Commit d31a5802 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
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x86/unwind/orc: Detect the end of the stack 



The existing UNWIND_HINT_EMPTY annotations happen to be good indicators
of where entry code calls into C code for the first time.  So also use
them to mark the end of the stack for the ORC unwinder.

Use that information to set unwind->error if the ORC unwinder doesn't
unwind all the way to the end.  This will be needed for enabling
HAVE_RELIABLE_STACKTRACE for the ORC unwinder so we can use it with the
livepatch consistency model.

Thanks to Jiri Slaby for teaching the ORCs about the unwind hints.

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarJiri Slaby <jslaby@suse.cz>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/lkml/20180518064713.26440-5-jslaby@suse.cz


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 0c414367

arch/x86/entry/entry_64.S

+1 −0
Original line number Diff line number Diff line
@@ -408,6 +408,7 @@ ENTRY(ret_from_fork) 


1:

	/* kernel thread */

	UNWIND_HINT_EMPTY

	movq	%r12, %rdi

	CALL_NOSPEC %rbx

	/*

arch/x86/include/asm/orc_types.h

+2 −0
Original line number Diff line number Diff line
@@ -88,6 +88,7 @@ struct orc_entry { 
	unsigned	sp_reg:4;

	unsigned	bp_reg:4;

	unsigned	type:2;

	unsigned	end:1;

} __packed;



/*
@@ -101,6 +102,7 @@ struct unwind_hint { 
	s16		sp_offset;

	u8		sp_reg;

	u8		type;

	u8		end;

};

#endif /* __ASSEMBLY__ */

arch/x86/include/asm/unwind_hints.h

+10 −6
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ 
 * the debuginfo as necessary.  It will also warn if it sees any

 * inconsistencies.

 */

.macro UNWIND_HINT sp_reg=ORC_REG_SP sp_offset=0 type=ORC_TYPE_CALL

.macro UNWIND_HINT sp_reg=ORC_REG_SP sp_offset=0 type=ORC_TYPE_CALL end=0

#ifdef CONFIG_STACK_VALIDATION

.Lunwind_hint_ip_\@:

	.pushsection .discard.unwind_hints
@@ -35,12 +35,14 @@ 
		.short \sp_offset

		.byte \sp_reg

		.byte \type

		.byte \end

		.balign 4

	.popsection

#endif

.endm



.macro UNWIND_HINT_EMPTY

	UNWIND_HINT sp_reg=ORC_REG_UNDEFINED

	UNWIND_HINT sp_reg=ORC_REG_UNDEFINED end=1

.endm



.macro UNWIND_HINT_REGS base=%rsp offset=0 indirect=0 extra=1 iret=0
@@ -86,7 +88,7 @@ 


#else /* !__ASSEMBLY__ */



#define UNWIND_HINT(sp_reg, sp_offset, type)			\

#define UNWIND_HINT(sp_reg, sp_offset, type, end)		\

	"987: \n\t"						\

	".pushsection .discard.unwind_hints\n\t"		\

	/* struct unwind_hint */				\
@@ -94,11 +96,13 @@ 
	".short " __stringify(sp_offset) "\n\t"			\

	".byte " __stringify(sp_reg) "\n\t"			\

	".byte " __stringify(type) "\n\t"			\

	".byte " __stringify(end) "\n\t"			\

	".balign 4 \n\t"					\

	".popsection\n\t"



#define UNWIND_HINT_SAVE UNWIND_HINT(0, 0, UNWIND_HINT_TYPE_SAVE)

#define UNWIND_HINT_SAVE UNWIND_HINT(0, 0, UNWIND_HINT_TYPE_SAVE, 0)



#define UNWIND_HINT_RESTORE UNWIND_HINT(0, 0, UNWIND_HINT_TYPE_RESTORE)

#define UNWIND_HINT_RESTORE UNWIND_HINT(0, 0, UNWIND_HINT_TYPE_RESTORE, 0)



#endif /* __ASSEMBLY__ */

arch/x86/kernel/unwind_orc.c

+31 −21
Original line number Diff line number Diff line
@@ -198,7 +198,7 @@ static int orc_sort_cmp(const void *_a, const void *_b) 
	 * whitelisted .o files which didn't get objtool generation.

	 */

	orc_a = cur_orc_table + (a - cur_orc_ip_table);

	return orc_a->sp_reg == ORC_REG_UNDEFINED ? -1 : 1;

	return orc_a->sp_reg == ORC_REG_UNDEFINED && !orc_a->end ? -1 : 1;

}



#ifdef CONFIG_MODULES
@@ -352,7 +352,7 @@ static bool deref_stack_iret_regs(struct unwind_state *state, unsigned long addr 


bool unwind_next_frame(struct unwind_state *state)

{

	unsigned long ip_p, sp, orig_ip, prev_sp = state->sp;

	unsigned long ip_p, sp, orig_ip = state->ip, prev_sp = state->sp;

	enum stack_type prev_type = state->stack_info.type;

	struct orc_entry *orc;

	bool indirect = false;
@@ -363,9 +363,9 @@ bool unwind_next_frame(struct unwind_state *state) 
	/* Don't let modules unload while we're reading their ORC data. */

	preempt_disable();



	/* Have we reached the end? */

	/* End-of-stack check for user tasks: */

	if (state->regs && user_mode(state->regs))

		goto done;

		goto the_end;



	/*

	 * Find the orc_entry associated with the text address.
@@ -374,9 +374,16 @@ bool unwind_next_frame(struct unwind_state *state) 
	 * calls and calls to noreturn functions.

