Commit 7213e5d7 authored by Zheng Yejian's avatar Zheng Yejian
Browse files

livepatch/powerpc: Support breakpoint exception optimization 

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8MGE6



--------------------------------

Add breakpoint exception optimization support to improve livepatch
success rate for ppc64/ppc32.

Signed-off-by: default avatarYang Jihong <yangjihong1@huawei.com>
Signed-off-by: default avatarLi Huafei <lihuafei1@huawei.com>
Signed-off-by: default avatarZheng Yejian <zhengyejian1@huawei.com>
parent 2ea69fe7

arch/powerpc/include/asm/livepatch.h

+9 −0
Original line number Diff line number Diff line
@@ -58,6 +58,7 @@ void livepatch_branch_stub(void); 
void livepatch_branch_stub_end(void);

void livepatch_branch_trampoline(void);

void livepatch_branch_trampoline_end(void);

void livepatch_brk_trampoline(void);



int livepatch_create_branch(unsigned long pc, unsigned long trampoline,

			    unsigned long addr, struct module *me);
@@ -75,6 +76,11 @@ struct arch_klp_data { 
#ifdef CONFIG_PPC64

	struct ppc64_klp_btramp_entry trampoline;

#endif

	/*

	 * Saved opcode at the entry of the old func (which maybe replaced

	 * with breakpoint).

	 */

	u32 saved_opcode;

};



#define KLP_MAX_REPLACE_SIZE sizeof_field(struct arch_klp_data, old_insns)
@@ -87,6 +93,9 @@ long arch_klp_save_old_code(struct arch_klp_data *arch_data, void *old_func); 
int arch_klp_check_calltrace(bool (*check_func)(void *, int *, unsigned long), void *data);

bool arch_check_jump_insn(unsigned long func_addr);

int klp_patch_text(u32 *dst, const u32 *src, int len);

int klp_brk_handler(struct pt_regs *regs);

int arch_klp_add_breakpoint(struct arch_klp_data *arch_data, void *old_func);

void arch_klp_remove_breakpoint(struct arch_klp_data *arch_data, void *old_func);



#endif /* CONFIG_LIVEPATCH_WO_FTRACE */

arch/powerpc/kernel/livepatch.c

+40 −0
Original line number Diff line number Diff line
@@ -282,3 +282,43 @@ int klp_patch_text(u32 *dst, const u32 *src, int len) 
	barrier();

	return patch_instruction(dst, ppc_inst(src[0]));

}



int arch_klp_add_breakpoint(struct arch_klp_data *arch_data, void *old_func)

{

	ppc_inst_t insn = ppc_inst_read((const u32 *)old_func);



	arch_data->saved_opcode = ppc_inst_val(insn);

	patch_instruction((u32 *)old_func, ppc_inst(BREAKPOINT_INSTRUCTION));

	return 0;

}



void arch_klp_remove_breakpoint(struct arch_klp_data *arch_data, void *old_func)

{

	patch_instruction((u32 *)old_func, ppc_inst(arch_data->saved_opcode));

}



int klp_brk_handler(struct pt_regs *regs)

{

	void *brk_func = NULL;

	unsigned long addr = regs->nip;



	if (user_mode(regs))

		return 0;



	brk_func = klp_get_brk_func((void *)addr);

	if (!brk_func)

		return 0;



#ifdef CONFIG_PPC64

	/*

	 * Only static trampoline can be used here to prevent

	 * resource release caused by rollback.

	 */

	regs->gpr[PT_R11] = (unsigned long)brk_func;

	regs->nip = ppc_function_entry((void *)livepatch_brk_trampoline);

#else

	regs->nip = (unsigned long)brk_func;

#endif



	return 1;

}

arch/powerpc/kernel/livepatch_tramp.S

+34 −0
Original line number Diff line number Diff line
@@ -90,3 +90,37 @@ _GLOBAL(livepatch_branch_trampoline) 
	blr

_GLOBAL(livepatch_branch_trampoline_end)

	nop



/*

 * This function is the trampoline of livepatch brk handler.

 *

 * brk -> traps

 *  - klp_brk_handler

 *   - set R11 to new_func address

 *   - set NIP to livepatch_brk_trampoline address

 * see arch/powerpc/kernel/livepatch.c

 */

_GLOBAL(livepatch_brk_trampoline)

	mflr	r0

	std	r0, 16(r1)

	std	r2, 24(r1)

	stdu    r1, -STACK_FRAME_MIN_SIZE(r1)



	/* Call NEW_FUNC */

	ld	r12, 0(r11)	/* load new func address to R12 */

	ld	r2,  8(r11)	/* set up new R2 */

	mtctr   r12		/* load R12(new func address) to CTR */

	bctrl			/* call new func */



	/*

	 * Now we are returning from the patched function to the original

	 * caller A. We are free to use r11, r12 and we can use r2 until we

	 * restore it.

	 */

	addi	r1, r1, STACK_FRAME_MIN_SIZE

	ld	r2, 24(r1)

	ld	r0, 16(r1)

	mtlr	r0



	/* Return to original caller of live patched function */

	blr

arch/powerpc/kernel/traps.c

+8 −0
Original line number Diff line number Diff line
@@ -70,6 +70,10 @@ 
#include <asm/disassemble.h>

#include <asm/udbg.h>



#ifdef CONFIG_LIVEPATCH_WO_FTRACE

#include <asm/livepatch.h>

#endif



#if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC_CORE)

int (*__debugger)(struct pt_regs *regs) __read_mostly;

int (*__debugger_ipi)(struct pt_regs *regs) __read_mostly;
@@ -1496,6 +1500,10 @@ static void do_program_check(struct pt_regs *regs) 
		if (kprobe_handler(regs))

			return;



#ifdef CONFIG_LIVEPATCH_WO_FTRACE

		if (klp_brk_handler(regs))

			return;

#endif

		/* trap exception */

		if (notify_die(DIE_BPT, "breakpoint", regs, 5, 5, SIGTRAP)

				== NOTIFY_STOP)