ARM: 7442/1: Revert "remove unused restart trampoline"

This reverts commit fa18484d0947b976a769d15c83c50617493c81c1.

We need the restart trampoline back so that we can revert a related
problematic patch 6b5c8045ecc7e726cdaa2a9d9c8e5008050e1252 ("arm: new
way of handling ERESTART_RESTARTBLOCK").

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index fd2392a..6d3bce5 100644 (file)
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -27,6 +27,7 @@
  */
 #define SWI_SYS_SIGRETURN      (0xef000000|(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE))
 #define SWI_SYS_RT_SIGRETURN   (0xef000000|(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE))
+#define SWI_SYS_RESTART                (0xef000000|__NR_restart_syscall|__NR_OABI_SYSCALL_BASE)
 
 /*
  * With EABI, the syscall number has to be loaded into r7.
@@ -46,6 +47,18 @@ const unsigned long sigreturn_codes[7] = {
        MOV_R7_NR_RT_SIGRETURN, SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN,
 };
 
+/*
+ * Either we support OABI only, or we have EABI with the OABI
+ * compat layer enabled.  In the later case we don't know if
+ * user space is EABI or not, and if not we must not clobber r7.
+ * Always using the OABI syscall solves that issue and works for
+ * all those cases.
+ */
+const unsigned long syscall_restart_code[2] = {
+       SWI_SYS_RESTART,        /* swi  __NR_restart_syscall */
+       0xe49df004,             /* ldr  pc, [sp], #4 */
+};
+
 /*
  * atomically swap in the new signal mask, and wait for a signal.
  */

diff --git a/arch/arm/kernel/signal.h b/arch/arm/kernel/signal.h
index 5ff067b..6fcfe83 100644 (file)
--- a/arch/arm/kernel/signal.h
+++ b/arch/arm/kernel/signal.h
@@ -8,5 +8,7 @@
  * published by the Free Software Foundation.
  */
 #define KERN_SIGRETURN_CODE    (CONFIG_VECTORS_BASE + 0x00000500)
+#define KERN_RESTART_CODE      (KERN_SIGRETURN_CODE + sizeof(sigreturn_codes))
 
 extern const unsigned long sigreturn_codes[7];
+extern const unsigned long syscall_restart_code[2];

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 4928d89..3647170 100644 (file)
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -820,6 +820,8 @@ void __init early_trap_init(void *vectors_base)
         */
        memcpy((void *)(vectors + KERN_SIGRETURN_CODE - CONFIG_VECTORS_BASE),
               sigreturn_codes, sizeof(sigreturn_codes));
+       memcpy((void *)(vectors + KERN_RESTART_CODE - CONFIG_VECTORS_BASE),
+              syscall_restart_code, sizeof(syscall_restart_code));
 
        flush_icache_range(vectors, vectors + PAGE_SIZE);
        modify_domain(DOMAIN_USER, DOMAIN_CLIENT);