[PATCH 1/4] powerpc: Add TIF_ELF2ABI flag.

[PATCH 1/4] powerpc: Add TIF_ELF2ABI flag.

[Rusty Russell]

Little endian ppc64 is getting an exciting new ABI.  This is reflected
by the bottom two bits of e_flags in the ELF header:

	0 == legacy binaries (v1 ABI)
	1 == binaries using the old ABI (compiled with a new toolchain)
	2 == binaries using the new ABI.

We store this in a thread flag, because we need to set it in core
dumps and for signal delivery.  Our chief concern is that it doesn't
use function descriptors.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 arch/powerpc/include/asm/elf.h         | 4 ++++
 arch/powerpc/include/asm/thread_info.h | 9 +++++++++
 2 files changed, 13 insertions(+)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index ac6ec6e..54c7445 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -85,6 +85,8 @@ typedef elf_vrregset_t elf_fpxregset_t;
 # ifdef CONFIG_COMPAT
 #  define SET_PERSONALITY(ex)					\
 do {								\
+	if (((ex).e_flags & 0x3) == 2)				\
+		set_thread_flag(TIF_ELF2ABI);			\
 	if ((ex).e_ident[EI_CLASS] == ELFCLASS32)		\
 		set_thread_flag(TIF_32BIT);			\
 	else							\
@@ -96,6 +98,8 @@ do {								\
 # else /* !COMPAT: */
 #  define SET_PERSONALITY(ex)					\
 do {								\
+	if (((ex).e_flags & 0x3) == 2)				\
+		set_thread_flag(TIF_ELF2ABI);			\
 	if (personality(current->personality) != PER_LINUX32)	\
 		set_personality(PER_LINUX |			\
 			(current->personality & (~PER_MASK)));	\
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index f66c2c1..460326f 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -109,6 +109,9 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_EMULATE_STACK_STORE	16	/* Is an instruction emulation
 						for stack store? */
 #define TIF_MEMDIE		17	/* is terminating due to OOM killer */
+#if defined(CONFIG_PPC64)
+#define TIF_ELF2ABI		18	/* function descriptors must die! */
+#endif
 
 /* as above, but as bit values */
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
@@ -193,6 +196,12 @@ static inline bool test_thread_local_flags(unsigned int flags)
 #define is_32bit_task()	(1)
 #endif
 
+#if defined(CONFIG_PPC64)
+#define is_elf2_task() (test_thread_flag(TIF_ELF2ABI))
+#else
+#define is_elf2_task() (0)
+#endif
+
 #endif	/* !__ASSEMBLY__ */
 
 #endif /* __KERNEL__ */
-- 
1.8.3.2

[PATCH 2/4] powerpc: Set eflags correctly for ELF ABIv2 core dumps.

[Rusty Russell]

We leave it at zero (though it could be 1) for old tasks.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 arch/powerpc/include/asm/elf.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/powerpc/include/asm/elf.h b/arch/powerpc/include/asm/elf.h
index 54c7445..8b89268 100644
--- a/arch/powerpc/include/asm/elf.h
+++ b/arch/powerpc/include/asm/elf.h
@@ -106,6 +106,8 @@ do {								\
 } while (0)
 # endif /* COMPAT */
 
+#define ELF_CORE_EFLAGS (is_elf2_task() ? 2 : 0)
+
 /*
  * An executable for which elf_read_implies_exec() returns TRUE will
  * have the READ_IMPLIES_EXEC personality flag set automatically. This
-- 
1.8.3.2

[PATCH 3/4] powerpc: ELF2 binaries launched directly.

[Rusty Russell]

No function descriptor, but we set r12 up and set TIF_RESTOREALL as it
normally isn't restored on return from syscall.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 arch/powerpc/kernel/process.c | 50 ++++++++++++++++++++++++++++++-------------
 1 file changed, 35 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 59967ea..6fa271a 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1078,25 +1078,45 @@ void start_thread(struct pt_regs *regs, unsigned long start, unsigned long sp)
 	regs->msr = MSR_USER;
 #else
 	if (!is_32bit_task()) {
-		unsigned long entry, toc;
+		unsigned long entry;
 
-		/* start is a relocated pointer to the function descriptor for
-		 * the elf _start routine.  The first entry in the function
-		 * descriptor is the entry address of _start and the second
-		 * entry is the TOC value we need to use.
-		 */
-		__get_user(entry, (unsigned long __user *)start);
-		__get_user(toc, (unsigned long __user *)start+1);
+		if (is_elf2_task()) {
+			/* Look ma, no function descriptors! */
+			entry = start;
 
