Unfinished/untested PLT trampoline code.

1 files changed, 87 insertions, 3 deletions

diff --git a/sysdeps/arm/nacl/dl-trampoline.S b/sysdeps/arm/nacl/dl-trampoline.S
index 052b61ab1f..24d4c08df4 100644
--- a/sysdeps/arm/nacl/dl-trampoline.S
+++ b/sysdeps/arm/nacl/dl-trampoline.S
@@ -1,11 +1,91 @@
-/* XXX temporary stubs */
+/* PLT trampolines.  ARM/NaCl version.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
 
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+
+	.syntax unified
 	.text
+
+@ Change &GOT[n+3] into 8*n.  Note relocs are 8 bytes each.
+.macro compute_reloc_arg pltgot, got2
+	sub r1, \pltgot, \got2	@ r1 = &GOT[n+3] - &GOT[2] = 4*(n-1)
+	sub r1, r1, #4		@ r1 = 4*n
+	add r1, r1, r1		@ r1 *= 2 = 8*n
+.endm
+
+	CFI_SECTIONS
 	.globl _dl_runtime_resolve
-	.type _dl_runtime_resolve, #function
+	.type _dl_runtime_resolve, %function
 	.p2align 4
 _dl_runtime_resolve:
-	sfi_trap
+	cfi_startproc
+	cfi_adjust_cfa_offset (8)
+
+	@ We get called with:
+	@ 	lr contains the return address from this call
+	@	stack[1] contains &GOT[n+3] (pointer to function)
+	@	stack[0] points to &GOT[2]
+
+	ldr ip, [sp]		@ ip gets &GOT[2]
+
+	@ Save the argument registers and the return address.
+	@ r4 doesn't need to be saved, but it makes the total
+	@ adjustment to sp (including the two words pushed by
+	@ the PLT code) an even eight words, so sp stays aligned.
+	push {r0-r4, lr}
+	cfi_adjust_cfa_offset (24)
+	cfi_rel_offset (r0, 0)
+	cfi_rel_offset (r1, 4)
+	cfi_rel_offset (r2, 8)
+	cfi_rel_offset (r3, 12)
+	cfi_rel_offset (r4, 16)
+	cfi_rel_offset (lr, 20)
+
+	ldr r1, [sp, #28]	@ r1 gets &GOT[n+3]
+
+	@ Get the 'struct link_map *' for first argument to _dl_fixup.
+	sfi_breg ip, ldr r0, [\B, #-4]
+
+	@ Get the reloc offset for the second argument to _dl_fixup.
+	compute_reloc_arg r1, ip
+
+	@ This does the real work, and returns the real call target.
+	sfi_bl _dl_fixup
+	mov ip, r0
+
+	@ Restore the saved registers.
+	pop {r0-r4, lr}
+	cfi_adjust_cfa_offset (-24)
+	cfi_restore (r0)
+	cfi_restore (r1)
+	cfi_restore (r2)
+	cfi_restore (r3)
+	cfi_restore (r4)
+	cfi_restore (lr)
+
+	@ Now compensate for the two words pushed by the PLT code.
+	sfi_sp add sp, #8
+	cfi_adjust_cfa_offset (-8)
+
+	@ Finally, jump to the newfound call target.
+	sfi_bx ip
+
+	cfi_endproc
 	.size _dl_runtime_resolve, .-_dl_runtime_resolve
 
 #ifndef PROF
@@ -13,7 +93,11 @@ _dl_runtime_resolve:
 	.type _dl_runtime_profile, #function
 	.p2align 4
 _dl_runtime_profile:
+	cfi_startproc
+	cfi_adjust_cfa_offset (8)
+	@ XXX tbd
 	sfi_trap
+	cfi_endproc
 	.size _dl_runtime_profile, .-_dl_runtime_profile
 #endif
 	.previous