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linux/arch/powerpc/kernel/vdso64/sigtramp.S
Ulrich Weigand 280270828f powerpc: Wrong DWARF CFI in the kernel vdso for little-endian / ELFv2 
I've finally tracked down why my CR signal-unwind test case still
fails on little-endian.  The problem turned to be that the kernel
installs a signal trampoline in the vDSO, and provides a DWARF CFI
record for that trampoline.  This CFI describes the save location
for CR:

  rsave (70, 38*RSIZE + (RSIZE - CRSIZE))

which is correct for big-endian, but points to the wrong word on
little-endian.   This is wrong no matter which ABI.

In addition, for the ELFv2 ABI, we should not only provide a CFI
record for register 70 (cr2), but for all CR fields separately.
Strictly speaking, I guess this would mean providing two separate
vDSO images, one for ELFv1 processes and one for ELFv2 processes (or
maybe playing some tricks with conditional DWARF expressions).
However, having CFI records for the other CR fields in ELFv1 is not
actually wrong, they just will be ignored.   So it seems the simplest
fix would be just to always provide CFI for all the fields.

Signed-off-by: Ulrich Weigand <Ulrich.Weigand@de.ibm.com>
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2013-11-21 09:19:23 +11:00

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/*
* Signal trampoline for 64 bits processes in a ppc64 kernel for
* use in the vDSO
*
* Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org), IBM Corp.
* Copyright (C) 2004 Alan Modra (amodra@au.ibm.com)), IBM Corp.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <asm/processor.h>
#include <asm/ppc_asm.h>
#include <asm/unistd.h>
#include <asm/vdso.h>
#include <asm/ptrace.h> /* XXX for __SIGNAL_FRAMESIZE */
.text
/* The nop here is a hack. The dwarf2 unwind routines subtract 1 from
the return address to get an address in the middle of the presumed
call instruction. Since we don't have a call here, we artificially
extend the range covered by the unwind info by padding before the
real start. */
nop
.balign 8
V_FUNCTION_BEGIN(__kernel_sigtramp_rt64)
.Lsigrt_start = . - 4
addi r1, r1, __SIGNAL_FRAMESIZE
li r0,__NR_rt_sigreturn
sc
.Lsigrt_end:
V_FUNCTION_END(__kernel_sigtramp_rt64)
/* The ".balign 8" above and the following zeros mimic the old stack
trampoline layout. The last magic value is the ucontext pointer,
chosen in such a way that older libgcc unwind code returns a zero
for a sigcontext pointer. */
.long 0,0,0
.quad 0,-21*8
/* Register r1 can be found at offset 8 of a pt_regs structure.
A pointer to the pt_regs is stored in memory at the old sp plus PTREGS. */
#define cfa_save \
.byte 0x0f; /* DW_CFA_def_cfa_expression */ \
.uleb128 9f - 1f; /* length */ \
1: \
.byte 0x71; .sleb128 PTREGS; /* DW_OP_breg1 */ \
.byte 0x06; /* DW_OP_deref */ \
.byte 0x23; .uleb128 RSIZE; /* DW_OP_plus_uconst */ \
.byte 0x06; /* DW_OP_deref */ \
9:
/* Register REGNO can be found at offset OFS of a pt_regs structure.
A pointer to the pt_regs is stored in memory at the old sp plus PTREGS. */
#define rsave(regno, ofs) \
.byte 0x10; /* DW_CFA_expression */ \
.uleb128 regno; /* regno */ \
.uleb128 9f - 1f; /* length */ \
1: \
.byte 0x71; .sleb128 PTREGS; /* DW_OP_breg1 */ \
.byte 0x06; /* DW_OP_deref */ \
.ifne ofs; \
.byte 0x23; .uleb128 ofs; /* DW_OP_plus_uconst */ \
.endif; \
9:
