[PATCH 2/9] Support fs_base and gs_base on FreeBSD/i386.

John Baldwin
2019-01-22T18:43:46Z

The i386 BSD native target uses the same ptrace operations
(PT_[GS]ET[FG]SBASE) as the amd64 BSD native target to fetch and store
the registers.

The amd64 BSD native now uses 'tdep->fsbase_regnum' instead of
hardcoding AMD64_FSBASE_REGNUM and AMD64_GSBASE_REGNUM to support
32-bit targets. In addition, the store operations explicitly zero the
new register value before fetching it from the register cache to
ensure 32-bit values are zero-extended.

gdb/ChangeLog:

* amd64-bsd-nat.c (amd64bsd_fetch_inferior_registers): Use
tdep->fsbase_regnum instead of constants for fs_base and gs_base.
(amd64bsd_store_inferior_registers): Likewise.
* amd64-fbsd-nat.c (amd64_fbsd_nat_target::read_description):
Enable segment base registers.
* i386-bsd-nat.c (i386bsd_fetch_inferior_registers): Use
PT_GETFSBASE and PT_GETGSBASE.
(i386bsd_store_inferior_registers): Use PT_SETFSBASE and PT_SETGSBASE.
* i386-fbsd-nat.c (i386_fbsd_nat_target::read_description): Enable
segment base registers.
* i386-fbsd-tdep.c (i386fbsd_core_read_description): Likewise.
---
gdb/ChangeLog | 14 ++++++++++++
gdb/amd64-bsd-nat.c | 26 ++++++++++++++-------
gdb/amd64-fbsd-nat.c | 4 ++--
gdb/i386-bsd-nat.c | 54 ++++++++++++++++++++++++++++++++++++++++++++
gdb/i386-fbsd-nat.c | 2 +-
gdb/i386-fbsd-tdep.c | 2 +-
6 files changed, 90 insertions(+), 12 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 4afd5b664e..056a60fa23 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,17 @@
+2019-01-22 John Baldwin <jhb@FreeBSD.org>
+
+ * amd64-bsd-nat.c (amd64bsd_fetch_inferior_registers): Use
+ tdep->fsbase_regnum instead of constants for fs_base and gs_base.
+ (amd64bsd_store_inferior_registers): Likewise.
+ * amd64-fbsd-nat.c (amd64_fbsd_nat_target::read_description):
+ Enable segment base registers.
+ * i386-bsd-nat.c (i386bsd_fetch_inferior_registers): Use
+ PT_GETFSBASE and PT_GETGSBASE.
+ (i386bsd_store_inferior_registers): Use PT_SETFSBASE and PT_SETGSBASE.
+ * i386-fbsd-nat.c (i386_fbsd_nat_target::read_description): Enable
+ segment base registers.
+ * i386-fbsd-tdep.c (i386fbsd_core_read_description): Likewise.
+
2019-01-22 John Baldwin <jhb@FreeBSD.org>

* amd64-fbsd-nat.c (amd64_fbsd_nat_target::read_description):
diff --git a/gdb/amd64-bsd-nat.c b/gdb/amd64-bsd-nat.c
index a2a91abb91..0f47ff6c61 100644
--- a/gdb/amd64-bsd-nat.c
+++ b/gdb/amd64-bsd-nat.c
@@ -43,6 +43,9 @@ amd64bsd_fetch_inferior_registers (struct regcache *regcache, int regnum)
{
struct gdbarch *gdbarch = regcache->arch ();
pid_t pid = get_ptrace_pid (regcache->ptid ());
+#ifdef PT_GETFSBASE
+ const struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+#endif

if (regnum == -1 || amd64_native_gregset_supplies_p (gdbarch, regnum))
{
@@ -57,27 +60,27 @@ amd64bsd_fetch_inferior_registers (struct regcache *regcache, int regnum)
}

