linux/arch/s390/kernel/vmlinux.lds.S
Heiko Carstens f5730d44e0 s390: Add stackprotector support
Stackprotector support was previously unavailable on s390 because by
default compilers generate code which is not suitable for the kernel:
the canary value is accessed via thread local storage, where the address
of thread local storage is within access registers 0 and 1.

Using those registers also for the kernel would come with a significant
performance impact and more complicated kernel entry/exit code, since
access registers contents would have to be exchanged on every kernel entry
and exit.

With the upcoming gcc 16 release new compiler options will become available
which allow to generate code suitable for the kernel. [1]

Compiler option -mstack-protector-guard=global instructs gcc to generate
stackprotector code that refers to a global stackprotector canary value via
symbol __stack_chk_guard. Access to this value is guaranteed to occur via
larl and lgrl instructions.

Furthermore, compiler option -mstack-protector-guard-record generates a
section containing all code addresses that reference the canary value.

To allow for per task canary values the instructions which load the address
of __stack_chk_guard are patched so they access a lowcore field instead: a
per task canary value is available within the task_struct of each task, and
is written to the per-cpu lowcore location on each context switch.

Also add sanity checks and debugging option to be consistent with other
kernel code patching mechanisms.

Full debugging output can be enabled with the following kernel command line
options:

debug_stackprotector
bootdebug
ignore_loglevel
earlyprintk
dyndbg="file stackprotector.c +p"

Example debug output:

stackprot: 0000021e402d4eda: c010005a9ae3 -> c01f00070240

where "<insn address>: <old insn> -> <new insn>".

[1] gcc commit 0cd1f03939d5 ("s390: Support global stack protector")

Reviewed-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
2025-11-24 11:45:21 +01:00

