Messages in this thread Patch in this message | | | Date | Fri, 11 May 2018 10:12:52 -0500 | From | Josh Poimboeuf <> | Subject | Re: [PATCH 1/2] x86/stacktrace: do not fail when regs on stack for ORC |
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On Fri, May 11, 2018 at 09:01:30AM +0200, Jiri Slaby wrote: > On 05/10/2018, 02:49 PM, Josh Poimboeuf wrote: > > On Thu, May 10, 2018 at 02:33:03PM +0200, Jiri Slaby wrote: > >> On 04/19/2018, 03:42 PM, Josh Poimboeuf wrote: > >>> On Mon, Apr 16, 2018 at 05:16:53PM -0500, Josh Poimboeuf wrote: > >>>> On Wed, Dec 20, 2017 at 08:07:17PM +0100, Jiri Slaby wrote: > >>>>> On 12/20/2017, 06:45 PM, Josh Poimboeuf wrote: > >>>>>> It might not be until 2018 though. But in the meantime you can go ahead > >>>>>> and update your patches accordingly and then we can combine them for > >>>>>> testing next year. > >>>>> > >>>>> I already did ;). So when you have that ready, I will send it on top > >>>>> right after. > >>>> > >>>> Sorry for the delay... Here's a (lightly tested) patch. Can you test > >>>> it with the latest version of your patches? > >>> > >>> This one actually compiles: > >>> > >>> From: Josh Poimboeuf <jpoimboe@redhat.com> > >>> Subject: [PATCH] x86/unwind/orc: Detect the end of the stack > >> > >> With this patch applied, livepatching never completes. Kthreads are in > >> the unpatched state forever. I have no details yet. > > > > Hm, I thought I had tested that, but now I'm not sure. Let me try it > > again. > > We need to propagate end from hints to orcs. This works for me™:
Ah, right, I forgot to connect the dots. Here's an updated patch with a few more tweaks. Can you test? I assume you're going to carry this as part of your patches to enable HAVE_RELIABLE_STACKTRACE?
From: Josh Poimboeuf <jpoimboe@redhat.com> Subject: [PATCH] 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.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> --- arch/x86/entry/entry_64.S | 1 + arch/x86/include/asm/orc_types.h | 2 + arch/x86/include/asm/unwind_hints.h | 16 +++--- arch/x86/kernel/unwind_orc.c | 52 +++++++++++-------- .../objtool/arch/x86/include/asm/orc_types.h | 2 + tools/objtool/check.c | 1 + tools/objtool/check.h | 2 +- tools/objtool/orc_dump.c | 3 +- tools/objtool/orc_gen.c | 1 + 9 files changed, 51 insertions(+), 29 deletions(-)
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index ab4f451aeb97..e35dbc507425 100644 --- 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 9c9dc579bd7d..46f516dd80ce 100644 --- 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 bae46fc6b9de..0bcdb1279361 100644 --- 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 feb28fee6cea..26038eacf74a 100644 --- 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 9c9dc579bd7d..46f516dd80ce 100644 --- 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 5409f6f6c48d..fef15cea9f1e 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -1109,6 +1109,7 @@ 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 c6b68fcb926f..95700a2bcb7c 100644 --- 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 c3343820916a..faa444270ee3 100644 --- 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 18384d9be4e1..229c12e3fcf6 100644 --- a/tools/objtool/orc_gen.c +++ b/tools/objtool/orc_gen.c @@ -86,6 +86,7 @@ int create_orc(struct objtool_file *file) orc->sp_offset = cfa->offset; orc->bp_offset = bp->offset; orc->type = insn->state.type; + orc->end = insn->state.end; } return 0; -- 2.17.0
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