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SubjectIncorrect order of last two arguments of ptrace for requests PPC_PTRACE_GETREGS, SETREGS, GETFPREGS, SETFPREGS
In ptrace, when request is PPC_PTRACE_GETREGS, SETREGS, GETFPREGS and 
SETFPREGS, order of the last two arguments is not correct.

General format of ptrace is ptrace (request, pid, addr, data). For the
above mentioned request ids in ppc64, if we use ptrace like

long reg[32];
ptrace (PPC_PTRACE_GETREGS, pid, 0, &reg[0]);

the return value is always -1.

If we exchange the last two arguments like,

ptrace (PPC_PTRACE_GETREGS, pid, &reg[0], 0);

it works!

This is because PPC_PTRACE_GETREGS option for powerpc is implemented
such that general purpose
registers of the child process get copied to the address variable
instead of data variable. Same is
the case with other PPC request options PPC_PTRACE_SETREGS, GETFPREGS
and SETFPREGS.

Prepared a patch for this problem and tested with 2.6.18-rc6 kernel.
This patch can be applied directly to
2.6.19-rc3 kernel.
diff -Naurp linux-2.6.18-rc6/arch/powerpc/kernel/ptrace.c linux-2.6.18-rc6-mod/arch/powerpc/kernel/ptrace.c
--- linux-2.6.18-rc6/arch/powerpc/kernel/ptrace.c 2006-10-19 18:09:01.000000000 +0530
+++ linux-2.6.18-rc6-mod/arch/powerpc/kernel/ptrace.c 2006-10-19 18:11:37.000000000 +0530
@@ -406,7 +406,7 @@ long arch_ptrace(struct task_struct *chi
case PPC_PTRACE_GETREGS: { /* Get GPRs 0 - 31. */
int i;
unsigned long *reg = &((unsigned long *)child->thread.regs)[0];
- unsigned long __user *tmp = (unsigned long __user *)addr;
+ unsigned long __user *tmp = (unsigned long __user *)data;

for (i = 0; i < 32; i++) {
ret = put_user(*reg, tmp);
@@ -421,7 +421,7 @@ long arch_ptrace(struct task_struct *chi
case PPC_PTRACE_SETREGS: { /* Set GPRs 0 - 31. */
int i;
unsigned long *reg = &((unsigned long *)child->thread.regs)[0];
- unsigned long __user *tmp = (unsigned long __user *)addr;
+ unsigned long __user *tmp = (unsigned long __user *)data;

for (i = 0; i < 32; i++) {
ret = get_user(*reg, tmp);
@@ -436,7 +436,7 @@ long arch_ptrace(struct task_struct *chi
case PPC_PTRACE_GETFPREGS: { /* Get FPRs 0 - 31. */
int i;
unsigned long *reg = &((unsigned long *)child->thread.fpr)[0];
- unsigned long __user *tmp = (unsigned long __user *)addr;
+ unsigned long __user *tmp = (unsigned long __user *)data;

flush_fp_to_thread(child);

@@ -453,7 +453,7 @@ long arch_ptrace(struct task_struct *chi
case PPC_PTRACE_SETFPREGS: { /* Get FPRs 0 - 31. */
int i;
unsigned long *reg = &((unsigned long *)child->thread.fpr)[0];
- unsigned long __user *tmp = (unsigned long __user *)addr;
+ unsigned long __user *tmp = (unsigned long __user *)data;

flush_fp_to_thread(child);

diff -Naurp linux-2.6.18-rc6/arch/powerpc/kernel/ptrace32.c linux-2.6.18-rc6-mod/arch/powerpc/kernel/ptrace32.c
--- linux-2.6.18-rc6/arch/powerpc/kernel/ptrace32.c 2006-10-19 18:09:01.000000000 +0530
+++ linux-2.6.18-rc6-mod/arch/powerpc/kernel/ptrace32.c 2006-10-19 18:11:41.000000000 +0530
@@ -345,7 +345,7 @@ long compat_sys_ptrace(int request, int
case PPC_PTRACE_GETREGS: { /* Get GPRs 0 - 31. */
int i;
unsigned long *reg = &((unsigned long *)child->thread.regs)[0];
- unsigned int __user *tmp = (unsigned int __user *)addr;
+ unsigned int __user *tmp = (unsigned int __user *)data;

for (i = 0; i < 32; i++) {
ret = put_user(*reg, tmp);
@@ -360,7 +360,7 @@ long compat_sys_ptrace(int request, int
case PPC_PTRACE_SETREGS: { /* Set GPRs 0 - 31. */
int i;
unsigned long *reg = &((unsigned long *)child->thread.regs)[0];
- unsigned int __user *tmp = (unsigned int __user *)addr;
+ unsigned int __user *tmp = (unsigned int __user *)data;

for (i = 0; i < 32; i++) {
ret = get_user(*reg, tmp);
@@ -375,7 +375,7 @@ long compat_sys_ptrace(int request, int
case PPC_PTRACE_GETFPREGS: { /* Get FPRs 0 - 31. */
int i;
unsigned long *reg = &((unsigned long *)child->thread.fpr)[0];
- unsigned int __user *tmp = (unsigned int __user *)addr;
+ unsigned int __user *tmp = (unsigned int __user *)data;

flush_fp_to_thread(child);

@@ -392,7 +392,7 @@ long compat_sys_ptrace(int request, int
case PPC_PTRACE_SETFPREGS: { /* Get FPRs 0 - 31. */
int i;
unsigned long *reg = &((unsigned long *)child->thread.fpr)[0];
- unsigned int __user *tmp = (unsigned int __user *)addr;
+ unsigned int __user *tmp = (unsigned int __user *)data;

flush_fp_to_thread(child);
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