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Meta+LibC: Don't allow text relocations in SerenityOS libraries

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The `-z,text` linker flag causes the linker to reject shared libraries
and PIE executables that have textrels. Our code mostly did not use
these except in one place in LibC, which is changed in this commit.
This makes GNU ld match LLD's behavior, which has this option enabled by
default.

TEXTRELs pose a security risk, as performing these relocations require
executable pages to be written to by the dynamic linker. This can
significantly weaken W^X hardening mitigations.

Note that after this change, TEXTRELs can still be used in ports, as the
dynamic loader code is not changed. There are also uses of it in the
kernel, removing which are outside the scope of this PR. To allow those,
`-z,notext` is added.
This commit is contained in:
Daniel Bertalan 2021-08-18 17:39:04 +02:00 committed by Gunnar Beutner
parent 446bd1e0de
commit bd6dc5ccec
Notes: sideshowbarker 2024-07-18 05:32:03 +09:00 
Author: https://github.com/BertalanD
Commit: https://github.com/SerenityOS/serenity/commit/bd6dc5ccec7
Pull-request: https://github.com/SerenityOS/serenity/pull/9492
4 changed files with 6 additions and 3 deletions
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2
CMakeLists.txt
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@ -299,6 +299,8 @@ else()
add_compile_options(-Wdouble-promotion)
endif()
add_link_options(LINKER:-z,text)
if("${SERENITY_ARCH}" STREQUAL "i686")
add_compile_options(-march=i686)
else()

3
Kernel/CMakeLists.txt
View file

@ -437,8 +437,9 @@ add_compile_definitions(KERNEL)
# It's needed because CLion doesn't understand the way we switch compilers mid-build.
add_compile_definitions(__serenity__)
add_link_options(LINKER:-z,notext)
if (USE_CLANG_TOOLCHAIN)
add_link_options(LINKER:-z,notext)
add_link_options(LINKER:--build-id=none)
endif()

2
Userland/Libraries/LibC/arch/i386/setjmp.S
View file

@ -31,7 +31,7 @@ sigsetjmp:
push %eax
push $0 // Set argument set
push $0 // Set argument how
call sigprocmask
call sigprocmask@plt
add $12, %esp
.Lsaveregs:

2
Userland/Libraries/LibC/arch/x86_64/setjmp.S
View file

@ -25,7 +25,7 @@ sigsetjmp:
mov $0, %rdi // Set argument how
mov $0, %rsi // Set argument set
lea 64(%rdi), %rdx // Set argument oldset
call sigprocmask
call sigprocmask@plt
mov %r12, %rdi // Restore sigjmp_buf argument
.Lsaveregs: