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Subject[RFC Patch v1 33/55] ARC: ptrace support
Date
From: Vineet Gupta <vgupta@synopsys.com>

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
arch/arc/Kconfig | 1 +
arch/arc/include/asm/ptrace.h | 18 ++++-
arch/arc/kernel/Makefile | 3 +
arch/arc/kernel/entry.S | 69 +++++++++++++++++
arch/arc/kernel/ptrace.c | 164 ++++++++++++++++++++++++++++++++++++++++-
5 files changed, 251 insertions(+), 4 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 71e55c0..198c7d0 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -20,6 +20,7 @@ config ARC
select GENERIC_KERNEL_THREAD
select GENERIC_PENDING_IRQ if SMP
select GENERIC_SMP_IDLE_THREAD
+ select HAVE_ARCH_TRACEHOOK
select HAVE_GENERIC_HARDIRQS
select HOTPLUG if !INITRAMFS_SOURCE=""
select MODULES_USE_ELF_RELA
diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h
index bc2229f..bb621e8 100644
--- a/arch/arc/include/asm/ptrace.h
+++ b/arch/arc/include/asm/ptrace.h
@@ -42,6 +42,8 @@
#define PT_orig_r0 96
#define PT_orig_r8 100

+#ifdef __KERNEL__
+
#ifndef __ASSEMBLY__

/* THE pt_regs: Defines how regs are saved during entry into kernel */
@@ -115,7 +117,6 @@ struct user_regs_struct {
/* return 1 if user mode or 0 if kernel mode */
#define user_mode(regs) (regs->status32 & STATUS_U_MASK)

-
/* return 1 if in syscall, 0 if Intr or Exception */
#define in_syscall(regs) (((regs->orig_r8) >= 0 && \
(regs->orig_r8 <= NR_syscalls)) ? 1 : 0)
@@ -128,6 +129,19 @@ struct user_regs_struct {
(struct pt_regs *)(pg_start + THREAD_SIZE - 4) - 1; \
})

-#endif /* __ASSEMBLY__ */
+#define in_brkpt_trap(regs) (((regs->orig_r8) == (NR_syscalls + 2)) ? 1 : 0)
+
+#define user_stack_pointer(regs)\
+({ unsigned int sp; \
+ if (user_mode(regs)) \
+ sp = (regs)->sp;\
+ else \
+ sp = -1; \
+ sp; \
+})
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* __KERNEL__ */

#endif /* __ASM_PTRACE_H */
diff --git a/arch/arc/kernel/Makefile b/arch/arc/kernel/Makefile
index 47f6b33..4ddef9a 100644
--- a/arch/arc/kernel/Makefile
+++ b/arch/arc/kernel/Makefile
@@ -5,6 +5,9 @@
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.

+# Pass UTS_MACHINE for user_regset definition
+CFLAGS_ptrace.o += -DUTS_MACHINE='"$(UTS_MACHINE)"'
+
obj-y := arcksyms.o setup.o irq.o time.o reset.o ptrace.o entry.o process.o \
signal.o traps.o sys.o troubleshoot.o stacktrace.o

diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index 35406da..93cde5e 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -10,6 +10,14 @@
* TBD:
* -remove the low level wrappers for execve/fork/vfork
* needed before task_pt_regs was invented. This saves a branch per call
+ * and more importantly allows clean invocation of post-syscall ptrace hook
+ *
+ * vineetg: Feb 2011 (ptrace low level code fixes)
+ * -traced syscall return code (r0) was not saved into pt_regs for restoring
+ * into user reg-file when traded task rets to user space.
+ * -syscalls needing arch-wrappers (mainly for passing sp as pt_regs)
+ * were not invoking post-syscall trace hook (jumping directly into
+ * ret_from_system_call)
*
* vineetg: Nov 2010:
* -Vector table jumps (@8 bytes) converted into branches (@4 bytes)
@@ -351,6 +359,50 @@ ARC_ENTRY EV_Extension
b ret_from_exception
ARC_EXIT EV_Extension

+;######################### System Call Tracing #########################
+
+tracesys:
+ ; save EFA in case tracer wants the PC of traced task
+ ; using ERET won't work since next-PC has already committed
+ lr r12, [efa]
+ GET_CURR_TASK_FIELD_PTR TASK_THREAD, r11
+ st r12, [r11, THREAD_FAULT_ADDR]
+
+ ; PRE Sys Call Ptrace hook
+ mov r0, sp ; pt_regs needed
+ bl @syscall_trace_entry
+
+ ; Tracing code now returns the syscall num (orig or modif)
+ mov r8, r0
+
+ ; Do the Sys Call as we normally would.
+ ; Validate the Sys Call number
+ cmp r8, NR_syscalls
+ mov.hi r0, -ENOSYS
+ bhi tracesys_exit
+
+ ; Restore the sys-call args. Mere invocation of the hook abv could have
+ ; clobbered them (since they are in scratch regs). The tracer could also
+ ; have deliberately changed the syscall args: r0-r7
+ ld r0, [sp, PT_r0]
+ ld r1, [sp, PT_r1]
+ ld r2, [sp, PT_r2]
+ ld r3, [sp, PT_r3]
+ ld r4, [sp, PT_r4]
+ ld r5, [sp, PT_r5]
+ ld r6, [sp, PT_r6]
+ ld r7, [sp, PT_r7]
+ ld.as r9, [sys_call_table, r8]
+ jl [r9] ; Entry into Sys Call Handler
+
+tracesys_exit:
+ st r0, [sp, PT_r0] ; sys call return value in pt_regs
+
+ ;POST Sys Call Ptrace Hook
+ bl @syscall_trace_exit
+ b ret_from_exception ; NOT ret_from_system_call at is saves r0 which
+ ; we'd done before calling post hook above
+
;################### Break Point TRAP ##########################

; ======= (5b) Trap is due to Break-Point =========
@@ -416,6 +468,11 @@ ARC_ENTRY EV_Trap
; Before doing anything, return from CPU Exception Mode
FAKE_RET_FROM_EXCPN r11

+ ; If syscall tracing ongoing, invoke pre-pos-hooks
+ GET_CURR_THR_INFO_FLAGS r10
+ btst r10, TIF_SYSCALL_TRACE
+ bnz tracesys ; this never comes back
+
;============ This is normal System Call case ==========
; Sys-call num shd not exceed the total system calls avail
cmp r8, NR_syscalls
@@ -621,6 +678,10 @@ ARC_ENTRY sys_fork_wrapper
bl @sys_fork
DISCARD_CALLEE_SAVED_USER

+ GET_CURR_THR_INFO_FLAGS r10
+ btst r10, TIF_SYSCALL_TRACE
+ bnz tracesys_exit
+
b ret_from_system_call
ARC_EXIT sys_fork_wrapper

@@ -631,6 +692,10 @@ ARC_ENTRY sys_vfork_wrapper
bl @sys_vfork
DISCARD_CALLEE_SAVED_USER

+ GET_CURR_THR_INFO_FLAGS r10
+ btst r10, TIF_SYSCALL_TRACE
+ bnz tracesys_exit
+
b ret_from_system_call
ARC_EXIT sys_vfork_wrapper

@@ -645,5 +710,9 @@ ARC_ENTRY sys_clone_wrapper
bl @sys_clone
DISCARD_CALLEE_SAVED_USER

+ GET_CURR_THR_INFO_FLAGS r10
+ btst r10, TIF_SYSCALL_TRACE
+ bnz tracesys_exit
+
b ret_from_system_call
ARC_EXIT sys_clone_wrapper
diff --git a/arch/arc/kernel/ptrace.c b/arch/arc/kernel/ptrace.c
index 1cf944a..93c7420 100644
--- a/arch/arc/kernel/ptrace.c
+++ b/arch/arc/kernel/ptrace.c
@@ -7,6 +7,122 @@
*/

