Merge branch 'fdpic' of http://git.linaro.org/people/nicolas.pitre/linux into devel-stable

This series provides the needed changes to suport the ELF_FDPIC binary
format on ARM. Both MMU and non-MMU systems are supported. This format
has many advantages over the BFLT format used on MMU-less systems, such
as being real ELF that can be parsed by standard tools, can support
shared dynamic libs, etc.

6 files changed, 130 insertions, 21 deletions

diff --git a/arch/arm/kernel/asm-offsets.c b/arch/arm/kernel/asm-offsets.c
index 608008229c7d..13c155850822 100644
--- a/arch/arm/kernel/asm-offsets.c
+++ b/arch/arm/kernel/asm-offsets.c
@@ -28,6 +28,7 @@
 #include <asm/vdso_datapage.h>
 #include <asm/hardware/cache-l2x0.h>
 #include <linux/kbuild.h>
+#include "signal.h"
 
 /*
  * Make sure that the compiler and target are compatible.
@@ -112,6 +113,9 @@ int main(void)
   DEFINE(SVC_ADDR_LIMIT,	offsetof(struct svc_pt_regs, addr_limit));
   DEFINE(SVC_REGS_SIZE,		sizeof(struct svc_pt_regs));
   BLANK();
+  DEFINE(SIGFRAME_RC3_OFFSET,	offsetof(struct sigframe, retcode[3]));
+  DEFINE(RT_SIGFRAME_RC3_OFFSET, offsetof(struct rt_sigframe, sig.retcode[3]));
+  BLANK();
 #ifdef CONFIG_CACHE_L2X0
   DEFINE(L2X0_R_PHY_BASE,	offsetof(struct l2x0_regs, phy_base));
   DEFINE(L2X0_R_AUX_CTRL,	offsetof(struct l2x0_regs, aux_ctrl));
diff --git a/arch/arm/kernel/elf.c b/arch/arm/kernel/elf.c
index d0d1e83150c9..569e69ece5ca 100644
--- a/arch/arm/kernel/elf.c
+++ b/arch/arm/kernel/elf.c
@@ -3,6 +3,7 @@
 #include <linux/personality.h>
 #include <linux/binfmts.h>
 #include <linux/elf.h>
+#include <linux/elf-fdpic.h>
 #include <asm/system_info.h>
 
 int elf_check_arch(const struct elf32_hdr *x)
@@ -80,7 +81,7 @@ EXPORT_SYMBOL(elf_set_personality);
  *  - the binary requires an executable stack
  *  - we're running on a CPU which doesn't support NX.
  */
-int arm_elf_read_implies_exec(const struct elf32_hdr *x, int executable_stack)
+int arm_elf_read_implies_exec(int executable_stack)
 {
 	if (executable_stack != EXSTACK_DISABLE_X)
 		return 1;
@@ -89,3 +90,24 @@ int arm_elf_read_implies_exec(const struct elf32_hdr *x, int executable_stack)
 	return 0;
 }
 EXPORT_SYMBOL(arm_elf_read_implies_exec);
+
+#if defined(CONFIG_MMU) && defined(CONFIG_BINFMT_ELF_FDPIC)
+
+void elf_fdpic_arch_lay_out_mm(struct elf_fdpic_params *exec_params,
+			       struct elf_fdpic_params *interp_params,
+			       unsigned long *start_stack,
+			       unsigned long *start_brk)
+{
+	elf_set_personality(&exec_params->hdr);
+
+	exec_params->load_addr = 0x8000;
+	interp_params->load_addr = ELF_ET_DYN_BASE;
+	*start_stack = TASK_SIZE - SZ_16M;
+
+	if ((exec_params->flags & ELF_FDPIC_FLAG_ARRANGEMENT) == ELF_FDPIC_FLAG_INDEPENDENT) {
+		exec_params->flags &= ~ELF_FDPIC_FLAG_ARRANGEMENT;
+		exec_params->flags |= ELF_FDPIC_FLAG_CONSTDISP;
+	}
+}
+
+#endif
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index e2de50bf8742..237973492479 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -19,11 +19,12 @@
 #include <asm/elf.h>
 #include <asm/cacheflush.h>
 #include <asm/traps.h>
-#include <asm/ucontext.h>
 #include <asm/unistd.h>
 #include <asm/vfp.h>
 
