From: Paolo 'Blaisorblade' Giarrusso <[email protected]>
I hadn't been running a SKAS3 host when testing the "uml: fix hang in TT mode on
fault" patch (commit 546fe1cbf91d4d62e3849517c31a2327c992e5c5), and I didn't
think enough to the missing trap_no in SKAS3 mode.
In fact, the resulting kernel doesn't work at all in SKAS3 mode.
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <[email protected]>
---
arch/um/include/sysdep-i386/sigcontext.h | 10 +++++++++-
arch/um/include/sysdep-x86_64/sigcontext.h | 5 ++++-
arch/um/kernel/trap_kern.c | 5 ++++-
3 files changed, 17 insertions(+), 3 deletions(-)
diff --git a/arch/um/include/sysdep-i386/sigcontext.h b/arch/um/include/sysdep-i386/sigcontext.h
--- a/arch/um/include/sysdep-i386/sigcontext.h
+++ b/arch/um/include/sysdep-i386/sigcontext.h
@@ -6,6 +6,7 @@
#ifndef __SYS_SIGCONTEXT_I386_H
#define __SYS_SIGCONTEXT_I386_H
+#include "uml-config.h"
#include <sysdep/sc.h>
#define IP_RESTART_SYSCALL(ip) ((ip) -= 2)
@@ -26,7 +27,14 @@
#define SC_START_SYSCALL(sc) do SC_EAX(sc) = -ENOSYS; while(0)
/* This is Page Fault */
-#define SEGV_IS_FIXABLE(fi) ((fi)->trap_no == 14)
+#define SEGV_IS_FIXABLE(fi) ((fi)->trap_no == 14)
+
+/* SKAS3 has no trap_no on i386, but get_skas_faultinfo() sets it to 0. */
+#ifdef UML_CONFIG_MODE_SKAS
+#define SEGV_MAYBE_FIXABLE(fi) ((fi)->trap_no == 0 && ptrace_faultinfo)
+#else
+#define SEGV_MAYBE_FIXABLE(fi) 0
+#endif
extern unsigned long *sc_sigmask(void *sc_ptr);
extern int sc_get_fpregs(unsigned long buf, void *sc_ptr);
diff --git a/arch/um/include/sysdep-x86_64/sigcontext.h b/arch/um/include/sysdep-x86_64/sigcontext.h
--- a/arch/um/include/sysdep-x86_64/sigcontext.h
+++ b/arch/um/include/sysdep-x86_64/sigcontext.h
@@ -31,7 +31,10 @@
#define SC_START_SYSCALL(sc) do SC_RAX(sc) = -ENOSYS; while(0)
/* This is Page Fault */
-#define SEGV_IS_FIXABLE(fi) ((fi)->trap_no == 14)
+#define SEGV_IS_FIXABLE(fi) ((fi)->trap_no == 14)
+
+/* No broken SKAS API, which doesn't pass trap_no, here. */
+#define SEGV_MAYBE_FIXABLE(fi) 0
extern unsigned long *sc_sigmask(void *sc_ptr);
diff --git a/arch/um/kernel/trap_kern.c b/arch/um/kernel/trap_kern.c
--- a/arch/um/kernel/trap_kern.c
+++ b/arch/um/kernel/trap_kern.c
@@ -26,6 +26,9 @@
#include "mconsole_kern.h"
#include "mem.h"
#include "mem_kern.h"
+#ifdef CONFIG_MODE_SKAS
+#include "skas.h"
+#endif
/* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
int handle_page_fault(unsigned long address, unsigned long ip,
@@ -134,7 +137,7 @@ unsigned long segv(struct faultinfo fi,
else if(current->mm == NULL)
panic("Segfault with no mm");
- if (SEGV_IS_FIXABLE(&fi))
+ if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
else {
err = -EFAULT;
-
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