From 2b10be23ac0f8e107fd575397361ddbaebc2944b Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 17 Apr 2020 23:15:00 +0200 Subject: objtool: Clean up elf_write() condition With there being multiple ways to change the ELF data, let's more concisely track modification. Signed-off-by: Peter Zijlstra (Intel) --- tools/objtool/check.c | 4 +++- tools/objtool/elf.c | 13 +++++++++++-- tools/objtool/elf.h | 5 +++-- tools/objtool/orc_gen.c | 2 +- 4 files changed, 18 insertions(+), 6 deletions(-) (limited to 'tools') diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 5fbb90a80d23..91a67db26165 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -2740,7 +2740,7 @@ int check(const char *_objname, bool orc) objname = _objname; - file.elf = elf_open_read(objname, orc ? O_RDWR : O_RDONLY); + file.elf = elf_open_read(objname, O_RDWR); if (!file.elf) return 1; @@ -2801,7 +2801,9 @@ int check(const char *_objname, bool orc) ret = create_orc_sections(&file); if (ret < 0) goto out; + } + if (file.elf->changed) { ret = elf_write(file.elf); if (ret < 0) goto out; diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index 84225679f96d..bc6723a502c3 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -713,6 +713,8 @@ struct section *elf_create_section(struct elf *elf, const char *name, elf_hash_add(elf->section_hash, &sec->hash, sec->idx); elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name)); + elf->changed = true; + return sec; } @@ -746,7 +748,7 @@ struct section *elf_create_rela_section(struct elf *elf, struct section *base) return sec; } -int elf_rebuild_rela_section(struct section *sec) +int elf_rebuild_rela_section(struct elf *elf, struct section *sec) { struct rela *rela; int nr, idx = 0, size; @@ -763,6 +765,9 @@ int elf_rebuild_rela_section(struct section *sec) return -1; } + sec->changed = true; + elf->changed = true; + sec->data->d_buf = relas; sec->data->d_size = size; @@ -779,7 +784,7 @@ int elf_rebuild_rela_section(struct section *sec) return 0; } -int elf_write(const struct elf *elf) +int elf_write(struct elf *elf) { struct section *sec; Elf_Scn *s; @@ -796,6 +801,8 @@ int elf_write(const struct elf *elf) WARN_ELF("gelf_update_shdr"); return -1; } + + sec->changed = false; } } @@ -808,6 +815,8 @@ int elf_write(const struct elf *elf) return -1; } + elf->changed = false; + return 0; } diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h index f4fe1d6ea392..aa9c64da379f 100644 --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -76,6 +76,7 @@ struct elf { Elf *elf; GElf_Ehdr ehdr; int fd; + bool changed; char *name; struct list_head sections; DECLARE_HASHTABLE(symbol_hash, ELF_HASH_BITS); @@ -118,7 +119,7 @@ struct elf *elf_open_read(const char *name, int flags); struct section *elf_create_section(struct elf *elf, const char *name, size_t entsize, int nr); struct section *elf_create_rela_section(struct elf *elf, struct section *base); void elf_add_rela(struct elf *elf, struct rela *rela); -int elf_write(const struct elf *elf); +int elf_write(struct elf *elf); void elf_close(struct elf *elf); struct section *find_section_by_name(const struct elf *elf, const char *name); @@ -130,7 +131,7 @@ struct rela *find_rela_by_dest(const struct elf *elf, struct section *sec, unsig struct rela *find_rela_by_dest_range(const struct elf *elf, struct section *sec, unsigned long offset, unsigned int len); struct symbol *find_func_containing(struct section *sec, unsigned long offset); -int elf_rebuild_rela_section(struct section *sec); +int elf_rebuild_rela_section(struct elf *elf, struct section *sec); #define for_each_sec(file, sec) \ list_for_each_entry(sec, &file->elf->sections, list) diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c index c9549988121a..4c37f80eb987 100644 --- a/tools/objtool/orc_gen.c +++ b/tools/objtool/orc_gen.c @@ -222,7 +222,7 @@ int create_orc_sections(struct objtool_file *file) } } - if (elf_rebuild_rela_section(ip_relasec)) + if (elf_rebuild_rela_section(file->elf, ip_relasec)) return -1; return 0; -- cgit v1.2.3 From fdabdd0b05e0bdf232340d5da86563ed142a99a7 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 12 Jun 2020 15:43:00 +0200 Subject: objtool: Provide elf_write_{insn,reloc}() This provides infrastructure to rewrite instructions; this is immediately useful for helping out with KCOV-vs-noinstr, but will also come in handy for a bunch of variable sized jump-label patches that are still on ice. Signed-off-by: Peter Zijlstra (Intel) --- tools/objtool/elf.c | 40 +++++++++++++++++++++++++++++++++++++++- tools/objtool/elf.h | 7 ++++++- 2 files changed, 45 insertions(+), 2 deletions(-) (limited to 'tools') diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index bc6723a502c3..26d11d821941 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -529,8 +529,9 @@ static int read_relas(struct elf *elf) rela->addend = rela->rela.r_addend; rela->offset = rela->rela.r_offset; symndx = GELF_R_SYM(rela->rela.r_info); - rela->sym = find_symbol_by_index(elf, symndx); rela->sec = sec; + rela->idx = i; + rela->sym = find_symbol_by_index(elf, symndx); if (!rela->sym) { WARN("can't find rela entry symbol %d for %s", symndx, sec->name); @@ -784,6 +785,43 @@ int elf_rebuild_rela_section(struct elf *elf, struct section *sec) return 0; } +int elf_write_insn(struct elf *elf, struct section *sec, + unsigned long offset, unsigned int len, + const char *insn) +{ + Elf_Data *data = sec->data; + + if (data->d_type != ELF_T_BYTE || data->d_off) { + WARN("write to unexpected data for section: %s", sec->name); + return -1; + } + + memcpy(data->d_buf + offset, insn, len); + elf_flagdata(data, ELF_C_SET, ELF_F_DIRTY); + + elf->changed = true; + + return 0; +} + +int elf_write_rela(struct elf *elf, struct rela *rela) +{ + struct section *sec = rela->sec; + + rela->rela.r_info = GELF_R_INFO(rela->sym->idx, rela->type); + rela->rela.r_addend = rela->addend; + rela->rela.r_offset = rela->offset; + + if (!gelf_update_rela(sec->data, rela->idx, &rela->rela)) { + WARN_ELF("gelf_update_rela"); + return -1; + } + + elf->changed = true; + + return 0; +} + int elf_write(struct elf *elf) { struct section *sec; diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h index aa9c64da379f..7324e772583e 100644 --- a/tools/objtool/elf.h +++ b/tools/objtool/elf.h @@ -64,9 +64,10 @@ struct rela { GElf_Rela rela; struct section *sec; struct symbol *sym; - unsigned int type; unsigned long offset; + unsigned int type; int addend; + int idx; bool jump_table_start; }; @@ -119,6 +120,10 @@ struct elf *elf_open_read(const char *name, int flags); struct section *elf_create_section(struct elf *elf, const char *name, size_t entsize, int nr); struct section *elf_create_rela_section(struct elf *elf, struct section *base); void elf_add_rela(struct elf *elf, struct rela *rela); +int elf_write_insn(struct elf *elf, struct section *sec, + unsigned long offset, unsigned int len, + const char *insn); +int elf_write_rela(struct elf *elf, struct rela *rela); int elf_write(struct elf *elf); void elf_close(struct elf *elf); -- cgit v1.2.3 From 0f1441b44e823a74f3f3780902a113e07c73fbf6 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 12 Jun 2020 16:05:26 +0200 Subject: objtool: Fix noinstr vs KCOV Since many compilers cannot disable KCOV with a function attribute, help it to NOP out any __sanitizer_cov_*() calls injected in noinstr code. This turns: 12: e8 00 00 00 00 callq 17 13: R_X86_64_PLT32 __sanitizer_cov_trace_pc-0x4 into: 12: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) 13: R_X86_64_NONE __sanitizer_cov_trace_pc-0x4 Just like recordmcount does. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Dmitry Vyukov --- tools/objtool/arch.h | 2 ++ tools/objtool/arch/x86/decode.c | 18 ++++++++++++++++++ tools/objtool/arch/x86/include/arch_elf.h | 6 ++++++ tools/objtool/check.c | 19 +++++++++++++++++++ 4 files changed, 45 insertions(+) create mode 100644 tools/objtool/arch/x86/include/arch_elf.h (limited to 'tools') diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h index eda15a5a285e..3c5967748abb 100644 --- a/tools/objtool/arch.h +++ b/tools/objtool/arch.h @@ -84,4 +84,6 @@ unsigned long arch_jump_destination(struct instruction *insn); unsigned long arch_dest_rela_offset(int addend); +const char *arch_nop_insn(int len); + #endif /* _ARCH_H */ diff --git a/tools/objtool/arch/x86/decode.c b/tools/objtool/arch/x86/decode.c index 4b504fc90bbb..9872195f998b 100644 --- a/tools/objtool/arch/x86/decode.c +++ b/tools/objtool/arch/x86/decode.c @@ -565,3 +565,21 @@ void arch_initial_func_cfi_state(struct cfi_init_state *state) state->regs[16].base = CFI_CFA; state->regs[16].offset = -8; } + +const char *arch_nop_insn(int len) +{ + static const char nops[5][5] = { + /* 1 */ { 0x90 }, + /* 2 */ { 0x66, 0x90 }, + /* 3 */ { 0x0f, 0x1f, 0x00 }, + /* 4 */ { 0x0f, 0x1f, 0x40, 0x00 }, + /* 5 */ { 0x0f, 0x1f, 0x44, 0x00, 0x00 }, + }; + + if (len < 1 || len > 5) { + WARN("invalid NOP size: %d\n", len); + return NULL; + } + + return nops[len-1]; +} diff --git a/tools/objtool/arch/x86/include/arch_elf.h b/tools/objtool/arch/x86/include/arch_elf.h new file mode 100644 index 000000000000..69cc4264b28a --- /dev/null +++ b/tools/objtool/arch/x86/include/arch_elf.h @@ -0,0 +1,6 @@ +#ifndef _OBJTOOL_ARCH_ELF +#define _OBJTOOL_ARCH_ELF + +#define R_NONE R_X86_64_NONE + +#endif /* _OBJTOOL_ARCH_ELF */ diff --git a/tools/objtool/check.c b/tools/objtool/check.c index 91a67db26165..478267a072d0 100644 --- a/tools/objtool/check.c +++ b/tools/objtool/check.c @@ -12,6 +12,7 @@ #include "check.h" #include "special.h" #include "warn.h" +#include "arch_elf.h" #include #include @@ -765,6 +766,24 @@ static int add_call_destinations(struct objtool_file *file) } else insn->call_dest = rela->sym; + /* + * 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 (rela) { + rela->type = R_NONE; + elf_write_rela(file->elf, rela); + } + + elf_write_insn(file->elf, insn->sec, + insn->offset, insn->len, + arch_nop_insn(insn->len)); + insn->type = INSN_NOP; + } + /* * Whatever stack impact regular CALLs have, should be undone * by the RETURN of the called function. -- cgit v1.2.3