Messages in this thread | | | Date | Fri, 25 Jun 2021 13:05:39 +0200 | From | Marco Elver <> | Subject | Re: [PATCH v2 03/24] objtool: Handle __sanitize_cov*() tail calls |
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On Thu, Jun 24, 2021 at 11:41AM +0200, Peter Zijlstra wrote: > Turns out the compilers also generate tail calls to __sanitize_cov*(), > make sure to also patch those out in noinstr code. > > Fixes: 0f1441b44e82 ("objtool: Fix noinstr vs KCOV") > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Marco Elver <elver@google.com>
Thanks! More reason to not even try to do the same for other architectures, and the compiler needing the attribute...
> --- > tools/objtool/arch/x86/decode.c | 20 ++++ > tools/objtool/check.c | 153 ++++++++++++++++++----------------- > tools/objtool/include/objtool/arch.h | 1 > 3 files changed, 100 insertions(+), 74 deletions(-) > > --- a/tools/objtool/arch/x86/decode.c > +++ b/tools/objtool/arch/x86/decode.c > @@ -659,6 +659,26 @@ const char *arch_nop_insn(int len) > return nops[len-1]; > } > > +#define BYTE_RET 0xC3 > + > +const char *arch_ret_insn(int len) > +{ > + static const char ret[5][5] = { > + { BYTE_RET }, > + { BYTE_RET, BYTES_NOP1 }, > + { BYTE_RET, BYTES_NOP2 }, > + { BYTE_RET, BYTES_NOP3 }, > + { BYTE_RET, BYTES_NOP4 }, > + }; > + > + if (len < 1 || len > 5) { > + WARN("invalid RET size: %d\n", len); > + return NULL; > + } > + > + return ret[len-1]; > +} > + > /* asm/alternative.h ? */ > > #define ALTINSTR_FLAG_INV (1 << 15) > --- a/tools/objtool/check.c > +++ b/tools/objtool/check.c > @@ -828,6 +828,74 @@ static struct reloc *insn_reloc(struct o > return insn->reloc; > } > > +static void remove_insn_ops(struct instruction *insn) > +{ > + struct stack_op *op, *tmp; > + > + list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) { > + list_del(&op->list); > + free(op); > + } > +} > + > +static void add_call_dest(struct objtool_file *file, struct instruction *insn, > + struct symbol *dest, bool sibling) > +{ > + struct reloc *reloc = insn_reloc(file, insn); > + > + insn->call_dest = dest; > + if (!dest) > + return; > + > + if (insn->call_dest->static_call_tramp) { > + list_add_tail(&insn->call_node, > + &file->static_call_list); > + } > + > + if (insn->sec->noinstr && > + !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) { > + if (reloc) { > + reloc->type = R_NONE; > + elf_write_reloc(file->elf, reloc); > + } > + > + elf_write_insn(file->elf, insn->sec, > + insn->offset, insn->len, > + sibling ? arch_ret_insn(insn->len) > + : arch_nop_insn(insn->len)); > + > + insn->type = sibling ? INSN_RETURN : INSN_NOP; > + } > + > + if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) { > + if (sibling) > + WARN_FUNC("Tail call to __fentry__ !?!?", insn->sec, insn->offset); > + > + if (reloc) { > + reloc->type = R_NONE; > + elf_write_reloc(file->elf, reloc); > + } > + > + elf_write_insn(file->elf, insn->sec, > + insn->offset, insn->len, > + arch_nop_insn(insn->len)); > + > + insn->type = INSN_NOP; > + > + list_add_tail(&insn->mcount_loc_node, > + &file->mcount_loc_list); > + } > + > + /* > + * Whatever stack impact regular CALLs have, should be undone > + * by the RETURN of the called function. > + * > + * Annotated intra-function calls retain the stack_ops but > + * are converted to JUMP, see read_intra_function_calls(). > + */ > + remove_insn_ops(insn); > +} > + > /* > * Find the destination instructions for all jumps. > */ > @@ -866,11 +934,7 @@ static int add_jump_destinations(struct > continue; > } else if (insn->func) { > /* internal or external sibling call (with reloc) */ > - insn->call_dest = reloc->sym; > - if (insn->call_dest->static_call_tramp) { > - list_add_tail(&insn->call_node, > - &file->static_call_list); > - } > + add_call_dest(file, insn, reloc->sym, true); > continue; > } else if (reloc->sym->sec->idx) { > dest_sec = reloc->sym->sec; > @@ -926,13 +990,8 @@ static int add_jump_destinations(struct > > } else