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aarch64: configure check for pac-ret code generation
Return address signing requires unwinder support, which is present in libgcc since >=gcc-7, however due to bugs the support may be broken in <gcc-10 (and similarly there may be issues in custom unwinders), so pac-ret is not always safe to use. So in assembly code glibc should only use pac-ret if the compiler uses it too. Unfortunately there is no predefined feature macro for it set by the compiler so pac-ret is inferred from the code generation. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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@ -112,6 +112,9 @@
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/* AArch64 BTI support enabled. */
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#define HAVE_AARCH64_BTI 0
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/* AArch64 PAC-RET code generation is enabled. */
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#define HAVE_AARCH64_PAC_RET 0
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/* C-SKY ABI version. */
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#undef CSKYABI
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39
sysdeps/aarch64/configure
vendored
39
sysdeps/aarch64/configure
vendored
@ -216,3 +216,42 @@ if test $libc_cv_aarch64_bti = yes; then
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$as_echo "#define HAVE_AARCH64_BTI 1" >>confdefs.h
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fi
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# Check if glibc is built with return address signing, i.e.
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# if -mbranch-protection=pac-ret is on. We need this because
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# pac-ret relies on unwinder support so it's not safe to use
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# it in assembly code unconditionally, but there is no
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# feature test macro for it in gcc.
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{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if pac-ret is enabled" >&5
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$as_echo_n "checking if pac-ret is enabled... " >&6; }
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if ${libc_cv_aarch64_pac_ret+:} false; then :
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$as_echo_n "(cached) " >&6
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else
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cat > conftest.c <<EOF
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int bar (void);
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int foo (void) { return bar () + 1; }
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EOF
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libc_cv_aarch64_pac_ret=no
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if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -S -o conftest.s conftest.c'
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{ { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
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(eval $ac_try) 2>&5
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ac_status=$?
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$as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
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test $ac_status = 0; }; } \
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&& { ac_try='grep -q -E '\''(hint( | )+25|paciasp)'\'' conftest.s'
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{ { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
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(eval $ac_try) 2>&5
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ac_status=$?
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$as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
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test $ac_status = 0; }; }
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then
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libc_cv_aarch64_pac_ret=yes
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fi
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rm -rf conftest.*
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fi
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{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_aarch64_pac_ret" >&5
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$as_echo "$libc_cv_aarch64_pac_ret" >&6; }
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if test $libc_cv_aarch64_pac_ret = yes; then
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$as_echo "#define HAVE_AARCH64_PAC_RET 1" >>confdefs.h
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fi
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@ -40,3 +40,24 @@ LIBC_CONFIG_VAR([aarch64-bti], [$libc_cv_aarch64_bti])
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if test $libc_cv_aarch64_bti = yes; then
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AC_DEFINE(HAVE_AARCH64_BTI)
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fi
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# Check if glibc is built with return address signing, i.e.
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# if -mbranch-protection=pac-ret is on. We need this because
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# pac-ret relies on unwinder support so it's not safe to use
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# it in assembly code unconditionally, but there is no
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# feature test macro for it in gcc.
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AC_CACHE_CHECK([if pac-ret is enabled], [libc_cv_aarch64_pac_ret], [dnl
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cat > conftest.c <<EOF
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int bar (void);
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int foo (void) { return bar () + 1; }
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EOF
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libc_cv_aarch64_pac_ret=no
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if AC_TRY_COMMAND([${CC-cc} $CFLAGS $CPPFLAGS -S -o conftest.s conftest.c]) \
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&& AC_TRY_COMMAND([grep -q -E '\''(hint( | )+25|paciasp)'\'' conftest.s])
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then
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libc_cv_aarch64_pac_ret=yes
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fi
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rm -rf conftest.*])
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if test $libc_cv_aarch64_pac_ret = yes; then
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AC_DEFINE(HAVE_AARCH64_PAC_RET)
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fi
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