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Re: [PATCH] Port GDB to Hurd x86_64.


From: John Baldwin
Subject: Re: [PATCH] Port GDB to Hurd x86_64.
Date: Thu, 22 Feb 2024 16:25:43 -0800
User-agent: Mozilla Thunderbird

On 2/12/24 8:31 PM, Flavio Cruz wrote:
This port extends the existing i686 port to support x86_64 by trying to
reuse existing code whenever it makes sense.

* gdb/amd64-gnu-tdep.c: Adds logic for handling signal frames and
   position of amd64 registers in the different Hurd structs, including
   i386_thread_state. The signal code is very similar to i686, except the
   trampoline code is adapted.
* gdb/amd64-gnu-tdep.h: export register offsets for x86-gnu-nat.c.
* gdb/config/i386/nm-i386gnu.h: renamed to gdb/config/i386/nm-x86-gnu.h
   and adapt it for x86_64.
* gdb/config/i386/i386gnu.mn: renamed to gdb/config/i386/nm-x86-gnu.mn
   and reuse it for x86_64.
* gdb/configure.host: recognize gnu64 as a host.
* gdb/configure.nat: recognize gnu64 host and update existing i386gnu to
   reuse the new shared files.
* gdb/configure.tgt: recognize x86_64-*-gnu* triplet and use
   amd64-gnu-tdep.c.
* gdb/i386-gnu-tdep.c: added i386_gnu_thread_state_reg_offset that is
   copied from i386-gnu-nat.c. This makes it similar to amd64.
* gdb/i386-gnu-tdep.h: export register offsets and number of registers.
* gdb/i386-gnu-nat.c: rename it to x86-gnu-nat.c since we reuse this for
   i386 and amd64. Updated REG_ADDR to use one of the structures. Added
   VALID_REGISTER to make sure it's a register we can provide at this time
   (not all of them are available in amd64). FLAGS_REGISTER is either rfl
   or efl depending on the arch. Renamed functions and class from i386 to x86
   whenever they can be reused.

Tested on Hurd x86_64 and i686.
---

For Hurd x86_64 to work, "[PATCH] Hurd port: update interface to match
upstream and fix warnings" needs to be applied too.

  gdb/amd64-gnu-tdep.c                          | 256 ++++++++++++++++++
  gdb/amd64-gnu-tdep.h                          |  29 ++
  .../i386/{nm-i386gnu.h => nm-x86-gnu.h}       |   7 +
  gdb/config/i386/{i386gnu.mn => x86-gnu.mn}    |   0
  gdb/configure.host                            |   1 +
  gdb/configure.nat                             |  27 +-
  gdb/configure.tgt                             |   4 +
  gdb/i386-gnu-tdep.c                           |  37 ++-
  gdb/i386-gnu-tdep.h                           |  29 ++
  gdb/{i386-gnu-nat.c => x86-gnu-nat.c}         | 128 +++++----
  10 files changed, 457 insertions(+), 61 deletions(-)
  create mode 100644 gdb/amd64-gnu-tdep.c
  create mode 100644 gdb/amd64-gnu-tdep.h
  rename gdb/config/i386/{nm-i386gnu.h => nm-x86-gnu.h} (83%)
  rename gdb/config/i386/{i386gnu.mn => x86-gnu.mn} (100%)
  create mode 100644 gdb/i386-gnu-tdep.h
  rename gdb/{i386-gnu-nat.c => x86-gnu-nat.c} (75%)

