[PATCH v6 08/15] gdb: Update x86 Linux architectures to support XSAVE layouts.

John Baldwin
2023-07-14T15:57:52Z

Refactor i386_linux_core_read_xcr0 to fetch and return a corresponding
x86_xsave_layout as well as xcr0 using the size of an existing
NT_X86_XSTATE core dump to determine the offsets via
i387_set_xsave_layout. Use this to add an implementation of
gdbarch_core_xfer_x86_xsave_layout.

Use tdep->xsave_layout.sizeof_xsave as the size of the XSTATE register
set.
---
gdb/amd64-linux-tdep.c | 11 +++++--
gdb/i386-linux-tdep.c | 67 ++++++++++++++++++++++++------------------
gdb/i386-linux-tdep.h | 25 +++++++++-------
3 files changed, 61 insertions(+), 42 deletions(-)

diff --git a/gdb/amd64-linux-tdep.c b/gdb/amd64-linux-tdep.c
index cbbac1a0c64..d51f4d5af53 100644
--- a/gdb/amd64-linux-tdep.c
+++ b/gdb/amd64-linux-tdep.c
@@ -1616,7 +1616,8 @@ amd64_linux_core_read_description (struct gdbarch *gdbarch,
bfd *abfd)
{
/* Linux/x86-64. */
- uint64_t xcr0 = i386_linux_core_read_xcr0 (abfd);
+ x86_xsave_layout layout;
+ uint64_t xcr0 = i386_linux_core_read_xsave_info (abfd, layout);

return amd64_linux_read_description (xcr0 & X86_XSTATE_ALL_MASK,
gdbarch_ptr_bit (gdbarch) == 32);
@@ -1661,8 +1662,10 @@ amd64_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,

cb (".reg", 27 * 8, 27 * 8, &i386_gregset, NULL, cb_data);
cb (".reg2", 512, 512, &amd64_fpregset, NULL, cb_data);
- cb (".reg-xstate", X86_XSTATE_SIZE (tdep->xcr0), X86_XSTATE_SIZE (tdep->xcr0),
- &amd64_linux_xstateregset, "XSAVE extended state", cb_data);
+ if (tdep->xsave_layout.sizeof_xsave != 0)
+ cb (".reg-xstate", tdep->xsave_layout.sizeof_xsave,
+ tdep->xsave_layout.sizeof_xsave, &amd64_linux_xstateregset,
+ "XSAVE extended state", cb_data);
}

/* The instruction sequences used in x86_64 machines for a
@@ -1804,6 +1807,8 @@ amd64_linux_init_abi_common(struct gdbarch_info info, struct gdbarch *gdbarch,
tdep->sc_num_regs = ARRAY_SIZE (amd64_linux_sc_reg_offset);

tdep->xsave_xcr0_offset = I386_LINUX_XSAVE_XCR0_OFFSET;
+ set_gdbarch_core_read_x86_xsave_layout
+ (gdbarch, i386_linux_core_read_x86_xsave_layout);

/* Add the %orig_rax register used for syscall restarting. */
set_gdbarch_write_pc (gdbarch, amd64_linux_write_pc);
diff --git a/gdb/i386-linux-tdep.c b/gdb/i386-linux-tdep.c
index 554c1455a5f..f27efbb1d59 100644
--- a/gdb/i386-linux-tdep.c
+++ b/gdb/i386-linux-tdep.c
@@ -638,45 +638,51 @@ static int i386_linux_sc_reg_offset[] =
0 * 4 /* %gs */
};

-/* Get XSAVE extended state xcr0 from core dump. */
+/* See i386-linux-tdep.h. */

uint64_t
-i386_linux_core_read_xcr0 (bfd *abfd)
+i386_linux_core_read_xsave_info (bfd *abfd, x86_xsave_layout &layout)
{
asection *xstate = bfd_get_section_by_name (abfd, ".reg-xstate");
- uint64_t xcr0;
+ if (xstate == nullptr)
+ return X86_XSTATE_SSE_MASK;

- if (xstate)
+ /* Check extended state size. */
+ size_t size = bfd_section_size (xstate);
+ if (size < X86_XSTATE_AVX_SIZE)
+ return X86_XSTATE_SSE_MASK;
+
+ char contents[8];
+ if (! bfd_get_section_contents (abfd, xstate, contents,
+ I386_LINUX_XSAVE_XCR0_OFFSET, 8))
{
- size_t size = bfd_section_size (xstate);
-
- /* Check extended state size. */
- if (size < X86_XSTATE_AVX_SIZE)
- xcr0 = X86_XSTATE_SSE_MASK;
- else
- {
- char contents[8];
-
- if (! bfd_get_section_contents (abfd, xstate, contents,
- I386_LINUX_XSAVE_XCR0_OFFSET,
- 8))
- {
- warning (_("Couldn't read `xcr0' bytes from "
- "`.reg-xstate' section in core file."));
- return 0;
- }
-
- xcr0 = bfd_get_64 (abfd, contents);
- }
+ warning (_("Couldn't read `xcr0' bytes from "
+ "`.reg-xstate' section in core file."));
+ return X86_XSTATE_SSE_MASK;
}
- else
- xcr0 = 0;
+
+ uint64_t xcr0 = bfd_get_64 (abfd, contents);
+
+ if (!i387_set_xsave_layout (xcr0, size, layout))
+ return X86_XSTATE_SSE_MASK;

