[arch-commits] Commit in gdb/trunk (2 files)

Anatol Pomozov anatolik at archlinux.org
Wed May 19 21:34:28 UTC 2021


    Date: Wednesday, May 19, 2021 @ 21:34:27
  Author: anatolik
Revision: 415775

upgpkg: gdb 10.2-2: FS#70879: apply upstream patch that fixes debugging for 32bit apps

Added:
  gdb/trunk/gdb_dont_overwrite_fs-gs_base_with_-m32.patch
Modified:
  gdb/trunk/PKGBUILD

-----------------------------------------------+
 PKGBUILD                                      |   14 +-
 gdb_dont_overwrite_fs-gs_base_with_-m32.patch |  163 ++++++++++++++++++++++++
 2 files changed, 173 insertions(+), 4 deletions(-)

Modified: PKGBUILD
===================================================================
--- PKGBUILD	2021-05-19 20:57:17 UTC (rev 415774)
+++ PKGBUILD	2021-05-19 21:34:27 UTC (rev 415775)
@@ -8,7 +8,7 @@
 # of gdb (for arm/avr/...)
 pkgname=(gdb gdb-common)
 pkgver=10.2
-pkgrel=1
+pkgrel=2
 pkgdesc='The GNU Debugger'
 arch=(x86_64)
 url='https://www.gnu.org/software/gdb/'
@@ -15,16 +15,22 @@
 license=(GPL3)
 makedepends=(glibc gcc-libs texinfo python guile ncurses expat xz mpfr source-highlight
              readline)
-source=(https://ftp.gnu.org/gnu/gdb/${pkgname}-${pkgver}.tar.xz{,.sig})
+source=(https://ftp.gnu.org/gnu/gdb/${pkgname}-${pkgver}.tar.xz{,.sig}
+        gdb_dont_overwrite_fs-gs_base_with_-m32.patch)
+
 sha1sums=('1056e2743a825ecce46ec9eec37f0b357831012b'
-          'SKIP')
+          'SKIP'
+          '7a78c03b563797e5c0ee85a0618a47e4c6677dc4')
 b2sums=('c5d31d80d2b454767d6f844e8471b012ad437c3872391b618fd7b14c5cf251b78e55d28c12e81382fd600f67e2f618ff5dbe3a7b737a5d5161ceb3542afbb90b'
-        'SKIP')
+        'SKIP'
+        '4337167930ecc045b9d19125b975bc98b4b16e05954c45bfa41f0e21471ed7ab5c5a8e9a8479056d7019cd127beed936c664e37d38ee3e99dbe861f8c1a67540')
 validpgpkeys=('F40ADB902B24264AA42E50BF92EDB04BFF325CF3') # Joel Brobecker
 
 prepare() {
   cd gdb-$pkgver
 
+  patch -p1 < ../gdb_dont_overwrite_fs-gs_base_with_-m32.patch # FS#70879
+
   # hack! - libiberty configure tests for header files using "$CPP $CPPFLAGS"
   sed -i "/ac_cpp=/s/\$CPPFLAGS/\$CPPFLAGS -O2/" libiberty/configure
 }