/* If msr bit 1<<25 is set, then VMX register REGNO is at offset REGNO*16
of the VMX reg struct. A pointer to the VMX reg struct is at VREGS in
the pt_regs struct. This macro is for REGNO == 0, and contains
'subroutines' that the other macros jump to. */
#define vsave_msr0(regno) \
.byte 0x10; /* DW_CFA_expression */ \
.uleb128 regno + 77; /* regno */ \
.uleb128 9f - 1f; /* length */ \
1: \
.byte 0x30 + regno; /* DW_OP_lit0 */ \
2: \
.byte 0x40; /* DW_OP_lit16 */ \
.byte 0x1e; /* DW_OP_mul */ \
3: \
.byte 0x71; .sleb128 PTREGS; /* DW_OP_breg1 */ \
.byte 0x06; /* DW_OP_deref */ \
.byte 0x12; /* DW_OP_dup */ \
.byte 0x23; /* DW_OP_plus_uconst */ \
.uleb128 33*RSIZE; /* msr offset */ \
.byte 0x06; /* DW_OP_deref */ \
.byte 0x0c; .long 1 << 25; /* DW_OP_const4u */ \
.byte 0x1a; /* DW_OP_and */ \
.byte 0x12; /* DW_OP_dup, ret 0 if bra taken */ \
.byte 0x30; /* DW_OP_lit0 */ \
.byte 0x29; /* DW_OP_eq */ \
.byte 0x28; .short 0x7fff; /* DW_OP_bra to end */ \
.byte 0x13; /* DW_OP_drop, pop the 0 */ \
.byte 0x23; .uleb128 VREGS; /* DW_OP_plus_uconst */ \
.byte 0x06; /* DW_OP_deref */ \
.byte 0x22; /* DW_OP_plus */ \
.byte 0x2f; .short 0x7fff; /* DW_OP_skip to end */ \
9:
/* If msr bit 1<<25 is set, then VMX register REGNO is at offset REGNO*16
of the VMX reg struct. REGNO is 1 thru 31. */
#define vsave_msr1(regno) \
.byte 0x10; /* DW_CFA_expression */ \
.uleb128 regno + 77; /* regno */ \
.uleb128 9f - 1f; /* length */ \
1: \
.byte 0x30 + regno; /* DW_OP_lit n */ \
.byte 0x2f; .short 2b - 9f; /* DW_OP_skip */ \
9:
/* If msr bit 1<<25 is set, then VMX register REGNO is at offset OFS of
the VMX save block. */
#define vsave_msr2(regno, ofs) \
.byte 0x10; /* DW_CFA_expression */ \
.uleb128 regno + 77; /* regno */ \
.uleb128 9f - 1f; /* length */ \
1: \
.byte 0x0a; .short ofs; /* DW_OP_const2u */ \
.byte 0x2f; .short 3b - 9f; /* DW_OP_skip */ \
9:
/* VMX register REGNO is at offset OFS of the VMX save area. */
#define vsave(regno, ofs) \
.byte 0x10; /* DW_CFA_expression */ \
.uleb128 regno + 77; /* regno */ \
.uleb128 9f - 1f; /* length */ \
1: \
.byte 0x71; .sleb128 PTREGS; /* DW_OP_breg1 */ \
.byte 0x06; /* DW_OP_deref */ \
.byte 0x23; .uleb128 VREGS; /* DW_OP_plus_uconst */ \
.byte 0x06; /* DW_OP_deref */ \
.byte 0x23; .uleb128 ofs; /* DW_OP_plus_uconst */ \
9:
/* This is where the pt_regs pointer can be found on the stack. */
#define PTREGS 128+168+56
/* Size of regs. */
#define RSIZE 8
/* Size of CR reg in DWARF unwind info. */
#define CRSIZE 4
/* Offset of CR reg within a full word. */
#ifdef __LITTLE_ENDIAN__
#define CROFF 0
#else
#define CROFF (RSIZE - CRSIZE)
#endif
/* This is the offset of the VMX reg pointer. */
#define VREGS 48*RSIZE+33*8
/* Describe where general purpose regs are saved. */
#define EH_FRAME_GEN \
cfa_save; \
rsave ( 0, 0*RSIZE); \
rsave ( 2, 2*RSIZE); \
rsave ( 3, 3*RSIZE); \
rsave ( 4, 4*RSIZE); \
rsave ( 5, 5*RSIZE); \
rsave ( 6, 6*RSIZE); \
rsave ( 7, 7*RSIZE); \
rsave ( 8, 8*RSIZE); \
rsave ( 9, 9*RSIZE); \
rsave (10, 10*RSIZE); \
rsave (11, 11*RSIZE); \
rsave (12, 12*RSIZE); \
rsave (13, 13*RSIZE); \
rsave (14, 14*RSIZE); \
rsave (15, 15*RSIZE); \
rsave (16, 16*RSIZE); \
rsave (17, 17*RSIZE); \
rsave (18, 18*RSIZE); \
rsave (19, 19*RSIZE); \
rsave (20, 20*RSIZE); \
rsave (21, 21*RSIZE); \
rsave (22, 22*RSIZE); \
rsave (23, 23*RSIZE); \
rsave (24, 24*RSIZE); \
rsave (25, 25*RSIZE); \
rsave (26, 26*RSIZE); \
rsave (27, 27*RSIZE); \
