Modify stack(9) stack_print() and stack_sbuf_print() routines to use new
linker interfaces for looking up function names and offsets from instruction pointers. Create two variants of each call: one that is "DDB-safe" and avoids locking in the linker, and one that is safe for use in live kernels, by virtue of observing locking, and in particular safe when kernel modules are being loaded and unloaded simultaneous to their use. This will allow them to be used outside of debugging contexts. Modify two of three current stack(9) consumers to use the DDB-safe interfaces, as they run in low-level debugging contexts, such as inside lockmgr(9) and the kernel memory allocator. Update man page.
This commit is contained in:
parent
66e7bdd4dc
commit
9ccca7d1b1
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=174137
@ -1074,6 +1074,7 @@ MLINKS+=stack.9 stack_copy.9 \
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stack.9 stack_put.9 \
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stack.9 stack_save.9 \
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stack.9 stack_sbuf_print.9 \
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stack.9 stack_sbuf_print_ddb.9 \
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stack.9 stack_zero.9
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MLINKS+=store.9 subyte.9 \
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store.9 suswintr.9 \
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@ -54,6 +54,8 @@ In kernel configuration files:
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.Ft void
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.Fn stack_sbuf_print "struct sbuf sb*" "struct stack *st"
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.Ft void
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.Fn stack_sbuf_print_ddb "struct sbuf sb*" "struct stack *st"
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.Ft void
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.Fn stack_save "struct stack *st"
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.Sh DESCRIPTION
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The
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@ -96,7 +98,17 @@ as described in
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.Xr sbuf 9 .
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This function may sleep if an auto-extending
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.Dv struct sbuf
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is used.
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is used, and because the kernel linker (used to look up symbol names) uses
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.Xr sx 9
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locks.
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.Pp
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In locking-sensitive environments, such as
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.Xr DDB 4 ,
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the unsynchronized
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.Fn stack_sbuf_print_ddb
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variant may be invoked; this makes use of kernel linker data structures to
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look up symbol names without following locking protocols, so is appropriate
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for use in the debugger but not while the system is live.
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.Pp
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The utility functions
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.Nm stack_zero ,
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@ -107,7 +119,8 @@ may be used to manipulate stack data structures directly.
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.Sh SEE ALSO
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.Xr DDB 4 ,
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.Xr printf 9 ,
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.Xr sbuf 9
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.Xr sbuf 9 ,
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.Xr sx 9
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.Sh AUTHORS
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.An -nosplit
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The
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@ -625,7 +625,7 @@ lockmgr_printinfo(lkp)
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if (lkp->lk_waitcount > 0)
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printf(" with %d pending", lkp->lk_waitcount);
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#ifdef DEBUG_LOCKS
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stack_print(&lkp->lk_stack);
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stack_print_ddb(&lkp->lk_stack);
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#endif
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}
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@ -24,6 +24,8 @@
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* SUCH DAMAGE.
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*/
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#include "opt_ddb.h"
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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@ -40,7 +42,12 @@ __FBSDID("$FreeBSD$");
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MALLOC_DEFINE(M_STACK, "stack", "Stack Traces");
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static void stack_symbol(vm_offset_t pc, const char **name, long *offset);
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static void stack_symbol(vm_offset_t pc, char *namebuf, u_int buflen,
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long *offset);
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#ifdef DDB
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static void stack_symbol_ddb(vm_offset_t pc, char *namebuf, u_int buflen,
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long *offset);
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#endif
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struct stack *
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stack_create(void)
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@ -86,30 +93,67 @@ stack_zero(struct stack *st)
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void
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stack_print(struct stack *st)
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{
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const char *name;
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char namebuf[64];
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long offset;
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int i;
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KASSERT(st->depth <= STACK_MAX, ("bogus stack"));
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for (i = 0; i < st->depth; i++) {
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stack_symbol(st->pcs[i], &name, &offset);
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stack_symbol(st->pcs[i], namebuf, sizeof(namebuf), &offset);
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printf("#%d %p at %s+%#lx\n", i, (void *)st->pcs[i],
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name, offset);
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namebuf, offset);
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}
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}
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void
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stack_sbuf_print(struct sbuf *sb, struct stack *st)
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stack_print_ddb(struct stack *st)
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{
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const char *name;
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char namebuf[64];
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long offset;
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int i;
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KASSERT(st->depth <= STACK_MAX, ("bogus stack"));
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for (i = 0; i < st->depth; i++) {
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stack_symbol(st->pcs[i], &name, &offset);
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stack_symbol_ddb(st->pcs[i], namebuf, sizeof(namebuf),
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&offset);
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printf("#%d %p at %s+%#lx\n", i, (void *)st->pcs[i],
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namebuf, offset);
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}
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}
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/*
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* Two print routines -- one for use from DDB and DDB-like contexts, the
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* other for use in the live kernel.
