kernel.git/arch/x86/kernel/head_32.S, branch linux-5.13.y

x86/stackprotector/32: Make the canary into a regular percpu variable

2021-03-08T12:19:05Z

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 Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/c0ff7dba14041c7e5d1cae5d4df052f03759bef3.1613243844.git.luto@kernel.org

x86/xen: remove 32-bit Xen PV guest support

2020-08-11T06:26:48Z

Xen is requiring 64-bit machines today and since Xen 4.14 it can be built without 32-bit PV guest support. There is no need to carry the burden of 32-bit PV guest support in the kernel any longer, as new guests can be either HVM or PVH, or they can use a 64 bit kernel. Remove the 32-bit Xen PV support from the kernel. Signed-off-by: Juergen Gross Reviewed-by: Boris Ostrovsky Signed-off-by: Juergen Gross

x86/boot: Remove KEEP_SEGMENTS support

2020-02-22T22:37:37Z

Commit a24e785111a3 ("i386: paravirt boot sequence") added this flag for use by paravirtualized environments such as Xen. However, Xen never made use of this flag [1], and it was only ever used by lguest [2]. Commit ecda85e70277 ("x86/lguest: Remove lguest support") removed lguest, so KEEP_SEGMENTS has lost its last user. [1] https://lore.kernel.org/lkml/4D4B097C.5050405@goop.org [2] https://www.mail-archive.com/lguest@lists.ozlabs.org/msg00469.html Signed-off-by: Arvind Sankar Link: https://lore.kernel.org/r/20200202171353.3736319-2-nivedita@alum.mit.edu Signed-off-by: Ard Biesheuvel

Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2019-11-26T18:42:40Z

Pull x86 asm updates from Ingo Molnar: "The main changes in this cycle were: - Cross-arch changes to move the linker sections for NOTES and EXCEPTION_TABLE into the RO_DATA area, where they belong on most architectures. (Kees Cook) - Switch the x86 linker fill byte from x90 (NOP) to 0xcc (INT3), to trap jumps into the middle of those padding areas instead of sliding execution. (Kees Cook) - A thorough cleanup of symbol definitions within x86 assembler code. The rather randomly named macros got streamlined around a (hopefully) straightforward naming scheme: SYM_START(name, linkage, align...) SYM_END(name, sym_type) SYM_FUNC_START(name) SYM_FUNC_END(name) SYM_CODE_START(name) SYM_CODE_END(name) SYM_DATA_START(name) SYM_DATA_END(name) etc - with about three times of these basic primitives with some label, local symbol or attribute variant, expressed via postfixes. No change in functionality intended. (Jiri Slaby) - Misc other changes, cleanups and smaller fixes" * 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (67 commits) x86/entry/64: Remove pointless jump in paranoid_exit x86/entry/32: Remove unused resume_userspace label x86/build/vdso: Remove meaningless CFLAGS_REMOVE_*.o m68k: Convert missed RODATA to RO_DATA x86/vmlinux: Use INT3 instead of NOP for linker fill bytes x86/mm: Report actual image regions in /proc/iomem x86/mm: Report which part of kernel image is freed x86/mm: Remove redundant address-of operators on addresses xtensa: Move EXCEPTION_TABLE to RO_DATA segment powerpc: Move EXCEPTION_TABLE to RO_DATA segment parisc: Move EXCEPTION_TABLE to RO_DATA segment microblaze: Move EXCEPTION_TABLE to RO_DATA segment ia64: Move EXCEPTION_TABLE to RO_DATA segment h8300: Move EXCEPTION_TABLE to RO_DATA segment c6x: Move EXCEPTION_TABLE to RO_DATA segment arm64: Move EXCEPTION_TABLE to RO_DATA segment alpha: Move EXCEPTION_TABLE to RO_DATA segment x86/vmlinux: Move EXCEPTION_TABLE to RO_DATA segment x86/vmlinux: Actually use _etext for the end of the text segment vmlinux.lds.h: Allow EXCEPTION_TABLE to live in RO_DATA ...

