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powerpc: Add support for function error injection

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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: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Naveen N. Rao 2018-06-07 15:22:02 +05:30 committed by Michael Ellerman
parent b4d16ab58c
commit 7cd01b08d3
5 changed files with 37 additions and 0 deletions
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1
arch/powerpc/Kconfig
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@ -190,6 +190,7 @@ config PPC
select HAVE_EBPF_JIT if PPC64
select HAVE_EFFICIENT_UNALIGNED_ACCESS if !(CPU_LITTLE_ENDIAN && POWER7_CPU)
select HAVE_FTRACE_MCOUNT_RECORD
select HAVE_FUNCTION_ERROR_INJECTION
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
select HAVE_GCC_PLUGINS if GCC_VERSION >= 50200 # plugin support on gcc <= 5.1 is buggy on PPC

13
arch/powerpc/include/asm/error-injection.h Normal file
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@ -0,0 +1,13 @@
/* 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 */

5
arch/powerpc/include/asm/ptrace.h
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@ -133,6 +133,11 @@ static inline long regs_return_value(struct pt_regs *regs)
return -regs->gpr[3];
}
static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
{
regs->gpr[3] = rc;
}
#ifdef __powerpc64__
#define user_mode(regs) ((((regs)->msr) >> MSR_PR_LG) & 0x1)
#else

2
arch/powerpc/lib/Makefile
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@ -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_FUNCTION_ERROR_INJECTION) += error-inject.o
# See corresponding test in arch/powerpc/Makefile
# 64-bit linker creates .sfpr on demand for final link (vmlinux),
# so it is only needed for modules, and only for older linkers which

16
arch/powerpc/lib/error-inject.c Normal file
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@ -0,0 +1,16 @@
// 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);