Commit 2bc56fda authored by Masami Hiramatsu (Google)'s avatar Masami Hiramatsu (Google) Committed by Steven Rostedt (Google)
Browse files

ftrace: Add ftrace_get_symaddr to convert fentry_ip to symaddr 

This introduces ftrace_get_symaddr() which tries to convert fentry_ip
passed by ftrace or fgraph callback to symaddr without calling
kallsyms API. It returns the symbol address or 0 if it fails to
convert it.

Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Florent Revest <revest@chromium.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: bpf <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Alan Maguire <alan.maguire@oracle.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/173519011487.391279.5450806886342723151.stgit@devnote2


Signed-off-by: default avatarMasami Hiramatsu (Google) <mhiramat@kernel.org>
Reported-by: default avatarkernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202412061423.K79V55Hd-lkp@intel.com/
Closes: https://lore.kernel.org/oe-kbuild-all/202412061804.5VRzF14E-lkp@intel.com/


Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 54b6b4a3

arch/arm64/include/asm/ftrace.h

+2 −0
Original line number Diff line number Diff line
@@ -52,6 +52,8 @@ extern unsigned long ftrace_graph_call; 
extern void return_to_handler(void);



unsigned long ftrace_call_adjust(unsigned long addr);

unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip);

#define ftrace_get_symaddr(fentry_ip) arch_ftrace_get_symaddr(fentry_ip)



#ifdef CONFIG_DYNAMIC_FTRACE_WITH_ARGS

#define HAVE_ARCH_FTRACE_REGS

arch/arm64/kernel/ftrace.c

+63 −0
Original line number Diff line number Diff line
@@ -143,6 +143,69 @@ unsigned long ftrace_call_adjust(unsigned long addr) 
	return addr;

}



/* Convert fentry_ip to the symbol address without kallsyms */

unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)

{

	u32 insn;



	/*

	 * When using patchable-function-entry without pre-function NOPS, ftrace

	 * entry is the address of the first NOP after the function entry point.

	 *

	 * The compiler has either generated:

	 *

	 * func+00:	func:	NOP		// To be patched to MOV X9, LR

	 * func+04:		NOP		// To be patched to BL <caller>

	 *

	 * Or:

	 *

	 * func-04:		BTI	C

	 * func+00:	func:	NOP		// To be patched to MOV X9, LR

	 * func+04:		NOP		// To be patched to BL <caller>

	 *

	 * The fentry_ip is the address of `BL <caller>` which is at `func + 4`

	 * bytes in either case.

	 */

	if (!IS_ENABLED(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS))

		return fentry_ip - AARCH64_INSN_SIZE;



	/*

	 * When using patchable-function-entry with pre-function NOPs, BTI is

	 * a bit different.

	 *

	 * func+00:	func:	NOP		// To be patched to MOV X9, LR

	 * func+04:		NOP		// To be patched to BL <caller>

	 *

	 * Or:

	 *

	 * func+00:	func:	BTI	C

	 * func+04:		NOP		// To be patched to MOV X9, LR

	 * func+08:		NOP		// To be patched to BL <caller>

	 *

	 * The fentry_ip is the address of `BL <caller>` which is at either

	 * `func + 4` or `func + 8` depends on whether there is a BTI.

	 */



	/* If there is no BTI, the func address should be one instruction before. */

	if (!IS_ENABLED(CONFIG_ARM64_BTI_KERNEL))

		return fentry_ip - AARCH64_INSN_SIZE;



	/* We want to be extra safe in case entry ip is on the page edge,

	 * but otherwise we need to avoid get_kernel_nofault()'s overhead.

	 */

	if ((fentry_ip & ~PAGE_MASK) < AARCH64_INSN_SIZE * 2) {

		if (get_kernel_nofault(insn, (u32 *)(fentry_ip - AARCH64_INSN_SIZE * 2)))

			return 0;

	} else {

		insn = *(u32 *)(fentry_ip - AARCH64_INSN_SIZE * 2);

	}



	if (aarch64_insn_is_bti(le32_to_cpu((__le32)insn)))

		return fentry_ip - AARCH64_INSN_SIZE * 2;



	return fentry_ip - AARCH64_INSN_SIZE;

}



/*

 * Replace a single instruction, which may be a branch or NOP.

 * If @validate == true, a replaced instruction is checked against 'old'.

arch/x86/include/asm/ftrace.h

+21 −0
Original line number Diff line number Diff line
@@ -34,6 +34,27 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr) 
	return addr;

}



static inline unsigned long arch_ftrace_get_symaddr(unsigned long fentry_ip)

{

#ifdef CONFIG_X86_KERNEL_IBT

	u32 instr;



	/* We want to be extra safe in case entry ip is on the page edge,

	 * but otherwise we need to avoid get_kernel_nofault()'s overhead.

	 */

	if ((fentry_ip & ~PAGE_MASK) < ENDBR_INSN_SIZE) {

		if (get_kernel_nofault(instr, (u32 *)(fentry_ip - ENDBR_INSN_SIZE)))

			return fentry_ip;

	} else {

		instr = *(u32 *)(fentry_ip - ENDBR_INSN_SIZE);

	}

	if (is_endbr(instr))

		fentry_ip -= ENDBR_INSN_SIZE;

#endif

	return fentry_ip;

}

#define ftrace_get_symaddr(fentry_ip)	arch_ftrace_get_symaddr(fentry_ip)



#ifdef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS



#include <linux/ftrace_regs.h>

include/linux/ftrace.h

+13 −0
Original line number Diff line number Diff line
@@ -622,6 +622,19 @@ enum { 
	FTRACE_MAY_SLEEP		= (1 << 5),

};



/* Arches can override ftrace_get_symaddr() to convert fentry_ip to symaddr. */

#ifndef ftrace_get_symaddr

/**

 * ftrace_get_symaddr - return the symbol address from fentry_ip

 * @fentry_ip: the address of ftrace location

 *

 * Get the symbol address from @fentry_ip (fast path). If there is no fast

 * search path, this returns 0.

 * User may need to use kallsyms API to find the symbol address.

 */

#define ftrace_get_symaddr(fentry_ip) (0)

#endif



#ifdef CONFIG_DYNAMIC_FTRACE



void ftrace_arch_code_modify_prepare(void);