unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
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x86: Remove __USER32_DS

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Replace all users with the equivalent __USER_DS, which will make merging
native and compat code simpler.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Link: https://lore.kernel.org/r/20220606203802.158958-5-brgerst@gmail.com
Signed-off-by: Borislav Petkov <bp@suse.de>
This commit is contained in:
Brian Gerst 2022-06-06 16:37:58 -04:00 committed by Borislav Petkov
parent 653714220f
commit 695c39bc5b
5 changed files with 13 additions and 18 deletions
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4
arch/x86/entry/entry_64_compat.S
View file

@ -61,7 +61,7 @@ SYM_CODE_START(entry_SYSENTER_compat)
movq PER_CPU_VAR(cpu_current_top_of_stack), %rsp
/* Construct struct pt_regs on stack */
pushq $__USER32_DS /* pt_regs->ss */
pushq $__USER_DS /* pt_regs->ss */
pushq $0 /* pt_regs->sp = 0 (placeholder) */
/*
@ -197,7 +197,7 @@ SYM_INNER_LABEL(entry_SYSCALL_compat_safe_stack, SYM_L_GLOBAL)
ANNOTATE_NOENDBR
/* Construct struct pt_regs on stack */
pushq $__USER32_DS /* pt_regs->ss */
pushq $__USER_DS /* pt_regs->ss */
pushq %r8 /* pt_regs->sp */
pushq %r11 /* pt_regs->flags */
pushq $__USER32_CS /* pt_regs->cs */

14
arch/x86/ia32/ia32_signal.c
View file

@ -212,7 +212,7 @@ static void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
if (ksig->ka.sa.sa_flags & SA_ONSTACK)
sp = sigsp(sp, ksig);
/* This is the legacy signal stack switching. */
else if (regs->ss != __USER32_DS &&
else if (regs->ss != __USER_DS &&
!(ksig->ka.sa.sa_flags & SA_RESTORER) &&
ksig->ka.sa.sa_restorer)
sp = (unsigned long) ksig->ka.sa.sa_restorer;
@ -284,11 +284,11 @@ int ia32_setup_frame(struct ksignal *ksig, struct pt_regs *regs)
regs->dx = 0;
regs->cx = 0;
loadsegment(ds, __USER32_DS);
loadsegment(es, __USER32_DS);
loadsegment(ds, __USER_DS);
loadsegment(es, __USER_DS);
regs->cs = __USER32_CS;
regs->ss = __USER32_DS;
regs->ss = __USER_DS;
return 0;
Efault:
@ -361,11 +361,11 @@ int ia32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs)
regs->dx = (unsigned long) &frame->info;
regs->cx = (unsigned long) &frame->uc;
loadsegment(ds, __USER32_DS);
loadsegment(es, __USER32_DS);
loadsegment(ds, __USER_DS);
loadsegment(es, __USER_DS);
regs->cs = __USER32_CS;
regs->ss = __USER32_DS;
regs->ss = __USER_DS;
return 0;
Efault:

4
arch/x86/include/asm/elf.h
View file

@ -152,10 +152,6 @@ do { \
(elf_check_arch_ia32(x) || \
(IS_ENABLED(CONFIG_X86_X32_ABI) && (x)->e_machine == EM_X86_64))
#if __USER32_DS != __USER_DS
# error "The following code assumes __USER32_DS == __USER_DS"
#endif
static inline void elf_common_init(struct thread_struct *t,
struct pt_regs *regs, const u16 ds)
{

1
arch/x86/include/asm/segment.h
View file

@ -210,7 +210,6 @@
#define __KERNEL_DS (GDT_ENTRY_KERNEL_DS*8)
#define __USER32_CS (GDT_ENTRY_DEFAULT_USER32_CS*8 + 3)
#define __USER_DS (GDT_ENTRY_DEFAULT_USER_DS*8 + 3)
#define __USER32_DS __USER_DS
#define __USER_CS (GDT_ENTRY_DEFAULT_USER_CS*8 + 3)
#define __CPUNODE_SEG (GDT_ENTRY_CPUNODE*8 + 3)

8
arch/x86/xen/xen-asm.S
View file

@ -262,10 +262,10 @@ SYM_CODE_START(xen_entry_SYSCALL_compat)
/*
* Neither Xen nor the kernel really knows what the old SS and
* CS were. The kernel expects __USER32_DS and __USER32_CS, so
* CS were. The kernel expects __USER_DS and __USER32_CS, so
* report those values even though Xen will guess its own values.
*/
movq $__USER32_DS, 4*8(%rsp)
movq $__USER_DS, 4*8(%rsp)
movq $__USER32_CS, 1*8(%rsp)
jmp entry_SYSCALL_compat_after_hwframe
@ -284,10 +284,10 @@ SYM_CODE_START(xen_entry_SYSENTER_compat)
/*
* Neither Xen nor the kernel really knows what the old SS and
* CS were. The kernel expects __USER32_DS and __USER32_CS, so
* CS were. The kernel expects __USER_DS and __USER32_CS, so
* report those values even though Xen will guess its own values.
*/
movq $__USER32_DS, 4*8(%rsp)
movq $__USER_DS, 4*8(%rsp)
movq $__USER32_CS, 1*8(%rsp)
jmp entry_SYSENTER_compat_after_hwframe