diff options
| author | Christoph Hellwig <hch@lst.de> | 2020-09-03 17:22:38 +0300 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2020-09-09 05:21:34 +0300 |
| commit | 999c83e8ffd90caa00ee6caf054e037cf8a27d0e (patch) | |
| tree | cbb1bdea654262bd8e7cf181d195f88146152609 /arch/x86/include/asm/page_64_types.h | |
| parent | c6f7c753f71cccb21d1a7f0c1127ce7804374c5e (diff) | |
| download | linux-999c83e8ffd90caa00ee6caf054e037cf8a27d0e.tar.xz | |
x86: move PAGE_OFFSET, TASK_SIZE & friends to page_{32,64}_types.h
At least for 64-bit this moves them closer to some of the defines
they are based on, and it prepares for using the TASK_SIZE_MAX
definition from assembly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'arch/x86/include/asm/page_64_types.h')
| -rw-r--r-- | arch/x86/include/asm/page_64_types.h | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h index 288b065955b7..996595c9897e 100644 --- a/arch/x86/include/asm/page_64_types.h +++ b/arch/x86/include/asm/page_64_types.h @@ -59,6 +59,44 @@ #endif /* + * User space process size. This is the first address outside the user range. + * There are a few constraints that determine this: + * + * On Intel CPUs, if a SYSCALL instruction is at the highest canonical + * address, then that syscall will enter the kernel with a + * non-canonical return address, and SYSRET will explode dangerously. + * We avoid this particular problem by preventing anything executable + * from being mapped at the maximum canonical address. + * + * On AMD CPUs in the Ryzen family, there's a nasty bug in which the + * CPUs malfunction if they execute code from the highest canonical page. + * They'll speculate right off the end of the canonical space, and + * bad things happen. This is worked around in the same way as the + * Intel problem. + * + * With page table isolation enabled, we map the LDT in ... [stay tuned] + */ +#define TASK_SIZE_MAX ((1UL << __VIRTUAL_MASK_SHIFT) - PAGE_SIZE) + +#define DEFAULT_MAP_WINDOW ((1UL << 47) - PAGE_SIZE) + +/* This decides where the kernel will search for a free chunk of vm + * space during mmap's. + */ +#define IA32_PAGE_OFFSET ((current->personality & ADDR_LIMIT_3GB) ? \ + 0xc0000000 : 0xFFFFe000) + +#define TASK_SIZE_LOW (test_thread_flag(TIF_ADDR32) ? \ + IA32_PAGE_OFFSET : DEFAULT_MAP_WINDOW) +#define TASK_SIZE (test_thread_flag(TIF_ADDR32) ? \ + IA32_PAGE_OFFSET : TASK_SIZE_MAX) +#define TASK_SIZE_OF(child) ((test_tsk_thread_flag(child, TIF_ADDR32)) ? \ + IA32_PAGE_OFFSET : TASK_SIZE_MAX) + +#define STACK_TOP TASK_SIZE_LOW +#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). * |