From: Peter Zijlstra <peterz@infradead.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org, dvyukov@google.com,
elver@google.com, andreyknvl@google.com, mark.rutland@arm.com,
mhelsley@vmware.com, rostedt@goodmis.org, jthierry@redhat.com,
mbenes@suse.cz, peterz@infradead.org
Subject: [PATCH 7/7] objtool: Fix noinstr vs KCOV
Date: Thu, 18 Jun 2020 16:44:14 +0200 [thread overview]
Message-ID: <20200618144801.995733773@infradead.org> (raw)
In-Reply-To: 20200618144407.520952071@infradead.org
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>
---
arch/x86/Kconfig | 2 +-
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 +++++++++++++++++++
5 files changed, 46 insertions(+), 1 deletion(-)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -67,7 +67,7 @@ config X86
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
--- a/tools/objtool/arch.h
+++ b/tools/objtool/arch.h
@@ -84,4 +84,6 @@ unsigned long arch_jump_destination(stru
unsigned long arch_dest_reloc_offset(int addend);
+const char *arch_nop_insn(int len);
+
#endif /* _ARCH_H */
--- 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
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];
+}
--- /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 */
--- 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
insn->call_dest = reloc->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 (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;
+ }
+
+ /*
* Whatever stack impact regular CALLs have, should be undone
* by the RETURN of the called function.
*
prev parent reply other threads:[~2020-06-18 14:51 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-18 14:44 [PATCH 0/7] x86/entry: noinstr fixes Peter Zijlstra
2020-06-18 14:44 ` [PATCH 1/7] x86/entry: Fix #UD vs WARN more Peter Zijlstra
2020-06-18 14:57 ` Andy Lutomirski
2020-06-18 15:50 ` Peter Zijlstra
2020-06-18 18:36 ` Andy Lutomirski
2020-06-18 19:02 ` Peter Zijlstra
2020-06-18 19:29 ` Andy Lutomirski
2020-06-18 21:18 ` Peter Zijlstra
2020-06-22 11:47 ` Peter Zijlstra
2020-06-24 22:37 ` Andy Lutomirski
2020-06-25 11:53 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 2/7] objtool: Dont consider vmlinux a C-file Peter Zijlstra
2020-06-25 11:53 ` [tip: x86/entry] objtool: Don't " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 3/7] x86/entry: Fixup bad_iret vs noinstr Peter Zijlstra
2020-06-18 15:13 ` Marco Elver
2020-06-25 11:53 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 4/7] x86/entry: Increase entry_stack size to a full page Peter Zijlstra
2020-06-18 15:06 ` Marco Elver
2020-06-19 3:10 ` Lai Jiangshan
2020-06-25 11:53 ` [tip: x86/entry] " tip-bot2 for Peter Zijlstra
2020-06-18 14:44 ` [PATCH 5/7] objtool: Clean up elf_write() condition Peter Zijlstra
2020-06-18 14:44 ` [PATCH 6/7] objtool: Provide elf_write_{insn,reloc}() Peter Zijlstra
2020-06-18 14:44 ` Peter Zijlstra [this message]
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