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authorLinus Torvalds <torvalds@linux-foundation.org>2020-12-14 13:54:50 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-12-14 13:54:50 -0800
commit84292fffc2468125632a21c09533a89426ea212e (patch)
treed2ec4f5d668ebb45ada890c6c9c9b9e042b2a6dd
parent8ba27ae36b416a1507e783dbee4bb521fd6bb519 (diff)
parent2838307b019dfec0c309c4e8e589658736cff4c9 (diff)
downloadlinux-84292fffc2468125632a21c09533a89426ea212e.tar.bz2
Merge tag 'x86_build_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 build updates from Borislav Petkov: "Two x86 build fixes: - Fix the vmlinux size check on 64-bit along with adding useful clarifications on the topic (Arvind Sankar) - Remove -m16 workaround now that the GCC versions that need it are unsupported (Nick Desaulniers)" * tag 'x86_build_for_v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/build: Remove -m16 workaround for unsupported versions of GCC x86/build: Fix vmlinux size check on 64-bit
-rw-r--r--arch/x86/Makefile9
-rw-r--r--arch/x86/boot/code16gcc.h12
-rw-r--r--arch/x86/include/asm/page_32_types.h8
-rw-r--r--arch/x86/include/asm/page_64_types.h6
-rw-r--r--arch/x86/include/asm/pgtable_32.h18
-rw-r--r--arch/x86/kernel/head_64.S20
-rw-r--r--arch/x86/kernel/vmlinux.lds.S12
7 files changed, 30 insertions, 55 deletions
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 1bf21746f4ce..7116da3980be 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -24,14 +24,7 @@ endif
# How to compile the 16-bit code. Note we always compile for -march=i386;
# that way we can complain to the user if the CPU is insufficient.
-#
-# The -m16 option is supported by GCC >= 4.9 and clang >= 3.5. For
-# older versions of GCC, include an *assembly* header to make sure that
-# gcc doesn't play any games behind our back.
-CODE16GCC_CFLAGS := -m32 -Wa,$(srctree)/arch/x86/boot/code16gcc.h
-M16_CFLAGS := $(call cc-option, -m16, $(CODE16GCC_CFLAGS))
-
-REALMODE_CFLAGS := $(M16_CFLAGS) -g -Os -DDISABLE_BRANCH_PROFILING \
+REALMODE_CFLAGS := -m16 -g -Os -DDISABLE_BRANCH_PROFILING \
-Wall -Wstrict-prototypes -march=i386 -mregparm=3 \
-fno-strict-aliasing -fomit-frame-pointer -fno-pic \
-mno-mmx -mno-sse
diff --git a/arch/x86/boot/code16gcc.h b/arch/x86/boot/code16gcc.h
deleted file mode 100644
index e19fd7536307..000000000000
--- a/arch/x86/boot/code16gcc.h
+++ /dev/null
@@ -1,12 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#
-# code16gcc.h
-#
-# This file is added to the assembler via -Wa when compiling 16-bit C code.
-# This is done this way instead via asm() to make sure gcc does not reorder
-# things around us.
-#
-# gcc 4.9+ has a real -m16 option so we can drop this hack long term.
-#
-
- .code16gcc
diff --git a/arch/x86/include/asm/page_32_types.h b/arch/x86/include/asm/page_32_types.h
index f462895a33e4..faf9cc1c14bb 100644
--- a/arch/x86/include/asm/page_32_types.h
+++ b/arch/x86/include/asm/page_32_types.h
@@ -53,7 +53,13 @@
#define STACK_TOP_MAX STACK_TOP
/*
- * Kernel image size is limited to 512 MB (see in arch/x86/kernel/head_32.S)
+ * In spite of the name, KERNEL_IMAGE_SIZE is a limit on the maximum virtual
+ * address for the kernel image, rather than the limit on the size itself. On
+ * 32-bit, this is not a strict limit, but this value is used to limit the
+ * link-time virtual address range of the kernel, and by KASLR to limit the
+ * randomized address from which the kernel is executed. A relocatable kernel
+ * can be loaded somewhat higher than KERNEL_IMAGE_SIZE as long as enough space
+ * remains for the vmalloc area.