if (insn->jump_dest->func->pfunc != insn->func->pfunc && > insn->jump_dest->offset == insn->jump_dest->func->offset) { > - > /* internal sibling call (without reloc) */ > - insn->call_dest = insn->jump_dest->func; > - if (insn->call_dest->static_call_tramp) { > - list_add_tail(&insn->call_node, > - &file->static_call_list); > - } > + add_call_dest(file, insn, insn->jump_dest->func, true); > } > } > } > @@ -940,16 +999,6 @@ static int add_jump_destinations(struct > return 0; > } > > -static void remove_insn_ops(struct instruction *insn) > -{ > - struct stack_op *op, *tmp; > - > - list_for_each_entry_safe(op, tmp, &insn->stack_ops, list) { > - list_del(&op->list); > - free(op); > - } > -} > - > static struct symbol *find_call_destination(struct section *sec, unsigned long offset) > { > struct symbol *call_dest; > @@ -968,6 +1017,7 @@ static int add_call_destinations(struct > { > struct instruction *insn; > unsigned long dest_off; > + struct symbol *dest; > struct reloc *reloc; > > for_each_insn(file, insn) { > @@ -977,7 +1027,9 @@ static int add_call_destinations(struct > reloc = insn_reloc(file, insn); > if (!reloc) { > dest_off = arch_jump_destination(insn); > - insn->call_dest = find_call_destination(insn->sec, dest_off); > + dest = find_call_destination(insn->sec, dest_off); > + > + add_call_dest(file, insn, dest, false); > > if (insn->ignore) > continue; > @@ -995,9 +1047,8 @@ static int add_call_destinations(struct > > } else if (reloc->sym->type == STT_SECTION) { > dest_off = arch_dest_reloc_offset(reloc->addend); > - insn->call_dest = find_call_destination(reloc->sym->sec, > - dest_off); > - if (!insn->call_dest) { > + dest = find_call_destination(reloc->sym->sec, dest_off); > + if (!dest) { > WARN_FUNC("can't find call dest symbol at %s+0x%lx", > insn->sec, insn->offset, > reloc->sym->sec->name, > @@ -1005,6 +1056,8 @@ static int add_call_destinations(struct > return -1; > } > > + add_call_dest(file, insn, dest, false); > + > } else if (arch_is_retpoline(reloc->sym)) { > /* > * Retpoline calls are really dynamic calls in > @@ -1020,55 +1073,7 @@ static int add_call_destinations(struct > continue; > > } else > - insn->call_dest = reloc->sym; > - > - if (insn->call_dest && insn->call_dest->static_call_tramp) { > - list_add_tail(&insn->call_node, > - &file->static_call_list); > - } > - > - /* > - * Many compilers cannot disable KCOV with a function attribute > - * so they need a little help, NOP out any KCOV calls from noinstr > - * text. > - */ > - if (insn->sec->noinstr && > - !strncmp(insn->call_dest->name, "__sanitizer_cov_", 16)) { > - if (reloc) { > - reloc->type = R_NONE; > - elf_write_reloc(file->elf, reloc); > - } > - > - elf_write_insn(file->elf, insn->sec, > - insn->offset, insn->len, > - arch_nop_insn(insn->len)); > - insn->type = INSN_NOP; > - } > - > - if (mcount && !strcmp(insn->call_dest->name, "__fentry__")) { > - if (reloc) { > - reloc->type = R_NONE; > - elf_write_reloc(file->elf, reloc); > - } > - > - elf_write_insn(file->elf, insn->sec, > - insn->offset, insn->len, > - arch_nop_insn(insn->len)); > - > - insn->type = INSN_NOP; > - > - list_add_tail(&insn->mcount_loc_node, > - &file->mcount_loc_list); > - } > - > - /* > - * Whatever stack impact regular CALLs have, should be undone > - * by the RETURN of the called function. > - * > - * Annotated intra-function calls retain the stack_ops but > - * are converted to JUMP, see read_intra_function_calls(). > - */ > - remove_insn_ops(insn); > + add_call_dest(file, insn, reloc->sym, false); > } > > return 0; > --- a/tools/objtool/include/objtool/arch.h > +++ b/tools/objtool/include/objtool/arch.h > @@ -82,6 +82,7 @@ unsigned long arch_jump_destination(stru > unsigned long arch_dest_reloc_offset(int addend); > > const char *arch_nop_insn(int len); > +const char *arch_ret_insn(int len); > > int arch_decode_hint_reg(struct instruction *insn, u8 sp_reg); > > >
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