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linux/arch/arm/kernel/ftrace.c
Ard Biesheuvel e3cf20e5c6 ARM: 9405/1: ftrace: Don't assume stack frames are contiguous in memory
The frame pointer unwinder relies on a standard layout of the stack
frame, consisting of (in downward order)

   Calling frame:
     PC   <---------+
     LR             |
     SP             |
     FP             |
     .. locals ..   |
   Callee frame:    |
     PC             |
     LR             |
     SP             |
     FP   ----------+

where after storing its previous value on the stack, FP is made to point
at the location of PC in the callee stack frame, using the canonical
prologue:

   mov     ip, sp
   stmdb   sp!, {fp, ip, lr, pc}
   sub     fp, ip, #4

The ftrace code assumes that this activation record is pushed first, and
that any stack space for locals is allocated below this. Strict
adherence to this would imply that the caller's value of SP at the time
of the function call can always be obtained by adding 4 to FP (which
points to PC in the callee frame).

However, recent versions of GCC appear to deviate from this rule, and so
the only reliable way to obtain the caller's value of SP is to read it
from the activation record. Since this involves a read from memory
rather than simple arithmetic, we need to use the uaccess API here which
protects against inadvertent data aborts resulting from attempts to
dereference bogus FP values.

The plain uaccess API is ftrace instrumented itself, so to avoid
unbounded recursion, use the __get_kernel_nofault() primitive directly.

Closes: https://lore.kernel.org/all/alp44tukzo6mvcwl4ke4ehhmojrqnv6xfcdeuliybxfjfvgd3e@gpjvwj33cc76

Closes: https://lore.kernel.org/all/d870c149-4363-43de-b0ea-7125dec5608e@broadcom.com/

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reported-by: Justin Chen <justin.chen@broadcom.com>
Tested-by: Thorsten Scherer <t.scherer@eckelmann.de>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
2024-06-10 12:00:27 +01:00

