Add register_get_kernel_argument() for a rudimentary way to access
kernel function arguments.
Signed-off-by: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com>
---
arch/powerpc/Kconfig | 1 +
arch/powerpc/include/asm/ptrace.h | 31 +++++++++++++++++++++++++++++++
2 files changed, 32 insertions(+)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e9f13fe084929b..cfc6dd787f532c 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -202,6 +202,7 @@ config PPC
select HAVE_EFFICIENT_UNALIGNED_ACCESS if !(CPU_LITTLE_ENDIAN &&
POWER7_CPU)
select HAVE_FAST_GUP
select HAVE_FTRACE_MCOUNT_RECORD
+ select HAVE_FUNCTION_ARG_ACCESS_API
select HAVE_FUNCTION_ERROR_INJECTION
select HAVE_FUNCTION_GRAPH_TRACER
select HAVE_FUNCTION_TRACER
diff --git a/arch/powerpc/include/asm/ptrace.h
b/arch/powerpc/include/asm/ptrace.h
index e2c778c176a3a6..956828c07abd70 100644
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -62,6 +62,8 @@ struct pt_regs
};
#endif
+#define NR_REG_ARGUMENTS 8
+
#ifdef __powerpc64__
/*
@@ -85,8 +87,10 @@ struct pt_regs
#ifdef PPC64_ELF_ABI_v2
#define STACK_FRAME_MIN_SIZE 32
+#define STACK_FRAME_PARM_SAVE 32
#else
#define STACK_FRAME_MIN_SIZE STACK_FRAME_OVERHEAD
+#define STACK_FRAME_PARM_SAVE 48
#endif
/* Size of dummy stack frame allocated when calling signal handler. */
@@ -103,6 +107,7 @@ struct pt_regs
#define STACK_INT_FRAME_SIZE (sizeof(struct pt_regs) + STACK_FRAME_OVERHEAD)
#define STACK_FRAME_MARKER 2
#define STACK_FRAME_MIN_SIZE STACK_FRAME_OVERHEAD
+#define STACK_FRAME_PARM_SAVE 8
/* Size of stack frame allocated when calling signal handler. */
#define __SIGNAL_FRAMESIZE 64
@@ -309,6 +314,32 @@ static inline unsigned long
regs_get_kernel_stack_nth(struct pt_regs *regs,
return 0;
}
+/**
+ * regs_get_kernel_argument() - get Nth function argument in kernel
+ * @regs: pt_regs of that context
+ * @n: function argument number (start from 0)
+ *
+ * regs_get_argument() returns @n th argument of the function call.
+ * Note that this chooses most probable assignment, and is incorrect
+ * in scenarios where double or fp/vector parameters are involved.
+ * This also doesn't take into account stack alignment requirements.
+ *
+ * This is expected to be called from kprobes or ftrace with regs
+ * at function entry, so the current function has not setup its stack.
+ */
+static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs,
+ unsigned int n)
+{
+ if (n >= NR_REG_ARGUMENTS) {
+#ifndef __powerpc64__
+ n -= NR_REG_ARGUMENTS;
+#endif
+ n += STACK_FRAME_PARM_SAVE / sizeof(unsigned long);
+ return regs_get_kernel_stack_nth(regs, n);
+ } else {
+ return regs_get_register(regs, offsetof(struct pt_regs, gpr[n +
3]));
+ }
+}
#endif /* __ASSEMBLY__ */
#ifndef __powerpc64__
--
2.25.4