Added: gdb_dont_overwrite_fs-gs_base_with_-m32.patch
===================================================================
--- gdb_dont_overwrite_fs-gs_base_with_-m32.patch	                        (rev 0)
+++ gdb_dont_overwrite_fs-gs_base_with_-m32.patch	2021-05-19 21:34:27 UTC (rev 415775)
@@ -0,0 +1,163 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Tom de Vries <tdevries at suse.de>
+Date: Wed, 20 Jan 2021 16:29:30 +0100
+Subject: [PATCH] [gdb/server] Don't overwrite fs/gs_base with -m32
+
+Consider a minimal test-case test.c:
+...
+int main (void) { return 0; }
+...
+compiled with -m32:
+...
+$ gcc test.c -m32
+...
+
+When running the exec using gdbserver on openSUSE Factory (currently running a
+linux kernel version 5.10.5):
+...
+$ gdbserver localhost:12345 a.out
+...
+to which we connect in a gdb session, we run into a segfault in the inferior:
+...
+$ gdb -batch -q -ex "target remote localhost:12345" -ex continue
+Program received signal SIGSEGV, Segmentation fault.
+0xf7dd8bd2 in init_cacheinfo () at ../sysdeps/x86/cacheinfo.c:761
+...
+
+The segfault is caused by gdbserver overwriting $gs_base with 0 using
+PTRACE_SETREGS.  After it is overwritten, the next use of $gs in the inferior
+will trigger the segfault.
+
+Before linux kernel version 5.9, the value used by PTRACE_SETREGS for $gs_base
+was ignored, but starting version 5.9, the linux kernel has support for
+intel architecture extension FSGSBASE, which allows users to modify $gs_base,
+and consequently PTRACE_SETREGS can no longer ignore the $gs_base value.
+
+The overwrite of $gs_base with 0 is done by a memset in x86_fill_gregset,
+which was added in commit 9e0aa64f551 "Fix gdbserver qGetTLSAddr for
+x86_64 -m32".  The memset intends to zero-extend 32-bit registers that are
+tracked in the regcache to 64-bit when writing them into the PTRACE_SETREGS
+data argument.  But in addition, it overwrites other registers that are
+not tracked in the regcache, such as $gs_base.
+
+Fix the segfault by redoing the fix from commit 9e0aa64f551 in minimal form.
+
+Tested on x86_64-linux:
+- openSUSE Leap 15.2 (using kernel version 5.3.18):
+  - native
+  - gdbserver -m32
+  - -m32
+- openSUSE Factory (using kernel version 5.10.5):
+  - native
+  - m32
+
+gdbserver/ChangeLog:
+
+2021-01-20  Tom de Vries  <tdevries at suse.de>
+
+	* linux-x86-low.cc (collect_register_i386): New function.
+	(x86_fill_gregset):  Remove memset.  Use collect_register_i386.
+
+(cherry picked from commit 037e8112b9794a633248e5aa5943f3be273e0a20)
+
+Conflicts:
+	gdbserver/ChangeLog
+	gdbserver/linux-x86-low.cc
+---
+ gdbserver/ChangeLog        |  5 ++++
+ gdbserver/linux-x86-low.cc | 55 +++++++++++++++++++++++---------------
+ 2 files changed, 38 insertions(+), 22 deletions(-)
+
+diff --git a/gdbserver/ChangeLog b/gdbserver/ChangeLog
+index 28d0f9bfccb..b87174ce4e3 100644
+--- a/gdbserver/ChangeLog
++++ b/gdbserver/ChangeLog
+@@ -1,3 +1,8 @@
++2021-01-20  Tom de Vries  <tdevries at suse.de>
++
++	* linux-x86-low.cc (collect_register_i386): New function.
++	(x86_fill_gregset):  Remove memset.  Use collect_register_i386.
++
+ 2021-01-01  Joel Brobecker  <brobecker at adacore.com>
+ 
+ 	* server.cc (gdbserver_version): Update copyright year.
+diff --git a/gdbserver/linux-x86-low.cc b/gdbserver/linux-x86-low.cc
+index 79284473f14..ea95f3ea2ae 100644
+--- a/gdbserver/linux-x86-low.cc
++++ b/gdbserver/linux-x86-low.cc
+@@ -397,6 +397,35 @@ x86_target::low_cannot_fetch_register (int regno)
+   return regno >= I386_NUM_REGS;
+ }
+ 
++static void
++collect_register_i386 (struct regcache *regcache, int regno, void *buf)
++{
++  collect_register (regcache, regno, buf);
++
++#ifdef __x86_64__
++  /* In case of x86_64 -m32, collect_register only writes 4 bytes, but the
++     space reserved in buf for the register is 8 bytes.  Make sure the entire
++     reserved space is initialized.  */
++
++  gdb_assert (register_size (regcache->tdesc, regno) == 4);
++
++  if (regno == RAX)
++    {
++      /* Sign extend EAX value to avoid potential syscall restart
++	 problems.
++
++	 See amd64_linux_collect_native_gregset() in
++	 gdb/amd64-linux-nat.c for a detailed explanation.  */
++      *(int64_t *) buf = *(int32_t *) buf;
++    }
++  else
++    {
++      /* Zero-extend.  */
++      *(uint64_t *) buf = *(uint32_t *) buf;
++    }
++#endif
++}
++
+ static void
+ x86_fill_gregset (struct regcache *regcache, void *buf)
+ {
+@@ -411,32 +440,14 @@ x86_fill_gregset (struct regcache *regcache, void *buf)
+ 
+       return;
+     }
+-
+-  /* 32-bit inferior registers need to be zero-extended.
+-     Callers would read uninitialized memory otherwise.  */
+-  memset (buf, 0x00, X86_64_USER_REGS * 8);
+ #endif
+ 
+   for (i = 0; i < I386_NUM_REGS; i++)
+-    collect_register (regcache, i, ((char *) buf) + i386_regmap[i]);
+-
+-  collect_register_by_name (regcache, "orig_eax",
+-			    ((char *) buf) + ORIG_EAX * REGSIZE);
++    collect_register_i386 (regcache, i, ((char *) buf) + i386_regmap[i]);
+ 
+-#ifdef __x86_64__
+-  /* Sign extend EAX value to avoid potential syscall restart
+-     problems. 
+-
+-     See amd64_linux_collect_native_gregset() in gdb/amd64-linux-nat.c
+-     for a detailed explanation.  */
+-  if (register_size (regcache->tdesc, 0) == 4)
+-    {
+-      void *ptr = ((gdb_byte *) buf
+-                   + i386_regmap[find_regno (regcache->tdesc, "eax")]);
+-
+-      *(int64_t *) ptr = *(int32_t *) ptr;
+-    }
+-#endif
++  /* Handle ORIG_EAX, which is not in i386_regmap.  */
++  collect_register_i386 (regcache, find_regno (regcache->tdesc, "orig_eax"),
++			 ((char *) buf) + ORIG_EAX * REGSIZE);
+ }
+ 
+ static void
+-- 
+2.29.2
+



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