mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-10-02 07:04:24 +00:00
3fb0fdb3bb
On 32-bit kernels, the stackprotector canary is quite nasty -- it is stored at %gs:(20), which is nasty because 32-bit kernels use %fs for percpu storage. It's even nastier because it means that whether %gs contains userspace state or kernel state while running kernel code depends on whether stackprotector is enabled (this is CONFIG_X86_32_LAZY_GS), and this setting radically changes the way that segment selectors work. Supporting both variants is a maintenance and testing mess. Merely rearranging so that percpu and the stack canary share the same segment would be messy as the 32-bit percpu address layout isn't currently compatible with putting a variable at a fixed offset. Fortunately, GCC 8.1 added options that allow the stack canary to be accessed as %fs:__stack_chk_guard, effectively turning it into an ordinary percpu variable. This lets us get rid of all of the code to manage the stack canary GDT descriptor and the CONFIG_X86_32_LAZY_GS mess. (That name is special. We could use any symbol we want for the %fs-relative mode, but for CONFIG_SMP=n, gcc refuses to let us use any name other than __stack_chk_guard.) Forcibly disable stackprotector on older compilers that don't support the new options and turn the stack canary into a percpu variable. The "lazy GS" approach is now used for all 32-bit configurations. Also makes load_gs_index() work on 32-bit kernels. On 64-bit kernels, it loads the GS selector and updates the user GSBASE accordingly. (This is unchanged.) On 32-bit kernels, it loads the GS selector and updates GSBASE, which is now always the user base. This means that the overall effect is the same on 32-bit and 64-bit, which avoids some ifdeffery. [ bp: Massage commit message. ] Signed-off-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/c0ff7dba14041c7e5d1cae5d4df052f03759bef3.1613243844.git.luto@kernel.org
37 lines
876 B
C
37 lines
876 B
C
/* SPDX-License-Identifier: GPL-2.0 */
|
|
/*
|
|
* Copyright 2001-2002 Pavel Machek <pavel@suse.cz>
|
|
* Based on code
|
|
* Copyright 2001 Patrick Mochel <mochel@osdl.org>
|
|
*/
|
|
#ifndef _ASM_X86_SUSPEND_32_H
|
|
#define _ASM_X86_SUSPEND_32_H
|
|
|
|
#include <asm/desc.h>
|
|
#include <asm/fpu/api.h>
|
|
|
|
/* image of the saved processor state */
|
|
struct saved_context {
|
|
/*
|
|
* On x86_32, all segment registers except gs are saved at kernel
|
|
* entry in pt_regs.
|
|
*/
|
|
u16 gs;
|
|
unsigned long cr0, cr2, cr3, cr4;
|
|
u64 misc_enable;
|
|
bool misc_enable_saved;
|
|
struct saved_msrs saved_msrs;
|
|
struct desc_ptr gdt_desc;
|
|
struct desc_ptr idt;
|
|
u16 ldt;
|
|
u16 tss;
|
|
unsigned long tr;
|
|
unsigned long safety;
|
|
unsigned long return_address;
|
|
} __attribute__((packed));
|
|
|
|
/* routines for saving/restoring kernel state */
|
|
extern char core_restore_code[];
|
|
extern char restore_registers[];
|
|
|
|
#endif /* _ASM_X86_SUSPEND_32_H */
|