return xcr0;
}

/* See i386-linux-tdep.h. */

+bool
+i386_linux_core_read_x86_xsave_layout (struct gdbarch *gdbarch,
+ x86_xsave_layout &layout)
+{
+ if (i386_linux_core_read_xsave_info (core_bfd, layout) == X86_XSTATE_SSE_MASK)
+ return false;
+
+ return true;
+}
+
+/* See i386-linux-tdep.h. */
+
const struct target_desc *
i386_linux_read_description (uint64_t xcr0)
{
@@ -708,7 +714,8 @@ i386_linux_core_read_description (struct gdbarch *gdbarch,
bfd *abfd)
{
/* Linux/i386. */
- uint64_t xcr0 = i386_linux_core_read_xcr0 (abfd);
+ x86_xsave_layout layout;
+ uint64_t xcr0 = i386_linux_core_read_xsave_info (abfd, layout);
const struct target_desc *tdesc = i386_linux_read_description (xcr0);

if (tdesc != NULL)
@@ -768,8 +775,8 @@ i386_linux_iterate_over_regset_sections (struct gdbarch *gdbarch,
cb (".reg", 68, 68, &i386_gregset, NULL, cb_data);

if (tdep->xcr0 & X86_XSTATE_AVX)
- cb (".reg-xstate", X86_XSTATE_SIZE (tdep->xcr0),
- X86_XSTATE_SIZE (tdep->xcr0), &i386_linux_xstateregset,
+ cb (".reg-xstate", tdep->xsave_layout.sizeof_xsave,
+ tdep->xsave_layout.sizeof_xsave, &i386_linux_xstateregset,
"XSAVE extended state", cb_data);
else if (tdep->xcr0 & X86_XSTATE_SSE)
cb (".reg-xfp", 512, 512, &i386_fpregset, "extended floating-point",
@@ -872,6 +879,8 @@ i386_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
tdep->sc_num_regs = ARRAY_SIZE (i386_linux_sc_reg_offset);

tdep->xsave_xcr0_offset = I386_LINUX_XSAVE_XCR0_OFFSET;
+ set_gdbarch_core_read_x86_xsave_layout
+ (gdbarch, i386_linux_core_read_x86_xsave_layout);

set_gdbarch_process_record (gdbarch, i386_process_record);
set_gdbarch_process_record_signal (gdbarch, i386_linux_record_signal);
diff --git a/gdb/i386-linux-tdep.h b/gdb/i386-linux-tdep.h
index c0fd1f7f300..66f08aae22d 100644
--- a/gdb/i386-linux-tdep.h
+++ b/gdb/i386-linux-tdep.h
@@ -20,6 +20,8 @@
#ifndef I386_LINUX_TDEP_H
#define I386_LINUX_TDEP_H

+#include "gdbsupport/x86-xstate.h"
+
/* The Linux kernel pretends there is an additional "orig_eax"
register. Since GDB needs access to that register to be able to
properly restart system calls when necessary (see
@@ -34,8 +36,18 @@
/* Total number of registers for GNU/Linux. */
#define I386_LINUX_NUM_REGS (I386_LINUX_ORIG_EAX_REGNUM + 1)

-/* Get XSAVE extended state xcr0 from core dump. */
-extern uint64_t i386_linux_core_read_xcr0 (bfd *abfd);
+/* Read the XSAVE extended state xcr0 value from the ABFD core file.
+ If it appears to be valid, return it and fill LAYOUT with values
+ inferred from that value.
+
+ Otherwise, return X86_XSTATE_SSE_MASK as a fallback and leave
+ LAYOUT untouched. */
+extern uint64_t i386_linux_core_read_xsave_info (bfd *abfd,
+ x86_xsave_layout &layout);
+
+/* Implement the core_read_x86_xsave_layout gdbarch method. */
+extern bool i386_linux_core_read_x86_xsave_layout (struct gdbarch *gdbarch,
+ x86_xsave_layout &layout);

/* Handle and display information related to the MPX bound violation
to the user. */
@@ -52,14 +64,7 @@ extern const struct target_desc *i386_linux_read_description (uint64_t xcr0);
fxsave_bytes[0..463]
sw_usable_bytes[464..511]
xstate_hdr_bytes[512..575]
- avx_bytes[576..831]
- mpx_bytes [960..1032]
- avx512_k_regs[1088..1152]
- avx512_zmmh_regs0-7[1153..1407]
- avx512_zmmh_regs8-15[1408..1663]
- avx512_zmm_regs16-31[1664..2687]
- pkru[2688..2752]
- future_state etc
+ extended state regions (AVX, MPX, AVX512, PKRU, etc.)
};

Same memory layout will be used for the coredump NT_X86_XSTATE
--
2.40.0