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authorPeter Zijlstra <peterz@infradead.org>2020-06-12 17:05:26 +0300
committerPeter Zijlstra <peterz@infradead.org>2020-06-18 18:36:33 +0300
commit0f1441b44e823a74f3f3780902a113e07c73fbf6 (patch)
tree5ef3755754810974096c758d5878dc31d23d7c20 /tools
parentfdabdd0b05e0bdf232340d5da86563ed142a99a7 (diff)
downloadlinux-0f1441b44e823a74f3f3780902a113e07c73fbf6.tar.xz
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 <lockdep_hardirqs_on+0x17> 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) <peterz@infradead.org> Acked-by: Dmitry Vyukov <dvyukov@google.com>
Diffstat (limited to 'tools')
-rw-r--r--tools/objtool/arch.h2
-rw-r--r--tools/objtool/arch/x86/decode.c18
-rw-r--r--tools/objtool/arch/x86/include/arch_elf.h6
-rw-r--r--tools/objtool/check.c19
4 files changed, 45 insertions, 0 deletions
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 <linux/hashtable.h>
#include <linux/kernel.h>
@@ -766,6 +767,24 @@ static int add_call_destinations(struct objtool_file *file)
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.
*