cr: generalize the type to store the value of the TLS register

Supported machine architectures provide TLS stogares of different sizes:
the size of the TLS storage in x86-64 is 24 bytes, ARM --- 4 bytes
and upcoming AArch64 --- 8 bytes. This means every supported architecture
needs a specific type to store the value of the TLS register.

This patch reworks the insterface of the routines arch_get_tls()
and restore_tls() passing them the TLS storage by pointer
rather than by value to simplify the TLS stub for x86.
Signed-off-by: Alexander Kartashov <alekskartashov@parallels.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Reviewed-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

arch/arm/include/asm/dump.h

@@ -6,7 +6,7 @@ extern int arch_alloc_thread_info(CoreEntry *core);
 extern void arch_free_thread_info(CoreEntry *core);
 
 
-static inline void core_put_tls(CoreEntry *core, u32 tls)
+static inline void core_put_tls(CoreEntry *core, tls_t tls)
 {
 	core->ti_arm->tls = tls;
 }

arch/arm/include/asm/parasite.h

 #ifndef __ASM_PARASITE_H__
 #define __ASM_PARASITE_H__
 
-static inline u32 arch_get_tls(void)
+static inline void arch_get_tls(tls_t *ptls)
 {
-	return ((u32 (*)())0xffff0fe0)();
+	*ptls = ((tls_t (*)())0xffff0fe0)();
 }
 
 #endif

arch/arm/include/asm/restore.h

@@ -18,7 +18,7 @@
 		       "r"(task_args)					\
 		     : "sp", "r0", "r1", "memory")
 
-static inline void core_get_tls(CoreEntry *pcore, u32 *ptls)
+static inline void core_get_tls(CoreEntry *pcore, tls_t *ptls)
 {
 	*ptls = pcore->ti_arm->tls;
 }

arch/arm/include/asm/restorer.h

@@ -136,16 +136,16 @@ int restore_nonsigframe_gpregs(UserArmRegsEntry *r);
 
 static inline int sigreturn_prep_fpu_frame(struct rt_sigframe *sigframe, fpu_state_t *fpu_state) { return 0; }
 
-static inline void restore_tls(u32 tls) {
+static inline void restore_tls(tls_t *ptls) {
 	asm (
 	     "mov %%r7, #15  \n"
 	     "lsl %%r7, #16  \n"
 	     "mov %%r0, #5   \n"
 	     "add %%r7, %%r0 \n"	/* r7 = 0xF005 */
-	     "mov %%r0, %0   \n"
+	     "ldr %%r0, [%0] \n"
 	     "svc #0         \n"
 	     :
-	     : "r"(tls)
+	     : "r"(ptls)
 	     : "r0", "r7"
 	     );
 }

arch/arm/include/asm/types.h

@@ -110,6 +110,7 @@ typedef UserArmRegsEntry UserRegsEntry;
 #define TI_SP(core) ((core)->ti_arm->gpregs->sp)
 
 typedef u32 auxv_t;
+typedef u32 tls_t;
 
 static inline void *decode_pointer(u64 v) { return (void*)(u32)v; }
 static inline u64 encode_pointer(void *p) { return (u32)p; }

arch/x86/include/asm/parasite.h

 #ifndef __ASM_PARASITE_H__
 #define __ASM_PARASITE_H__
 
-static inline u32 arch_get_tls()
-{
-	return 0;
-}
+static inline void arch_get_tls(tls_t *ptls) { (void)ptls; }
 
 #endif

arch/x86/include/asm/restorer.h

@@ -143,6 +143,6 @@ int restore_nonsigframe_gpregs(UserX86RegsEntry *r);
 
 int sigreturn_prep_fpu_frame(struct rt_sigframe *sigframe, fpu_state_t *fpu_state);
 
-static inline void restore_tls(u32 tls) { }
+static inline void restore_tls(tls_t *ptls) { (void)ptls; }
 
 #endif

arch/x86/include/asm/types.h

@@ -112,6 +112,7 @@ typedef struct {
 #define TASK_SIZE ((1UL << 47) - PAGE_SIZE)
 
 typedef u64 auxv_t;
+typedef u32 tls_t;
 
 #define REG_RES(regs) ((regs).ax)
 #define REG_IP(regs)  ((regs).ip)

include/parasite.h

@@ -138,7 +138,7 @@ static inline int posix_timers_dump_size(int timer_n)
 struct parasite_dump_thread {
 	unsigned int		*tid_addr;
 	pid_t			tid;
-	u32			tls;
+	tls_t			tls;
 	stack_t			sas;
 };
 

include/restorer.h

@@ -85,7 +85,7 @@ struct thread_restore_args {
 
 	struct task_restore_args	*ta;
 
-	u32				tls;
+	tls_t				tls;
 
 	siginfo_t			*siginfo;
 	unsigned int			siginfo_nr;

pie/parasite.c

@@ -142,7 +142,7 @@ static int dump_thread_common(struct parasite_dump_thread *ti)
 {
 	int ret;
 
-	ti->tls = arch_get_tls();
+	arch_get_tls(&ti->tls);
 	ret = sys_prctl(PR_GET_TID_ADDRESS, (unsigned long) &ti->tid_addr, 0, 0, 0);
 	if (ret == 0)
 		ret = sys_sigaltstack(NULL, &ti->sas);

pie/restorer.c

@@ -256,7 +256,7 @@ static int restore_thread_common(struct rt_sigframe *sigframe,
 	if (restore_nonsigframe_gpregs(&args->gpregs))
 		return -1;
 
-	restore_tls(args->tls);
+	restore_tls(&args->tls);
 
 	return 0;
 }