Introduce new API for allocating space for code generaed at run-time
leveraging from module_alloc() and module_memfree() code. Use this to
perform memory allocations in the kprobes code in order to loose the
bound between kprobes and modules subsystem.
Initially, use this API only with arch/x86 and define a new config
flag CONFIG_ARCH_HAS_TEXT_ALLOC to promote the availability of the
new API.
Cc: Andi Kleen <a...@linux.intel.com>
Suggested-by: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>
---
arch/Kconfig | 2 +-
arch/x86/Kconfig | 3 ++
arch/x86/kernel/Makefile | 1 +
arch/x86/kernel/module.c | 49 ---------------------------
arch/x86/kernel/text.c | 71 ++++++++++++++++++++++++++++++++++++++++
include/linux/text.h | 17 ++++++++++
kernel/kprobes.c | 11 +++++++
kernel/module.c | 10 ++++++
8 files changed, 114 insertions(+), 50 deletions(-)
create mode 100644 arch/x86/kernel/text.c
create mode 100644 include/linux/text.h
diff --git a/arch/Kconfig b/arch/Kconfig
index 8cc35dc556c7..e3d6b6868ccb 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -61,7 +61,7 @@ config OPROFILE_NMI_TIMER
config KPROBES
bool "Kprobes"
- depends on MODULES
+ depends on MODULES || ARCH_HAS_TEXT_ALLOC
depends on HAVE_KPROBES
select KALLSYMS
help
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 0dea7fdd7a00..a4ee5d1300f6 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2035,6 +2035,9 @@ config KEXEC_FILE
config ARCH_HAS_KEXEC_PURGATORY
def_bool KEXEC_FILE
+config ARCH_HAS_TEXT_ALLOC
+ def_bool y
+
config KEXEC_SIG
bool "Verify kernel signature during kexec_file_load() syscall"
depends on KEXEC_FILE
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index e77261db2391..2878e4b753a0 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -68,6 +68,7 @@ obj-y += tsc.o tsc_msr.o io_delay.o rtc.o
obj-y += pci-iommu_table.o
obj-y += resource.o
obj-y += irqflags.o
+obj-y += text.o
obj-y += process.o
obj-y += fpu/
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index 34b153cbd4ac..261df078f127 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -36,55 +36,6 @@ do { \
} while (0)
#endif
-#ifdef CONFIG_RANDOMIZE_BASE
-static unsigned long module_load_offset;
-
-/* Mutex protects the module_load_offset. */
-static DEFINE_MUTEX(module_kaslr_mutex);
-
-static unsigned long int get_module_load_offset(void)
-{
- if (kaslr_enabled()) {
- mutex_lock(&module_kaslr_mutex);
- /*
- * Calculate the module_load_offset the first time this
- * code is called. Once calculated it stays the same until
- * reboot.
- */
- if (module_load_offset == 0)
- module_load_offset =
- (get_random_int() % 1024 + 1) * PAGE_SIZE;
- mutex_unlock(&module_kaslr_mutex);
- }
- return module_load_offset;
-}
-#else
-static unsigned long int get_module_load_offset(void)
-{
- return 0;
-}
-#endif
-
-void *module_alloc(unsigned long size)
-{
- void *p;
-
- if (PAGE_ALIGN(size) > MODULES_LEN)
- return NULL;
-
- p = __vmalloc_node_range(size, MODULE_ALIGN,
- MODULES_VADDR + get_module_load_offset(),
- MODULES_END, GFP_KERNEL,
- PAGE_KERNEL, 0, NUMA_NO_NODE,
- __builtin_return_address(0));
- if (p && (kasan_module_alloc(p, size) < 0)) {
- vfree(p);
- return NULL;
- }
-
- return p;
-}
-
#ifdef CONFIG_X86_32
int apply_relocate(Elf32_Shdr *sechdrs,
const char *strtab,
diff --git a/arch/x86/kernel/text.c b/arch/x86/kernel/text.c
new file mode 100644
index 000000000000..986b92ff1434
--- /dev/null
+++ b/arch/x86/kernel/text.c
@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Kernel module help for x86.
+ * Copyright (C) 2001 Rusty Russell.
+ */
+
+#include <linux/kasan.h>
+#include <linux/mm.h>
+#include <linux/moduleloader.h>
+#include <linux/vmalloc.h>
+#include <asm/setup.h>
+
+#ifdef CONFIG_RANDOMIZE_BASE
+static unsigned long module_load_offset;
+
+/* Mutex protects the module_load_offset. */
+static DEFINE_MUTEX(module_kaslr_mutex);
+
+static unsigned long get_module_load_offset(void)
+{
+ if (kaslr_enabled()) {
+ mutex_lock(&module_kaslr_mutex);
+ /*
+ * Calculate the module_load_offset the first time this
+ * code is called. Once calculated it stays the same until
+ * reboot.
