liblzma: Fix false Valgrind error report with GCC.

With GCC and a certain combination of flags, Valgrind will falsely
trigger an invalid write. This appears to be due to the omission of
instructions to properly save, set up, and restore the frame pointer.

The IFUNC resolver is a leaf function since it only calls a function
that is inlined. So sometimes GCC omits the frame pointer instructions
in the resolver unless this optimization is explictly disabled.

This fixes https://bugzilla.redhat.com/show_bug.cgi?id=2267598.

diff --git a/src/liblzma/check/crc32_fast.c b/src/liblzma/check/crc32_fast.c
index 079051f12058978581388283c7507d3feef3c702..719d696c2d9c18e9958ce749adf00c30fadddd8a 100644 (file)
--- a/src/liblzma/check/crc32_fast.c
+++ b/src/liblzma/check/crc32_fast.c
@@ -135,15 +135,12 @@ typedef uint32_t (*crc32_func_type)(
 // This resolver is shared between all three dispatch methods. It serves as
 // the ifunc resolver if ifunc is supported, otherwise it is called as a
 // regular function by the constructor or first call resolution methods.
-// The __no_profile_instrument_function__ attribute support is checked when
-// determining if ifunc can be used, so it is safe to use here.
-#ifdef CRC_USE_IFUNC
-__attribute__((__no_profile_instrument_function__))
-#endif
+// The funcion attributes are needed for safe IFUNC resolver usage with GCC.
+lzma_resolver_attributes
 static crc32_func_type
 crc32_resolve(void)
 {
-       return is_arch_extension_supported()
+       return  is_arch_extension_supported()
                        ? &crc32_arch_optimized : &crc32_generic;
 }
 

diff --git a/src/liblzma/check/crc64_fast.c b/src/liblzma/check/crc64_fast.c
index 5728b45ea06ea68d2430cc89acc940064440e1f9..330a50164a7ee887e3ae74f66b9e4e2558034310 100644 (file)
--- a/src/liblzma/check/crc64_fast.c
+++ b/src/liblzma/check/crc64_fast.c
@@ -98,13 +98,12 @@ typedef uint64_t (*crc64_func_type)(
 #      pragma GCC diagnostic ignored "-Wunused-function"
 #endif
 
-#ifdef CRC_USE_IFUNC
-__attribute__((__no_profile_instrument_function__))
-#endif
+// The funcion attributes are needed for safe IFUNC resolver usage with GCC.
+lzma_resolver_attributes
 static crc64_func_type
 crc64_resolve(void)
 {
-       return is_arch_extension_supported()
+       return  is_arch_extension_supported()
                        ? &crc64_arch_optimized : &crc64_generic;
 }
 

diff --git a/src/liblzma/check/crc_common.h b/src/liblzma/check/crc_common.h
index 856665db79a8d8793cbaf17b0ebab3aa3a0f06c8..5a86556f7a52cca54b679a98396badc0785ee9ce 100644 (file)
--- a/src/liblzma/check/crc_common.h
+++ b/src/liblzma/check/crc_common.h
@@ -128,6 +128,31 @@
 #      endif
 #endif
 
+#ifdef CRC_USE_IFUNC
+// Two function attributes are needed to make IFUNC safe with GCC.
+//
+// no-omit-frame-pointer prevents false Valgrind issues when combined with
+// a few other compiler flags. The optimize attribute is supported on
+// GCC >= 4.4 and is not supported with Clang.
+#      if TUKLIB_GNUC_REQ(4,4) && !defined(__clang__)
+#              define no_omit_frame_pointer \
+                       __attribute__((optimize("no-omit-frame-pointer")))
+#      else
+#              define no_omit_frame_pointer
+#      endif
+
+// The __no_profile_instrument_function__ attribute support is checked when
+// determining if ifunc can be used, so it is safe to use unconditionally.
+// This attribute is needed because GCC can add profiling to the IFUNC
+// resolver, which calls functions that have not yet been relocated leading
+// to a crash on liblzma start up.
+#      define lzma_resolver_attributes \
+               __attribute__((__no_profile_instrument_function__)) \
+               no_omit_frame_pointer
+#else
+#      define lzma_resolver_attributes
+#endif
+
 // For CRC32 use the generic slice-by-eight implementation if no optimized
 // version is available.
 #if !defined(CRC32_ARCH_OPTIMIZED) && !defined(CRC32_GENERIC)