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 <[email protected]> --- arch/powerpc/Kconfig | 1 + arch/powerpc/include/asm/error-injection.h | 13 +++++++++++++ arch/powerpc/include/asm/ptrace.h | 5 +++++ arch/powerpc/lib/Makefile | 2 ++ arch/powerpc/lib/error-inject.c | 12 ++++++++++++ 5 files changed, 33 insertions(+) create mode 100644 arch/powerpc/include/asm/error-injection.h create mode 100644 arch/powerpc/lib/error-inject.c diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index f674006dea2f..8e61bc0f25cb 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -186,6 +186,7 @@ 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 diff --git a/arch/powerpc/include/asm/error-injection.h b/arch/powerpc/include/asm/error-injection.h new file mode 100644 index 000000000000..740c3075bdf4 --- /dev/null +++ b/arch/powerpc/include/asm/error-injection.h @@ -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 */ diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h index e4923686e43a..c0705296c2f0 100644 --- a/arch/powerpc/include/asm/ptrace.h +++ b/arch/powerpc/include/asm/ptrace.h @@ -101,6 +101,11 @@ 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 diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile index 653901042ad7..e0ed195eaa4b 100644 --- a/arch/powerpc/lib/Makefile +++ b/arch/powerpc/lib/Makefile @@ -14,6 +14,8 @@ obj-y += string.o alloc.o code-patching.o feature-fixups.o obj-$(CONFIG_PPC32) += div64.o copy_32.o crtsavres.o +obj-$(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 diff --git a/arch/powerpc/lib/error-inject.c b/arch/powerpc/lib/error-inject.c new file mode 100644 index 000000000000..6d3d57f68024 --- /dev/null +++ b/arch/powerpc/lib/error-inject.c @@ -0,0 +1,12 @@ +// 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' instruction */ + regs->nip = regs->link; +} +NOKPROBE_SYMBOL(override_function_with_return); -- 2.17.0
