linux/arch/s390/kernel/ftrace.c
Steven Rostedt 7888af4166 ftrace: Make ftrace_regs abstract from direct use
ftrace_regs was created to hold registers that store information to save
function parameters, return value and stack. Since it is a subset of
pt_regs, it should only be used by its accessor functions. But because
pt_regs can easily be taken from ftrace_regs (on most archs), it is
tempting to use it directly. But when running on other architectures, it
may fail to build or worse, build but crash the kernel!

Instead, make struct ftrace_regs an empty structure and have the
architectures define __arch_ftrace_regs and all the accessor functions
will typecast to it to get to the actual fields. This will help avoid
usage of ftrace_regs directly.

Link: https://lore.kernel.org/all/20241007171027.629bdafd@gandalf.local.home/

Cc: "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Cc: "x86@kernel.org" <x86@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Naveen N Rao <naveen@kernel.org>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Paul  Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas  Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Borislav  Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/20241008230628.958778821@goodmis.org
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Heiko Carstens <hca@linux.ibm.com> # s390
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
2024-10-10 20:18:01 -04:00

359 lines
9.8 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Dynamic function tracer architecture backend.
*
* Copyright IBM Corp. 2009,2014
*
* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
*/
#include <linux/hardirq.h>
#include <linux/uaccess.h>
#include <linux/ftrace.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/kmsan-checks.h>
#include <linux/kprobes.h>
#include <linux/execmem.h>
#include <trace/syscall.h>
#include <asm/asm-offsets.h>
#include <asm/text-patching.h>
#include <asm/cacheflush.h>
#include <asm/ftrace.lds.h>
#include <asm/nospec-branch.h>
#include <asm/set_memory.h>
#include "entry.h"
#include "ftrace.h"
/*
* To generate function prologue either gcc's hotpatch feature (since gcc 4.8)
* or a combination of -pg -mrecord-mcount -mnop-mcount -mfentry flags
* (since gcc 9 / clang 10) is used.
* In both cases the original and also the disabled function prologue contains
* only a single six byte instruction and looks like this:
* > brcl 0,0 # offset 0
* To enable ftrace the code gets patched like above and afterwards looks
* like this:
* > brasl %r0,ftrace_caller # offset 0
*
* The instruction will be patched by ftrace_make_call / ftrace_make_nop.
* The ftrace function gets called with a non-standard C function call ABI
* where r0 contains the return address. It is also expected that the called
* function only clobbers r0 and r1, but restores r2-r15.
* For module code we can't directly jump to ftrace caller, but need a
* trampoline (ftrace_plt), which clobbers also r1.
*/
void *ftrace_func __read_mostly = ftrace_stub;
struct ftrace_insn {
u16 opc;
s32 disp;
} __packed;
static const char *ftrace_shared_hotpatch_trampoline(const char **end)
{
const char *tstart, *tend;
tstart = ftrace_shared_hotpatch_trampoline_br;
tend = ftrace_shared_hotpatch_trampoline_br_end;
#ifdef CONFIG_EXPOLINE
if (!nospec_disable) {
tstart = ftrace_shared_hotpatch_trampoline_exrl;
tend = ftrace_shared_hotpatch_trampoline_exrl_end;
}
#endif /* CONFIG_EXPOLINE */
if (end)
*end = tend;
return tstart;
}
bool ftrace_need_init_nop(void)
{
return !MACHINE_HAS_SEQ_INSN;
}
int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
{
static struct ftrace_hotpatch_trampoline *next_vmlinux_trampoline =
__ftrace_hotpatch_trampolines_start;
static const struct ftrace_insn orig = { .opc = 0xc004, .disp = 0 };
static struct ftrace_hotpatch_trampoline *trampoline;
struct ftrace_hotpatch_trampoline **next_trampoline;
struct ftrace_hotpatch_trampoline *trampolines_end;
struct ftrace_hotpatch_trampoline tmp;
struct ftrace_insn *insn;
struct ftrace_insn old;
const char *shared;
s32 disp;
BUILD_BUG_ON(sizeof(struct ftrace_hotpatch_trampoline) !=
SIZEOF_FTRACE_HOTPATCH_TRAMPOLINE);
next_trampoline = &next_vmlinux_trampoline;
trampolines_end = __ftrace_hotpatch_trampolines_end;
shared = ftrace_shared_hotpatch_trampoline(NULL);
#ifdef CONFIG_MODULES
