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Message-Id: <20200730094652.28297-5-jthierry@redhat.com>
Date: Thu, 30 Jul 2020 10:46:47 +0100
From: Julien Thierry <jthierry@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: jpoimboe@...hat.com, peterz@...radead.org, mbenes@...e.cz,
raphael.gault@....com, benh@...nel.crashing.org,
Julien Thierry <jthierry@...hat.com>
Subject: [PATCH v2 4/9] objtool: Abstract alternative special case handling
Some alternatives associated with a specific feature need to be treated
in a special way. Since the features and how to treat them vary from one
architecture to another, move the special case handling to arch specific
code.
Reviewed-by: Miroslav Benes <mbenes@...e.cz>
Signed-off-by: Julien Thierry <jthierry@...hat.com>
---
tools/objtool/arch/x86/Build | 1 +
tools/objtool/arch/x86/arch_special.c | 37 +++++++++++++++++++++++++++
tools/objtool/objtool.h | 2 ++
tools/objtool/special.c | 32 ++++-------------------
tools/objtool/special.h | 2 ++
tools/objtool/weak.c | 2 --
6 files changed, 47 insertions(+), 29 deletions(-)
create mode 100644 tools/objtool/arch/x86/arch_special.c
diff --git a/tools/objtool/arch/x86/Build b/tools/objtool/arch/x86/Build
index 7c5004008e97..2c3ac13cfa8b 100644
--- a/tools/objtool/arch/x86/Build
+++ b/tools/objtool/arch/x86/Build
@@ -1,3 +1,4 @@
+objtool-y += arch_special.o
objtool-y += decode.o
inat_tables_script = ../arch/x86/tools/gen-insn-attr-x86.awk
diff --git a/tools/objtool/arch/x86/arch_special.c b/tools/objtool/arch/x86/arch_special.c
new file mode 100644
index 000000000000..823561e4015c
--- /dev/null
+++ b/tools/objtool/arch/x86/arch_special.c
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include "../../special.h"
+#include "../../builtin.h"
+
+#define X86_FEATURE_POPCNT (4 * 32 + 23)
+#define X86_FEATURE_SMAP (9 * 32 + 20)
+
+void arch_handle_alternative(unsigned short feature, struct special_alt *alt)
+{
+ switch (feature) {
+ case X86_FEATURE_SMAP:
+ /*
+ * If UACCESS validation is enabled; force that alternative;
+ * otherwise force it the other way.
+ *
+ * What we want to avoid is having both the original and the
+ * alternative code flow at the same time, in that case we can
+ * find paths that see the STAC but take the NOP instead of
+ * CLAC and the other way around.
+ */
+ if (uaccess)
+ alt->skip_orig = true;
+ else
+ alt->skip_alt = true;
+ break;
+ case X86_FEATURE_POPCNT:
+ /*
+ * It has been requested that we don't validate the !POPCNT
+ * feature path which is a "very very small percentage of
+ * machines".
+ */
+ alt->skip_orig = true;
+ break;
+ default:
+ break;
+ }
+}
diff --git a/tools/objtool/objtool.h b/tools/objtool/objtool.h
index e61b486d4c05..1f85409a57f9 100644
--- a/tools/objtool/objtool.h
+++ b/tools/objtool/objtool.h
@@ -12,6 +12,8 @@
#include "elf.h"
+#define __weak __attribute__((weak))
+
struct objtool_file {
struct elf *elf;
struct list_head insn_list;
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index b04f395de5de..1a2420febd08 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -16,9 +16,6 @@
#include "warn.h"
#include "arch_special.h"
-#define X86_FEATURE_POPCNT (4*32+23)
-#define X86_FEATURE_SMAP (9*32+20)
-
struct special_entry {
const char *sec;
bool group, jump_or_nop;
@@ -54,6 +51,10 @@ struct special_entry entries[] = {
{},
};
+void __weak arch_handle_alternative(unsigned short feature, struct special_alt *alt)
+{
+}
+
static int get_alt_entry(struct elf *elf, struct special_entry *entry,
struct section *sec, int idx,
struct special_alt *alt)
@@ -78,30 +79,7 @@ static int get_alt_entry(struct elf *elf, struct special_entry *entry,
feature = *(unsigned short *)(sec->data->d_buf + offset +
entry->feature);
-
- /*
- * It has been requested that we don't validate the !POPCNT
- * feature path which is a "very very small percentage of
- * machines".
- */
- if (feature == X86_FEATURE_POPCNT)
- alt->skip_orig = true;
-
- /*
- * If UACCESS validation is enabled; force that alternative;
- * otherwise force it the other way.
- *
- * What we want to avoid is having both the original and the
- * alternative code flow at the same time, in that case we can
- * find paths that see the STAC but take the NOP instead of
- * CLAC and the other way around.
- */
- if (feature == X86_FEATURE_SMAP) {
- if (uaccess)
- alt->skip_orig = true;
- else
- alt->skip_alt = true;
- }
+ arch_handle_alternative(feature, alt);
}
orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig);
diff --git a/tools/objtool/special.h b/tools/objtool/special.h
index 35061530e46e..44da89afeda2 100644
--- a/tools/objtool/special.h
+++ b/tools/objtool/special.h
@@ -28,4 +28,6 @@ struct special_alt {
int special_get_alts(struct elf *elf, struct list_head *alts);
+void arch_handle_alternative(unsigned short feature, struct special_alt *alt);
+
#endif /* _SPECIAL_H */
diff --git a/tools/objtool/weak.c b/tools/objtool/weak.c
index 29180d599b08..7843e9a7a72f 100644
--- a/tools/objtool/weak.c
+++ b/tools/objtool/weak.c
@@ -9,8 +9,6 @@
#include <errno.h>
#include "objtool.h"
-#define __weak __attribute__((weak))
-
#define UNSUPPORTED(name) \
({ \
fprintf(stderr, "error: objtool: " name " not implemented\n"); \
--
2.21.3
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