	 */

	orc = orc_find(state->signal ? state->ip : state->ip - 1);

	if (!orc || orc->sp_reg == ORC_REG_UNDEFINED)

		goto done;

	orig_ip = state->ip;

	if (!orc)

		goto err;



	/* End-of-stack check for kernel threads: */

	if (orc->sp_reg == ORC_REG_UNDEFINED) {

		if (!orc->end)

			goto err;



		goto the_end;

	}



	/* Find the previous frame's stack: */

	switch (orc->sp_reg) {
@@ -402,7 +409,7 @@ bool unwind_next_frame(struct unwind_state *state) 
		if (!state->regs || !state->full_regs) {

			orc_warn("missing regs for base reg R10 at ip %pB\n",

				 (void *)state->ip);

			goto done;

			goto err;

		}

		sp = state->regs->r10;

		break;
@@ -411,7 +418,7 @@ bool unwind_next_frame(struct unwind_state *state) 
		if (!state->regs || !state->full_regs) {

			orc_warn("missing regs for base reg R13 at ip %pB\n",

				 (void *)state->ip);

			goto done;

			goto err;

		}

		sp = state->regs->r13;

		break;
@@ -420,7 +427,7 @@ bool unwind_next_frame(struct unwind_state *state) 
		if (!state->regs || !state->full_regs) {

			orc_warn("missing regs for base reg DI at ip %pB\n",

				 (void *)state->ip);

			goto done;

			goto err;

		}

		sp = state->regs->di;

		break;
@@ -429,7 +436,7 @@ bool unwind_next_frame(struct unwind_state *state) 
		if (!state->regs || !state->full_regs) {

			orc_warn("missing regs for base reg DX at ip %pB\n",

				 (void *)state->ip);

			goto done;

			goto err;

		}

		sp = state->regs->dx;

		break;
@@ -437,12 +444,12 @@ bool unwind_next_frame(struct unwind_state *state) 
	default:

		orc_warn("unknown SP base reg %d for ip %pB\n",

			 orc->sp_reg, (void *)state->ip);

		goto done;

		goto err;

	}



	if (indirect) {

		if (!deref_stack_reg(state, sp, &sp))

			goto done;

			goto err;

	}



	/* Find IP, SP and possibly regs: */
@@ -451,7 +458,7 @@ bool unwind_next_frame(struct unwind_state *state) 
		ip_p = sp - sizeof(long);



		if (!deref_stack_reg(state, ip_p, &state->ip))

			goto done;

			goto err;



		state->ip = ftrace_graph_ret_addr(state->task, &state->graph_idx,

						  state->ip, (void *)ip_p);
@@ -465,7 +472,7 @@ bool unwind_next_frame(struct unwind_state *state) 
		if (!deref_stack_regs(state, sp, &state->ip, &state->sp)) {

			orc_warn("can't dereference registers at %p for ip %pB\n",

				 (void *)sp, (void *)orig_ip);

			goto done;

			goto err;

		}



		state->regs = (struct pt_regs *)sp;
@@ -477,7 +484,7 @@ bool unwind_next_frame(struct unwind_state *state) 
		if (!deref_stack_iret_regs(state, sp, &state->ip, &state->sp)) {

			orc_warn("can't dereference iret registers at %p for ip %pB\n",

				 (void *)sp, (void *)orig_ip);

			goto done;

			goto err;

		}



		state->regs = (void *)sp - IRET_FRAME_OFFSET;
@@ -500,18 +507,18 @@ bool unwind_next_frame(struct unwind_state *state) 


	case ORC_REG_PREV_SP:

		if (!deref_stack_reg(state, sp + orc->bp_offset, &state->bp))

			goto done;

			goto err;

		break;



	case ORC_REG_BP:

		if (!deref_stack_reg(state, state->bp + orc->bp_offset, &state->bp))

			goto done;

			goto err;

		break;



	default:

		orc_warn("unknown BP base reg %d for ip %pB\n",

			 orc->bp_reg, (void *)orig_ip);

		goto done;

		goto err;

	}



	/* Prevent a recursive loop due to bad ORC data: */
@@ -520,13 +527,16 @@ bool unwind_next_frame(struct unwind_state *state) 
	    state->sp <= prev_sp) {

		orc_warn("stack going in the wrong direction? ip=%pB\n",

			 (void *)orig_ip);

		goto done;

		goto err;

	}



	preempt_enable();

	return true;



done:

err:

	state->error = true;



the_end:

	preempt_enable();

	state->stack_info.type = STACK_TYPE_UNKNOWN;

	return false;

tools/objtool/arch/x86/include/asm/orc_types.h

+2 −0
Original line number Diff line number Diff line
@@ -88,6 +88,7 @@ struct orc_entry { 
	unsigned	sp_reg:4;

	unsigned	bp_reg:4;

	unsigned	type:2;

	unsigned	end:1;

} __packed;



/*
@@ -101,6 +102,7 @@ struct unwind_hint { 
	s16		sp_offset;

	u8		sp_reg;

	u8		type;

	u8		end;

};

#endif /* __ASSEMBLY__ */

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