Commit 9cdc3b6a authored by Youling Tang's avatar Youling Tang Committed by Huacai Chen
Browse files

LoongArch: ftrace: Add direct call support 



Select the HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS to provide the
register_ftrace_direct[_multi] interfaces allowing users to register
the customed trampoline (direct_caller) as the mcount for one or more
target functions. And modify_ftrace_direct[_multi] are also provided
for modifying direct_caller.

There are a few cases to distinguish:
- If a direct call ops is the only one tracing a function AND the direct
  called trampoline is within the reach of a 'bl' instruction
  -> the ftrace patchsite jumps to the trampoline
- Else
  -> the ftrace patchsite jumps to the ftrace_regs_caller trampoline points
     to ftrace_list_ops so it iterates over all registered ftrace ops,
     including the direct call ops and calls its call_direct_funcs handler
     which stores the direct called trampoline's address in the ftrace_regs
     and the ftrace_regs_caller trampoline will return to that address
     instead of returning to the traced function

Signed-off-by: default avatarQing Zhang <zhangqing@loongson.cn>
Signed-off-by: default avatarYouling Tang <tangyouling@loongson.cn>
Signed-off-by: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 24d4f527

arch/loongarch/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -93,6 +93,7 @@ config LOONGARCH 
	select HAVE_DMA_CONTIGUOUS

	select HAVE_DYNAMIC_FTRACE

	select HAVE_DYNAMIC_FTRACE_WITH_ARGS

	select HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS

	select HAVE_DYNAMIC_FTRACE_WITH_REGS

	select HAVE_EBPF_JIT

	select HAVE_EFFICIENT_UNALIGNED_ACCESS if !ARCH_STRICT_ALIGN

arch/loongarch/include/asm/ftrace.h

+12 −0
Original line number Diff line number Diff line
@@ -82,6 +82,18 @@ ftrace_regs_set_instruction_pointer(struct ftrace_regs *fregs, unsigned long ip) 
#define ftrace_graph_func ftrace_graph_func

void ftrace_graph_func(unsigned long ip, unsigned long parent_ip,

		       struct ftrace_ops *op, struct ftrace_regs *fregs);



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS

static inline void

__arch_ftrace_set_direct_caller(struct pt_regs *regs, unsigned long addr)

{

	regs->regs[13] = addr;	/* t1 */

}



#define arch_ftrace_set_direct_caller(fregs, addr) \

	__arch_ftrace_set_direct_caller(&(fregs)->regs, addr)

#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */



#endif



#endif /* __ASSEMBLY__ */

arch/loongarch/kernel/ftrace_dyn.c

+8 −0
Original line number Diff line number Diff line
@@ -65,6 +65,14 @@ static bool ftrace_find_callable_addr(struct dyn_ftrace *rec, struct module *mod 
	unsigned long pc = rec->ip + LOONGARCH_INSN_SIZE;

	struct plt_entry *plt;



	/*

	 * If a custom trampoline is unreachable, rely on the ftrace_regs_caller

	 * trampoline which knows how to indirectly reach that trampoline through

	 * ops->direct_call.

	 */

	if (*addr != FTRACE_ADDR && *addr != FTRACE_REGS_ADDR && !reachable_by_bl(*addr, pc))

		*addr = FTRACE_REGS_ADDR;



	/*

	 * When the target is within range of the 'bl' instruction, use 'addr'

	 * as-is and branch to that directly.

arch/loongarch/kernel/mcount_dyn.S

+12 −1
Original line number Diff line number Diff line
@@ -42,7 +42,6 @@ 
	.if \allregs

	PTR_S		tp, sp, PT_R2

	PTR_S		t0, sp, PT_R12

	PTR_S		t1, sp, PT_R13

	PTR_S		t2, sp, PT_R14

	PTR_S		t3, sp, PT_R15

	PTR_S		t4, sp, PT_R16
@@ -64,6 +63,8 @@ 
	PTR_S		zero, sp, PT_R0

	.endif

	PTR_S		ra, sp, PT_ERA /* Save trace function ra at PT_ERA */

	move		t1, zero

	PTR_S		t1, sp, PT_R13

	PTR_ADDI	t8, sp, PT_SIZE

	PTR_S		t8, sp, PT_R3

	.endm
@@ -104,8 +105,12 @@ ftrace_common_return: 
	PTR_L		a7, sp, PT_R11

	PTR_L		fp, sp, PT_R22

	PTR_L		t0, sp, PT_ERA

	PTR_L		t1, sp, PT_R13

	PTR_ADDI	sp, sp, PT_SIZE

	bnez		t1, .Ldirect

	jr		t0

.Ldirect:

	jr		t1

SYM_CODE_END(ftrace_common)



SYM_CODE_START(ftrace_caller)
@@ -147,3 +152,9 @@ SYM_CODE_START(return_to_handler) 
	jr		ra

SYM_CODE_END(return_to_handler)

#endif



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS

SYM_CODE_START(ftrace_stub_direct_tramp)

	jr		t0

SYM_CODE_END(ftrace_stub_direct_tramp)

#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */