In linux-5.2, the following commit allows the kdump kernel to be loaded
at a higher address than 896M
9ca5c8e632ce ("x86/kdump: Have crashkernel=X reserve under 4G by
default")
While this limit does indeed seem unnecessary for x86_64 kernels, it
still is required to boot to or from i386 kernels. Therefore,
kexec-tools continues to enforce it when using the i386 bzImage loader.
However, the i386 bzImage loader may also be used to load an x86_64
kernel from i386 user space to be kexeced by an x86_64 kernel. In this
case, the limit was incorrectly enforced.
This commit adds an additional check for an x86_64 image kexeced by an
x86_64 kernel in the i386 loader and bumps the limit to the maximum
addressable 4G in that case.
Signed-off-by: Kevin Mitchell <kevmitch@xxxxxxxxxx>
---
kexec/arch/i386/kexec-bzImage.c | 41 ++++++++++++++++++++++-----------
1 file changed, 28 insertions(+), 13 deletions(-)
diff --git a/kexec/arch/i386/kexec-bzImage.c b/kexec/arch/i386/kexec-bzImage.c
index df8985d..7b8e36e 100644
--- a/kexec/arch/i386/kexec-bzImage.c
+++ b/kexec/arch/i386/kexec-bzImage.c
@@ -22,6 +22,7 @@
#include <string.h>
#include <stdlib.h>
#include <errno.h>
+#include <limits.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
@@ -114,6 +115,7 @@ int do_bzImage_load(struct kexec_info *info,
struct entry32_regs regs32;
struct entry16_regs regs16;
unsigned int relocatable_kernel = 0;
+ unsigned int kernel64 = 0;
unsigned long kernel32_load_addr;
char *modified_cmdline;
unsigned long cmdline_end;
@@ -155,6 +157,13 @@ int do_bzImage_load(struct kexec_info *info,
dbgprintf("bzImage is relocatable\n");
}
+ if ((setup_header.protocol_version >= 0x020C) &&
+ (info->kexec_flags & KEXEC_ARCH_X86_64) &&
+ (setup_header.xloadflags & 1)) {
+ kernel64 = 1;
+ dbgprintf("loading x86_64 bzImage from an x86_64 kernel\n");
+ }
+
/* Can't use bzImage for crash dump purposes with real mode entry */
if((info->kexec_flags & KEXEC_ON_CRASH) && real_mode_entry) {
fprintf(stderr, "Can't use bzImage for crash dump purposes"
@@ -197,17 +206,17 @@ int do_bzImage_load(struct kexec_info *info,
/* Load the trampoline. This must load at a higher address
* than the argument/parameter segment or the kernel will stomp
* it's gdt.
- *
- * x86_64 purgatory code has got relocations type R_X86_64_32S
- * that means purgatory got to be loaded within first 2G otherwise
- * overflow takes place while applying relocations.
*/
- if (!real_mode_entry && relocatable_kernel)
+ if (!real_mode_entry && relocatable_kernel) {
+ /* x86_64 purgatory could be anywhere */
+ unsigned long purg_max_addr = kernel64 ? ULONG_MAX : 0x7fffffff;
+
elf_rel_build_load(info, &info->rhdr, purgatory, purgatory_size,
- 0x3000, 0x7fffffff, -1, 0);
- else
+ 0x3000, purg_max_addr, -1, 0);
+ } else {
elf_rel_build_load(info, &info->rhdr, purgatory, purgatory_size,
0x3000, 640*1024, -1, 0);
+ }
dbgprintf("Loaded purgatory at addr 0x%lx\n", info->rhdr.rel_addr);
/* The argument/parameter segment */
@@ -277,14 +286,20 @@ int do_bzImage_load(struct kexec_info *info,
if (real_mode->protocol_version >=0x0205 && relocatable_kernel) {
/* Relocatable bzImage */
unsigned long kern_align = real_mode->kernel_alignment;
- unsigned long kernel32_max_addr = DEFAULT_BZIMAGE_ADDR_MAX;
+ unsigned long kernel_max_addr = DEFAULT_BZIMAGE_ADDR_MAX;
- if (kernel32_max_addr > real_mode->initrd_addr_max)
- kernel32_max_addr = real_mode->initrd_addr_max;
+ /*
+ * x86_64 kernels can be kexeced by an x86_64 kernel
+ * from any addressable location
+ */
+ if (kernel64)
+ kernel_max_addr = ULONG_MAX;
+ else if (kernel_max_addr > real_mode->initrd_addr_max)
+ kernel_max_addr = real_mode->initrd_addr_max;
kernel32_load_addr = add_buffer(info, kernel + kern16_size,
size, size, kern_align,
- 0x100000, kernel32_max_addr,
+ 0x100000, kernel_max_addr,
1);
}
else {
@@ -296,9 +311,9 @@ int do_bzImage_load(struct kexec_info *info,
dbgprintf("Loaded 32bit kernel at 0x%lx\n", kernel32_load_addr);
/* Tell the kernel what is going on */
- setup_linux_bootloader_parameters(info, real_mode, setup_base,
+ setup_linux_bootloader_parameters_high(info, real_mode, setup_base,
kern16_size_needed, command_line, command_line_len,
- initrd, initrd_len);
+ initrd, initrd_len, kernel64); /* put x86_64 initrd high too */
if (real_mode_entry && real_mode->protocol_version >= 0x0201) {
real_mode->loader_flags |= 0x80; /* CAN_USE_HEAP */
--
2.32.0
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