if (mod) {
next_trampoline = &mod->arch.next_trampoline;
trampolines_end = mod->arch.trampolines_end;
}
#endif
if (WARN_ON_ONCE(*next_trampoline >= trampolines_end))
return -ENOMEM;
trampoline = (*next_trampoline)++;
if (copy_from_kernel_nofault(&old, (void *)rec->ip, sizeof(old)))
return -EFAULT;
/* Check for the compiler-generated fentry nop (brcl 0, .). */
if (WARN_ON_ONCE(memcmp(&orig, &old, sizeof(old))))
return -EINVAL;
/* Generate the trampoline. */
tmp.brasl_opc = 0xc015; /* brasl %r1, shared */
tmp.brasl_disp = (shared - (const char *)&trampoline->brasl_opc) / 2;
tmp.interceptor = FTRACE_ADDR;
tmp.rest_of_intercepted_function = rec->ip + sizeof(struct ftrace_insn);
s390_kernel_write(trampoline, &tmp, sizeof(tmp));
/* Generate a jump to the trampoline. */
disp = ((char *)trampoline - (char *)rec->ip) / 2;
insn = (struct ftrace_insn *)rec->ip;
s390_kernel_write(&insn->disp, &disp, sizeof(disp));
return 0;
}
static struct ftrace_hotpatch_trampoline *ftrace_get_trampoline(struct dyn_ftrace *rec)
{
struct ftrace_hotpatch_trampoline *trampoline;
struct ftrace_insn insn;
s64 disp;
u16 opc;
if (copy_from_kernel_nofault(&insn, (void *)rec->ip, sizeof(insn)))
return ERR_PTR(-EFAULT);
disp = (s64)insn.disp * 2;
trampoline = (void *)(rec->ip + disp);
if (get_kernel_nofault(opc, &trampoline->brasl_opc))
return ERR_PTR(-EFAULT);
if (opc != 0xc015)
return ERR_PTR(-EINVAL);
return trampoline;
}
static inline struct ftrace_insn
ftrace_generate_branch_insn(unsigned long ip, unsigned long target)
{
/* brasl r0,target or brcl 0,0 */
return (struct ftrace_insn){ .opc = target ? 0xc005 : 0xc004,
.disp = target ? (target - ip) / 2 : 0 };
}
static int ftrace_patch_branch_insn(unsigned long ip, unsigned long old_target,
unsigned long target)
{
struct ftrace_insn orig = ftrace_generate_branch_insn(ip, old_target);
struct ftrace_insn new = ftrace_generate_branch_insn(ip, target);
struct ftrace_insn old;
if (!IS_ALIGNED(ip, 8))
return -EINVAL;
if (copy_from_kernel_nofault(&old, (void *)ip, sizeof(old)))
return -EFAULT;
/* Verify that the to be replaced code matches what we expect. */
if (memcmp(&orig, &old, sizeof(old)))
return -EINVAL;
s390_kernel_write((void *)ip, &new, sizeof(new));
return 0;
}
static int ftrace_modify_trampoline_call(struct dyn_ftrace *rec,
unsigned long old_addr,
unsigned long addr)
{
struct ftrace_hotpatch_trampoline *trampoline;
u64 old;
trampoline = ftrace_get_trampoline(rec);
if (IS_ERR(trampoline))
return PTR_ERR(trampoline);
if (get_kernel_nofault(old, &trampoline->interceptor))
return -EFAULT;
if (old != old_addr)
return -EINVAL;
s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
return 0;
}
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
if (MACHINE_HAS_SEQ_INSN)
return ftrace_patch_branch_insn(rec->ip, old_addr, addr);
else
return ftrace_modify_trampoline_call(rec, old_addr, addr);
}
static int ftrace_patch_branch_mask(void *addr, u16 expected, bool enable)
{
u16 old;
u8 op;
if (get_kernel_nofault(old, addr))
return -EFAULT;
if (old != expected)
return -EINVAL;
/* set mask field to all ones or zeroes */
op = enable ? 0xf4 : 0x04;
s390_kernel_write((char *)addr + 1, &op, sizeof(op));
return 0;
}
int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
unsigned long addr)
{
/* Expect brcl 0xf,... for the !MACHINE_HAS_SEQ_INSN case */
if (MACHINE_HAS_SEQ_INSN)
return ftrace_patch_branch_insn(rec->ip, addr, 0);
else
return ftrace_patch_branch_mask((void *)rec->ip, 0xc0f4, false);
}
static int ftrace_make_trampoline_call(struct dyn_ftrace *rec, unsigned long addr)
{
struct ftrace_hotpatch_trampoline *trampoline;
trampoline = ftrace_get_trampoline(rec);
if (IS_ERR(trampoline))
return PTR_ERR(trampoline);
s390_kernel_write(&trampoline->interceptor, &addr, sizeof(addr));
/* Expect brcl 0x0,... */
return ftrace_patch_branch_mask((void *)rec->ip, 0xc004, true);
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
if (MACHINE_HAS_SEQ_INSN)
return ftrace_patch_branch_insn(rec->ip, 0, addr);
else
return ftrace_make_trampoline_call(rec, addr);
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
ftrace_func = func;
return 0;
}
void arch_ftrace_update_code(int command)
{
ftrace_modify_all_code(command);
}
void ftrace_arch_code_modify_post_process(void)
{
/*
* Flush any pre-fetched instructions on all
* CPUs to make the new code visible.
