Date: Tue, 21 Jul 2015 23:13:12 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r285775 - in head/sys: amd64/amd64 i386/i386 Message-ID: <201507212313.t6LNDCpr006757@repo.freebsd.org>
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Author: markj Date: Tue Jul 21 23:13:11 2015 New Revision: 285775 URL: https://svnweb.freebsd.org/changeset/base/285775 Log: Improve stack unwinding on i386 and amd64 after an IP fault. 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 Modified: head/sys/amd64/amd64/db_trace.c head/sys/i386/i386/db_trace.c Modified: head/sys/amd64/amd64/db_trace.c ============================================================================== --- head/sys/amd64/amd64/db_trace.c Tue Jul 21 23:07:55 2015 (r285774) +++ head/sys/amd64/amd64/db_trace.c Tue Jul 21 23:13:11 2015 (r285775) @@ -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 } 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 t */ 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 t 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 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 Modified: head/sys/i386/i386/db_trace.c ============================================================================== --- head/sys/i386/i386/db_trace.c Tue Jul 21 23:07:55 2015 (r285774) +++ head/sys/i386/i386/db_trace.c Tue Jul 21 23:13:11 2015 (r285775) @@ -389,7 +389,7 @@ db_nextframe(struct i386_frame **fp, db_ 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 t */ 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 t 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 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
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