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Date: Wed, 4 Jul 2018 09:59:23 +0200
From: Heiko Carstens <heiko.carstens@...ibm.com>
To: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-s390@...r.kernel.org, linux-arch@...r.kernel.org,
Arnd Bergmann <arnd@...db.de>,
Kees Cook <keescook@...omium.org>,
Will Deacon <will.deacon@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Catalin Marinas <catalin.marinas@....com>,
Ingo Molnar <mingo@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Jessica Yu <jeyu@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v2 0/8] add support for relative references in jump tables
On Mon, Jul 02, 2018 at 08:11:37PM +0200, Ard Biesheuvel wrote:
> This series implements support for emitting the data structures associated
> with jump tables as 32-bit relative references instead of absolute
> references, which take up more space on builds that target 64-bit
> architectures, or implement self relocation [or both].
>
> This series enables it for arm64 and x86, although other architectures
> might benefit as well.
Hello Ard,
feel free to add the patch below which adds support for s390 to your series.
> Changes since v1:
> - change the relative reference to the static key to a 64-bit wide one on 64
> bit architectures; this is necessary on arm64, which allows modules to
> reside anywhere within a 4 GB window covering the core kernel text, which
> means a 32-bit signed quantity with its +/- 2 GB range is insufficient.
> Note that x86_64 changes are in preparation that widen the relocation
> range as well (using the PIE linker), so I assumed that the same change
> is appropriate for x86 as well.
FWIW, kernel modules on s390 are since ages more than 2GB away from the
core kernel text. So this is required for s390 as well.
>From 77d87236f3d5474f33c25534d8ba2c7c54c88c55 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@...ibm.com>
Date: Wed, 4 Jul 2018 09:13:37 +0200
Subject: [PATCH] s390/jump_label: switch to relative references
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
---
arch/s390/Kconfig | 1 +
arch/s390/include/asm/jump_label.h | 40 +++++++++++++++-----------------------
arch/s390/kernel/jump_label.c | 11 ++++++-----
3 files changed, 23 insertions(+), 29 deletions(-)
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index baed39772c84..0349fb06a2ec 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -121,6 +121,7 @@ config S390
select HAVE_ALIGNED_STRUCT_PAGE if SLUB
select HAVE_ARCH_AUDITSYSCALL
select HAVE_ARCH_JUMP_LABEL
+ select HAVE_ARCH_JUMP_LABEL_RELATIVE
select CPU_NO_EFFICIENT_FFS if !HAVE_MARCH_Z9_109_FEATURES
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_SOFT_DIRTY
diff --git a/arch/s390/include/asm/jump_label.h b/arch/s390/include/asm/jump_label.h
index 40f651292aa7..e2d3e6c43395 100644
--- a/arch/s390/include/asm/jump_label.h
+++ b/arch/s390/include/asm/jump_label.h
@@ -14,41 +14,33 @@
* We use a brcl 0,2 instruction for jump labels at compile time so it
* can be easily distinguished from a hotpatch generated instruction.
*/
-static __always_inline bool arch_static_branch(struct static_key *key, bool branch)
+static inline bool arch_static_branch(struct static_key *key, bool branch)
{
- asm_volatile_goto("0: brcl 0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n"
- ".pushsection __jump_table, \"aw\"\n"
- ".balign 8\n"
- ".quad 0b, %l[label], %0\n"
- ".popsection\n"
- : : "X" (&((char *)key)[branch]) : : label);
-
+ asm_volatile_goto("0: brcl 0,"__stringify(JUMP_LABEL_NOP_OFFSET)"\n"
+ ".pushsection __jump_table,\"aw\"\n"
+ ".balign 8\n"
+ ".long 0b-.,%l[label]-.\n"
+ ".quad %0-.\n"
+ ".popsection\n"
+ : : "X" (&((char *)key)[branch]) : : label);
return false;
label:
return true;
}
-static __always_inline bool arch_static_branch_jump(struct static_key *key, bool branch)
+static inline bool arch_static_branch_jump(struct static_key *key, bool branch)
{
- asm_volatile_goto("0: brcl 15, %l[label]\n"
- ".pushsection __jump_table, \"aw\"\n"
- ".balign 8\n"
- ".quad 0b, %l[label], %0\n"
- ".popsection\n"
- : : "X" (&((char *)key)[branch]) : : label);
-
+ asm_volatile_goto("0: brcl 15,%l[label]\n"
+ ".pushsection __jump_table,\"aw\"\n"
+ ".balign 8\n"
+ ".long 0b-.,%l[label]-.\n"
+ ".quad %0-.\n"
+ ".popsection\n"
+ : : "X" (&((char *)key)[branch]) : : label);
return false;
label:
return true;
}
-typedef unsigned long jump_label_t;
-
-struct jump_entry {
- jump_label_t code;
- jump_label_t target;
- jump_label_t key;
-};
-
#endif /* __ASSEMBLY__ */
#endif
diff --git a/arch/s390/kernel/jump_label.c b/arch/s390/kernel/jump_label.c
index 43f8430fb67d..50a1798604a8 100644
--- a/arch/s390/kernel/jump_label.c
+++ b/arch/s390/kernel/jump_label.c
@@ -33,13 +33,13 @@ static void jump_label_make_branch(struct jump_entry *entry, struct insn *insn)
{
/* brcl 15,offset */
insn->opcode = 0xc0f4;
- insn->offset = (entry->target - entry->code) >> 1;
+ insn->offset = (jump_entry_target(entry) - jump_entry_code(entry)) >> 1;
}
static void jump_label_bug(struct jump_entry *entry, struct insn *expected,
struct insn *new)
{
- unsigned char *ipc = (unsigned char *)entry->code;
+ unsigned char *ipc = (unsigned char *)jump_entry_code(entry);
unsigned char *ipe = (unsigned char *)expected;
unsigned char *ipn = (unsigned char *)new;
@@ -59,6 +59,7 @@ static void __jump_label_transform(struct jump_entry *entry,
enum jump_label_type type,
int init)
{
+ void *code = (void *)jump_entry_code(entry);
struct insn old, new;
if (type == JUMP_LABEL_JMP) {
@@ -69,13 +70,13 @@ static void __jump_label_transform(struct jump_entry *entry,
jump_label_make_nop(entry, &new);
}
if (init) {
- if (memcmp((void *)entry->code, &orignop, sizeof(orignop)))
+ if (memcmp(code, &orignop, sizeof(orignop)))
jump_label_bug(entry, &orignop, &new);
} else {
- if (memcmp((void *)entry->code, &old, sizeof(old)))
+ if (memcmp(code, &old, sizeof(old)))
jump_label_bug(entry, &old, &new);
}
- s390_kernel_write((void *)entry->code, &new, sizeof(new));
+ s390_kernel_write(code, &new, sizeof(new));
}
static int __sm_arch_jump_label_transform(void *data)
--
2.16.4
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