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| author |  Arvind Sankar <nivedita@alum.mit.edu>
| 2020-10-29 12:19:03 -0400 |
|---|---|---|
| committer |  Borislav Petkov <bp@suse.de>
| 2020-10-29 21:54:35 +0100 |
| commit | ea3186b9572a1b0299448697cfc44920061872cf (patch) | |
| tree | 82474a7fd03a53c744ee9c491b4018c96eda4c63 /arch/x86/kernel/vmlinux.lds.S | |
| parent | Linux 5.10-rc1 (diff) | |
| download | linux-ea3186b9572a1b0299448697cfc44920061872cf.tar.gz linux-ea3186b9572a1b0299448697cfc44920061872cf.tar.bz2 linux-ea3186b9572a1b0299448697cfc44920061872cf.zip | |
x86/build: Fix vmlinux size check on 64-bit
Commit
b4e0409a36f4 ("x86: check vmlinux limits, 64-bit")
added a check that the size of the 64-bit kernel is less than
KERNEL_IMAGE_SIZE.
The check uses (_end - _text), but this is not enough. The initial
PMD used in startup_64() (level2_kernel_pgt) can only map upto
KERNEL_IMAGE_SIZE from __START_KERNEL_map, not from _text, and the
modules area (MODULES_VADDR) starts at KERNEL_IMAGE_SIZE.
The correct check is what is currently done for 32-bit, since
LOAD_OFFSET is defined appropriately for the two architectures. Just
check (_end - LOAD_OFFSET) against KERNEL_IMAGE_SIZE unconditionally.
Note that on 32-bit, the limit is not strict: KERNEL_IMAGE_SIZE is not
really used by the main kernel. The higher the kernel is located, the
less the space available for the vmalloc area. However, it is used by
KASLR in the compressed stub to limit the maximum address of the kernel
to a safe value.
Clean up various comments to clarify that despite the name,
KERNEL_IMAGE_SIZE is not a limit on the size of the kernel image, but a
limit on the maximum virtual address that the image can occupy.
Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20201029161903.2553528-1-nivedita@alum.mit.edu
Diffstat (limited to 'arch/x86/kernel/vmlinux.lds.S')
| -rw-r--r-- | arch/x86/kernel/vmlinux.lds.S | 12 |
1 files changed, 3 insertions, 9 deletions
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index bf9e0adb5b7e..efd9e9ea17f2 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -454,13 +454,13 @@ SECTIONS ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!") } -#ifdef CONFIG_X86_32 /* * The ASSERT() sink to . is intentional, for binutils 2.14 compatibility: */ . = ASSERT((_end - LOAD_OFFSET <= KERNEL_IMAGE_SIZE), "kernel image bigger than KERNEL_IMAGE_SIZE"); -#else + +#ifdef CONFIG_X86_64 /* * Per-cpu symbols which need to be offset from __per_cpu_load * for the boot processor. @@ -470,18 +470,12 @@ INIT_PER_CPU(gdt_page); INIT_PER_CPU(fixed_percpu_data); INIT_PER_CPU(irq_stack_backing_store); -/* - * Build-time check on the image size: - */ -. = ASSERT((_end - _text <= KERNEL_IMAGE_SIZE), - "kernel image bigger than KERNEL_IMAGE_SIZE"); - #ifdef CONFIG_SMP . = ASSERT((fixed_percpu_data == 0), "fixed_percpu_data is not at start of per-cpu area"); #endif -#endif /* CONFIG_X86_32 */ +#endif /* CONFIG_X86_64 */ #ifdef CONFIG_KEXEC_CORE #include <asm/kexec.h> |