Re: [PATCH v13 01/10] arm64: Add HAVE_REGS_AND_STACK_ACCESS_API feature

From: David Long
Date: Thu Jun 23 2016 - 09:50:01 EST

On 06/19/2016 10:43 PM, Li Bin wrote:


on 2016/6/3 11:26, David Long wrote:
From: "David A. Long" <dave.long@xxxxxxxxxx>

Add HAVE_REGS_AND_STACK_ACCESS_API feature for arm64, including supporting
functions and defines.

Signed-off-by: David A. Long <dave.long@xxxxxxxxxx>
---
arch/arm64/Kconfig | 1 +
arch/arm64/include/asm/ptrace.h | 54 +++++++++++++++++-
arch/arm64/kernel/ptrace.c | 118 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 172 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 76747d9..0f7a624 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -85,6 +85,7 @@ config ARM64
select HAVE_PERF_EVENTS
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
+ select HAVE_REGS_AND_STACK_ACCESS_API
select HAVE_RCU_TABLE_FREE
select HAVE_SYSCALL_TRACEPOINTS
select IOMMU_DMA if IOMMU_SUPPORT
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
index a307eb6..c130f2b 100644
--- a/arch/arm64/include/asm/ptrace.h
+++ b/arch/arm64/include/asm/ptrace.h
@@ -74,6 +74,7 @@
#define COMPAT_PT_DATA_ADDR 0x10004
#define COMPAT_PT_TEXT_END_ADDR 0x10008
#ifndef __ASSEMBLY__
+#include <linux/bug.h>

/* sizeof(struct user) for AArch32 */
#define COMPAT_USER_SZ 296
@@ -119,6 +120,8 @@ struct pt_regs {
u64 syscallno;
};

+#define MAX_REG_OFFSET offsetof(struct pt_regs, pstate)
+
#define arch_has_single_step() (1)

#ifdef CONFIG_COMPAT
@@ -147,6 +150,55 @@ struct pt_regs {
#define user_stack_pointer(regs) \
(!compat_user_mode(regs) ? (regs)->sp : (regs)->compat_sp)

+extern int regs_query_register_offset(const char *name);
+extern const char *regs_query_register_name(unsigned int offset);
+extern bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr);
+extern unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
+ unsigned int n);
+
+/**
+ * regs_get_register() - get register value from its offset
+ * @regs: pt_regs from which register value is gotten
+ * @offset: offset 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 u64 regs_get_register(struct pt_regs *regs,
+ unsigned int offset)
+{
+ u64 val = 0;
+
+ WARN_ON(offset & 7);
+
+ offset >>= 3;

Here, the offset is 3-bits right shifted. So,

+ switch (offset) {
+ case 0 ... 30:
+ val = regs->regs[offset];
+ break;
+ case offsetof(struct pt_regs, sp):

here should be shifted too, as

case offsetof(struct pt_regs, sp) >> 3:


+ val = regs->sp;
+ break;
+ case offsetof(struct pt_regs, pc):

and here,

+ val = regs->pc;
+ break;
+ case offsetof(struct pt_regs, pstate):

and here.

thanks,
Li Bin


Thanks for pointing this out. It has been fixed now for the v14 patch.

+ val = regs->pstate;
+ break;
+ default:
+ val = 0;
+ }
+
+ return val;
+}
+
+/* Valid only for Kernel mode traps. */
+static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
+{
+ return regs->sp;
+}
+
static inline unsigned long regs_return_value(struct pt_regs *regs)
{
return regs->regs[0];
@@ -156,7 +208,7 @@ static inline unsigned long regs_return_value(struct pt_regs *regs)
struct task_struct;
int valid_user_regs(struct user_pt_regs *regs, struct task_struct *task);

-#define instruction_pointer(regs) ((unsigned long)(regs)->pc)
+#define instruction_pointer(regs) ((regs)->pc)

extern unsigned long profile_pc(struct pt_regs *regs);

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 3f6cd5c..2c88c33 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -48,6 +48,124 @@
#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>

+struct pt_regs_offset {
+ const char *name;
+ int offset;
+};
+
+#define REG_OFFSET_NAME(r) {.name = #r, .offset = offsetof(struct pt_regs, r)}
+#define REG_OFFSET_END {.name = NULL, .offset = 0}
+#define GPR_OFFSET_NAME(r) \
+ {.name = "x" #r, .offset = offsetof(struct pt_regs, regs[r])}
+
+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),
+ {.name = "lr", .offset = offsetof(struct pt_regs, regs[30])},
+ REG_OFFSET_NAME(sp),
+ REG_OFFSET_NAME(pc),
+ REG_OFFSET_NAME(pstate),
+ 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;
+}
+
+/**
+ * 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.
+ */
+bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
+{
+ return ((addr & ~(THREAD_SIZE - 1)) ==
+ (kernel_stack_pointer(regs) & ~(THREAD_SIZE - 1))) ||
+ on_irq_stack(addr, raw_smp_processor_id());
+}
+
+/**
+ * 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.
+ */
+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;
+}
+
/*
* TODO: does not yet catch signals sent when the child dies.
* in exit.c or in signal.c.




Thanks,
-dl