rsave (28, 28*RSIZE); \
rsave (29, 29*RSIZE); \
rsave (30, 30*RSIZE); \
rsave (31, 31*RSIZE); \
rsave (67, 32*RSIZE); /* ap, used as temp for nip */ \
rsave (65, 36*RSIZE); /* lr */ \
rsave (68, 38*RSIZE + CROFF); /* cr fields */ \
rsave (69, 38*RSIZE + CROFF); \
rsave (70, 38*RSIZE + CROFF); \
rsave (71, 38*RSIZE + CROFF); \
rsave (72, 38*RSIZE + CROFF); \
rsave (73, 38*RSIZE + CROFF); \
rsave (74, 38*RSIZE + CROFF); \
rsave (75, 38*RSIZE + CROFF)
/* Describe where the FP regs are saved. */
#define EH_FRAME_FP \
rsave (32, 48*RSIZE + 0*8); \
rsave (33, 48*RSIZE + 1*8); \
rsave (34, 48*RSIZE + 2*8); \
rsave (35, 48*RSIZE + 3*8); \
rsave (36, 48*RSIZE + 4*8); \
rsave (37, 48*RSIZE + 5*8); \
rsave (38, 48*RSIZE + 6*8); \
rsave (39, 48*RSIZE + 7*8); \
rsave (40, 48*RSIZE + 8*8); \
rsave (41, 48*RSIZE + 9*8); \
rsave (42, 48*RSIZE + 10*8); \
rsave (43, 48*RSIZE + 11*8); \
rsave (44, 48*RSIZE + 12*8); \
rsave (45, 48*RSIZE + 13*8); \
rsave (46, 48*RSIZE + 14*8); \
rsave (47, 48*RSIZE + 15*8); \
rsave (48, 48*RSIZE + 16*8); \
rsave (49, 48*RSIZE + 17*8); \
rsave (50, 48*RSIZE + 18*8); \
rsave (51, 48*RSIZE + 19*8); \
rsave (52, 48*RSIZE + 20*8); \
rsave (53, 48*RSIZE + 21*8); \
rsave (54, 48*RSIZE + 22*8); \
rsave (55, 48*RSIZE + 23*8); \
rsave (56, 48*RSIZE + 24*8); \
rsave (57, 48*RSIZE + 25*8); \
rsave (58, 48*RSIZE + 26*8); \
rsave (59, 48*RSIZE + 27*8); \
rsave (60, 48*RSIZE + 28*8); \
rsave (61, 48*RSIZE + 29*8); \
rsave (62, 48*RSIZE + 30*8); \
rsave (63, 48*RSIZE + 31*8)
/* Describe where the VMX regs are saved. */
#ifdef CONFIG_ALTIVEC
#define EH_FRAME_VMX \
vsave_msr0 ( 0); \
vsave_msr1 ( 1); \
vsave_msr1 ( 2); \
vsave_msr1 ( 3); \
vsave_msr1 ( 4); \
vsave_msr1 ( 5); \
vsave_msr1 ( 6); \
vsave_msr1 ( 7); \
vsave_msr1 ( 8); \
vsave_msr1 ( 9); \
vsave_msr1 (10); \
vsave_msr1 (11); \
vsave_msr1 (12); \
vsave_msr1 (13); \
vsave_msr1 (14); \
vsave_msr1 (15); \
vsave_msr1 (16); \
vsave_msr1 (17); \
vsave_msr1 (18); \
vsave_msr1 (19); \
vsave_msr1 (20); \
vsave_msr1 (21); \
vsave_msr1 (22); \
vsave_msr1 (23); \
vsave_msr1 (24); \
vsave_msr1 (25); \
vsave_msr1 (26); \
vsave_msr1 (27); \
vsave_msr1 (28); \
vsave_msr1 (29); \
vsave_msr1 (30); \
vsave_msr1 (31); \
vsave_msr2 (33, 32*16+12); \
vsave (32, 33*16)
#else
#define EH_FRAME_VMX
#endif
.section .eh_frame,"a",@progbits
.Lcie:
.long .Lcie_end - .Lcie_start
.Lcie_start:
.long 0 /* CIE ID */
.byte 1 /* Version number */
.string "zRS" /* NUL-terminated augmentation string */
.uleb128 4 /* Code alignment factor */
.sleb128 -8 /* Data alignment factor */
.byte 67 /* Return address register column, ap */
.uleb128 1 /* Augmentation value length */
.byte 0x14 /* DW_EH_PE_pcrel | DW_EH_PE_udata8. */
.byte 0x0c,1,0 /* DW_CFA_def_cfa: r1 ofs 0 */
.balign 8
.Lcie_end:
.long .Lfde0_end - .Lfde0_start
.Lfde0_start:
.long .Lfde0_start - .Lcie /* CIE pointer. */
.quad .Lsigrt_start - . /* PC start, length */
.quad .Lsigrt_end - .Lsigrt_start
.uleb128 0 /* Augmentation */
EH_FRAME_GEN
EH_FRAME_FP
EH_FRAME_VMX
# Do we really need to describe the frame at this point? ie. will
# we ever have some call chain that returns somewhere past the addi?
# I don't think so, since gcc doesn't support async signals.
# .byte 0x41 /* DW_CFA_advance_loc 1*4 */
#undef PTREGS
#define PTREGS 168+56
# EH_FRAME_GEN
# EH_FRAME_FP
# EH_FRAME_VMX
.balign 8
.Lfde0_end:
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