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crosstool-ng/packages/gdb/10.2/0006-arc-Add-support-for-signal-frames-for-Linux-targets.patch
Alexey Brodkin 8099a74750 gdb10: Fixes for ARC 
Here we add a couple of fixes and improvements for ARC processors.
All except 1 patch are already in the upstream "master" branch
and will be an essential part of GCC 11.x whenever it gets released.

The most important are first 4 patches (0005-0008) which introduce
support of full native GDB support in Linux on ARC.

And the rests are tiny, yet useful improvements.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
2021-09-14 04:30:17 -07:00

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From 27a456bbaa0c525e534195d17345c2e9268dd5d2 Mon Sep 17 00:00:00 2001
From: Anton Kolesov <Anton.Kolesov@synopsys.com>
Date: Thu, 22 Dec 2016 21:52:16 +0300
Subject: [PATCH 07/20] arc: Add support for signal frames for Linux targets
Implement functions needed to unwind signal frames on ARC Linux targets.
gdb/ChangeLog
* arc-linux-tdep.c (arc_linux_sc_reg_offsets): New static variable.
(arc_linux_is_sigtramp): New function.
(arc_linux_sigcontext_addr): Likewise.
(arc_linux_init_osabi): Use them.
Will be a part of GDB 11:
https://sourceware.org/git?p=binutils-gdb.git;a=commit;h=d4af727286e3a9f177ba11677fbd3a012d36558a
---
gdb/ChangeLog | 7 +
gdb/arc-linux-tdep.c | 181 +++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 188 insertions(+)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,12 @@
2020-12-22 Anton Kolesov <anton.kolesov@synopsys.com>
+ * arc-linux-tdep.c (arc_linux_sc_reg_offsets): New static variable.
+ (arc_linux_is_sigtramp): New function.
+ (arc_linux_sigcontext_addr): Likewise.
+ (arc_linux_init_osabi): Use them.
+
+2020-12-22 Anton Kolesov <anton.kolesov@synopsys.com>
+
* arc-tdep.c (arc_make_sigtramp_frame_cache): New function.
(arc_sigtramp_frame_this_id): Likewise.
(arc_sigtramp_frame_prev_register): Likewise.
--- a/gdb/arc-linux-tdep.c
+++ b/gdb/arc-linux-tdep.c
@@ -33,6 +33,60 @@
#define REGOFF(offset) (offset * ARC_REGISTER_SIZE)
+/* arc_linux_sc_reg_offsets[i] is the offset of register i in the `struct
+ sigcontext'. Array index is an internal GDB register number, as defined in
+ arc-tdep.h:arc_regnum.
+
+ From <include/uapi/asm/sigcontext.h> and <include/uapi/asm/ptrace.h>.
+
+ The layout of this struct is tightly bound to "arc_regnum" enum
+ in arc-tdep.h. Any change of order in there, must be reflected
+ here as well. */
+static const int arc_linux_sc_reg_offsets[] = {
+ /* R0 - R12. */
+ REGOFF (22), REGOFF (21), REGOFF (20), REGOFF (19),
+ REGOFF (18), REGOFF (17), REGOFF (16), REGOFF (15),
+ REGOFF (14), REGOFF (13), REGOFF (12), REGOFF (11),
+ REGOFF (10),
+
+ /* R13 - R25. */
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER,
+
+ REGOFF (9), /* R26 (GP) */
+ REGOFF (8), /* FP */
+ REGOFF (23), /* SP */
+ ARC_OFFSET_NO_REGISTER, /* ILINK */
+ ARC_OFFSET_NO_REGISTER, /* R30 */
+ REGOFF (7), /* BLINK */
+
+ /* R32 - R59. */
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER, ARC_OFFSET_NO_REGISTER,
+ ARC_OFFSET_NO_REGISTER,
+
+ REGOFF (4), /* LP_COUNT */
+ ARC_OFFSET_NO_REGISTER, /* RESERVED */
+ ARC_OFFSET_NO_REGISTER, /* LIMM */
+ ARC_OFFSET_NO_REGISTER, /* PCL */
+
+ REGOFF (6), /* PC */
+ REGOFF (5), /* STATUS32 */
+ REGOFF (2), /* LP_START */
+ REGOFF (3), /* LP_END */
+ REGOFF (1), /* BTA */
+};
+
/* arc_linux_core_reg_offsets[i] is the offset in the .reg section of GDB
regnum i. Array index is an internal GDB register number, as defined in
arc-tdep.h:arc_regnum.
@@ -87,6 +141,127 @@
REGOFF (6) /* ERET */
};
+/* Is THIS_FRAME a sigtramp function - the function that returns from
+ signal handler into normal execution flow? This is the case if the PC is
+ either at the start of, or in the middle of the two instructions:
+
+ mov r8, __NR_rt_sigreturn ; __NR_rt_sigreturn == 139
+ trap_s 0 ; `swi' for ARC700
+
+ On ARC uClibc Linux this function is called __default_rt_sa_restorer.
