[PATCH v3 1/3] kexec_load: Use new kexec flag for hotplug support
Sourabh Jain
sourabhjain at linux.ibm.com
Sun Jul 7 08:24:54 PDT 2024
Kernel commit 79365026f869 (crash: add a new kexec flag for hotplug
support) has introduced a new kexec flag to generalize hotplug support.
The newly introduced kexec flags for hotplug allow architectures to
exclude all the required kexec segments from SHA calculation so that
the kernel can update them on hotplug events. This was not possible
earlier with the KEXEC_UPDATE_ELFCOREHDR kexec flags since it was added
only for the elfcorehdr segment.
To enable architectures to control the list of kexec segments to exclude
when hotplug support is enabled, add a new architecture-specific
function named arch_do_exclude_segment. During the SHA calculation, this
function gets called to let the architecture decide whether a specific
kexec segment should be considered for SHA calculation or not.
Note: To avoid breaking backward compatibility, the new kexec flag
KEXEC_CRASH_HOTPLUG_SUPPORT is not used for x86 for now.
Cc: Aditya Gupta <adityag at linux.ibm.com>
Cc: Baoquan He <bhe at redhat.com>
Cc: Coiby Xu <coxu at redhat.com>
Cc: Hari Bathini <hbathini at linux.ibm.com>
Cc: Mahesh Salgaonkar <mahesh at linux.ibm.com>
Cc: Simon Horman <horms at kernel.org>
Signed-off-by: Sourabh Jain <sourabhjain at linux.ibm.com>
---
kexec/arch/arm/kexec-arm.c | 5 ++++
kexec/arch/arm64/kexec-arm64.c | 5 ++++
kexec/arch/cris/kexec-cris.c | 4 +++
kexec/arch/hppa/kexec-hppa.c | 5 ++++
kexec/arch/i386/kexec-x86.c | 8 ++++++
kexec/arch/ia64/kexec-ia64.c | 4 +++
kexec/arch/loongarch/kexec-loongarch.c | 5 ++++
kexec/arch/m68k/kexec-m68k.c | 5 ++++
kexec/arch/mips/kexec-mips.c | 4 +++
kexec/arch/ppc/kexec-ppc.c | 4 +++
kexec/arch/ppc64/kexec-ppc64.c | 5 ++++
kexec/arch/s390/kexec-s390.c | 5 ++++
kexec/arch/sh/kexec-sh.c | 5 ++++
kexec/arch/x86_64/kexec-x86_64.c | 8 ++++++
kexec/kexec-syscall.h | 1 +
kexec/kexec.c | 40 ++++++++++++++++++++++----
kexec/kexec.h | 2 ++
17 files changed, 109 insertions(+), 6 deletions(-)
diff --git a/kexec/arch/arm/kexec-arm.c b/kexec/arch/arm/kexec-arm.c
index 49f35b1..4216327 100644
--- a/kexec/arch/arm/kexec-arm.c
+++ b/kexec/arch/arm/kexec-arm.c
@@ -148,3 +148,8 @@ int have_sysfs_fdt(void)
{
return !access(SYSFS_FDT, F_OK);
}
+
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
index 4a67b0d..55e822b 100644
--- a/kexec/arch/arm64/kexec-arm64.c
+++ b/kexec/arch/arm64/kexec-arm64.c
@@ -1363,3 +1363,8 @@ void arch_reuse_initrd(void)
void arch_update_purgatory(struct kexec_info *UNUSED(info))
{
}
+
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/cris/kexec-cris.c b/kexec/arch/cris/kexec-cris.c
index 3b69709..6d048d3 100644
--- a/kexec/arch/cris/kexec-cris.c
+++ b/kexec/arch/cris/kexec-cris.c
@@ -109,3 +109,7 @@ unsigned long add_buffer(struct kexec_info *info, const void *buf,
buf_min, buf_max, buf_end, 1);
}
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/hppa/kexec-hppa.c b/kexec/arch/hppa/kexec-hppa.c
index 77c9739..b2c74ab 100644
--- a/kexec/arch/hppa/kexec-hppa.c
+++ b/kexec/arch/hppa/kexec-hppa.c
@@ -146,3 +146,8 @@ unsigned long virt_to_phys(unsigned long addr)
{
return addr - phys_offset;
}
+
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/i386/kexec-x86.c b/kexec/arch/i386/kexec-x86.c
index 444cb69..eac01e5 100644
--- a/kexec/arch/i386/kexec-x86.c
+++ b/kexec/arch/i386/kexec-x86.c
@@ -208,3 +208,11 @@ void arch_update_purgatory(struct kexec_info *info)
elf_rel_set_symbol(&info->rhdr, "panic_kernel",
&panic_kernel, sizeof(panic_kernel));
}
+
+int arch_do_exclude_segment(struct kexec_info *info, struct kexec_segment *segment)
+{
+ if (info->elfcorehdr == (unsigned long) segment->mem)
+ return 1;
+
+ return 0;
+}
diff --git a/kexec/arch/ia64/kexec-ia64.c b/kexec/arch/ia64/kexec-ia64.c
index 418d997..548a3af 100644
--- a/kexec/arch/ia64/kexec-ia64.c
+++ b/kexec/arch/ia64/kexec-ia64.c
