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>

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 73a522d53b5376b7eaa17cb3d0a7e7be317b02d1..c6f3677e6105b03b77e47265da41ccb6451cc6aa 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -408,6 +408,7 @@ ENTRY(ret_from_fork)
 
 1:
        /* kernel thread */
+       UNWIND_HINT_EMPTY
        movq    %r12, %rdi
        CALL_NOSPEC %rbx
        /*

diff --git a/arch/x86/include/asm/orc_types.h b/arch/x86/include/asm/orc_types.h
index 9c9dc579bd7db172287f5fdea9628cabaeff56af..46f516dd80ce9fbe0f01406b406ea9d582f6bbcc 100644 (file)
--- a/arch/x86/include/asm/orc_types.h
+++ b/arch/x86/include/asm/orc_types.h
@@ -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__ */
 

diff --git a/arch/x86/include/asm/unwind_hints.h b/arch/x86/include/asm/unwind_hints.h
index bae46fc6b9de3e97794f0576cae455ba15150cd7..0bcdb127936178cf1d53d0b9bfcf616f585dfc43 100644 (file)
--- a/arch/x86/include/asm/unwind_hints.h
+++ b/arch/x86/include/asm/unwind_hints.h
@@ -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__ */
 

diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index feb28fee6cea7f9fbad1a4b06ee9932ac8690d75..26038eacf74a7130d659f98e5e1348667d4d635e 100644 (file)
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -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;

diff --git a/tools/objtool/arch/x86/include/asm/orc_types.h b/tools/objtool/arch/x86/include/asm/orc_types.h
index 9c9dc579bd7db172287f5fdea9628cabaeff56af..46f516dd80ce9fbe0f01406b406ea9d582f6bbcc 100644 (file)
--- a/tools/objtool/arch/x86/include/asm/orc_types.h
+++ b/tools/objtool/arch/x86/include/asm/orc_types.h
@@ -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__ */
 

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 38047c6aa57576d170b3281eb0de0376894e9f41..8491beb1a636116af40b4b1c31ff5c0548552159 100644 (file)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -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;

diff --git a/tools/objtool/check.h b/tools/objtool/check.h
index c6b68fcb926ff76c6e44675ff636c16f3552a184..95700a2bcb7c1ee429c6b2e0270428a5bfb8b54a 100644 (file)
--- a/tools/objtool/check.h
+++ b/tools/objtool/check.h
@@ -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];
 };

diff --git a/tools/objtool/orc_dump.c b/tools/objtool/orc_dump.c
index c3343820916a6dccf0e49bf50cbfbc811b4525fd..faa444270ee3ab297933504b703e4628321087ae 100644 (file)
--- a/tools/objtool/orc_dump.c
+++ b/tools/objtool/orc_dump.c
@@ -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);

diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c
index 18384d9be4e170f5d15b5c8981d0a576e1fac87a..3f98dcfbc177b12147f491d9fd577916c02b2076 100644 (file)
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -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;