x86/pti/32: Size initial_page_table correctly

2019-11-21T18:37:43Z

Commit 945fd17ab6ba ("x86/cpu_entry_area: Sync cpu_entry_area to initial_page_table") introduced the sync for the initial page table for 32bit. sync_initial_page_table() uses clone_pgd_range() which does the update for the kernel page table. If PTI is enabled it also updates the user space page table counterpart, which is assumed to be in the next page after the target PGD. At this point in time 32-bit did not have PTI support, so the user space page table update was not taking place. The support for PTI on 32-bit which was introduced later on, did not take that into account and missed to add the user space counter part for the initial page table. As a consequence sync_initial_page_table() overwrites any data which is located in the page behing initial_page_table causing random failures, e.g. by corrupting doublefault_tss and wreckaging the doublefault handler on 32bit. Fix it by adding a "user" page table right after initial_page_table. Fixes: 7757d607c6b3 ("x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32") Signed-off-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Joerg Roedel Cc: stable@kernel.org

x86/asm: Replace WEAK uses by SYM_INNER_LABEL_ALIGN

2019-10-18T10:13:35Z

Use the new SYM_INNER_LABEL_ALIGN for WEAK entries in the middle of x86 assembly functions. And make sure WEAK is not defined for x86 anymore as these were the last users. Signed-off-by: Jiri Slaby Signed-off-by: Borislav Petkov Cc: Andrey Ryabinin Cc: Boris Ostrovsky Cc: Herbert Xu Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Josh Poimboeuf Cc: linux-arch@vger.kernel.org Cc: Mark Rutland Cc: Peter Zijlstra Cc: "Rafael J. Wysocki" Cc: "Steven Rostedt (VMware)" Cc: Thomas Gleixner Cc: x86-ml Link: https://lkml.kernel.org/r/20191011115108.12392-29-jslaby@suse.cz

x86/asm/32: Change all ENTRY+ENDPROC to SYM_FUNC_*

2019-10-18T10:03:43Z

These are all functions which are invoked from elsewhere, so annotate them as global using the new SYM_FUNC_START and their ENDPROC's by SYM_FUNC_END. Now, ENTRY/ENDPROC can be forced to be undefined on X86, so do so. Signed-off-by: Jiri Slaby Signed-off-by: Borislav Petkov Cc: Allison Randal Cc: Andrey Ryabinin Cc: Andy Lutomirski Cc: Andy Shevchenko Cc: Ard Biesheuvel Cc: Bill Metzenthen Cc: Boris Ostrovsky Cc: Darren Hart Cc: "David S. Miller" Cc: Greg Kroah-Hartman Cc: Herbert Xu Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: linux-arch@vger.kernel.org Cc: linux-crypto@vger.kernel.org Cc: linux-efi Cc: linux-efi@vger.kernel.org Cc: linux-pm@vger.kernel.org Cc: Mark Rutland Cc: Matt Fleming Cc: Pavel Machek Cc: platform-driver-x86@vger.kernel.org Cc: "Rafael J. Wysocki" Cc: Thomas Gleixner Cc: Will Deacon Cc: x86-ml Link: https://lkml.kernel.org/r/20191011115108.12392-28-jslaby@suse.cz

x86/asm/32: Add ENDs to some functions and relabel with SYM_CODE_*

2019-10-18T09:58:33Z

All these are functions which are invoked from elsewhere but they are not typical C functions. So annotate them using the new SYM_CODE_START. All these were not balanced with any END, so mark their ends by SYM_CODE_END, appropriately. Signed-off-by: Jiri Slaby Signed-off-by: Borislav Petkov Reviewed-by: Boris Ostrovsky [xen bits] Reviewed-by: Rafael J. Wysocki [hibernate] Cc: Andy Lutomirski Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Josh Poimboeuf Cc: Juergen Gross Cc: Len Brown Cc: linux-arch@vger.kernel.org Cc: linux-pm@vger.kernel.org Cc: Pavel Machek Cc: Peter Zijlstra Cc: Pingfan Liu Cc: Stefano Stabellini Cc: "Steven Rostedt (VMware)" Cc: Thomas Gleixner Cc: x86-ml Cc: xen-devel@lists.xenproject.org Link: https://lkml.kernel.org/r/20191011115108.12392-26-jslaby@suse.cz