*/
text_poke_sync_lock();
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
/*
* Hook the return address and push it in the stack of return addresses
* in current thread info.
*/
unsigned long prepare_ftrace_return(unsigned long ra, unsigned long sp,
unsigned long ip)
{
if (unlikely(ftrace_graph_is_dead()))
goto out;
if (unlikely(atomic_read(&current->tracing_graph_pause)))
goto out;
ip -= MCOUNT_INSN_SIZE;
if (!function_graph_enter(ra, ip, 0, (void *) sp))
ra = (unsigned long) return_to_handler;
out:
return ra;
}
NOKPROBE_SYMBOL(prepare_ftrace_return);
/*
* Patch the kernel code at ftrace_graph_caller location. The instruction
* there is branch relative on condition. To enable the ftrace graph code
* block, we simply patch the mask field of the instruction to zero and
* turn the instruction into a nop.
* To disable the ftrace graph code the mask field will be patched to
* all ones, which turns the instruction into an unconditional branch.
*/
int ftrace_enable_ftrace_graph_caller(void)
{
/* Expect brc 0xf,... */
return ftrace_patch_branch_mask(ftrace_graph_caller, 0xa7f4, false);
}
int ftrace_disable_ftrace_graph_caller(void)
{
/* Expect brc 0x0,... */
return ftrace_patch_branch_mask(ftrace_graph_caller, 0xa704, true);
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
#ifdef CONFIG_KPROBES_ON_FTRACE
void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
struct ftrace_ops *ops, struct ftrace_regs *fregs)
{
struct kprobe_ctlblk *kcb;
struct pt_regs *regs;
struct kprobe *p;
int bit;
if (unlikely(kprobe_ftrace_disabled))
return;
bit = ftrace_test_recursion_trylock(ip, parent_ip);
if (bit < 0)
return;
kmsan_unpoison_memory(fregs, ftrace_regs_size());
regs = ftrace_get_regs(fregs);
p = get_kprobe((kprobe_opcode_t *)ip);
if (!regs || unlikely(!p) || kprobe_disabled(p))
goto out;
if (kprobe_running()) {
kprobes_inc_nmissed_count(p);
goto out;
}
__this_cpu_write(current_kprobe, p);
kcb = get_kprobe_ctlblk();
kcb->kprobe_status = KPROBE_HIT_ACTIVE;
instruction_pointer_set(regs, ip);
if (!p->pre_handler || !p->pre_handler(p, regs)) {
instruction_pointer_set(regs, ip + MCOUNT_INSN_SIZE);
if (unlikely(p->post_handler)) {
kcb->kprobe_status = KPROBE_HIT_SSDONE;
p->post_handler(p, regs, 0);
}
}
__this_cpu_write(current_kprobe, NULL);
out:
ftrace_test_recursion_unlock(bit);
}
NOKPROBE_SYMBOL(kprobe_ftrace_handler);
int arch_prepare_kprobe_ftrace(struct kprobe *p)
{
p->ainsn.insn = NULL;
return 0;
}
#endif