-extern const unsigned long sigreturn_codes[7];
+#include "signal.h"
+
+extern const unsigned long sigreturn_codes[17];
 
 static unsigned long signal_return_offset;
 
@@ -172,15 +173,6 @@ static int restore_vfp_context(char __user **auxp)
 /*
  * Do a signal return; undo the signal stack.  These are aligned to 64-bit.
  */
-struct sigframe {
-	struct ucontext uc;
-	unsigned long retcode[2];
-};
-
-struct rt_sigframe {
-	struct siginfo info;
-	struct sigframe sig;
-};
 
 static int restore_sigframe(struct pt_regs *regs, struct sigframe __user *sf)
 {
@@ -366,9 +358,20 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
 	     unsigned long __user *rc, void __user *frame)
 {
 	unsigned long handler = (unsigned long)ksig->ka.sa.sa_handler;
+	unsigned long handler_fdpic_GOT = 0;
 	unsigned long retcode;
-	int thumb = 0;
+	unsigned int idx, thumb = 0;
 	unsigned long cpsr = regs->ARM_cpsr & ~(PSR_f | PSR_E_BIT);
+	bool fdpic = IS_ENABLED(CONFIG_BINFMT_ELF_FDPIC) &&
+		     (current->personality & FDPIC_FUNCPTRS);
+
+	if (fdpic) {
+		unsigned long __user *fdpic_func_desc =
+					(unsigned long __user *)handler;
+		if (__get_user(handler, &fdpic_func_desc[0]) ||
+		    __get_user(handler_fdpic_GOT, &fdpic_func_desc[1]))
+			return 1;
+	}
 
 	cpsr |= PSR_ENDSTATE;
 
@@ -408,9 +411,26 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
 
 	if (ksig->ka.sa.sa_flags & SA_RESTORER) {
 		retcode = (unsigned long)ksig->ka.sa.sa_restorer;
+		if (fdpic) {
+			/*
+			 * We need code to load the function descriptor.
+			 * That code follows the standard sigreturn code
+			 * (6 words), and is made of 3 + 2 words for each
+			 * variant. The 4th copied word is the actual FD
+			 * address that the assembly code expects.
+			 */
+			idx = 6 + thumb * 3;
+			if (ksig->ka.sa.sa_flags & SA_SIGINFO)
+				idx += 5;
+			if (__put_user(sigreturn_codes[idx],   rc  ) ||
+			    __put_user(sigreturn_codes[idx+1], rc+1) ||
+			    __put_user(sigreturn_codes[idx+2], rc+2) ||
+			    __put_user(retcode,                rc+3))
+				return 1;
+			goto rc_finish;
+		}
 	} else {
-		unsigned int idx = thumb << 1;
-
+		idx = thumb << 1;
 		if (ksig->ka.sa.sa_flags & SA_SIGINFO)
 			idx += 3;
 
@@ -422,6 +442,7 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
 		    __put_user(sigreturn_codes[idx+1], rc+1))
 			return 1;
 
+rc_finish:
 #ifdef CONFIG_MMU
 		if (cpsr & MODE32_BIT) {
 			struct mm_struct *mm = current->mm;
@@ -441,7 +462,7 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
 			 * the return code written onto the stack.
 			 */
 			flush_icache_range((unsigned long)rc,
-					   (unsigned long)(rc + 2));
+					   (unsigned long)(rc + 3));
 
 			retcode = ((unsigned long)rc) + thumb;
 		}
@@ -451,6 +472,8 @@ setup_return(struct pt_regs *regs, struct ksignal *ksig,
 	regs->ARM_sp = (unsigned long)frame;
 	regs->ARM_lr = retcode;
 	regs->ARM_pc = handler;
+	if (fdpic)
+		regs->ARM_r9 = handler_fdpic_GOT;
 	regs->ARM_cpsr = cpsr;
 