+
+ Returns TRUE if this is a sigtramp frame. */
+
+static bool
+arc_linux_is_sigtramp (struct frame_info *this_frame)
+{
+ struct gdbarch *gdbarch = get_frame_arch (this_frame);
+ CORE_ADDR pc = get_frame_pc (this_frame);
+
+ if (arc_debug)
+ {
+ debug_printf ("arc-linux: arc_linux_is_sigtramp, pc=%s\n",
+ paddress(gdbarch, pc));
+ }
+
+ static const gdb_byte insns_be_hs[] = {
+ 0x20, 0x8a, 0x12, 0xc2, /* mov r8,nr_rt_sigreturn */
+ 0x78, 0x1e /* trap_s 0 */
+ };
+ static const gdb_byte insns_be_700[] = {
+ 0x20, 0x8a, 0x12, 0xc2, /* mov r8,nr_rt_sigreturn */
+ 0x22, 0x6f, 0x00, 0x3f /* swi */
+ };
+
+ gdb_byte arc_sigtramp_insns[sizeof (insns_be_700)];
+ size_t insns_sz;
+ if (arc_mach_is_arcv2 (gdbarch))
+ {
+ insns_sz = sizeof (insns_be_hs);
+ memcpy (arc_sigtramp_insns, insns_be_hs, insns_sz);
+ }
+ else
+ {
+ insns_sz = sizeof (insns_be_700);
+ memcpy (arc_sigtramp_insns, insns_be_700, insns_sz);
+ }
+ if (gdbarch_byte_order (gdbarch) == BFD_ENDIAN_LITTLE)
+ {
+ /* On little endian targets, ARC code section is in what is called
+ "middle endian", where half-words are in the big-endian order,
+ only bytes inside the halfwords are in the little endian order.
+ As a result it is very easy to convert big endian instruction to
+ little endian, since it is needed to swap bytes in the halfwords,
+ so there is no need to have information on whether that is a
+ 4-byte instruction or 2-byte. */
+ gdb_assert ((insns_sz % 2) == 0);
+ for (int i = 0; i < insns_sz; i += 2)
+ std::swap (arc_sigtramp_insns[i], arc_sigtramp_insns[i+1]);
+ }
+
+ gdb_byte buf[insns_sz];
+
+ /* Read the memory at the PC. Since we are stopped, any breakpoint must
+ have been removed. */
+ if (!safe_frame_unwind_memory (this_frame, pc, buf, insns_sz))
+ {
+ /* Failed to unwind frame. */
+ return FALSE;
+ }
+
+ /* Is that code the sigtramp instruction sequence? */
+ if (memcmp (buf, arc_sigtramp_insns, insns_sz) == 0)
+ return TRUE;
+
+ /* No - look one instruction earlier in the code... */
+ if (!safe_frame_unwind_memory (this_frame, pc - 4, buf, insns_sz))
+ {
+ /* Failed to unwind frame. */
+ return FALSE;
+ }
+
+ return (memcmp (buf, arc_sigtramp_insns, insns_sz) == 0);
+}
+
+/* Get sigcontext structure of sigtramp frame - it contains saved
+ registers of interrupted frame.
+
+ Stack pointer points to the rt_sigframe structure, and sigcontext can
+ be found as in:
+
+ struct rt_sigframe {
+ struct siginfo info;
+ struct ucontext uc;
+ ...
+ };
+
+ struct ucontext {
+ unsigned long uc_flags;
+ struct ucontext *uc_link;
+ stack_t uc_stack;
+ struct sigcontext uc_mcontext;
+ sigset_t uc_sigmask;
+ };
+
+ sizeof (struct siginfo) == 0x80
+ offsetof (struct ucontext, uc_mcontext) == 0x14
+
+ GDB cannot include linux headers and use offsetof () because those are
+ target headers and GDB might be built for a different run host. There
+ doesn't seem to be an established mechanism to figure out those offsets
+ via gdbserver, so the only way is to hardcode values in the GDB,
+ meaning that GDB will be broken if values will change. That seems to
+ be a very unlikely scenario and other arches (aarch64, alpha, amd64,
+ etc) in GDB hardcode values. */
+
+static CORE_ADDR
+arc_linux_sigcontext_addr (struct frame_info *this_frame)
+{
+ const int ucontext_offset = 0x80;
+ const int sigcontext_offset = 0x14;
+ return get_frame_sp (this_frame) + ucontext_offset + sigcontext_offset;
+}
+
/* Implement the "cannot_fetch_register" gdbarch method. */
static int
@@ -504,6 +679,12 @@
if (arc_debug)
debug_printf ("arc-linux: GNU/Linux OS/ABI initialization.\n");
+ /* Fill in target-dependent info in ARC-private structure. */
+ tdep->is_sigtramp = arc_linux_is_sigtramp;
+ tdep->sigcontext_addr = arc_linux_sigcontext_addr;
+ tdep->sc_reg_offset = arc_linux_sc_reg_offsets;
+ tdep->sc_num_regs = ARRAY_SIZE (arc_linux_sc_reg_offsets);
+
/* If we are using Linux, we have in uClibc
(libc/sysdeps/linux/arc/bits/setjmp.h):
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