Re: [PATCH v5 3/6] arch/x86: Implement text_alloc() and text_free()
On Fri, Jul 24, 2020 at 11:22:58AM +0200, Ingo Molnar wrote:
>
> * Jarkko Sakkinen 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
Re: [PATCH v5 3/6] arch/x86: Implement text_alloc() and text_free()
* Jarkko Sakkinen 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
[PATCH v5 3/6] arch/x86: Implement text_alloc() and text_free()
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...@kvack.org
Cc: Masami Hiramatsu
Cc: Andi Kleen
Suggested-by: Peter Zijlstra
Signed-off-by: Jarkko Sakkinen
---
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
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 ..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
+#include
+#include
+#include
+#include
+
+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);
+}
--
2.25.1
[PATCH v5 3/6] arch/x86: Implement text_alloc() and text_free()
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...@kvack.org
Cc: Masami Hiramatsu
Cc: Andi Kleen
Suggested-by: Peter Zijlstra
Signed-off-by: Jarkko Sakkinen
---
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
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 ..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
+#include
+#include
+#include
+#include
+
+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);
+}
--
2.25.1
