Context information for dump-debuggers. */
static struct pcb dumppcb; /* Registers. */
/* Context information for dump-debuggers, saved by the dump_savectx() macro. */
struct pcb dumppcb; /* Registers. */
lwpid_t dumptid; /* Thread ID. */
static struct cdevsw reroot_cdevsw = {
@ -392,17 +392,6 @@ print_uptime(void)
printf("%lds\n", (long)ts.tv_sec);
}
/*
* Set up a context that can be extracted from the dump.
*/
void
dump_savectx(void)
{
savectx(&dumppcb);
dumptid = curthread->td_tid;
}
int
doadump(boolean_t textdump)
{

1
sys/kern/kern_vnodedumper.c
View File

@ -44,6 +44,7 @@
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <machine/pcb.h>
#include <machine/vmparam.h>
static dumper_start_t vnode_dumper_start;

16
sys/sys/conf.h
View File

@ -360,7 +360,21 @@ struct dumperinfo {
extern int dumping; /* system is dumping */
void dump_savectx(void);
/*
* Save registers for later extraction from a kernel dump.
*
* This must be inlined into the caller, which in turn must be the function that
* calls (mini)dumpsys(). Otherwise, the saved frame pointer will reference a
* stack frame that may be clobbered by subsequent function calls.
*/
#define dump_savectx() do { \
extern struct pcb dumppcb; \
extern lwpid_t dumptid; \
\
savectx(&dumppcb); \
dumptid = curthread->td_tid; \
} while (0)
int doadump(boolean_t);
struct diocskerneldump_arg;
int dumper_create(const struct dumperinfo *di_template, const char *devname,