[PATCH 1/2] kexec: Create a new config option CONFIG_KEXEC_FILE for new syscall

From: Vivek Goyal
Date: Wed Aug 13 2014 - 11:25:01 EST


Currently new system call kexec_file_load() and all the associated code
compiles if CONFIG_KEXEC=y. But new syscall also compiles purgatory code
which currently uses gcc option -mcmodel=large. This option seems to be
available only gcc 4.4 onwards.

Hiding new functionality behind a new config option will not break
existing users of old gcc. Those who wish to enable new functionality
will require new gcc. Having said that, I am trying to figure out how
can I move away from using -mcmodel=large but that can take a while.

I think there are other advantages of introducing this new config
option. As this option will be enabled only on x86_64, other arches
don't have to compile generic kexec code which will never be used.
This new code selects CRYPTO=y and CRYPTO_SHA256=y. And all other
arches had to do this for CONFIG_KEXEC. Now with introduction
of new config option, we can remove crypto dependency from other
arches.

Now CONFIG_KEXEC_FILE is available only on x86_64. So whereever I
had CONFIG_X86_64 defined, I got rid of that.

For CONFIG_KEXEC_FILE, instead of doing select CRYPTO=y, I changed
it to "depends on CRYPTO=y". This should be safer as "select" is
not recursive.

Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
arch/x86/Kbuild | 4 +---
arch/x86/Kconfig | 18 ++++++++++++++----
arch/x86/Makefile | 5 +----
arch/x86/kernel/Makefile | 2 +-
arch/x86/kernel/crash.c | 6 ++----
arch/x86/kernel/machine_kexec_64.c | 11 +++++++++++
arch/x86/purgatory/Makefile | 5 +----
kernel/kexec.c | 11 +++++++++++
8 files changed, 42 insertions(+), 20 deletions(-)

diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index 61b6d51..3942f74 100644
--- a/arch/x86/Kbuild
+++ b/arch/x86/Kbuild
@@ -17,6 +17,4 @@ obj-$(CONFIG_IA32_EMULATION) += ia32/
obj-y += platform/
obj-y += net/

-ifeq ($(CONFIG_X86_64),y)
-obj-$(CONFIG_KEXEC) += purgatory/
-endif
+obj-$(CONFIG_KEXEC_FILE) += purgatory/
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 4aafd32..a4bb9d0 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1582,9 +1582,6 @@ source kernel/Kconfig.hz

config KEXEC
bool "kexec system call"
- select BUILD_BIN2C
- select CRYPTO
- select CRYPTO_SHA256
---help---
kexec is a system call that implements the ability to shutdown your
current kernel, and to start another kernel. It is like a reboot
@@ -1599,9 +1596,22 @@ config KEXEC
interface is strongly in flux, so no good recommendation can be
made.

+config KEXEC_FILE
+ bool "kexec file based system call"
+ select BUILD_BIN2C
+ depends on KEXEC
+ depends on X86_64
+ depends on CRYPTO=y
+ depends on CRYPTO_SHA256=y
+ ---help---
+ This is new version of kexec system call. This system call is
+ file based and takes file descriptors as system call argument
+ for kernel and initramfs as opposed to list of segments as
+ accepted by previous system call.
+
config KEXEC_VERIFY_SIG
bool "Verify kernel signature during kexec_file_load() syscall"
- depends on KEXEC
+ depends on KEXEC_FILE
---help---
This option makes kernel signature verification mandatory for
kexec_file_load() syscall. If kernel is signature can not be
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index c1aa368..c96bcec 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -184,11 +184,8 @@ archheaders:
$(Q)$(MAKE) $(build)=arch/x86/syscalls all

archprepare:
-ifeq ($(CONFIG_KEXEC),y)
-# Build only for 64bit. No loaders for 32bit yet.
- ifeq ($(CONFIG_X86_64),y)
+ifeq ($(CONFIG_KEXEC_FILE),y)
$(Q)$(MAKE) $(build)=arch/x86/purgatory arch/x86/purgatory/kexec-purgatory.c
- endif
endif

###
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index b5ea75c..ada2e2d 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -71,6 +71,7 @@ obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o
obj-$(CONFIG_X86_TSC) += trace_clock.o
obj-$(CONFIG_KEXEC) += machine_kexec_$(BITS).o
obj-$(CONFIG_KEXEC) += relocate_kernel_$(BITS).o crash.o
+obj-$(CONFIG_KEXEC_FILE) += kexec-bzimage64.o
obj-$(CONFIG_CRASH_DUMP) += crash_dump_$(BITS).o
obj-y += kprobes/
obj-$(CONFIG_MODULES) += module.o
@@ -118,5 +119,4 @@ ifeq ($(CONFIG_X86_64),y)

obj-$(CONFIG_PCI_MMCONFIG) += mmconf-fam10h_64.o
obj-y += vsmp_64.o
- obj-$(CONFIG_KEXEC) += kexec-bzimage64.o
endif
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index 0553a34..a618fcd 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -182,8 +182,7 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
crash_save_cpu(regs, safe_smp_processor_id());
}

