powerpc: Add kprobe-based event tracer

This patch ports the kprobe-based event tracer to powerpc. This patch
is based on x86 port. This brings powerpc on par with x86.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2e19500921f9fbdc33f40321ae34f648171faba0..c4c4549c22bbe8a3ce06149429096d0c87207c73 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -140,6 +140,7 @@ config PPC
        select HAVE_SYSCALL_WRAPPERS if PPC64
        select GENERIC_ATOMIC64 if PPC32
        select HAVE_PERF_EVENTS
+       select HAVE_REGS_AND_STACK_ACCESS_API
 
 config EARLY_PRINTK
        bool

diff --git a/arch/powerpc/include/asm/ptrace.h b/arch/powerpc/include/asm/ptrace.h
index 9e2d84c06b749f569ff6f0aae1f4c3d6c93b6091..5d8be0416227590021287ef01eeee6982c4267c6 100644 (file)
--- a/arch/powerpc/include/asm/ptrace.h
+++ b/arch/powerpc/include/asm/ptrace.h
@@ -89,6 +89,7 @@ struct pt_regs {
 
 #define instruction_pointer(regs) ((regs)->nip)
 #define user_stack_pointer(regs) ((regs)->gpr[1])
+#define kernel_stack_pointer(regs) ((regs)->gpr[1])
 #define regs_return_value(regs) ((regs)->gpr[3])
 
 #ifdef CONFIG_SMP
@@ -141,6 +142,69 @@ do {                                                                             \
 #define arch_has_block_step()  (!cpu_has_feature(CPU_FTR_601))
 #define ARCH_HAS_USER_SINGLE_STEP_INFO
 
+/*
+ * kprobe-based event tracer support
+ */
+
+#include <linux/stddef.h>
+#include <linux/thread_info.h>
+extern int regs_query_register_offset(const char *name);
+extern const char *regs_query_register_name(unsigned int offset);
+#define MAX_REG_OFFSET (offsetof(struct pt_regs, dsisr))
+
+/**
+ * regs_get_register() - get register value from its offset
+ * @regs:         pt_regs from which register value is gotten
+ * @offset:    offset number of the register.
+ *
+ * regs_get_register returns the value of a register whose offset from @regs.
+ * The @offset is the offset of the register in struct pt_regs.
+ * If @offset is bigger than MAX_REG_OFFSET, this returns 0.
+ */
+static inline unsigned long regs_get_register(struct pt_regs *regs,
+                                               unsigned int offset)
+{
+       if (unlikely(offset > MAX_REG_OFFSET))
+               return 0;
+       return *(unsigned long *)((unsigned long)regs + offset);
+}
+
+/**
+ * regs_within_kernel_stack() - check the address in the stack
+ * @regs:      pt_regs which contains kernel stack pointer.
+ * @addr:      address which is checked.
+ *
+ * regs_within_kernel_stack() checks @addr is within the kernel stack page(s).
+ * If @addr is within the kernel stack, it returns true. If not, returns false.
+ */
+
+static inline bool regs_within_kernel_stack(struct pt_regs *regs,
+                                               unsigned long addr)
+{
+       return ((addr & ~(THREAD_SIZE - 1))  ==
+               (kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
+}
+
+/**
+ * regs_get_kernel_stack_nth() - get Nth entry of the stack
+ * @regs:      pt_regs which contains kernel stack pointer.
+ * @n:         stack entry number.
+ *
+ * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
+ * is specified by @regs. If the @n th entry is NOT in the kernel stack,
+ * this returns 0.
+ */
+static inline unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
+                                                     unsigned int n)
+{
+       unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
+       addr += n;
+       if (regs_within_kernel_stack(regs, (unsigned long)addr))
+               return *addr;
+       else
+               return 0;
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* __KERNEL__ */

diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index ed2cfe17d25eeaa5ffcd0f25b830f4e3c8eda547..7a0c0199ea28aeba289078943d3d18114dc2be6e 100644 (file)
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -38,6 +38,109 @@
 #include <asm/pgtable.h>
 #include <asm/system.h>
 