#include <linux/ptrace.h>
+#include <linux/tracehook.h>
+#include <linux/regset.h>
+#include <linux/unistd.h>
+#include <linux/elf.h>
+
+static struct callee_regs *task_callee_regs(struct task_struct *tsk)
+{
+ struct callee_regs *tmp = (struct callee_regs *)tsk->thread.callee_reg;
+ return tmp;
+}
+
+static int genregs_get(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int pos, unsigned int count,
+ void *kbuf, void __user *ubuf)
+{
+ const struct pt_regs *ptregs = task_pt_regs(target);
+ const struct callee_regs *cregs = task_callee_regs(target);
+ int ret = 0;
+ unsigned int stop_pc_val;
+
+#define REG_O_CHUNK(START, END, PTR) \
+ if (!ret) \
+ ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, PTR, \
+ offsetof(struct user_regs_struct, START), \
+ offsetof(struct user_regs_struct, END));
+
+#define REG_O_ONE(LOC, PTR) \
+ if (!ret) \
+ ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, PTR, \
+ offsetof(struct user_regs_struct, LOC), \
+ offsetof(struct user_regs_struct, LOC) + 4);
+
+ REG_O_CHUNK(scratch, callee, ptregs);
+ REG_O_CHUNK(callee, efa, cregs);
+ REG_O_CHUNK(efa, stop_pc, &target->thread.fault_address);
+
+ if (!ret) {
+ if (in_brkpt_trap(ptregs)) {
+ stop_pc_val = target->thread.fault_address;
+ pr_debug("\t\tstop_pc (brk-pt)\n");
+ } else {
+ stop_pc_val = ptregs->ret;
+ pr_debug("\t\tstop_pc (others)\n");
+ }
+
+ REG_O_ONE(stop_pc, &stop_pc_val);
+ }
+
+ return ret;
+}
+
+static int genregs_set(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int pos, unsigned int count,
+ const void *kbuf, const void __user *ubuf)
+{
+ const struct pt_regs *ptregs = task_pt_regs(target);
+ const struct callee_regs *cregs = task_callee_regs(target);
+ int ret = 0;
+
+#define REG_IN_CHUNK(FIRST, NEXT, PTR) \
+ if (!ret) \
+ ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, \
+ (void *)(PTR), \
+ offsetof(struct user_regs_struct, FIRST), \
+ offsetof(struct user_regs_struct, NEXT));
+
+#define REG_IN_ONE(LOC, PTR) \
+ if (!ret) \
+ ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, \
+ (void *)(PTR), \
+ offsetof(struct user_regs_struct, LOC), \
+ offsetof(struct user_regs_struct, LOC) + 4);
+
+#define REG_IGNORE_ONE(LOC) \
+ if (!ret) \
+ ret = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf, \
+ offsetof(struct user_regs_struct, LOC), \
+ offsetof(struct user_regs_struct, LOC) + 4);
+
+ /* TBD: disallow updates to STATUS32, orig_r8 etc*/
+ REG_IN_CHUNK(scratch, callee, ptregs); /* pt_regs[bta..orig_r8] */
+ REG_IN_CHUNK(callee, efa, cregs); /* callee_regs[r25..r13] */
+ REG_IGNORE_ONE(efa); /* efa update invalid */
+ REG_IN_ONE(stop_pc, &ptregs->ret); /* stop_pc: PC update */
+
+ return ret;
+}
+
+enum arc_getset {
+ REGSET_GENERAL,
+};
+
+static const struct user_regset arc_regsets[] = {
+ [REGSET_GENERAL] = {
+ .core_note_type = NT_PRSTATUS,
+ .n = ELF_NGREG,
+ .size = sizeof(unsigned long),
+ .align = sizeof(unsigned long),
+ .get = genregs_get,
+ .set = genregs_set,
+ }
+};
+
+static const struct user_regset_view user_arc_view = {
+ .name = UTS_MACHINE,
+ .e_machine = EM_ARCOMPACT,
+ .regsets = arc_regsets,
+ .n = ARRAY_SIZE(arc_regsets)
+};
+
+const struct user_regset_view *task_user_regset_view(struct task_struct *task)
+{
+ return &user_arc_view;
+}

void ptrace_disable(struct task_struct *child)
{
@@ -16,11 +132,55 @@ long arch_ptrace(struct task_struct *child, long request,
unsigned long addr, unsigned long data)
{
int ret = -EIO;
+ unsigned int count, pos;
+ unsigned int __user *u_addr;
+ void *kbuf;
+
+ pr_debug("REQ=%ld: ADDR =0x%lx, DATA=0x%lx)\n", request, addr, data);
+
+ switch (request) {
+
+ case PTRACE_PEEKUSR:
+ pos = addr; /* offset in struct user_regs_struct */
+ count = 4; /* 1 register only */
+ u_addr = (unsigned int __user *)data;
+ kbuf = NULL;
+ ret = genregs_get(child, NULL, pos, count, kbuf, u_addr);
+ break;
+
+ case PTRACE_POKEUSR:
+ pos = addr; /* offset in struct user_regs_struct */
+ count = 4; /* 1 register only */
+
+ /* Ideally @data would have abeen a user space buffer, from
+ * where, we do a copy_from_user.
+ * However this request only involves one word, which courtesy
+ * our ABI can be passed in a reg.
+ * regset interface however expects some buffer to copyin from
+ */
+ kbuf = &data;
+ u_addr = NULL;
+
+ ret = genregs_set(child, NULL, pos, count, kbuf, u_addr);
+ break;
+
+ default:
+ ret = ptrace_request(child, request, addr, data);
+ break;
+ }
+
return ret;
}

+asmlinkage int syscall_trace_entry(struct pt_regs *regs)
+{
+ if (tracehook_report_syscall_entry(regs))
+ return ULONG_MAX;

-const struct user_regset_view *task_user_regset_view(struct task_struct *task)
+ return regs->r8;
+}
+
+asmlinkage void syscall_trace_exit(struct pt_regs *regs)
{
- return (const struct user_regset_view *)NULL;
+ tracehook_report_syscall_exit(regs, 0);
}
--
1.7.4.1


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