[PATCH 2/7] um: Store syscall number after syscall_trace_enter()

From: Richard Weinberger
Date: Mon Oct 26 2015 - 05:49:50 EST


To support changing syscall numbers we have to store
it after syscall_trace_enter().

Signed-off-by: Richard Weinberger <richard@xxxxxx>
---
arch/um/include/shared/os.h | 1 +
arch/um/kernel/skas/syscall.c | 13 +++----------
arch/um/os-Linux/skas/process.c | 10 +++++++---
3 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/arch/um/include/shared/os.h b/arch/um/include/shared/os.h
index ad3fa3a..f3cbaef 100644
--- a/arch/um/include/shared/os.h
+++ b/arch/um/include/shared/os.h
@@ -274,6 +274,7 @@ extern void initial_thread_cb_skas(void (*proc)(void *),
void *arg);
extern void halt_skas(void);
extern void reboot_skas(void);
+extern int get_syscall(struct uml_pt_regs *regs);

/* irq.c */
extern int os_waiting_for_events(struct irq_fd *active_fds);
diff --git a/arch/um/kernel/skas/syscall.c b/arch/um/kernel/skas/syscall.c
index d9ec006..64a8fe5 100644
--- a/arch/um/kernel/skas/syscall.c
+++ b/arch/um/kernel/skas/syscall.c
@@ -8,6 +8,7 @@
#include <kern_util.h>
#include <sysdep/ptrace.h>
#include <sysdep/syscalls.h>
+#include <os.h>

extern int syscall_table_size;
#define NR_SYSCALLS (syscall_table_size / sizeof(void *))
@@ -23,16 +24,8 @@ void handle_syscall(struct uml_pt_regs *r)
goto out;
}

- /*
- * This should go in the declaration of syscall, but when I do that,
- * strace -f -c bash -c 'ls ; ls' breaks, sometimes not tracing
- * children at all, sometimes hanging when bash doesn't see the first
- * ls exit.
- * The assembly looks functionally the same to me. This is
- * gcc version 4.0.1 20050727 (Red Hat 4.0.1-5)
- * in case it's a compiler bug.
- */
- syscall = UPT_SYSCALL_NR(r);
+ syscall = get_syscall(r);
+
if ((syscall >= NR_SYSCALLS) || (syscall < 0))
result = -ENOSYS;
else result = EXECUTE_SYSCALL(syscall, regs);
diff --git a/arch/um/os-Linux/skas/process.c b/arch/um/os-Linux/skas/process.c
index 3dddedb..d38f495 100644
--- a/arch/um/os-Linux/skas/process.c
+++ b/arch/um/os-Linux/skas/process.c
@@ -137,9 +137,6 @@ static void handle_trap(int pid, struct uml_pt_regs *regs,
if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
fatal_sigsegv();

- /* Mark this as a syscall */
- UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
-
if (!local_using_sysemu)
{
err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
@@ -174,6 +171,13 @@ static void handle_trap(int pid, struct uml_pt_regs *regs,
handle_syscall(regs);
}

+int get_syscall(struct uml_pt_regs *regs)
+{
+ UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);
+
+ return UPT_SYSCALL_NR(regs);
+}
+
extern char __syscall_stub_start[];

static int userspace_tramp(void *stack)
--
1.8.4.5

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