Date: Tue, 12 Nov 2019 15:56:27 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r354647 - in head/sys/i386: i386 include Message-ID: <201911121556.xACFuR79010070@repo.freebsd.org>
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Author: kib Date: Tue Nov 12 15:56:27 2019 New Revision: 354647 URL: https://svnweb.freebsd.org/changeset/base/354647 Log: i386: stop guessing the address of the trap frame in ddb backtrace. Save the address of the trap frame in %ebp on kernel entry. This automatically provides it in struct i386_frame.f_frame to unwinder. While there, more accurately handle the terminating frames, Reviewed by: avg, markj Sponsored by: The FreeBSD Foundation MFC after: 1 week Differential revision: https://reviews.freebsd.org/D22321 Modified: head/sys/i386/i386/db_trace.c head/sys/i386/include/asmacros.h Modified: head/sys/i386/i386/db_trace.c ============================================================================== --- head/sys/i386/i386/db_trace.c Tue Nov 12 15:51:47 2019 (r354646) +++ head/sys/i386/i386/db_trace.c Tue Nov 12 15:56:27 2019 (r354647) @@ -297,7 +297,6 @@ db_nextframe(struct i386_frame **fp, db_addr_t *ip, st { struct trapframe *tf; int frame_type; - int narg; int eip, esp, ebp; db_expr_t offset; c_db_sym_t sym; @@ -317,14 +316,6 @@ db_nextframe(struct i386_frame **fp, db_addr_t *ip, st */ frame_type = NORMAL; - /* - * This is the number of arguments that a syscall / trap / interrupt - * service routine passes to its callee. This number is used only for - * special frame types. In most cases there is one argument: the trap - * frame address. - */ - narg = 1; - if (eip >= PMAP_TRM_MIN_ADDRESS) { sym = db_search_symbol(eip - 1 - setidt_disp, DB_STGY_ANY, &offset); @@ -338,8 +329,6 @@ db_nextframe(struct i386_frame **fp, db_addr_t *ip, st frame_type = TRAP; else if (strncmp(name, "Xatpic_intr", 11) == 0 || strncmp(name, "Xapic_isr", 9) == 0) { - /* Additional argument: vector number. */ - narg = 2; frame_type = INTERRUPT; } else if (strcmp(name, "Xlcall_syscall") == 0 || strcmp(name, "Xint0x80_syscall") == 0) @@ -353,7 +342,6 @@ db_nextframe(struct i386_frame **fp, db_addr_t *ip, st strcmp(name, "Xrendezvous") == 0 || strcmp(name, "Xipi_intr_bitmap_handler") == 0) { /* No arguments. */ - narg = 0; frame_type = INTERRUPT; } } @@ -387,13 +375,23 @@ db_nextframe(struct i386_frame **fp, db_addr_t *ip, st } /* - * Point to base of trapframe which is just above the - * current frame. Note that struct i386_frame already accounts for one - * argument. + * Point to base of trapframe which is just above the current + * frame. Pointer to it was put into %ebp by the kernel entry + * code. */ - tf = (struct trapframe *)((char *)*fp + sizeof(struct i386_frame) + - 4 * (narg - 1)); + tf = (struct trapframe *)(*fp)->f_frame; + /* + * This can be the case for e.g. fork_trampoline, last frame + * of a kernel thread stack. + */ + if (tf == NULL) { + *ip = 0; + *fp = 0; + db_printf("--- kthread start\n"); + return; + } + esp = get_esp(tf); eip = tf->tf_eip; ebp = tf->tf_ebp; @@ -413,15 +411,20 @@ db_nextframe(struct i386_frame **fp, db_addr_t *ip, st } db_printf(", eip = %#r, esp = %#r, ebp = %#r ---\n", eip, esp, ebp); + /* + * Detect the last (trap) frame on the kernel stack, where we + * entered kernel from usermode. Terminate tracing in this + * case. + */ switch (frame_type) { case TRAP: case INTERRUPT: - if ((tf->tf_eflags & PSL_VM) != 0 || - (tf->tf_cs & SEL_RPL_MASK) != 0) - ebp = 0; - break; + if (!TRAPF_USERMODE(tf)) + break; + /* FALLTHROUGH */ case SYSCALL: ebp = 0; + eip = 0; break; } @@ -575,9 +578,12 @@ out: * after printing the pc if it is the kernel. */ if (frame == NULL || frame <= actframe) { - sym = db_search_symbol(pc, DB_STGY_ANY, &offset); - db_symbol_values(sym, &name, NULL); - db_print_stack_entry(name, 0, 0, 0, pc, frame); + if (pc != 0) { + sym = db_search_symbol(pc, DB_STGY_ANY, + &offset); + db_symbol_values(sym, &name, NULL); + db_print_stack_entry(name, 0, 0, 0, pc, frame); + } break; } } Modified: head/sys/i386/include/asmacros.h ============================================================================== --- head/sys/i386/include/asmacros.h Tue Nov 12 15:51:47 2019 (r354646) +++ head/sys/i386/include/asmacros.h Tue Nov 12 15:56:27 2019 (r354647) @@ -157,6 +157,7 @@ movw %es,(%esp) pushl $0 movw %fs,(%esp) + movl %esp,%ebp .endm .macro PUSH_FRAME
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