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*/
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void
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stack_sbuf_print(struct sbuf *sb, struct stack *st)
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{
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char namebuf[64];
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long offset;
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int i;
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KASSERT(st->depth <= STACK_MAX, ("bogus stack"));
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for (i = 0; i < st->depth; i++) {
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stack_symbol(st->pcs[i], namebuf, sizeof(namebuf), &offset);
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sbuf_printf(sb, "#%d %p at %s+%#lx\n", i, (void *)st->pcs[i],
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name, offset);
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namebuf, offset);
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}
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}
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#ifdef DDB
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void
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stack_sbuf_print_ddb(struct sbuf *sb, struct stack *st)
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{
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char namebuf[64];
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long offset;
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int i;
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KASSERT(st->depth <= STACK_MAX, ("bogus stack"));
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for (i = 0; i < st->depth; i++) {
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stack_symbol_ddb(st->pcs[i], namebuf, sizeof(namebuf),
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&offset);
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sbuf_printf(sb, "#%d %p at %s+%#lx\n", i, (void *)st->pcs[i],
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namebuf, offset);
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}
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}
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@ -118,7 +162,7 @@ void
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stack_ktr(u_int mask, const char *file, int line, struct stack *st, u_int depth,
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int cheap)
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{
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const char *name;
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char namebuf[64];
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long offset;
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int i;
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@ -141,29 +185,40 @@ stack_ktr(u_int mask, const char *file, int line, struct stack *st, u_int depth,
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if (depth == 0 || st->depth < depth)
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depth = st->depth;
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for (i = 0; i < depth; i++) {
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stack_symbol(st->pcs[i], &name, &offset);
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stack_symbol_ddb(st->pcs[i], namebuf,
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sizeof(namebuf), &offset);
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ktr_tracepoint(mask, file, line, "#%d %p at %s+%#lx",
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i, st->pcs[i], (u_long)name, offset, 0, 0);
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i, st->pcs[i], (u_long)namebuf, offset, 0, 0);
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}
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}
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}
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#endif
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#endif
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/*
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* Two variants of stack symbol lookup -- one that uses the DDB interfaces
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* and bypasses linker locking, and the other that doesn't.
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*/
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static void
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stack_symbol(vm_offset_t pc, const char **name, long *offset)
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stack_symbol(vm_offset_t pc, char *namebuf, u_int buflen, long *offset)
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{
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linker_symval_t symval;
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c_linker_sym_t sym;
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if (linker_ddb_search_symbol((caddr_t)pc, &sym, offset) != 0)
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goto out;
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if (linker_ddb_symbol_values(sym, &symval) != 0)
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goto out;
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if (symval.name != NULL) {
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*name = symval.name;
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return;
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if (linker_search_symbol_name((caddr_t)pc, namebuf, buflen,
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offset) != 0) {
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*offset = 0;
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strlcpy(namebuf, "Unknown func", buflen);
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}
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out:
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*offset = 0;
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*name = "Unknown func";
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}
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#ifdef DDB
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static void
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stack_symbol_ddb(vm_offset_t pc, char *namebuf, u_int buflen, long *offset)
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{
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if (linker_ddb_search_symbol_name((caddr_t)pc, namebuf, buflen,
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offset) != 0) {
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*offset = 0;
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strlcpy(namebuf, "Unknown func", buflen);
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};
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}
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#endif
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void stack_copy(struct stack *, struct stack *);
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void stack_zero(struct stack *);
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void stack_print(struct stack *);
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void stack_print_ddb(struct stack *);
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void stack_sbuf_print(struct sbuf *, struct stack *);
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void stack_sbuf_print_ddb(struct sbuf *, struct stack *);
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#ifdef KTR
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void stack_ktr(u_int, const char *, int, struct stack *, u_int, int);
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#define CTRSTACK(m, st, depth, cheap) do { \
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"corrupted before %p (%lu bytes allocated).\n",
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ncorruptions, ncorruptions == 1 ? "" : "s", naddr, nsize);
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printf("Allocation backtrace:\n");
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stack_print(&ast);
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stack_print_ddb(&ast);
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printf("Free backtrace:\n");
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stack_save(&fst);
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stack_print(&fst);
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stack_print_ddb(&fst);
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if (redzone_panic)
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panic("Stopping here.");
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}
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@ -171,10 +171,10 @@ redzone_check(caddr_t naddr)
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"after %p (%lu bytes allocated).\n", ncorruptions,
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ncorruptions == 1 ? "" : "s", naddr + nsize, nsize);
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printf("Allocation backtrace:\n");
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stack_print(&ast);
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stack_print_ddb(&ast);
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printf("Free backtrace:\n");
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stack_save(&fst);
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stack_print(&fst);
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stack_print_ddb(&fst);
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if (redzone_panic)
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panic("Stopping here.");
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}
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