-#ifdef CONFIG_X86_64
-
+#ifdef CONFIG_KEXEC_FILE
static int get_nr_ram_ranges_callback(unsigned long start_pfn,
unsigned long nr_pfn, void *arg)
{
@@ -696,5 +695,4 @@ int crash_load_segments(struct kimage *image)

return ret;
}
-
-#endif /* CONFIG_X86_64 */
+#endif /* CONFIG_KEXEC_FILE */
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 8b04018..4859810 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -25,9 +25,11 @@
#include <asm/debugreg.h>
#include <asm/kexec-bzimage64.h>

+#ifdef CONFIG_KEXEC_FILE
static struct kexec_file_ops *kexec_file_loaders[] = {
&kexec_bzImage64_ops,
};
+#endif

static void free_transition_pgtable(struct kimage *image)
{
@@ -178,6 +180,7 @@ static void load_segments(void)
);
}

+#ifdef CONFIG_KEXEC_FILE
/* Update purgatory as needed after various image segments have been prepared */
static int arch_update_purgatory(struct kimage *image)
{
@@ -209,6 +212,12 @@ static int arch_update_purgatory(struct kimage *image)

return ret;
}
+#else /* !CONFIG_KEXEC_FILE */
+static inline int arch_update_purgatory(struct kimage *image)
+{
+ return 0;
+}
+#endif /* CONFIG_KEXEC_FILE */

int machine_kexec_prepare(struct kimage *image)
{
@@ -329,6 +338,7 @@ void arch_crash_save_vmcoreinfo(void)

/* arch-dependent functionality related to kexec file-based syscall */

+#ifdef CONFIG_KEXEC_FILE
int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
unsigned long buf_len)
{
@@ -522,3 +532,4 @@ overflow:
(int)ELF64_R_TYPE(rel[i].r_info), value);
return -ENOEXEC;
}
+#endif /* CONFIG_KEXEC_FILE */
diff --git a/arch/x86/purgatory/Makefile b/arch/x86/purgatory/Makefile
index 7fde9ee..c4ae06e 100644
--- a/arch/x86/purgatory/Makefile
+++ b/arch/x86/purgatory/Makefile
@@ -24,7 +24,4 @@ $(obj)/kexec-purgatory.c: $(obj)/purgatory.ro FORCE
$(call if_changed,bin2c)


-# No loaders for 32bits yet.
-ifeq ($(CONFIG_X86_64),y)
- obj-$(CONFIG_KEXEC) += kexec-purgatory.o
-endif
+obj-$(CONFIG_KEXEC_FILE) += kexec-purgatory.o
diff --git a/kernel/kexec.c b/kernel/kexec.c
index 0b49a0a..2bee072 100644
--- a/kernel/kexec.c
+++ b/kernel/kexec.c
@@ -64,7 +64,9 @@ bool kexec_in_progress = false;
char __weak kexec_purgatory[0];
size_t __weak kexec_purgatory_size = 0;

+#ifdef CONFIG_KEXEC_FILE
static int kexec_calculate_store_digests(struct kimage *image);
+#endif

/* Location of the reserved area for the crash kernel */
struct resource crashk_res = {
@@ -341,6 +343,7 @@ out_free_image:
return ret;
}

+#ifdef CONFIG_KEXEC_FILE
static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len)
{
struct fd f = fdget(fd);
@@ -612,6 +615,9 @@ out_free_image:
kfree(image);
return ret;
}
+#else /* CONFIG_KEXEC_FILE */
+static inline void kimage_file_post_load_cleanup(struct kimage *image) { }
+#endif /* CONFIG_KEXEC_FILE */

static int kimage_is_destination_range(struct kimage *image,
unsigned long start,
@@ -1375,6 +1381,7 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry,
}
#endif

+#ifdef CONFIG_KEXEC_FILE
SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd,
unsigned long, cmdline_len, const char __user *, cmdline_ptr,
unsigned long, flags)
@@ -1451,6 +1458,8 @@ out:
return ret;
}

+#endif /* CONFIG_KEXEC_FILE */
+
void crash_kexec(struct pt_regs *regs)
{
/* Take the kexec_mutex here to prevent sys_kexec_load
@@ -2006,6 +2015,7 @@ static int __init crash_save_vmcoreinfo_init(void)

subsys_initcall(crash_save_vmcoreinfo_init);

+#ifdef CONFIG_KEXEC_FILE
static int __kexec_add_segment(struct kimage *image, char *buf,
unsigned long bufsz, unsigned long mem,
unsigned long memsz)
@@ -2682,6 +2692,7 @@ int kexec_purgatory_get_set_symbol(struct kimage *image, const char *name,

return 0;
}
+#endif /* CONFIG_KEXEC_FILE */

/*
* Move into place and start executing a preloaded standalone
--
1.9.0

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