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s390/kernel: add support for kernel address space layout randomization (KASLR)

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This patch adds support for relocating the kernel to a random address.
The random kernel offset is obtained from cpacf, using either TRNG, PRNO,
or KMC_PRNG, depending on supported MSA level.

KERNELOFFSET is added to vmcoreinfo, for crash --kaslr support.

Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Reviewed-by: Philipp Rudo <prudo@linux.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Gerald Schaefer
2019-02-03 21:37:20 +01:00
committed by Martin Schwidefsky
parent a80313ff91
commit b2d24b97b2
9 changed files with 207 additions and 5 deletions
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31
arch/s390/boot/startup.c
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@@ -12,6 +12,7 @@
extern char __boot_data_start[], __boot_data_end[];
extern char __boot_data_preserved_start[], __boot_data_preserved_end[];
unsigned long __bootdata_preserved(__kaslr_offset);
/*
* Some code and data needs to stay below 2 GB, even when the kernel would be
@@ -113,6 +114,7 @@ static void handle_relocs(unsigned long offset)
void startup_kernel(void)
{
unsigned long random_lma;
unsigned long safe_addr;
void *img;
@@ -126,12 +128,37 @@ void startup_kernel(void)
parse_boot_command_line();
setup_memory_end();
detect_memory();
random_lma = __kaslr_offset = 0;
if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_enabled) {
random_lma = get_random_base(safe_addr);
if (random_lma) {
__kaslr_offset = random_lma - vmlinux.default_lma;
img = (void *)vmlinux.default_lma;
vmlinux.default_lma += __kaslr_offset;
vmlinux.entry += __kaslr_offset;
vmlinux.bootdata_off += __kaslr_offset;
vmlinux.bootdata_preserved_off += __kaslr_offset;
vmlinux.rela_dyn_start += __kaslr_offset;
vmlinux.rela_dyn_end += __kaslr_offset;
vmlinux.dynsym_start += __kaslr_offset;
}
}
if (!IS_ENABLED(CONFIG_KERNEL_UNCOMPRESSED)) {
img = decompress_kernel();
memmove((void *)vmlinux.default_lma, img, vmlinux.image_size);
}
} else if (__kaslr_offset)
memcpy((void *)vmlinux.default_lma, img, vmlinux.image_size);
copy_bootdata();
if (IS_ENABLED(CONFIG_RELOCATABLE))
handle_relocs(0);
handle_relocs(__kaslr_offset);
if (__kaslr_offset) {
/* Clear non-relocated kernel */
if (IS_ENABLED(CONFIG_KERNEL_UNCOMPRESSED))
memset(img, 0, vmlinux.image_size);
}
vmlinux.entry();
}