@@ -245,3 +245,7 @@ void arch_update_purgatory(struct kexec_info *UNUSED(info))
{
}
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/loongarch/kexec-loongarch.c b/kexec/arch/loongarch/kexec-loongarch.c
index ac75030..ea0c316 100644
--- a/kexec/arch/loongarch/kexec-loongarch.c
+++ b/kexec/arch/loongarch/kexec-loongarch.c
@@ -381,3 +381,8 @@ unsigned long add_buffer(struct kexec_info *info, const void *buf,
return add_buffer_phys_virt(info, buf, bufsz, memsz, buf_align,
buf_min, buf_max, buf_end, 1);
}
+
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/m68k/kexec-m68k.c b/kexec/arch/m68k/kexec-m68k.c
index cb54927..4824a02 100644
--- a/kexec/arch/m68k/kexec-m68k.c
+++ b/kexec/arch/m68k/kexec-m68k.c
@@ -108,3 +108,8 @@ void add_segment(struct kexec_info *info, const void *buf, size_t bufsz,
{
add_segment_phys_virt(info, buf, bufsz, base, memsz, 1);
}
+
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/mips/kexec-mips.c b/kexec/arch/mips/kexec-mips.c
index d8cbea8..fb5a5d4 100644
--- a/kexec/arch/mips/kexec-mips.c
+++ b/kexec/arch/mips/kexec-mips.c
@@ -189,3 +189,7 @@ unsigned long add_buffer(struct kexec_info *info, const void *buf,
buf_min, buf_max, buf_end, 1);
}
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/ppc/kexec-ppc.c b/kexec/arch/ppc/kexec-ppc.c
index 03bec36..d3dad0f 100644
--- a/kexec/arch/ppc/kexec-ppc.c
+++ b/kexec/arch/ppc/kexec-ppc.c
@@ -966,3 +966,7 @@ void arch_update_purgatory(struct kexec_info *UNUSED(info))
{
}
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/ppc64/kexec-ppc64.c b/kexec/arch/ppc64/kexec-ppc64.c
index bd5274c..90734fe 100644
--- a/kexec/arch/ppc64/kexec-ppc64.c
+++ b/kexec/arch/ppc64/kexec-ppc64.c
@@ -967,3 +967,8 @@ int arch_compat_trampoline(struct kexec_info *UNUSED(info))
void arch_update_purgatory(struct kexec_info *UNUSED(info))
{
}
+
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/s390/kexec-s390.c b/kexec/arch/s390/kexec-s390.c
index 33ba6b9..f4dd7dc 100644
--- a/kexec/arch/s390/kexec-s390.c
+++ b/kexec/arch/s390/kexec-s390.c
@@ -267,3 +267,8 @@ int get_crash_kernel_load_range(uint64_t *start, uint64_t *end)
{
return parse_iomem_single("Crash kernel\n", start, end);
}
+
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/sh/kexec-sh.c b/kexec/arch/sh/kexec-sh.c
index ce341c8..7b9ac1c 100644
--- a/kexec/arch/sh/kexec-sh.c
+++ b/kexec/arch/sh/kexec-sh.c
@@ -257,3 +257,8 @@ unsigned long add_buffer(struct kexec_info *info, const void *buf,
return add_buffer_phys_virt(info, buf, bufsz, memsz, buf_align,
buf_min, buf_max, buf_end, 1);
}
+
+int arch_do_exclude_segment(struct kexec_info *UNUSED(info), struct kexec_segment *UNUSED(segment))
+{
+ return 0;
+}
diff --git a/kexec/arch/x86_64/kexec-x86_64.c b/kexec/arch/x86_64/kexec-x86_64.c
index ffd84f0..7b2453f 100644
--- a/kexec/arch/x86_64/kexec-x86_64.c
+++ b/kexec/arch/x86_64/kexec-x86_64.c
@@ -188,3 +188,11 @@ void arch_update_purgatory(struct kexec_info *info)
elf_rel_set_symbol(&info->rhdr, "panic_kernel",
&panic_kernel, sizeof(panic_kernel));
}
+
+int arch_do_exclude_segment(struct kexec_info *info, struct kexec_segment *segment)
+{
+ if (info->elfcorehdr == (unsigned long) segment->mem)
+ return 1;
+
+ return 0;
+}
diff --git a/kexec/kexec-syscall.h b/kexec/kexec-syscall.h
index 73e5254..cc32c01 100644
--- a/kexec/kexec-syscall.h
+++ b/kexec/kexec-syscall.h
@@ -113,6 +113,7 @@ static inline long kexec_file_load(int kernel_fd, int initrd_fd,
#define KEXEC_ON_CRASH 0x00000001
#define KEXEC_PRESERVE_CONTEXT 0x00000002
#define KEXEC_UPDATE_ELFCOREHDR 0x00000004
+#define KEXEC_CRASH_HOTPLUG_SUPPORT 0x00000008
#define KEXEC_ARCH_MASK 0xffff0000
/* Flags for kexec file based system call */
diff --git a/kexec/kexec.c b/kexec/kexec.c
index 222f79e..59be075 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -701,10 +701,13 @@ static void update_purgatory(struct kexec_info *info)
continue;
}
- /* Don't include elfcorehdr in the checksum, if hotplug
- * support enabled.