 	return 0;
diff --git a/arch/arm/kernel/signal.h b/arch/arm/kernel/signal.h
new file mode 100644
index 000000000000..b7b838b05229
--- /dev/null
+++ b/arch/arm/kernel/signal.h
@@ -0,0 +1,11 @@
+#include <asm/ucontext.h>
+
+struct sigframe {
+	struct ucontext uc;
+	unsigned long retcode[4];
+};
+
+struct rt_sigframe {
+	struct siginfo info;
+	struct sigframe sig;
+};
diff --git a/arch/arm/kernel/sigreturn_codes.S b/arch/arm/kernel/sigreturn_codes.S
index b84d0cb13682..2c7b22e32152 100644
--- a/arch/arm/kernel/sigreturn_codes.S
+++ b/arch/arm/kernel/sigreturn_codes.S
@@ -14,6 +14,8 @@
  * GNU General Public License for more details.
  */
 
+#include <asm/assembler.h>
+#include <asm/asm-offsets.h>
 #include <asm/unistd.h>
 
 /*
@@ -51,6 +53,17 @@ ARM_OK(	.arm	)
 	.thumb
 	.endm
 
+	.macro arm_fdpic_slot n
+	.org	sigreturn_codes + 24 + 20 * (\n)
+ARM_OK(	.arm	)
+	.endm
+
+	.macro thumb_fdpic_slot n
+	.org	sigreturn_codes + 24 + 20 * (\n) + 12
+	.thumb
+	.endm
+
+
 #if __LINUX_ARM_ARCH__ <= 4
 	/*
 	 * Note we manually set minimally required arch that supports
@@ -90,13 +103,46 @@ ARM_OK(	swi	#(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE)	)
 	movs	r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
 	swi	#0
 
+	/* ARM sigreturn restorer FDPIC bounce code snippet */
+	arm_fdpic_slot 0
+ARM_OK(	ldr	r3, [sp, #SIGFRAME_RC3_OFFSET] )
+ARM_OK(	ldmia	r3, {r3, r9} )
+#ifdef CONFIG_ARM_THUMB
+ARM_OK(	bx	r3 )
+#else
+ARM_OK(	ret	r3 )
+#endif
+
+	/* Thumb sigreturn restorer FDPIC bounce code snippet */
+	thumb_fdpic_slot 0
+	ldr	r3, [sp, #SIGFRAME_RC3_OFFSET]
+	ldmia	r3, {r2, r3}
+	mov	r9, r3
+	bx	r2
+
+	/* ARM sigreturn_rt restorer FDPIC bounce code snippet */
+	arm_fdpic_slot 1
+ARM_OK(	ldr	r3, [sp, #RT_SIGFRAME_RC3_OFFSET] )
+ARM_OK(	ldmia	r3, {r3, r9} )
+#ifdef CONFIG_ARM_THUMB
+ARM_OK(	bx	r3 )
+#else
+ARM_OK(	ret	r3 )
+#endif
+
+	/* Thumb sigreturn_rt restorer FDPIC bounce code snippet */
+	thumb_fdpic_slot 1
+	ldr	r3, [sp, #RT_SIGFRAME_RC3_OFFSET]
+	ldmia	r3, {r2, r3}
+	mov	r9, r3
+	bx	r2
+
 	/*
-	 * Note on addtional space: setup_return in signal.c
-	 * algorithm uses two words copy regardless whether
-	 * it is thumb case or not, so we need additional
-	 * word after real last entry.
+	 * Note on additional space: setup_return in signal.c
+	 * always copies the same number of words regardless whether
+	 * it is thumb case or not, so we need one additional padding
+	 * word after the last entry.
 	 */
-	arm_slot 2
 	.space	4
 
 	.size	sigreturn_codes, . - sigreturn_codes
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 948c648fea00..43c0560f7b2d 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -647,6 +647,9 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
 		set_tls(regs->ARM_r0);
 		return 0;
 
+	case NR(get_tls):
+		return current_thread_info()->tp_value[0];
+
 	default:
 		/* Calls 9f00xx..9f07ff are defined to return -ENOSYS
 		   if not implemented, rather than raising SIGILL.  This