288 lines
6.2 KiB
ArmAsm

/* SPDX-License-Identifier: GPL-2.0 */
/* ld script to make s390 Linux kernel
* Written by Martin Schwidefsky (schwidefsky@de.ibm.com)
*/
#include <asm/thread_info.h>
#include <asm/page.h>
#include <asm/ftrace.lds.h>
/*
* Put .bss..swapper_pg_dir as the first thing in .bss. This will
* make sure it has 16k alignment.
*/
#define BSS_FIRST_SECTIONS *(.bss..swapper_pg_dir) \
*(.bss..invalid_pg_dir)
#define RO_EXCEPTION_TABLE_ALIGN 16
/* Handle ro_after_init data on our own. */
#define RO_AFTER_INIT_DATA
#define RUNTIME_DISCARD_EXIT
#define EMITS_PT_NOTE
#include <asm-generic/vmlinux.lds.h>
#include <asm/vmlinux.lds.h>
OUTPUT_FORMAT("elf64-s390", "elf64-s390", "elf64-s390")
OUTPUT_ARCH(s390:64-bit)
ENTRY(startup_continue)
jiffies = jiffies_64;
PHDRS {
text PT_LOAD FLAGS(5); /* R_E */
data PT_LOAD FLAGS(7); /* RWE */
note PT_NOTE FLAGS(0); /* ___ */
}
SECTIONS
{
. = TEXT_OFFSET;
.text : {
_stext = .; /* Start of text section */
_text = .; /* Text and read-only data */
HEAD_TEXT
TEXT_TEXT
SCHED_TEXT
LOCK_TEXT
KPROBES_TEXT
IRQENTRY_TEXT
SOFTIRQENTRY_TEXT
FTRACE_HOTPATCH_TRAMPOLINES_TEXT
*(.text.*_indirect_*)
*(.gnu.warning)
. = ALIGN(PAGE_SIZE);
_etext = .; /* End of text section */
} :text = 0x0700
RO_DATA(PAGE_SIZE)
. = ALIGN(PAGE_SIZE);
_sdata = .; /* Start of data section */
. = ALIGN(PAGE_SIZE);
__start_ro_after_init = .;
.data..ro_after_init : {
*(.data..ro_after_init)
JUMP_TABLE_DATA
} :data
. = ALIGN(PAGE_SIZE);
__end_ro_after_init = .;
. = ALIGN(8);
.skey_region_table : {
__skey_region_start = .;
KEEP(*(.skey_region))
__skey_region_end = .;
}
.data.rel.ro : {
*(.data.rel.ro .data.rel.ro.*)
}
.got : {
__got_start = .;
*(.got)
__got_end = .;
}
RW_DATA(0x100, PAGE_SIZE, THREAD_SIZE)
.data.rel : {
*(.data.rel*)
}
BOOT_DATA_PRESERVED
. = ALIGN(8);
.amode31.refs : {
_start_amode31_refs = .;
*(.amode31.refs)
_end_amode31_refs = .;
}
. = ALIGN(PAGE_SIZE);
_edata = .; /* End of data section */
/* will be freed after init */
. = ALIGN(PAGE_SIZE); /* Init code and data */
__init_begin = .;
. = ALIGN(PAGE_SIZE);
.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
_sinittext = .;
INIT_TEXT
. = ALIGN(PAGE_SIZE);
_einittext = .;
}
/*
* .exit.text is discarded at runtime, not link time,
* to deal with references from __bug_table
*/
.exit.text : {
EXIT_TEXT
}
.exit.data : {
EXIT_DATA
}
/*
* struct alt_inst entries. From the header (alternative.h):
* "Alternative instructions for different CPU types or capabilities"
* Think locking instructions on spinlocks.
* Note, that it is a part of __init region.
*/
. = ALIGN(8);
.altinstructions : {
__alt_instructions = .;
*(.altinstructions)
__alt_instructions_end = .;
}
/*
* And here are the replacement instructions. The linker sticks
* them as binary blobs. The .altinstructions has enough data to
* get the address and the length of them to patch the kernel safely.
* Note, that it is a part of __init region.
*/
.altinstr_replacement : {
*(.altinstr_replacement)
}
#ifdef CONFIG_STACKPROTECTOR
. = ALIGN(8);
.stack_prot_table : {
__stack_prot_start = .;
KEEP(*(__stack_protector_loc))
__stack_prot_end = .;
}
#endif
/*
* Table with the patch locations to undo expolines
*/
. = ALIGN(4);
.nospec_call_table : {
__nospec_call_start = . ;
*(.s390_indirect*)
__nospec_call_end = . ;
}
.nospec_return_table : {
__nospec_return_start = . ;
*(.s390_return*)
__nospec_return_end = . ;
}
BOOT_DATA
/*
* .amode31 section for code, data, ex_table that need to stay
* below 2 GB, even when the kernel is relocated above 2 GB.
*/
. = ALIGN(PAGE_SIZE);
_samode31 = .;
.amode31.text : {
_stext_amode31 = .;
*(.amode31.text)
*(.amode31.text.*_indirect_*)
. = ALIGN(PAGE_SIZE);
_etext_amode31 = .;
}
. = ALIGN(16);
.amode31.ex_table : {
_start_amode31_ex_table = .;
KEEP(*(.amode31.ex_table))
_stop_amode31_ex_table = .;
}
. = ALIGN(PAGE_SIZE);
.amode31.data : {
*(.amode31.data)
}
. = _samode31 + AMODE31_SIZE;
_eamode31 = .;
/* early.c uses stsi, which requires page aligned data. */
. = ALIGN(PAGE_SIZE);
INIT_DATA_SECTION(0x100)
RUNTIME_CONST_VARIABLES
PERCPU_SECTION(0x100)
. = ALIGN(PAGE_SIZE);
__init_end = .; /* freed after init ends here */
BSS_SECTION(PAGE_SIZE, 4 * PAGE_SIZE, PAGE_SIZE)
. = ALIGN(PAGE_SIZE);
_end = . ;
/* Debugging sections. */
STABS_DEBUG
DWARF_DEBUG
ELF_DETAILS
/*
* Make sure that the .got.plt is either completely empty or it
* contains only the three reserved double words.
*/
.got.plt : {
*(.got.plt)
}
ASSERT(SIZEOF(.got.plt) == 0 || SIZEOF(.got.plt) == 0x18, "Unexpected GOT/PLT entries detected!")
/*
* Sections that should stay zero sized, which is safer to
* explicitly check instead of blindly discarding.
*/
.plt : {
*(.plt) *(.plt.*) *(.iplt) *(.igot .igot.plt)
}
ASSERT(SIZEOF(.plt) == 0, "Unexpected run-time procedure linkages detected!")
.rela.dyn : {
*(.rela.*) *(.rela_*)
}
ASSERT(SIZEOF(.rela.dyn) == 0, "Unexpected run-time relocations (.rela) detected!")
/*
* uncompressed image info used by the decompressor
* it should match struct vmlinux_info
*/
.vmlinux.info 0 (INFO) : {
QUAD(startup_continue) /* entry */
QUAD(__bss_start - _stext) /* image_size */
QUAD(__bss_stop - __bss_start) /* bss_size */
QUAD(__boot_data_start) /* bootdata_off */
QUAD(__boot_data_end - __boot_data_start) /* bootdata_size */
QUAD(__boot_data_preserved_start) /* bootdata_preserved_off */
QUAD(__boot_data_preserved_end -
__boot_data_preserved_start) /* bootdata_preserved_size */
QUAD(__got_start) /* got_start */
QUAD(__got_end) /* got_end */
QUAD(_eamode31 - _samode31) /* amode31_size */
QUAD(init_mm)
QUAD(swapper_pg_dir)
QUAD(invalid_pg_dir)
QUAD(__alt_instructions)
QUAD(__alt_instructions_end)
#ifdef CONFIG_STACKPROTECTOR
QUAD(__stack_prot_start)
QUAD(__stack_prot_end)
#endif
#ifdef CONFIG_KASAN
QUAD(kasan_early_shadow_page)
QUAD(kasan_early_shadow_pte)
QUAD(kasan_early_shadow_pmd)
QUAD(kasan_early_shadow_pud)
QUAD(kasan_early_shadow_p4d)
#endif
} :NONE
/* Sections to be discarded */
DISCARDS
/DISCARD/ : {
*(.eh_frame)
*(.interp)
}
}