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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: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Josh 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Josh Poimboeuf 2018-05-18 08:47:12 +02:00 committed by Ingo Molnar
parent 0c414367c0
commit d31a580266
9 changed files with 52 additions and 29 deletions
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1
arch/x86/entry/entry_64.S
View File

@ -408,6 +408,7 @@ ENTRY(ret_from_fork)
1:
/* kernel thread */
UNWIND_HINT_EMPTY
movq %r12, %rdi
CALL_NOSPEC %rbx
/*

2
arch/x86/include/asm/orc_types.h
View File

@ -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__ */

16
arch/x86/include/asm/unwind_hints.h
View File

@ -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
@ -86,19 +88,21 @@
#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 */ \
".long 987b - .\n\t" \
".short " __stringify(sp_offset) "\n\t" \
".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__ */

52
arch/x86/kernel/unwind_orc.c
View File

@ -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;

2
tools/objtool/arch/x86/include/asm/orc_types.h
View File

@ -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__ */

1
tools/objtool/check.c
View File

@ -1156,6 +1156,7 @@ static int read_unwind_hints(struct objtool_file *file)
cfa->offset = hint->sp_offset;
insn->state.type = hint->type;
insn->state.end = hint->end;
}
return 0;

2
tools/objtool/check.h
View File

@ -31,7 +31,7 @@ struct insn_state {
int stack_size;
unsigned char type;
bool bp_scratch;
bool drap;
bool drap, end;
int drap_reg, drap_offset;
struct cfi_reg vals[CFI_NUM_REGS];
};

3
tools/objtool/orc_dump.c
View File

@ -203,7 +203,8 @@ int orc_dump(const char *_objname)
print_reg(orc[i].bp_reg, orc[i].bp_offset);
printf(" type:%s\n", orc_type_name(orc[i].type));
printf(" type:%s end:%d\n",
orc_type_name(orc[i].type), orc[i].end);
}
elf_end(elf);

2
tools/objtool/orc_gen.c
View File

@ -31,6 +31,8 @@ int create_orc(struct objtool_file *file)
struct cfi_reg *cfa = &insn->state.cfa;
struct cfi_reg *bp = &insn->state.regs[CFI_BP];
orc->end = insn->state.end;
if (cfa->base == CFI_UNDEFINED) {
orc->sp_reg = ORC_REG_UNDEFINED;
continue;