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Subject[PATCH 2/5] powerpc: tracehook syscall
Date
This changes powerpc syscall tracing to use the new tracehook.h entry
points. There is no change, only cleanup.

The assembly changes allow do_syscall_trace_enter() to abort the
syscall without losing the information about the original r0 value.

Signed-off-by: Roland McGrath <roland@redhat.com>
---
arch/powerpc/kernel/entry_32.S | 7 +++++-
arch/powerpc/kernel/entry_64.S | 7 +++++-
arch/powerpc/kernel/ptrace.c | 47 ++++++++++++++++++---------------------
3 files changed, 34 insertions(+), 27 deletions(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 81c8324..0efc1e6 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -343,7 +343,12 @@ syscall_dotrace:
stw r0,_TRAP(r1)
addi r3,r1,STACK_FRAME_OVERHEAD
bl do_syscall_trace_enter
- lwz r0,GPR0(r1) /* Restore original registers */
+ /*
+ * Restore argument registers possibly just changed.
+ * We use the return value of do_syscall_trace_enter
+ * for call number to look up in the table (r0).
+ */
+ mr r0,r3
lwz r3,GPR3(r1)
lwz r4,GPR4(r1)
lwz r5,GPR5(r1)
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index d736924..79c089e 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -214,7 +214,12 @@ syscall_dotrace:
bl .save_nvgprs
addi r3,r1,STACK_FRAME_OVERHEAD
bl .do_syscall_trace_enter
- ld r0,GPR0(r1) /* Restore original registers */
+ /*
+ * Restore argument registers possibly just changed.
+ * We use the return value of do_syscall_trace_enter
+ * for the call number to look up in the table (r0).
+ */
+ mr r0,r3
ld r3,GPR3(r1)
ld r4,GPR4(r1)
ld r5,GPR5(r1)
diff --git a/arch/powerpc/kernel/ptrace.c b/arch/powerpc/kernel/ptrace.c
index a5d0e78..3f9a942 100644
--- a/arch/powerpc/kernel/ptrace.c
+++ b/arch/powerpc/kernel/ptrace.c
@@ -22,6 +22,7 @@
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/regset.h>
+#include <linux/tracehook.h>
#include <linux/elf.h>
#include <linux/user.h>
#include <linux/security.h>
@@ -1013,31 +1014,24 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
return ret;
}

-static void do_syscall_trace(void)
+/*
+ * We must return the syscall number to actually look up in the table.
+ * This can be -1L to skip running any syscall at all.
+ */
+long do_syscall_trace_enter(struct pt_regs *regs)
{
- /* the 0x80 provides a way for the tracing parent to distinguish
- between a syscall stop and SIGTRAP delivery */
- ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
- ? 0x80 : 0));
-
- /*
- * this isn't the same as continuing with a signal, but it will do
- * for normal use. strace only continues with a signal if the
- * stopping signal is not SIGTRAP. -brl
- */
- if (current->exit_code) {
- send_sig(current->exit_code, current, 1);
- current->exit_code = 0;
- }
-}
+ long ret = 0;

-void do_syscall_trace_enter(struct pt_regs *regs)
-{
secure_computing(regs->gpr[0]);

- if (test_thread_flag(TIF_SYSCALL_TRACE)
- && (current->ptrace & PT_PTRACED))
- do_syscall_trace();
+ if (test_thread_flag(TIF_SYSCALL_TRACE) &&
+ tracehook_report_syscall_entry(regs))
+ /*
+ * Tracing decided this syscall should not happen.
+ * We'll return a bogus call number to get an ENOSYS
+ * error, but leave the original number in regs->gpr[0].
+ */
+ ret = -1L;

if (unlikely(current->audit_context)) {
#ifdef CONFIG_PPC64
@@ -1055,16 +1049,19 @@ void do_syscall_trace_enter(struct pt_regs *regs)
regs->gpr[5] & 0xffffffff,
regs->gpr[6] & 0xffffffff);
}
+
+ return ret ?: regs->gpr[0];
}

void do_syscall_trace_leave(struct pt_regs *regs)
{
+ int step;
+
if (unlikely(current->audit_context))
audit_syscall_exit((regs->ccr&0x10000000)?AUDITSC_FAILURE:AUDITSC_SUCCESS,
regs->result);

- if ((test_thread_flag(TIF_SYSCALL_TRACE)
- || test_thread_flag(TIF_SINGLESTEP))
- && (current->ptrace & PT_PTRACED))
- do_syscall_trace();
+ step = test_thread_flag(TIF_SINGLESTEP);
+ if (step || test_thread_flag(TIF_SYSCALL_TRACE))
+ tracehook_report_syscall_exit(regs, step);
}

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