-		/* Check whether the e_entry function descriptor entries
-		 * need to be relocated before we can use them.
-		 */
-		if (load_addr != 0) {
-			entry += load_addr;
-			toc   += load_addr;
+			/*
+			 * Ulrich says:
+			 *   The latest iteration of the ABI requires that when
+			 *   calling a function (at its global entry point),
+			 *   the caller must ensure r12 holds the entry point
+			 *   address (so that the function can quickly
+			 *   establish addressability).
+			 */
+			regs->gpr[12] = start;
+			/* Make sure that's restored on entry to userspace. */
+			set_thread_flag(TIF_RESTOREALL);
+		} else {
+			unsigned long toc;
+
+			/* start is a relocated pointer to the function
+			 * descriptor for the elf _start routine.  The first
+			 * entry in the function descriptor is the entry
+			 * address of _start and the second entry is the TOC
+			 * value we need to use.
+			 */
+			__get_user(entry, (unsigned long __user *)start);
+			__get_user(toc, (unsigned long __user *)start+1);
+
+			/* Check whether the e_entry function descriptor entries
+			 * need to be relocated before we can use them.
+			 */
+			if (load_addr != 0) {
+				entry += load_addr;
+				toc   += load_addr;
+			}
+			regs->gpr[2] = toc;
 		}
 		regs->nip = entry;
-		regs->gpr[2] = toc;
 		regs->msr = MSR_USER64;
 	} else {
 		regs->nip = start;
-- 
1.8.3.2

[PATCH 4/4] powerpc: ELF2 binaries signal handling

[Rusty Russell]

For the ELFv2 ABI, the hander is the entry point, not a function descriptor.
We also need to set up r12, and fortunately the fast_exception_return
exit path restores r12 for us so nothing else is required.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 arch/powerpc/kernel/signal_64.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/kernel/signal_64.c b/arch/powerpc/kernel/signal_64.c
index f7e61e0..af1f7ad 100644
--- a/arch/powerpc/kernel/signal_64.c
+++ b/arch/powerpc/kernel/signal_64.c
@@ -694,12 +694,6 @@ badframe:
 int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
 		sigset_t *set, struct pt_regs *regs)
 {
-	/* Handler is *really* a pointer to the function descriptor for
-	 * the signal routine.  The first entry in the function
-	 * descriptor is the entry address of signal and the second
-	 * entry is the TOC value we need to use.
-	 */
-	func_descr_t __user *funct_desc_ptr;
 	struct rt_sigframe __user *frame;
 	unsigned long newsp = 0;
 	long err = 0;
@@ -759,19 +753,32 @@ int handle_rt_signal64(int signr, struct k_sigaction *ka, siginfo_t *info,
 			goto badframe;
 		regs->link = (unsigned long) &frame->tramp[0];
 	}
-	funct_desc_ptr = (func_descr_t __user *) ka->sa.sa_handler;
 
 	/* Allocate a dummy caller frame for the signal handler. */
 	newsp = ((unsigned long)frame) - __SIGNAL_FRAMESIZE;
 	err |= put_user(regs->gpr[1], (unsigned long __user *)newsp);
 
 	/* Set up "regs" so we "return" to the signal handler. */
-	err |= get_user(regs->nip, &funct_desc_ptr->entry);
+	if (is_elf2_task()) {
+		regs->nip = (unsigned long) ka->sa.sa_handler;
+		regs->gpr[12] = regs->nip;
+	} else {
+		/* Handler is *really* a pointer to the function descriptor for
+		 * the signal routine.  The first entry in the function
+		 * descriptor is the entry address of signal and the second
+		 * entry is the TOC value we need to use.
+		 */
+		func_descr_t __user *funct_desc_ptr =
+			(func_descr_t __user *) ka->sa.sa_handler;
+
+		err |= get_user(regs->nip, &funct_desc_ptr->entry);
+		err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
+	}
+
 	/* enter the signal handler in native-endian mode */
 	regs->msr &= ~MSR_LE;
 	regs->msr |= (MSR_KERNEL & MSR_LE);
 	regs->gpr[1] = newsp;
-	err |= get_user(regs->gpr[2], &funct_desc_ptr->toc);
 	regs->gpr[3] = signr;
 	regs->result = 0;
 	if (ka->sa.sa_flags & SA_SIGINFO) {
-- 
1.8.3.2