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Improve stack unwinding on i386 and amd64 after an IP fault.

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If we can't find a symbol corresponding to the faulting instruction, assume
that the previously-executed function is a call and attempt to find the
calling function using the return address on the stack. Otherwise we end
up associating the last stack frame with the current call, which is
incorrect and causes the unwinder to skip printing of the calling function,
resulting in a confusing backtrace.

Reviewed by:	jhb
Sponsored by:	EMC / Isilon Storage Division
Differential Revision:	https://reviews.freebsd.org/D2859
This commit is contained in:
Mark Johnston 2015-07-21 23:13:11 +00:00
parent e31a60b486
commit f8a757d016
2 changed files with 37 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
sys/amd64/amd64/db_trace.c
View File

@ -200,7 +200,7 @@ static void
db_print_stack_entry(const char *name, db_addr_t callpc, void *frame)
{
db_printf("%s() at ", name);
db_printf("%s() at ", name != NULL ? name : "??");
db_printsym(callpc, DB_STGY_PROC);
if (frame != NULL)
db_printf("/frame 0x%lx", (register_t)frame);
@ -331,8 +331,8 @@ db_nextframe(struct amd64_frame **fp, db_addr_t *ip, struct thread *td)
}
static int
db_backtrace(struct thread *td, struct trapframe *tf,
struct amd64_frame *frame, db_addr_t pc, int count)
db_backtrace(struct thread *td, struct trapframe *tf, struct amd64_frame *frame,
db_addr_t pc, register_t sp, int count)
{
struct amd64_frame *actframe;
const char *name;
@ -361,7 +361,20 @@ db_backtrace(struct thread *td, struct trapframe *tf,
*/
actframe = frame;
if (first) {
if (tf != NULL) {
first = FALSE;
if (sym == C_DB_SYM_NULL && sp != 0) {
/*
* If a symbol couldn't be found, we've probably
* jumped to a bogus location, so try and use
* the return address to find our caller.
*/
db_print_stack_entry(name, pc, NULL);
pc = db_get_value(sp, 8, FALSE);
if (db_search_symbol(pc, DB_STGY_PROC,
&offset) == C_DB_SYM_NULL)
break;
continue;
} else if (tf != NULL) {
int instr;
instr = db_get_value(pc, 4, FALSE);
@ -390,7 +403,6 @@ db_backtrace(struct thread *td, struct trapframe *tf,
db_print_stack_entry(name, pc, actframe);
break;
}
first = FALSE;
}
db_print_stack_entry(name, pc, actframe);
@ -429,7 +441,7 @@ db_trace_self(void)
frame = (struct amd64_frame *)rbp;
callpc = (db_addr_t)db_get_value((long)&frame->f_retaddr, 8, FALSE);
frame = frame->f_frame;
db_backtrace(curthread, NULL, frame, callpc, -1);
db_backtrace(curthread, NULL, frame, callpc, 0, -1);
}
int
@ -439,7 +451,7 @@ db_trace_thread(struct thread *thr, int count)
ctx = kdb_thr_ctx(thr);
return (db_backtrace(thr, NULL, (struct amd64_frame *)ctx->pcb_rbp,
ctx->pcb_rip, count));
ctx->pcb_rip, ctx->pcb_rsp, count));
}
int

23
sys/i386/i386/db_trace.c
View File

@ -389,7 +389,7 @@ db_nextframe(struct i386_frame **fp, db_addr_t *ip, struct thread *td)
static int
db_backtrace(struct thread *td, struct trapframe *tf, struct i386_frame *frame,
db_addr_t pc, int count)
db_addr_t pc, register_t sp, int count)
{
struct i386_frame *actframe;
#define MAXNARG 16
@ -446,7 +446,21 @@ db_backtrace(struct thread *td, struct trapframe *tf, struct i386_frame *frame,
*/
actframe = frame;
if (first) {
if (tf != NULL) {
first = FALSE;
if (sym == C_DB_SYM_NULL && sp != 0) {
/*
* If a symbol couldn't be found, we've probably
* jumped to a bogus location, so try and use
* the return address to find our caller.
*/
db_print_stack_entry(name, 0, 0, 0, pc,
NULL);
pc = db_get_value(sp, 4, FALSE);
if (db_search_symbol(pc, DB_STGY_PROC,
&offset) == C_DB_SYM_NULL)
break;
continue;
} else if (tf != NULL) {
instr = db_get_value(pc, 4, FALSE);
if ((instr & 0xffffff) == 0x00e58955) {
/* pushl %ebp; movl %esp, %ebp */
@ -474,7 +488,6 @@ db_backtrace(struct thread *td, struct trapframe *tf, struct i386_frame *frame,
actframe);
break;
}
first = FALSE;
}
argp = &actframe->f_arg0;
@ -521,7 +534,7 @@ db_trace_self(void)
frame = (struct i386_frame *)ebp;
callpc = (db_addr_t)db_get_value((int)&frame->f_retaddr, 4, FALSE);
frame = frame->f_frame;
db_backtrace(curthread, NULL, frame, callpc, -1);
db_backtrace(curthread, NULL, frame, callpc, 0, -1);
}
int
@ -531,7 +544,7 @@ db_trace_thread(struct thread *thr, int count)
ctx = kdb_thr_ctx(thr);
return (db_backtrace(thr, NULL, (struct i386_frame *)ctx->pcb_ebp,
ctx->pcb_eip, count));
ctx->pcb_eip, ctx->pcb_esp, count));
}
int