+ /*
+ * Let architecture decide which segments to exclude from checksum
+ * if hotplug support is enabled.
*/
- if (do_hotplug && (info->segment[i].mem == (void *)info->elfcorehdr)) {
+ if (do_hotplug && arch_do_exclude_segment(info, &info->segment[i])) {
+ dbgprintf("Skipping segment mem: 0x%lx from SHA calculation\n",
+ (unsigned long)info->segment[i].mem);
continue;
}
@@ -1419,6 +1422,30 @@ static int do_kexec_file_load(int fileind, int argc, char **argv,
return ret;
}
+/*
+ * Hotplug support for x86 in the kernel was added with the
+ * `KEXEC_UPDATE_ELFCOREHDR` kexec bit, and later it was generalized
+ * with the `KEXEC_CRASH_HOTPLUG_SUPPORT` kexec bit.
+ *
+ * Passing the `KEXEC_CRASH_HOTPLUG_SUPPORT` kexec bit to kernel
+ * versions 6.5 to 6.9 on x86 with the `kexec_load` system call will
+ * fail with `-EINVAL`.
+ *
+ * So for now, pass `KEXEC_UPDATE_ELFCOREHDR` for x86, and for other
+ * architectures, use the `KEXEC_CRASH_HOTPLUG_SUPPORT` kexec bit. But
+ * in the future, we can decide to get rid of `KEXEC_UPDATE_ELFCOREHDR`.
+ *
+ * NOTE: Xen KEXEC_LIVE_UPDATE and KEXEC_UPDATE_ELFCOREHDR collide
+ */
+static inline unsigned long get_hotplug_kexec_flag(void)
+{
+#if defined(__i386__) || defined(__x86_64__)
+ return KEXEC_UPDATE_ELFCOREHDR;
+#else
+ return KEXEC_CRASH_HOTPLUG_SUPPORT;
+#endif
+}
+
static void print_crashkernel_region_size(void)
{
uint64_t start = 0, end = 0;
@@ -1651,7 +1678,6 @@ int main(int argc, char *argv[])
die("--load-live-update can only be used with xen\n");
}
- /* NOTE: Xen KEXEC_LIVE_UPDATE and KEXEC_UPDATE_ELFCOREHDR collide */
if (do_hotplug) {
const char *ces = "/sys/kernel/crash_elfcorehdr_size";
char *buf, *endptr = NULL;
@@ -1665,8 +1691,10 @@ int main(int argc, char *argv[])
if (!elfcorehdrsz || (endptr && *endptr != '\0'))
die("Path %s does not exist, the kernel needs CONFIG_CRASH_HOTPLUG\n", ces);
dbgprintf("ELFCOREHDR_SIZE %lu\n", elfcorehdrsz);
- /* Indicate to the kernel it is ok to modify the elfcorehdr */
- kexec_flags |= KEXEC_UPDATE_ELFCOREHDR;
+ /* Indicate to the kernel it is ok to modify the relevant kexec segments */
+
+ kexec_flags |= get_hotplug_kexec_flag();
+
}
fileind = optind;
diff --git a/kexec/kexec.h b/kexec/kexec.h
index 1004aff..31c323f 100644
--- a/kexec/kexec.h
+++ b/kexec/kexec.h
@@ -307,6 +307,8 @@ extern int do_hotplug;
#define BOOTLOADER_VERSION PACKAGE_VERSION
void arch_usage(void);
+/* Return non-zero if segment needs to be excluded from SHA calculation, else 0. */
+int arch_do_exclude_segment(struct kexec_info *info, struct kexec_segment *segment);
int arch_process_options(int argc, char **argv);
int arch_compat_trampoline(struct kexec_info *info);
void arch_update_purgatory(struct kexec_info *info);
--
2.45.1
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