*/
#define KERNEL_IMAGE_SIZE (512 * 1024 * 1024)
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 3f49dac03617..645bd1d0ee07 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -98,8 +98,10 @@
#define STACK_TOP_MAX TASK_SIZE_MAX
/*
- * Maximum kernel image size is limited to 1 GiB, due to the fixmap living
- * in the next 1 GiB (see level2_kernel_pgt in arch/x86/kernel/head_64.S).
+ * In spite of the name, KERNEL_IMAGE_SIZE is a limit on the maximum virtual
+ * address for the kernel image, rather than the limit on the size itself.
+ * This can be at most 1 GiB, due to the fixmap living in the next 1 GiB (see
+ * level2_kernel_pgt in arch/x86/kernel/head_64.S).
*
* On KASLR use 1 GiB by default, leaving 1 GiB for modules once the
* page tables are fully set up.
diff --git a/arch/x86/include/asm/pgtable_32.h b/arch/x86/include/asm/pgtable_32.h
index d7acae4120d5..7c9c968a42ef 100644
--- a/arch/x86/include/asm/pgtable_32.h
+++ b/arch/x86/include/asm/pgtable_32.h
@@ -57,19 +57,13 @@ do { \
#endif
/*
- * This is how much memory in addition to the memory covered up to
- * and including _end we need mapped initially.
- * We need:
- * (KERNEL_IMAGE_SIZE/4096) / 1024 pages (worst case, non PAE)
- * (KERNEL_IMAGE_SIZE/4096) / 512 + 4 pages (worst case for PAE)
+ * This is used to calculate the .brk reservation for initial pagetables.
+ * Enough space is reserved to allocate pagetables sufficient to cover all
+ * of LOWMEM_PAGES, which is an upper bound on the size of the direct map of
+ * lowmem.
*
- * Modulo rounding, each megabyte assigned here requires a kilobyte of
- * memory, which is currently unreclaimed.
- *
- * This should be a multiple of a page.
- *
- * KERNEL_IMAGE_SIZE should be greater than pa(_end)
- * and small than max_low_pfn, otherwise will waste some page table entries
+ * With PAE paging (PTRS_PER_PMD > 1), we allocate PTRS_PER_PGD == 4 pages for
+ * the PMD's in addition to the pages required for the last level pagetables.
*/
#if PTRS_PER_PMD > 1
#define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 29889ff3f46a..04bddaaba8e2 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -531,21 +531,19 @@ SYM_DATA_END(level3_kernel_pgt)
SYM_DATA_START_PAGE_ALIGNED(level2_kernel_pgt)
/*
- * 512 MB kernel mapping. We spend a full page on this pagetable
- * anyway.
+ * Kernel high mapping.
*
- * The kernel code+data+bss must not be bigger than that.
+ * The kernel code+data+bss must be located below KERNEL_IMAGE_SIZE in
+ * virtual address space, which is 1 GiB if RANDOMIZE_BASE is enabled,
+ * 512 MiB otherwise.
*
- * (NOTE: at +512MB starts the module area, see MODULES_VADDR.
- * If you want to increase this then increase MODULES_VADDR
- * too.)
+ * (NOTE: after that starts the module area, see MODULES_VADDR.)
*
- * This table is eventually used by the kernel during normal
- * runtime. Care must be taken to clear out undesired bits
- * later, like _PAGE_RW or _PAGE_GLOBAL in some cases.
+ * This table is eventually used by the kernel during normal runtime.
+ * Care must be taken to clear out undesired bits later, like _PAGE_RW
+ * or _PAGE_GLOBAL in some cases.
*/
- PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
- KERNEL_IMAGE_SIZE/PMD_SIZE)
+ PMDS(0, __PAGE_KERNEL_LARGE_EXEC, KERNEL_IMAGE_SIZE/PMD_SIZE)
SYM_DATA_END(level2_kernel_pgt)
SYM_DATA_START_PAGE_ALIGNED(level2_fixmap_pgt)
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>