Commit 7cd01b08 authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

powerpc: Add support for function error injection 



We implement regs_set_return_value() and override_function_with_return()
for this purpose.

On powerpc, a return from a function (blr) just branches to the location
contained in the link register. So, we can just update pt_regs rather
than redirecting execution to a dummy function that returns.

Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: default avatarSamuel Mendoza-Jonas <sam@mendozajonas.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent b4d16ab5

arch/powerpc/Kconfig

+1 −0
Original line number Original line Diff line number Diff line
@@ -190,6 +190,7 @@ config PPC 
	select HAVE_EBPF_JIT			if PPC64

	select HAVE_EBPF_JIT			if PPC64

	select HAVE_EFFICIENT_UNALIGNED_ACCESS	if !(CPU_LITTLE_ENDIAN && POWER7_CPU)

	select HAVE_EFFICIENT_UNALIGNED_ACCESS	if !(CPU_LITTLE_ENDIAN && POWER7_CPU)

	select HAVE_FTRACE_MCOUNT_RECORD

	select HAVE_FTRACE_MCOUNT_RECORD

	select HAVE_FUNCTION_ERROR_INJECTION

	select HAVE_FUNCTION_GRAPH_TRACER

	select HAVE_FUNCTION_GRAPH_TRACER

	select HAVE_FUNCTION_TRACER

	select HAVE_FUNCTION_TRACER

	select HAVE_GCC_PLUGINS			if GCC_VERSION >= 50200   # plugin support on gcc <= 5.1 is buggy on PPC

	select HAVE_GCC_PLUGINS			if GCC_VERSION >= 50200   # plugin support on gcc <= 5.1 is buggy on PPC

arch/powerpc/include/asm/error-injection.h

0 → 100644
+13 −0
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/* SPDX-License-Identifier: GPL-2.0+ */



#ifndef _ASM_ERROR_INJECTION_H

#define _ASM_ERROR_INJECTION_H



#include <linux/compiler.h>

#include <linux/linkage.h>

#include <asm/ptrace.h>

#include <asm-generic/error-injection.h>



void override_function_with_return(struct pt_regs *regs);



#endif /* _ASM_ERROR_INJECTION_H */

arch/powerpc/include/asm/ptrace.h

+5 −0
Original line number Original line Diff line number Diff line
@@ -133,6 +133,11 @@ static inline long regs_return_value(struct pt_regs *regs) 
		return -regs->gpr[3];

		return -regs->gpr[3];

}

}





static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)

{

	regs->gpr[3] = rc;

}



#ifdef __powerpc64__

#ifdef __powerpc64__

#define user_mode(regs) ((((regs)->msr) >> MSR_PR_LG) & 0x1)

#define user_mode(regs) ((((regs)->msr) >> MSR_PR_LG) & 0x1)

#else

#else

arch/powerpc/lib/Makefile

+2 −0
Original line number Original line Diff line number Diff line
@@ -12,6 +12,8 @@ obj-y += string.o alloc.o code-patching.o feature-fixups.o 




obj-$(CONFIG_PPC32)	+= div64.o copy_32.o crtsavres.o strlen_32.o

obj-$(CONFIG_PPC32)	+= div64.o copy_32.o crtsavres.o strlen_32.o





obj-$(CONFIG_FUNCTION_ERROR_INJECTION)	+= error-inject.o



# See corresponding test in arch/powerpc/Makefile

# See corresponding test in arch/powerpc/Makefile

# 64-bit linker creates .sfpr on demand for final link (vmlinux),

# 64-bit linker creates .sfpr on demand for final link (vmlinux),

# so it is only needed for modules, and only for older linkers which

# so it is only needed for modules, and only for older linkers which

arch/powerpc/lib/error-inject.c

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+16 −0
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// SPDX-License-Identifier: GPL-2.0+



#include <linux/error-injection.h>

#include <linux/kprobes.h>

#include <linux/uaccess.h>



void override_function_with_return(struct pt_regs *regs)

{

	/*

	 * Emulate 'blr'. 'regs' represents the state on entry of a predefined

	 * function in the kernel/module, captured on a kprobe. We don't need

	 * to worry about 32-bit userspace on a 64-bit kernel.

	 */

	regs->nip = regs->link;

}

NOKPROBE_SYMBOL(override_function_with_return);

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