#ifdef PT_GETFSBASE
- if (regnum == -1 || regnum == AMD64_FSBASE_REGNUM)
+ if (regnum == -1 || regnum == tdep->fsbase_regnum)
{
register_t base;

if (ptrace (PT_GETFSBASE, pid, (PTRACE_TYPE_ARG3) &base, 0) == -1)
perror_with_name (_("Couldn't get segment register fs_base"));

- regcache->raw_supply (AMD64_FSBASE_REGNUM, &base);
+ regcache->raw_supply (tdep->fsbase_regnum, &base);
if (regnum != -1)
return;
}
#endif
#ifdef PT_GETGSBASE
- if (regnum == -1 || regnum == AMD64_GSBASE_REGNUM)
+ if (regnum == -1 || regnum == tdep->fsbase_regnum + 1)
{
register_t base;

if (ptrace (PT_GETGSBASE, pid, (PTRACE_TYPE_ARG3) &base, 0) == -1)
perror_with_name (_("Couldn't get segment register gs_base"));

- regcache->raw_supply (AMD64_GSBASE_REGNUM, &base);
+ regcache->raw_supply (tdep->fsbase_regnum + 1, &base);
if (regnum != -1)
return;
}
@@ -116,6 +119,9 @@ amd64bsd_store_inferior_registers (struct regcache *regcache, int regnum)
{
struct gdbarch *gdbarch = regcache->arch ();
pid_t pid = get_ptrace_pid (regcache->ptid ());
+#ifdef PT_GETFSBASE
+ const struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+#endif

if (regnum == -1 || amd64_native_gregset_supplies_p (gdbarch, regnum))
{
@@ -134,11 +140,13 @@ amd64bsd_store_inferior_registers (struct regcache *regcache, int regnum)
}

#ifdef PT_SETFSBASE
- if (regnum == -1 || regnum == AMD64_FSBASE_REGNUM)
+ if (regnum == -1 || regnum == tdep->fsbase_regnum)
{
register_t base;

- regcache->raw_collect (AMD64_FSBASE_REGNUM, &base);
+ /* Clear the full base value to support 32-bit targets. */
+ base = 0;
+ regcache->raw_collect (tdep->fsbase_regnum, &base);

if (ptrace (PT_SETFSBASE, pid, (PTRACE_TYPE_ARG3) &base, 0) == -1)
perror_with_name (_("Couldn't write segment register fs_base"));
@@ -147,11 +155,13 @@ amd64bsd_store_inferior_registers (struct regcache *regcache, int regnum)
}
#endif
#ifdef PT_SETGSBASE
- if (regnum == -1 || regnum == AMD64_GSBASE_REGNUM)
+ if (regnum == -1 || regnum == tdep->fsbase_regnum + 1)
{
register_t base;

- regcache->raw_collect (AMD64_GSBASE_REGNUM, &base);
+ /* Clear the full base value to support 32-bit targets. */
+ base = 0;
+ regcache->raw_collect (tdep->fsbase_regnum + 1, &base);

if (ptrace (PT_SETGSBASE, pid, (PTRACE_TYPE_ARG3) &base, 0) == -1)
perror_with_name (_("Couldn't write segment register gs_base"));
diff --git a/gdb/amd64-fbsd-nat.c b/gdb/amd64-fbsd-nat.c
index 39ba69d9bf..e31232bd20 100644
--- a/gdb/amd64-fbsd-nat.c
+++ b/gdb/amd64-fbsd-nat.c
@@ -190,13 +190,13 @@ amd64_fbsd_nat_target::read_description ()
if (is64)
return amd64_target_description (xcr0, true);
else
- return i386_target_description (xcr0, false);
+ return i386_target_description (xcr0, true);
}
#endif
if (is64)
return amd64_target_description (X86_XSTATE_SSE_MASK, true);
else
- return i386_target_description (X86_XSTATE_SSE_MASK, false);
+ return i386_target_description (X86_XSTATE_SSE_MASK, true);
}