x86/asm/head: Annotate data appropriately

2019-10-18T08:42:01Z

Use the new SYM_DATA, SYM_DATA_START, and SYM_DATA_END in both 32 and 64 bit head_*.S. In the 64-bit version, define also SYM_DATA_START_PAGE_ALIGNED locally using the new SYM_START. It is used in the code instead of NEXT_PAGE() which was defined in this file and had been using the obsolete macro GLOBAL(). Now, the data in the 64-bit object file look sane: Value Size Type Bind Vis Ndx Name 0000 4096 OBJECT GLOBAL DEFAULT 15 init_level4_pgt 1000 4096 OBJECT GLOBAL DEFAULT 15 level3_kernel_pgt 2000 2048 OBJECT GLOBAL DEFAULT 15 level2_kernel_pgt 3000 4096 OBJECT GLOBAL DEFAULT 15 level2_fixmap_pgt 4000 4096 OBJECT GLOBAL DEFAULT 15 level1_fixmap_pgt 5000 2 OBJECT GLOBAL DEFAULT 15 early_gdt_descr 5002 8 OBJECT LOCAL DEFAULT 15 early_gdt_descr_base 500a 8 OBJECT GLOBAL DEFAULT 15 phys_base 0000 8 OBJECT GLOBAL DEFAULT 17 initial_code 0008 8 OBJECT GLOBAL DEFAULT 17 initial_gs 0010 8 OBJECT GLOBAL DEFAULT 17 initial_stack 0000 4 OBJECT GLOBAL DEFAULT 19 early_recursion_flag 1000 4096 OBJECT GLOBAL DEFAULT 19 early_level4_pgt 2000 0x40000 OBJECT GLOBAL DEFAULT 19 early_dynamic_pgts 0000 4096 OBJECT GLOBAL DEFAULT 22 empty_zero_page All have correct size and type now. Note that this also removes implicit 16B alignment previously inserted by ENTRY: * initial_code, setup_once_ref, initial_page_table, initial_stack, boot_gdt are still aligned * early_gdt_descr is now properly aligned as was intended before ENTRY was added there long time ago * phys_base's alignment is kept by an explicitly added new alignment Signed-off-by: Jiri Slaby Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Cao jin Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Josh Poimboeuf Cc: Juergen Gross Cc: linux-arch@vger.kernel.org Cc: Maran Wilson Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: x86-ml Link: https://lkml.kernel.org/r/20191011115108.12392-12-jslaby@suse.cz

x86/asm: Annotate local pseudo-functions

2019-10-18T08:04:04Z

Use the newly added SYM_CODE_START_LOCAL* to annotate beginnings of all pseudo-functions (those ending with END until now) which do not have ".globl" annotation. This is needed to balance END for tools that generate debuginfo. Note that ENDs are switched to SYM_CODE_END too so that everybody can see the pairing. C-like functions (which handle frame ptr etc.) are not annotated here, hence SYM_CODE_* macros are used here, not SYM_FUNC_*. Note that the 32bit version of early_idt_handler_common already had ENDPROC -- switch that to SYM_CODE_END for the same reason as above (and to be the same as 64bit). While early_idt_handler_common is LOCAL, it's name is not prepended with ".L" as it happens to appear in call traces. bad_get_user*, and bad_put_user are now aligned, as they are separate functions. They do not mind to be aligned -- no need to be compact there. early_idt_handler_common is aligned now too, as it is after early_idt_handler_array, so as well no need to be compact there. verify_cpu is self-standing and included in other .S files, so align it too. The others have alignment preserved to what it used to be (using the _NOALIGN variant of macros). Signed-off-by: Jiri Slaby Signed-off-by: Borislav Petkov Cc: Alexios Zavras Cc: Allison Randal Cc: Andy Lutomirski Cc: Cao jin Cc: Enrico Weigelt Cc: Greg Kroah-Hartman Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Josh Poimboeuf Cc: Juergen Gross Cc: linux-arch@vger.kernel.org Cc: Maran Wilson Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: x86-ml Link: https://lkml.kernel.org/r/20191011115108.12392-6-jslaby@suse.cz