powerpc: ELF2 binaries launched directly.

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>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 75c2d1009985eb8dbd9f3995fc900f9f21227d01..0650e18169f81bec509905a269a82d2d78fc584f 100644 (file)
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1086,25 +1086,45 @@ 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;