Merge tag 'objtool_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull objtool fixes from Borislav Petkov:
"Three fixes from Peter Zijlstra suppressing KCOV instrumentation in
noinstr sections.
Peter Zijlstra says:
"Address KCOV vs noinstr. There is no function attribute to
selectively suppress KCOV instrumentation, instead teach objtool
to NOP out the calls in noinstr functions"
This cures a bunch of KCOV crashes (as used by syzcaller)"
* tag 'objtool_urgent_for_5.8_rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
objtool: Fix noinstr vs KCOV
objtool: Provide elf_write_{insn,reloc}()
objtool: Clean up elf_write() condition
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6a0cc52..883da0a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -67,7 +67,7 @@
select ARCH_HAS_FILTER_PGPROT
select ARCH_HAS_FORTIFY_SOURCE
select ARCH_HAS_GCOV_PROFILE_ALL
- select ARCH_HAS_KCOV if X86_64
+ select ARCH_HAS_KCOV if X86_64 && STACK_VALIDATION
select ARCH_HAS_MEM_ENCRYPT
select ARCH_HAS_MEMBARRIER_SYNC_CORE
select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
diff --git a/tools/objtool/arch.h b/tools/objtool/arch.h
index eda15a5..3c59677 100644
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -84,4 +84,6 @@
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 4b504fc..9872195 100644
--- a/tools/objtool/arch/x86/decode.c
+++ b/tools/objtool/arch/x86/decode.c
@@ -565,3 +565,21 @@
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 0000000..69cc426
--- /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 d8eaa7d..5e0d70a 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 <linux/hashtable.h>
#include <linux/kernel.h>
@@ -766,6 +767,24 @@
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.
*
@@ -2766,7 +2785,7 @@
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;
@@ -2827,7 +2846,9 @@
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 8422567..26d11d8 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -529,8 +529,9 @@
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);
@@ -713,6 +714,8 @@
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 +749,7 @@
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 +766,9 @@
return -1;
}
+ sec->changed = true;
+ elf->changed = true;
+
sec->data->d_buf = relas;
sec->data->d_size = size;
@@ -779,7 +785,44 @@
return 0;
}
-int elf_write(const struct elf *elf)
+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;
Elf_Scn *s;
@@ -796,6 +839,8 @@
WARN_ELF("gelf_update_shdr");
return -1;
}
+
+ sec->changed = false;
}
}
@@ -808,6 +853,8 @@
return -1;
}
+ elf->changed = false;
+
return 0;
}
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index f4fe1d6..7324e77 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -64,9 +64,10 @@
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;
};
@@ -76,6 +77,7 @@
Elf *elf;
GElf_Ehdr ehdr;
int fd;
+ bool changed;
char *name;
struct list_head sections;
DECLARE_HASHTABLE(symbol_hash, ELF_HASH_BITS);
@@ -118,7 +120,11 @@
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_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);
struct section *find_section_by_name(const struct elf *elf, const char *name);
@@ -130,7 +136,7 @@
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 c954998..4c37f80 100644
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -222,7 +222,7 @@
}
}
- if (elf_rebuild_rela_section(ip_relasec))
+ if (elf_rebuild_rela_section(file->elf, ip_relasec))
return -1;
return 0;