#if defined(HAVE_PT_GETDBREGS) && defined(USE_SIGTRAP_SIGINFO)
diff --git a/gdb/i386-bsd-nat.c b/gdb/i386-bsd-nat.c
index 009a8dc1b2..a10b496096 100644
--- a/gdb/i386-bsd-nat.c
+++ b/gdb/i386-bsd-nat.c
@@ -144,6 +144,33 @@ i386bsd_fetch_inferior_registers (struct regcache *regcache, int regnum)
return;
}

+#ifdef PT_GETFSBASE
+ if (regnum == -1 || regnum == I386_FSBASE_REGNUM)
+ {
+ register_t base;
+
+ if (ptrace (PT_GETFSBASE, pid, (PTRACE_TYPE_ARG3) &base, 0) == -1)
+ perror_with_name (_("Couldn't get segment register fs_base"));
+
+ regcache->raw_supply (I386_FSBASE_REGNUM, &base);
+ if (regnum != -1)
+ return;
+ }
+#endif
+#ifdef PT_GETGSBASE
+ if (regnum == -1 || regnum == I386_GSBASE_REGNUM)
+ {
+ register_t base;
+
+ if (ptrace (PT_GETGSBASE, pid, (PTRACE_TYPE_ARG3) &base, 0) == -1)
+ perror_with_name (_("Couldn't get segment register gs_base"));
+
+ regcache->raw_supply (I386_GSBASE_REGNUM, &base);
+ if (regnum != -1)
+ return;
+ }
+#endif
+
if (regnum == -1 || regnum >= I386_ST0_REGNUM)
{
struct fpreg fpregs;
@@ -211,6 +238,33 @@ i386bsd_store_inferior_registers (struct regcache *regcache, int regnum)
return;
}

+#ifdef PT_SETFSBASE
+ if (regnum == -1 || regnum == I386_FSBASE_REGNUM)
+ {
+ register_t base;
+
+ regcache->raw_collect (I386_FSBASE_REGNUM, &base);
+
+ if (ptrace (PT_SETFSBASE, pid, (PTRACE_TYPE_ARG3) &base, 0) == -1)
+ perror_with_name (_("Couldn't write segment register fs_base"));
+ if (regnum != -1)
+ return;
+ }
+#endif
+#ifdef PT_SETGSBASE
+ if (regnum == -1 || regnum == I386_GSBASE_REGNUM)
+ {
+ register_t base;
+
+ regcache->raw_collect (I386_GSBASE_REGNUM, &base);
+
+ if (ptrace (PT_SETGSBASE, pid, (PTRACE_TYPE_ARG3) &base, 0) == -1)
+ perror_with_name (_("Couldn't write segment register gs_base"));
+ if (regnum != -1)
+ return;
+ }
+#endif
+
if (regnum == -1 || regnum >= I386_ST0_REGNUM)
{
struct fpreg fpregs;
diff --git a/gdb/i386-fbsd-nat.c b/gdb/i386-fbsd-nat.c
index 8ff104cf72..f2703a3c75 100644
--- a/gdb/i386-fbsd-nat.c
+++ b/gdb/i386-fbsd-nat.c
@@ -160,7 +160,7 @@ i386_fbsd_nat_target::read_description ()
if (x86bsd_xsave_len == 0)
xcr0 = X86_XSTATE_SSE_MASK;

- return i386_target_description (xcr0, false);
+ return i386_target_description (xcr0, true);
}
#endif

diff --git a/gdb/i386-fbsd-tdep.c b/gdb/i386-fbsd-tdep.c
index 43b15167ae..239ca91abe 100644
--- a/gdb/i386-fbsd-tdep.c
+++ b/gdb/i386-fbsd-tdep.c
@@ -267,7 +267,7 @@ i386fbsd_core_read_description (struct gdbarch *gdbarch,
struct target_ops *target,
bfd *abfd)
{
- return i386_target_description (i386fbsd_core_read_xcr0 (abfd), false);
+ return i386_target_description (i386fbsd_core_read_xcr0 (abfd), true);
}

/* Similar to i386_supply_fpregset, but use XSAVE extended state. */
--
2.19.2