324 lines
7.8 KiB
C

/*
* Dynamic function tracing support.
*
* Copyright (C) 2008 Abhishek Sagar <sagar.abhishek@gmail.com>
* Copyright (C) 2010 Rabin Vincent <rabin@rab.in>
*
* For licencing details, see COPYING.
*
* Defines low-level handling of mcount calls when the kernel
* is compiled with the -pg flag. When using dynamic ftrace, the
* mcount call-sites get patched with NOP till they are enabled.
* All code mutation routines here are called under stop_machine().
*/
#include <linux/ftrace.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/stop_machine.h>
#include <asm/cacheflush.h>
#include <asm/opcodes.h>
#include <asm/ftrace.h>
#include <asm/insn.h>
#include <asm/set_memory.h>
#include <asm/stacktrace.h>
#include <asm/patch.h>
/*
* The compiler emitted profiling hook consists of
*
* PUSH {LR}
* BL __gnu_mcount_nc
*
* To turn this combined sequence into a NOP, we need to restore the value of
* SP before the PUSH. Let's use an ADD rather than a POP into LR, as LR is not
* modified anyway, and reloading LR from memory is highly likely to be less
* efficient.
*/
#ifdef CONFIG_THUMB2_KERNEL
#define NOP 0xf10d0d04 /* add.w sp, sp, #4 */
#else
#define NOP 0xe28dd004 /* add sp, sp, #4 */
#endif
#ifdef CONFIG_DYNAMIC_FTRACE
static int __ftrace_modify_code(void *data)
{
int *command = data;
ftrace_modify_all_code(*command);
return 0;
}
void arch_ftrace_update_code(int command)
{
stop_machine(__ftrace_modify_code, &command, NULL);
}
static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
{
return NOP;
}
void ftrace_caller_from_init(void);
void ftrace_regs_caller_from_init(void);
static unsigned long __ref adjust_address(struct dyn_ftrace *rec,
unsigned long addr)
{
if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE) ||
system_state >= SYSTEM_FREEING_INITMEM ||
likely(!is_kernel_inittext(rec->ip)))
return addr;
if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_REGS) ||
addr == (unsigned long)&ftrace_caller)
return (unsigned long)&ftrace_caller_from_init;
return (unsigned long)&ftrace_regs_caller_from_init;
}
void ftrace_arch_code_modify_prepare(void)
{
}
void ftrace_arch_code_modify_post_process(void)
{
/* Make sure any TLB misses during machine stop are cleared. */
flush_tlb_all();
}
static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
bool warn)
{
return arm_gen_branch_link(pc, addr, warn);
}
static int ftrace_modify_code(unsigned long pc, unsigned long old,
unsigned long new, bool validate)
{
unsigned long replaced;
if (IS_ENABLED(CONFIG_THUMB2_KERNEL))
old = __opcode_to_mem_thumb32(old);
else
old = __opcode_to_mem_arm(old);
if (validate) {
if (copy_from_kernel_nofault(&replaced, (void *)pc,
MCOUNT_INSN_SIZE))
return -EFAULT;
if (replaced != old)
return -EINVAL;
}
__patch_text((void *)pc, new);
return 0;
}
int ftrace_update_ftrace_func(ftrace_func_t func)
{
unsigned long pc;
unsigned long new;
int ret;
pc = (unsigned long)&ftrace_call;
new = ftrace_call_replace(pc, (unsigned long)func, true);
ret = ftrace_modify_code(pc, 0, new, false);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
if (!ret) {
pc = (unsigned long)&ftrace_regs_call;
new = ftrace_call_replace(pc, (unsigned long)func, true);
ret = ftrace_modify_code(pc, 0, new, false);
}
#endif
return ret;
}
int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long new, old;
unsigned long ip = rec->ip;
unsigned long aaddr = adjust_address(rec, addr);
struct module *mod = NULL;
#ifdef CONFIG_ARM_MODULE_PLTS
mod = rec->arch.mod;
#endif
old = ftrace_nop_replace(rec);
new = ftrace_call_replace(ip, aaddr, !mod);
#ifdef CONFIG_ARM_MODULE_PLTS
if (!new && mod) {
aaddr = get_module_plt(mod, ip, aaddr);
new = ftrace_call_replace(ip, aaddr, true);
}
#endif
return ftrace_modify_code(rec->ip, old, new, true);
}
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
unsigned long addr)
{
unsigned long new, old;
unsigned long ip = rec->ip;
old = ftrace_call_replace(ip, adjust_address(rec, old_addr), true);
new = ftrace_call_replace(ip, adjust_address(rec, addr), true);
return ftrace_modify_code(rec->ip, old, new, true);
}
#endif
int ftrace_make_nop(struct module *mod,
struct dyn_ftrace *rec, unsigned long addr)
{
unsigned long aaddr = adjust_address(rec, addr);
unsigned long ip = rec->ip;
unsigned long old;
unsigned long new;
int ret;
#ifdef CONFIG_ARM_MODULE_PLTS
/* mod is only supplied during module loading */
if (!mod)
mod = rec->arch.mod;
else
rec->arch.mod = mod;
#endif
old = ftrace_call_replace(ip, aaddr,
!IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
#ifdef CONFIG_ARM_MODULE_PLTS
if (!old && mod) {
aaddr = get_module_plt(mod, ip, aaddr);
old = ftrace_call_replace(ip, aaddr, true);
}
#endif
new = ftrace_nop_replace(rec);
/*
* Locations in .init.text may call __gnu_mcount_mc via a linker
* emitted veneer if they are too far away from its implementation, and
* so validation may fail spuriously in such cases. Let's work around
* this by omitting those from validation.
*/
ret = ftrace_modify_code(ip, old, new, !is_kernel_inittext(ip));
return ret;
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
asmlinkage
void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
unsigned long frame_pointer,
unsigned long stack_pointer)
{
unsigned long return_hooker = (unsigned long) &return_to_handler;
unsigned long old;
if (unlikely(atomic_read(&current->tracing_graph_pause)))
err_out:
return;
if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER)) {
/*
* Usually, the stack frames are contiguous in memory but cases
* have been observed where the next stack frame does not live
* at 'frame_pointer + 4' as this code used to assume.
*
* Instead, dereference the field in the stack frame that
* stores the SP of the calling frame: to avoid unbounded
* recursion, this cannot involve any ftrace instrumented
* functions, so use the __get_kernel_nofault() primitive
* directly.
*/
__get_kernel_nofault(&frame_pointer,
(unsigned long *)(frame_pointer - 8),
unsigned long, err_out);
} else {
struct stackframe frame = {
.fp = frame_pointer,
.sp = stack_pointer,
.lr = self_addr,
.pc = self_addr,
};
if (unwind_frame(&frame) < 0)
return;
if (frame.lr != self_addr)
parent = frame.lr_addr;
frame_pointer = frame.sp;
}
old = *parent;
*parent = return_hooker;
if (function_graph_enter(old, self_addr, frame_pointer, NULL))
*parent = old;
}
#ifdef CONFIG_DYNAMIC_FTRACE
extern unsigned long ftrace_graph_call;
extern unsigned long ftrace_graph_call_old;
extern void ftrace_graph_caller_old(void);
extern unsigned long ftrace_graph_regs_call;
extern void ftrace_graph_regs_caller(void);
static int __ftrace_modify_caller(unsigned long *callsite,
void (*func) (void), bool enable)
{
unsigned long caller_fn = (unsigned long) func;
unsigned long pc = (unsigned long) callsite;
unsigned long branch = arm_gen_branch(pc, caller_fn);
unsigned long nop = arm_gen_nop();
unsigned long old = enable ? nop : branch;
unsigned long new = enable ? branch : nop;
return ftrace_modify_code(pc, old, new, true);
}
static int ftrace_modify_graph_caller(bool enable)
{
int ret;
ret = __ftrace_modify_caller(&ftrace_graph_call,
ftrace_graph_caller,
enable);
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
if (!ret)
ret = __ftrace_modify_caller(&ftrace_graph_regs_call,
ftrace_graph_regs_caller,
enable);
#endif
return ret;
}
int ftrace_enable_ftrace_graph_caller(void)
{
return ftrace_modify_graph_caller(true);
}
int ftrace_disable_ftrace_graph_caller(void)
{
return ftrace_modify_graph_caller(false);
}
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */