glibc/ulp-prologue-into-asm-functions.patch

From 65bb10c34ff3734373a8b4be4e707f0494449f17 Mon Sep 17 00:00:00 2001
From: Giuliano Belinassi <gbelinassi@suse.de>
Date: Wed, 24 May 2023 18:03:15 -0300
Subject: [PATCH] Add Userspace Livepatch prologue into ASM functions

Userspace Live Patching (ULP) refers to the process of applying
patches to the libraries used by a running process, without
interrupting it. In order to archive this, functions must have
the NOP prologue. This prologue is included automatically when
compiled with -fpatchable-function-entry, but for ASM functions
this have to be included manually. This patch does this.

Signed-off-by: Giuliano Belinassi <gbelinassi@suse.de>
---
 Makeconfig                               |  5 +++++
 config.h.in                              |  3 +++
 config.make.in                           |  1 +
 configure                                | 21 +++++++++++++++++++++
 configure.ac                             | 13 +++++++++++++
 sysdeps/x86/sysdep.h                     | 22 ++++++++++++++++++----
 sysdeps/x86_64/multiarch/strcmp-avx2.S   |  5 +----
 sysdeps/x86_64/multiarch/strcmp-evex.S   |  5 +----
 sysdeps/x86_64/multiarch/strcmp-sse4_2.S |  5 +----
 sysdeps/x86_64/sysdep.h                  | 13 +++++++++++++
 10 files changed, 77 insertions(+), 16 deletions(-)

diff --git a/Makeconfig b/Makeconfig
index 77d7fd14df..765d72bcf5 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -984,6 +984,11 @@ else
 +cflags += $(no-fortify-source)
 endif
 
+# Add flags for Userspace Livepatching support.
+ifeq (yes,$(enable-userspace-livepatch))
++cflags	+= -fpatchable-function-entry=16,14
+endif
+
 # Each sysdeps directory can contain header files that both will be
 # used to compile and will be installed.  Each can also contain an
 # include/ subdirectory, whose header files will be used to compile
diff --git a/config.h.in b/config.h.in
index 0dedc124f7..08b1868002 100644
--- a/config.h.in
+++ b/config.h.in
@@ -204,6 +204,9 @@
 /* Define to 1 if libpthread actually resides in libc.  */
 #define PTHREAD_IN_LIBC 0
 
+/* Define to 1 if support for userspace livepatching is enabled.  */
+#define ENABLE_USERSPACE_LIVEPATCH 0
+
 /* An integer used to scale the timeout of test programs.  */
 #define TIMEOUTFACTOR 1
 
diff --git a/config.make.in b/config.make.in
index d487a4f4e9..e48351c59a 100644
--- a/config.make.in
+++ b/config.make.in
@@ -85,6 +85,7 @@ nss-crypt = @libc_cv_nss_crypt@
 static-nss-crypt = @libc_cv_static_nss_crypt@
 
 # Configuration options.
+enable-userspace-livepatch = @enable_userspace_livepatch@
 build-shared = @shared@
 build-profile = @profile@
 build-static-nss = @static_nss@
diff --git a/configure b/configure
index c02c0b5825..e2000fdc4a 100755
--- a/configure
+++ b/configure
@@ -622,6 +622,7 @@ LIBOBJS
 pthread_in_libc
 RELEASE
 VERSION
+enable_userspace_livepatch
 mach_interface_list
 DEFINES
 static_nss
@@ -819,6 +820,7 @@ enable_cet
 enable_scv
 enable_fortify_source
 with_cpu
+enable_userspace_livepatch
 '
       ac_precious_vars='build_alias
 host_alias
@@ -1501,6 +1503,8 @@ Optional Features:
                           Use -D_FORTIFY_SOURCE=[1|2|3] to control code
                           hardening, defaults to highest possible value
                           supported by the build compiler.
+  --enable-userspace-livepatch
+                          build with userspace livepatch support [default=no]
 
 Optional Packages:
   --with-PACKAGE[=ARG]    use PACKAGE [ARG=yes]
@@ -8004,6 +8008,23 @@ libc_cv_multidir=`${CC-cc} $CFLAGS $CPPFLAGS -print-multi-directory`
 
 
 
+# Check whether --enable-userspace-livepatch was given.
+if test ${enable_userspace_livepatch+y}
+then :
+  enableval=$enable_userspace_livepatch; enable_userspace_livepatch=$enableval
+else $as_nop
+  enable_userspace_livepatch=no
+fi
+
+
+# Libpulp uses -fpatchable-function-entry to add padding NOPS to the
+# prologue of all functions.
+if test "x$enable_userspace_livepatch" = xyes; then
+  printf "%s\n" "#define ENABLE_USERSPACE_LIVEPATCH 1" >>confdefs.h
+
+fi
+
+
 VERSION=`sed -n -e 's/^#define VERSION "\([^"]*\)"/\1/p' < $srcdir/version.h`
 RELEASE=`sed -n -e 's/^#define RELEASE "\([^"]*\)"/\1/p' < $srcdir/version.h`
 
diff --git a/configure.ac b/configure.ac
index 09553541fb..a07e3d6284 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1827,6 +1827,19 @@ AC_SUBST(DEFINES)
 dnl See sysdeps/mach/configure.ac for this variable.
 AC_SUBST(mach_interface_list)
 
+AC_ARG_ENABLE([userspace-livepatch],
+	      AS_HELP_STRING([--enable-userspace-livepatch],
+			     [build with userspace livepatch support @<:@default=no@:>@]),
+	      [enable_userspace_livepatch=$enableval],
+	      [enable_userspace_livepatch=no])
+
+# Libpulp uses -fpatchable-function-entry to add padding NOPS to the
+# prologue of all functions.
+if test "x$enable_userspace_livepatch" = xyes; then
+  AC_DEFINE(ENABLE_USERSPACE_LIVEPATCH)
+fi
+AC_SUBST(enable_userspace_livepatch)
+
 VERSION=`sed -n -e 's/^#define VERSION "\([^"]*\)"/\1/p' < $srcdir/version.h`
 RELEASE=`sed -n -e 's/^#define RELEASE "\([^"]*\)"/\1/p' < $srcdir/version.h`
 AC_SUBST(VERSION)
diff --git a/sysdeps/x86/sysdep.h b/sysdeps/x86/sysdep.h
index 0b3483a77a..329c16306e 100644
--- a/sysdeps/x86/sysdep.h
+++ b/sysdeps/x86/sysdep.h
@@ -77,15 +77,29 @@ enum cf_protection_level
 #define ALIGNARG(log2) 1<<log2
 #define ASM_SIZE_DIRECTIVE(name) .size name,.-name;
 
+/* For 32-bit glibc then define those macros as empty.  */
+#ifndef ULP_PRE_PROLOGUE
+# define ULP_PRE_PROLOGUE
+#endif
+#ifndef ULP_POST_PROLOGUE
+# define ULP_POST_PROLOGUE
+#endif
+
+/* Define the first instructions of a function.  */
+#define FUNCTION_START(name) \
+  ULP_PRE_PROLOGUE; \
+  C_LABEL(name); \
+  cfi_startproc; \
+  _CET_ENDBR; \
+  ULP_POST_PROLOGUE; \
+  CALL_MCOUNT;
+
 /* Define an entry point visible from C.  */
 #define	ENTRY_P2ALIGN(name, alignment)					      \
   .globl C_SYMBOL_NAME(name);						      \
   .type C_SYMBOL_NAME(name),@function;					      \
   .align ALIGNARG(alignment);						      \
-  C_LABEL(name)								      \
-  cfi_startproc;							      \
-  _CET_ENDBR;								      \
-  CALL_MCOUNT
+  FUNCTION_START(name)
 
 /* Common entry 16 byte aligns.  */
 #define ENTRY(name) ENTRY_P2ALIGN (name, 4)
diff --git a/sysdeps/x86_64/multiarch/strcmp-avx2.S b/sysdeps/x86_64/multiarch/strcmp-avx2.S
index 8804338d75..d3584b2c5d 100644
--- a/sysdeps/x86_64/multiarch/strcmp-avx2.S
+++ b/sysdeps/x86_64/multiarch/strcmp-avx2.S
@@ -201,10 +201,7 @@ END (STRCASECMP)
 # endif
 
 	.p2align 4
-STRCMP:
-	cfi_startproc
-	_CET_ENDBR
-	CALL_MCOUNT
+FUNCTION_START(STRCMP)
 
 # if defined USE_AS_STRCASECMP_L
 	/* We have to fall back on the C implementation for locales with
diff --git a/sysdeps/x86_64/multiarch/strcmp-evex.S b/sysdeps/x86_64/multiarch/strcmp-evex.S
index ae39cdf217..44a8d4cee7 100644
--- a/sysdeps/x86_64/multiarch/strcmp-evex.S
+++ b/sysdeps/x86_64/multiarch/strcmp-evex.S
@@ -224,10 +224,7 @@ END (STRCASECMP)
 # endif
 
 	.p2align 4
-STRCMP:
-	cfi_startproc
-	_CET_ENDBR
-	CALL_MCOUNT
+FUNCTION_START(STRCMP)
 
 # if defined USE_AS_STRCASECMP_L
 	/* We have to fall back on the C implementation for locales with
diff --git a/sysdeps/x86_64/multiarch/strcmp-sse4_2.S b/sysdeps/x86_64/multiarch/strcmp-sse4_2.S
index cbb22884eb..327377daa6 100644
--- a/sysdeps/x86_64/multiarch/strcmp-sse4_2.S
+++ b/sysdeps/x86_64/multiarch/strcmp-sse4_2.S
@@ -103,10 +103,7 @@ END (STRCASECMP)
 
 # define arg arg
 
-STRCMP:
-	cfi_startproc
-	_CET_ENDBR
-	CALL_MCOUNT
+FUNCTION_START(STRCMP)
 
 /*
  * This implementation uses SSE to compare up to 16 bytes at a time.
diff --git a/sysdeps/x86_64/sysdep.h b/sysdeps/x86_64/sysdep.h
index 6ca169573d..c18f0ef914 100644
--- a/sysdeps/x86_64/sysdep.h
+++ b/sysdeps/x86_64/sysdep.h
@@ -24,6 +24,19 @@
 
 #ifdef	__ASSEMBLER__
 
+/* Libpulp uses -fpatchable-function-entry to add padding NOPS to the
+   prologue of all functions. This works for C functions. For functions
+   written in ASM, the way we do this is by adding this prologue manually.  */
+
+#if ENABLE_USERSPACE_LIVEPATCH
+# undef ULP_PRE_PROLOGUE
+# undef ULP_POST_PROLOGUE
+# define ULP_PRE_PROLOGUE \
+  .rept 14; nop; .endr
+# define ULP_POST_PROLOGUE \
+  xchg %ax, %ax
+#endif
+
 /* Syntactic details of assembler.  */
 
 /* This macro is for setting proper CFI with DW_CFA_expression describing
-- 
2.41.0