[PATCH -tip v6 4/5] x86: add pt_regs register and stack access APIs

[Masami Hiramatsu <mhiramat@redhat.com>]

Add following APIs for accessing registers and stack entries from pt_regs.

- query_register_offset(const char *name)
   Query the offset of "name" register.

- query_register_name(unsigned offset)
   Query the name of register by its offset.

- get_register(struct pt_regs *regs, unsigned offset)
   Get the value of a register by its offset.

- within_kernel_stack(struct pt_regs *regs, unsigned long addr)
   Check the address is in the kernel stack.

- get_kernel_stack_nth(struct pt_regs *reg, unsigned nth)
   Get Nth entry of the kernel stack. (N >= 0)

- get_argument_nth(struct pt_regs *reg, unsigned nth)
   Get Nth argument at function call. (N >= 0)

Changes from v5:
- Rename valid_stack_address to within_kernel_stack.
- Rename get_stack_nth to get_kernel_stack_nth.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Roland McGrath <roland@redhat.com>
---

 arch/x86/include/asm/ptrace.h |   67 +++++++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/ptrace.c      |   60 +++++++++++++++++++++++++++++++++++++
 2 files changed, 127 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 0f0d908..577d625 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -7,6 +7,7 @@
 
 #ifdef __KERNEL__
 #include <asm/segment.h>
+#include <asm/page_types.h>
 #endif
 
 #ifndef __ASSEMBLY__
@@ -216,6 +217,72 @@ static inline unsigned long user_stack_pointer(struct pt_regs *regs)
 	return regs->sp;
 }
 
+/* Query offset/name of register from its name/offset */
+extern int query_register_offset(const char *name);
+extern const char *query_register_name(unsigned offset);
+#define MAX_REG_OFFSET (offsetof(struct pt_regs, ss))
+
+/* Get register value from its offset */
+static inline unsigned long get_register(struct pt_regs *regs, unsigned offset)
+{
+	if (unlikely(offset > MAX_REG_OFFSET))
+		return 0;
+	return *(unsigned long *)((unsigned long)regs + offset);
+}
+
+/* Check the address in the stack */
+static inline int within_kernel_stack(struct pt_regs *regs, unsigned long addr)
+{
+	return ((addr & ~(THREAD_SIZE - 1))  ==
+		(kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1)));
+}
+
+/* Get Nth entry of the stack */
+static inline unsigned long get_kernel_stack_nth(struct pt_regs *regs,
+						 unsigned n)
+{
+	unsigned long *addr = (unsigned long *)kernel_stack_pointer(regs);
+	addr += n;
+	if (within_kernel_stack(regs, (unsigned long)addr))
+		return *addr;
+	else
+		return 0;
+}
+
+/* Get Nth argument at function call */
+static inline unsigned long get_argument_nth(struct pt_regs *regs, unsigned n)
+{
+#ifdef CONFIG_X86_32
+#define NR_REGPARMS 3
+	if (n < NR_REGPARMS) {
+		switch (n) {
+		case 0: return regs->ax;
+		case 1: return regs->dx;
+		case 2: return regs->cx;
+		}
+		return 0;
+#else /* CONFIG_X86_64 */
+#define NR_REGPARMS 6
+	if (n < NR_REGPARMS) {
+		switch (n) {
+		case 0: return regs->di;
+		case 1: return regs->si;
+		case 2: return regs->dx;
+		case 3: return regs->cx;
+		case 4: return regs->r8;
+		case 5: return regs->r9;
+		}
+		return 0;
+#endif
+	} else {
+		/*
+		 * The typical case: arg n is on the stack.
+		 * (Note: stack[0] = return address, so skip it)
+		 */
+		return get_kernel_stack_nth(regs, 1 + n - NR_REGPARMS);
+	}
+}
+
 /*
  * These are defined as per linux/ptrace.h, which see.
  */
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 09ecbde..00eb9d7 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -48,6 +48,66 @@ enum x86_regset {
 	REGSET_IOPERM32,
 };
 
+struct pt_regs_offset {
+	const char *name;
+	int offset;
+};
+
+#define REG_OFFSET(r) offsetof(struct pt_regs, r)
+#define REG_OFFSET_NAME(r) {.name = #r, .offset = REG_OFFSET(r)}
+#define REG_OFFSET_END {.name = NULL, .offset = 0}
+
+static const struct pt_regs_offset regoffset_table[] = {
+#ifdef CONFIG_X86_64
+	REG_OFFSET_NAME(r15),
+	REG_OFFSET_NAME(r14),
+	REG_OFFSET_NAME(r13),
+	REG_OFFSET_NAME(r12),
+	REG_OFFSET_NAME(r11),
+	REG_OFFSET_NAME(r10),
+	REG_OFFSET_NAME(r9),
+	REG_OFFSET_NAME(r8),
+#endif
+	REG_OFFSET_NAME(bx),
+	REG_OFFSET_NAME(cx),
+	REG_OFFSET_NAME(dx),
+	REG_OFFSET_NAME(si),
+	REG_OFFSET_NAME(di),
+	REG_OFFSET_NAME(bp),
+	REG_OFFSET_NAME(ax),
+#ifdef CONFIG_X86_32
+	REG_OFFSET_NAME(ds),
+	REG_OFFSET_NAME(es),
+	REG_OFFSET_NAME(fs),
+	REG_OFFSET_NAME(gs),
+#endif
+	REG_OFFSET_NAME(orig_ax),
+	REG_OFFSET_NAME(ip),
+	REG_OFFSET_NAME(cs),
+	REG_OFFSET_NAME(flags),
+	REG_OFFSET_NAME(sp),
+	REG_OFFSET_NAME(ss),
+	REG_OFFSET_END,
+};
+
+int 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;
+}
+
+const char *query_register_name(unsigned 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.


-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America) Inc.
Software Solutions Division

e-mail: mhiramat@redhat.com