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Subject[PATCH] arch/tile: provide PT_FLAGS_COMPAT value in pt_regs
This flag is set for ptrace GETREGS or PEEKUSER for processes
that are COMPAT, i.e. 32-bit. This allows things like strace
to easily discover what personality to use, for example.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
---
arch/tile/include/uapi/asm/ptrace.h | 6 ++++
arch/tile/kernel/ptrace.c | 57 ++++++++++++++++++++++++-----------
2 files changed, 46 insertions(+), 17 deletions(-)

diff --git a/arch/tile/include/uapi/asm/ptrace.h b/arch/tile/include/uapi/asm/ptrace.h
index c717d0f..0d22088 100644
--- a/arch/tile/include/uapi/asm/ptrace.h
+++ b/arch/tile/include/uapi/asm/ptrace.h
@@ -84,5 +84,11 @@ struct pt_regs {
#define PTRACE_O_TRACEMIGRATE 0x00010000
#define PTRACE_EVENT_MIGRATE 16

+/*
+ * Flag bits in pt_regs.flags that are part of the ptrace API.
+ * We start our numbering higher up to avoid confusion with the
+ * non-ABI kernel-internal values that use the low 16 bits.
+ */
+#define PT_FLAGS_COMPAT 0x10000 /* process is an -m32 compat process */

#endif /* _UAPI_ASM_TILE_PTRACE_H */
diff --git a/arch/tile/kernel/ptrace.c b/arch/tile/kernel/ptrace.c
index e92e405..64ba102 100644
--- a/arch/tile/kernel/ptrace.c
+++ b/arch/tile/kernel/ptrace.c
@@ -45,6 +45,41 @@ void ptrace_disable(struct task_struct *child)
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
}

+/*
+ * Get registers from task and ready the result for userspace.
+ * Note that we localize the API issues to getregs() and putregs() at
+ * some cost in performance, e.g. we need a full pt_regs copy for
+ * PEEKUSR, and two copies for POKEUSR. But in general we expect
+ * GETREGS/PUTREGS to be the API of choice anyway.
+ */
+static char *getregs(struct task_struct *child, struct pt_regs *uregs)
+{
+ *uregs = *task_pt_regs(child);
+
+ /* Set up flags ABI bits. */
+ uregs->flags = 0;
+#ifdef CONFIG_COMPAT
+ if (task_thread_info(child)->status & TS_COMPAT)
+ uregs->flags |= PT_FLAGS_COMPAT;
+#endif
+
+ return (char *)uregs;
+}
+
+/* Put registers back to task. */
+static void putregs(struct task_struct *child, struct pt_regs *uregs)
+{
+ struct pt_regs *regs = task_pt_regs(child);
+
+ /* Don't allow overwriting the kernel-internal flags word. */
+ uregs->flags = regs->flags;
+
+ /* Only allow setting the ICS bit in the ex1 word. */
+ uregs->ex1 = PL_ICS_EX1(USER_PL, EX1_ICS(uregs->ex1));
+
+ *regs = *uregs;
+}
+
long arch_ptrace(struct task_struct *child, long request,
unsigned long addr, unsigned long data)
{
@@ -53,14 +88,13 @@ long arch_ptrace(struct task_struct *child, long request,
long ret = -EIO;
char *childreg;
struct pt_regs copyregs;
- int ex1_offset;

switch (request) {

case PTRACE_PEEKUSR: /* Read register from pt_regs. */
if (addr >= PTREGS_SIZE)
break;
- childreg = (char *)task_pt_regs(child) + addr;
+ childreg = getregs(child, &copyregs) + addr;
#ifdef CONFIG_COMPAT
if (is_compat_task()) {
if (addr & (sizeof(compat_long_t)-1))
@@ -79,17 +113,7 @@ long arch_ptrace(struct task_struct *child, long request,
case PTRACE_POKEUSR: /* Write register in pt_regs. */
if (addr >= PTREGS_SIZE)
break;
- childreg = (char *)task_pt_regs(child) + addr;
-
- /* Guard against overwrites of the privilege level. */
- ex1_offset = PTREGS_OFFSET_EX1;
-#if defined(CONFIG_COMPAT) && defined(__BIG_ENDIAN)
- if (is_compat_task()) /* point at low word */
- ex1_offset += sizeof(compat_long_t);
-#endif
- if (addr == ex1_offset)
- data = PL_ICS_EX1(USER_PL, EX1_ICS(data));
-
+ childreg = getregs(child, &copyregs) + addr;
#ifdef CONFIG_COMPAT
if (is_compat_task()) {
if (addr & (sizeof(compat_long_t)-1))
@@ -102,11 +126,12 @@ long arch_ptrace(struct task_struct *child, long request,
break;
*(long *)childreg = data;
}
+ putregs(child, &copyregs);
ret = 0;
break;

case PTRACE_GETREGS: /* Get all registers from the child. */
- if (copy_to_user(datap, task_pt_regs(child),
+ if (copy_to_user(datap, getregs(child, &copyregs),
sizeof(struct pt_regs)) == 0) {
ret = 0;
}
@@ -115,9 +140,7 @@ long arch_ptrace(struct task_struct *child, long request,
case PTRACE_SETREGS: /* Set all registers in the child. */
if (copy_from_user(&copyregs, datap,
sizeof(struct pt_regs)) == 0) {
- copyregs.ex1 =
- PL_ICS_EX1(USER_PL, EX1_ICS(copyregs.ex1));
- *task_pt_regs(child) = copyregs;
+ putregs(child, &copyregs);
ret = 0;
}
break;
--
1.7.10.3


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