diff --git a/gdb/amd64-gnu-tdep.c b/gdb/amd64-gnu-tdep.c
new file mode 100644
index 00000000000..57aeccea8b9
--- /dev/null
+++ b/gdb/amd64-gnu-tdep.c
@@ -0,0 +1,256 @@
+/* Mapping between the general-purpose registers in `struct
+   sigcontext' format (starting at sc_i386_thread_state)
+   and GDB's register cache layout.  */
+
+/* From <bits/sigcontext.h>.  */
+static int amd64_gnu_sc_reg_offset[] =
+{
+  15 * 8,                      /* %rax */
+  12 * 8,                      /* %rbx */
+  14 * 8,                      /* %rcx */
+  13 * 8,                      /* %rdx */
+  10 * 8,                      /* %rsi */
+  9 * 8,                       /* %rdi */
+  10 * 8,                      /* %rbp */
+  11 * 8,                      /* %rsp */
+  0 * 8,                       /* %r8 ...  */
+  8 * 8,
+  7 * 8,
+  6 * 8,
+  3 * 8,
+  2 * 8,
+  1 * 8,
+  0 * 8,                       /* ... %r15 */
+  16 * 8,                      /* %rip */
+  18 * 8,                      /* %eflags */
+  17 * 8,                      /* %cs */
+};
+
+/* From <sys/ucontext.h>.  */
+static int amd64_gnu_gregset_reg_offset[] =
+{
+  10 * 8,                      /* %rax */
+  5 * 8,                       /* %rbx */
+  11 * 8,                      /* %rcx */
+  12 * 8,                      /* %rdx */
+  13 * 8,                      /* %rsi */
+  14 * 8,                      /* %rdi */
+  4 * 8,                       /* %rbp */
+  19 * 8,                      /* %rsp */
+  9 * 8,                       /* %r8 ...  */
+  8 * 8,
+  7 * 8,
+  6 * 8,
+  3 * 8,
+  2 * 8,
+  1 * 8,
+  0 * 8,                       /* ... %r15 */
+  16 * 8,                      /* %rip */
+  18 * 8,                      /* %eflags */
+  17 * 8,                      /* %cs */
+  -1,                            /* %ss */
+  -1,                            /* %ds */
+  -1,                            /* %es */
+  -1,                            /* %fs */
+  -1,                            /* %gs */
+};
+
+/* Offset to the thread_state_t location where REG is stored.  */
+#define REG_OFFSET(reg) offsetof (struct i386_thread_state, reg)

You can't use a reference to this OS-specific type in a tdep.c file,
only in a nat.c file.  tdep.c should be buildable on other platforms
to permit cross debugging of core dumps, remote targets, etc.

+/* At REG_OFFSET[N] is the offset to the thread_state_t location where
+   the GDB register N is stored.  */
+int amd64_gnu_thread_state_reg_offset[] =
+{
+  REG_OFFSET (rax),            /* %rax */
+  REG_OFFSET (rbx),            /* %rbx */
+  REG_OFFSET (rcx),            /* %rcx */
+  REG_OFFSET (rdx),            /* %rdx */
+  REG_OFFSET (rsi),            /* %rsi */
+  REG_OFFSET (rdi),            /* %rdi */
+  REG_OFFSET (rbp),            /* %rbp */
+  REG_OFFSET (ursp),   /* %rsp */
+  REG_OFFSET (r8),             /* %r8 ...  */
+  REG_OFFSET (r9),
+  REG_OFFSET (r10),
+  REG_OFFSET (r11),
+  REG_OFFSET (r12),
+  REG_OFFSET (r13),
+  REG_OFFSET (r14),
+  REG_OFFSET (r15),            /* ... %r15 */
+  REG_OFFSET (rip),            /* %rip */
+  REG_OFFSET (rfl),            /* %rflags */
+  REG_OFFSET (cs)          /* %cs */
+};
+
+const int amd64_gnu_thread_state_num_regs =
+  ARRAY_SIZE (amd64_gnu_thread_state_reg_offset);

That said, I also don't see any references to amd64_gnu_thread_state_*
in this file, and it looks to only be used in x86-gnu-nat.c, so I think
you should instead move this array to x86-gnu-nat.c instead (and
similarly for i386_gnu_thread_state_* you added in i386-gnu-tdep.c).

--
John Baldwin




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