[v5,3/6] arch/x86: Implement text_alloc() and text_free()
diff mbox series

Message ID 20200724050553.1724168-4-jarkko.sakkinen@linux.intel.com
State New
Headers show
Series
  • arch/x86: kprobes: Remove MODULES dependency
Related show

Commit Message

Jarkko Sakkinen July 24, 2020, 5:05 a.m. UTC
Implement text_alloc() and text_free() with with the vmalloc API. These can
be used to allocate pages for trampoline code without relying on the module
loader code.

Cc: linux-mm@kvack.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andi Kleen <ak@linux.intel.com>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 arch/x86/Kconfig             |  3 +++
 arch/x86/kernel/Makefile     |  1 +
 arch/x86/kernel/text_alloc.c | 41 ++++++++++++++++++++++++++++++++++++
 3 files changed, 45 insertions(+)
 create mode 100644 arch/x86/kernel/text_alloc.c

Comments

Ingo Molnar July 24, 2020, 9:22 a.m. UTC | #1
* Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> wrote:

> +void text_free(void *region)
> +{
> +	/*
> +	 * This memory may be RO, and freeing RO memory in an interrupt is not
> +	 * supported by vmalloc.
> +	 */
> +	lockdep_assert_irqs_enabled();
> +
> +	vfree(region);

Had to dig around a bit to find the source of this restriction. Might 
make sense to clarify this comment to:

	/*
	 * This memory may be read-only, and freeing VM_FLUSH_RESET_PERMS memory
	 * in an interrupt is not supported by vmalloc.
	 */

Thanks,

	Ingo
Jarkko Sakkinen July 25, 2020, 2:03 a.m. UTC | #2
On Fri, Jul 24, 2020 at 11:22:58AM +0200, Ingo Molnar wrote:
> 
> * Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> wrote:
> 
> > +void text_free(void *region)
> > +{
> > +	/*
> > +	 * This memory may be RO, and freeing RO memory in an interrupt is not
> > +	 * supported by vmalloc.
> > +	 */
> > +	lockdep_assert_irqs_enabled();
> > +
> > +	vfree(region);
> 
> Had to dig around a bit to find the source of this restriction. Might 
> make sense to clarify this comment to:
> 
> 	/*
> 	 * This memory may be read-only, and freeing VM_FLUSH_RESET_PERMS memory
> 	 * in an interrupt is not supported by vmalloc.
> 	 */

This definitely clarifies and is a better explanation. I updated the
commit accordingly. Thank you.

> 
> Thanks,
> 
> 	Ingo

/Jarkko

Patch
diff mbox series

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..fa1415424ae3 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_alloc.o
 
 obj-y				+= process.o
 obj-y				+= fpu/
diff --git a/arch/x86/kernel/text_alloc.c b/arch/x86/kernel/text_alloc.c
new file mode 100644
index 000000000000..f31c2d82c258
--- /dev/null
+++ b/arch/x86/kernel/text_alloc.c
@@ -0,0 +1,41 @@ 
+// 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>
+
+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, 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.
+	 */
+	lockdep_assert_irqs_enabled();
+
+	vfree(region);
+}