+/*
+ * The parameter save area on the stack is used to store arguments being passed
+ * to callee function and is located at fixed offset from stack pointer.
+ */
+#ifdef CONFIG_PPC32
+#define PARAMETER_SAVE_AREA_OFFSET     24  /* bytes */
+#else /* CONFIG_PPC32 */
+#define PARAMETER_SAVE_AREA_OFFSET     48  /* bytes */
+#endif
+
+struct pt_regs_offset {
+       const char *name;
+       int offset;
+};
+
+#define STR(s) #s                      /* convert to string */
+#define REG_OFFSET_NAME(r) {.name = #r, .offset = offsetof(struct pt_regs, r)}
+#define GPR_OFFSET_NAME(num)   \
+       {.name = STR(gpr##num), .offset = offsetof(struct pt_regs, gpr[num])}
+#define REG_OFFSET_END {.name = NULL, .offset = 0}
+
+static const struct pt_regs_offset regoffset_table[] = {
+       GPR_OFFSET_NAME(0),
+       GPR_OFFSET_NAME(1),
+       GPR_OFFSET_NAME(2),
+       GPR_OFFSET_NAME(3),
+       GPR_OFFSET_NAME(4),
+       GPR_OFFSET_NAME(5),
+       GPR_OFFSET_NAME(6),
+       GPR_OFFSET_NAME(7),
+       GPR_OFFSET_NAME(8),
+       GPR_OFFSET_NAME(9),
+       GPR_OFFSET_NAME(10),
+       GPR_OFFSET_NAME(11),
+       GPR_OFFSET_NAME(12),
+       GPR_OFFSET_NAME(13),
+       GPR_OFFSET_NAME(14),
+       GPR_OFFSET_NAME(15),
+       GPR_OFFSET_NAME(16),
+       GPR_OFFSET_NAME(17),
+       GPR_OFFSET_NAME(18),
+       GPR_OFFSET_NAME(19),
+       GPR_OFFSET_NAME(20),
+       GPR_OFFSET_NAME(21),
+       GPR_OFFSET_NAME(22),
+       GPR_OFFSET_NAME(23),
+       GPR_OFFSET_NAME(24),
+       GPR_OFFSET_NAME(25),
+       GPR_OFFSET_NAME(26),
+       GPR_OFFSET_NAME(27),
+       GPR_OFFSET_NAME(28),
+       GPR_OFFSET_NAME(29),
+       GPR_OFFSET_NAME(30),
+       GPR_OFFSET_NAME(31),
+       REG_OFFSET_NAME(nip),
+       REG_OFFSET_NAME(msr),
+       REG_OFFSET_NAME(ctr),
+       REG_OFFSET_NAME(link),
+       REG_OFFSET_NAME(xer),
+       REG_OFFSET_NAME(ccr),
+#ifdef CONFIG_PPC64
+       REG_OFFSET_NAME(softe),
+#else
+       REG_OFFSET_NAME(mq),
+#endif
+       REG_OFFSET_NAME(trap),
+       REG_OFFSET_NAME(dar),
+       REG_OFFSET_NAME(dsisr),
+       REG_OFFSET_END,
+};
+
+/**
+ * regs_query_register_offset() - query register offset from its name
+ * @name:      the name of a register
+ *
+ * regs_query_register_offset() returns the offset of a register in struct
+ * pt_regs from its name. If the name is invalid, this returns -EINVAL;
+ */
+int regs_query_register_offset(const char *name)
+{
+       const struct pt_regs_offset *roff;
+       for (roff = regoffset_table; roff->name != NULL; roff++)
+               if (!strcmp(roff->name, name))
+                       return roff->offset;
+       return -EINVAL;
+}
+
+/**
+ * regs_query_register_name() - query register name from its offset
+ * @offset:    the offset of a register in struct pt_regs.
+ *
+ * regs_query_register_name() returns the name of a register from its
+ * offset in struct pt_regs. If the @offset is invalid, this returns NULL;
+ */
+const char *regs_query_register_name(unsigned int offset)
+{
+       const struct pt_regs_offset *roff;
+       for (roff = regoffset_table; roff->name != NULL; roff++)
+               if (roff->offset == offset)
+                       return roff->name;
+       return NULL;
+}
+
 /*
  * does not yet catch signals sent when the child dies.
  * in exit.c or in signal.c.