Re: kexec fails to boot kernels where CONFIG_RANDOMIZE_BASE=y is set

["Thomas D." <whissi@whissi.de>]

Hi,

the patch works!

I am able to reboot my system using kexec when the kernel has this patch.

I had to slightly modify the patch, so it will apply against linux-3.15.10:

--- arch/x86/boot/compressed/misc.c.old	2014-08-22 14:52:20.792158801 +0200
+++ arch/x86/boot/compressed/misc.c	2014-08-22 14:58:21.250506919 +0200
@@ -230,8 +230,9 @@
 		asm("hlt");
 }

-#if CONFIG_X86_NEED_RELOCS
-static void handle_relocations(void *output, unsigned long output_len)
+#ifdef CONFIG_X86_NEED_RELOCS
+static void handle_relocations(void *output_orig, void *output,
+			       unsigned long output_len)
 {
 	int *reloc;
 	unsigned long delta, map, ptr;
@@ -242,7 +243,7 @@
 	 * Calculate the delta between where vmlinux was linked to load
 	 * and where it was actually loaded.
 	 */
-	delta = min_addr - LOAD_PHYSICAL_ADDR;
+	delta = min_addr - (unsigned long)output_orig;
 	if (!delta) {
 		debug_putstr("No relocation needed... ");
 		return;
@@ -299,7 +300,8 @@
 #endif
 }
 #else
-static inline void handle_relocations(void *output, unsigned long
output_len)
+static inline void handle_relocations(void *output_orig, void *output,
+				      unsigned long output_len)
 { }
 #endif

@@ -360,6 +362,8 @@
 				  unsigned char *output,
 				  unsigned long output_len)
 {
+	unsigned char *output_orig = output;
+
 	real_mode = rmode;

 	sanitize_boot_params(real_mode);
@@ -402,7 +406,7 @@
 	debug_putstr("\nDecompressing Linux... ");
 	decompress(input_data, input_len, NULL, NULL, output, NULL, error);
 	parse_elf(output);
-	handle_relocations(output, output_len);
+	handle_relocations(output_orig, output, output_len);
 	debug_putstr("done.\nBooting the kernel.\n");
 	return output;
 }




So now we have two "solutions":

1) Using kexec with "--entry-32bit" parameter

2) Use a patched kernel


-Thomas

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