+ */
+ if (module_load_offset == 0)
+ module_load_offset =
+ (get_random_int() % 1024 + 1) * PAGE_SIZE;
+ mutex_unlock(&module_kaslr_mutex);
+ }
+ return module_load_offset;
+}
+#else
+static unsigned long get_module_load_offset(void)
+{
+ return 0;
+}
+#endif
+
+void *text_alloc(unsigned long size)
+{
+ void *p;
+
+ if (PAGE_ALIGN(size) > MODULES_LEN)
+ return NULL;
+
+ p = __vmalloc_node_range(size, MODULE_ALIGN,
+ MODULES_VADDR + get_module_load_offset(),
+ MODULES_END, GFP_KERNEL,
+ PAGE_KERNEL, 0, NUMA_NO_NODE,
+ __builtin_return_address(0));
+ if (p && (kasan_module_alloc(p, size) < 0)) {
+ vfree(p);
+ return NULL;
+ }
+
+ return p;
+}
+
+void text_free(void *region)
+{
+ /*
+ * This memory may be RO, and freeing RO memory in an interrupt is not
+ * supported by vmalloc.
+ */
+ WARN_ON(in_interrupt());
+
+ vfree(region);
+}
diff --git a/include/linux/text.h b/include/linux/text.h
new file mode 100644
index 000000000000..a27d4a42ecda
--- /dev/null
+++ b/include/linux/text.h
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _LINUX_TEXT_H
+#define _LINUX_TEXT_H
+
+/*
+ * An allocator used for allocating modules, core sections and init sections.
+ * Returns NULL on failure.
+ */
+void *text_alloc(unsigned long size);
+
+/*
+ * Free memory returned from text_alloc().
+ */
+void text_free(void *region);
+
+#endif /* _LINUX_TEXT_H */
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 2e97febeef77..fa7687eb0c0e 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -35,6 +35,7 @@
#include <linux/ftrace.h>
#include <linux/cpu.h>
#include <linux/jump_label.h>
+#include <linux/text.h>
#include <asm/sections.h>
#include <asm/cacheflush.h>
@@ -111,12 +112,20 @@ enum kprobe_slot_state {
void __weak *alloc_insn_page(void)
{
+#ifdef CONFIG_ARCH_HAS_TEXT_ALLOC
+ return text_alloc(PAGE_SIZE);
+#else
return module_alloc(PAGE_SIZE);
+#endif
}
void __weak free_insn_page(void *page)
{
+#ifdef CONFIG_ARCH_HAS_TEXT_ALLOC
+ text_free(page);
+#else
module_memfree(page);
+#endif
}
struct kprobe_insn_cache kprobe_insn_slots = {
@@ -1608,6 +1617,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
goto out;
}
+#ifdef CONFIG_MODULES
/*
* If the module freed .init.text, we couldn't insert
* kprobes in there.
@@ -1618,6 +1628,7 @@ static int check_kprobe_address_safe(struct kprobe *p,
*probed_mod = NULL;
ret = -ENOENT;
}
+#endif
}
out:
preempt_enable();
diff --git a/kernel/module.c b/kernel/module.c
index aa183c9ac0a2..8adeb126b02c 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -56,6 +56,7 @@
#include <linux/bsearch.h>
#include <linux/dynamic_debug.h>
#include <linux/audit.h>
+#include <linux/text.h>
#include <uapi/linux/module.h>
#include "module-internal.h"
@@ -2151,7 +2152,12 @@ void __weak module_memfree(void *module_region)
* supported by vmalloc.
*/
WARN_ON(in_interrupt());
+
+#ifdef CONFIG_ARCH_HAS_TEXT_ALLOC
+ text_free(module_region);
+#else
vfree(module_region);
+#endif
}
void __weak module_arch_cleanup(struct module *mod)
@@ -2786,9 +2792,13 @@ static void dynamic_debug_remove(struct module *mod,
struct _ddebug *debug)
void * __weak module_alloc(unsigned long size)
{
+#ifdef CONFIG_ARCH_HAS_TEXT_ALLOC
+ return text_alloc(size);
+#else
return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END,
GFP_KERNEL, PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS,
NUMA_NO_NODE, __builtin_return_address(0));
+#endif
}
bool __weak module_init_section(const char *name)
--
2.25.1
