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This patch fixes segfault of all user space processes (including init, which caused a panic) on recent buildroot powerpc32 builds.
The issue has been reported by Romain Naour in this thread: https://mailman.uclibc-ng.org/pipermail/devel/2021-May/002068.html
Recent buildroot toolchain enables secure PLT in powerpc gcc.
The latter will then supply -msecure-plt to gas invocations by default.
Recent buildroot also enables PIE by defaults.
For the secure PLT to work in PIC, the r30 register needs to point to the GOT.
Old "bss plt" was just a one-instruction-wide PLT slot, pointed-to by a R_PPC_JMP_SLOT relocation, which was written on-the-fly to contain a branch instruction to the correct address. It therefore had to stay writable.
New secure PLT only contains read-only code which loads the branch address from the writable GOT.
Note: secure PLT without PIC does not need r30 to be set. Because offset between plt stub code and got is known at link-time. In this case the PLT entry looks like:
1009b3e0 <__uClibc_main@plt>:
1009b3e0: 3d 60 10 0e lis r11,4110
1009b3e4: 81 6b 03 74 lwz r11,884(r11)
1009b3e8: 7d 69 03 a6 mtctr r11
1009b3ec: 4e 80 04 20 bctr
Whereas secure PLT with PIC - offset between plt and got is unknown at link-time - looks like this:
000af800 <00000000.plt_pic32.__uClibc_main>:
af800: 81 7e 03 80 lwz r11,896(r30)
af804: 7d 69 03 a6 mtctr r11
af808: 4e 80 04 20 bctr
af80c: 60 00 00 00 nop
Signed-off-by: Yann Sionneau <yann@sionneau.net>
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There's no need to export this symbol, so mark them all hidden.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
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They expand into the same code, but using the ELF_xxx()/ElfW() macros
makes it much easier to spot similarities between code bases.
Acked-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
Acked-by: Carmelo Amoroso <carmelo.amoroso@st.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
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ldso/ldso/avr32/dl-startup.h: remove superfluous definition of START() macro.
ldso/ldso/*/dl-startup.h: fix a typo in comment
text data bss dec hex filename
- 16752 244 92 17088 42c0 lib/ld-uClibc.so
+ 16709 240 92 17041 4291 lib/ld-uClibc.so
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config option --enable-secureplt. The assembler must also
supports R_PPC_REL16* relocations. gcc 4.1.1 and binutils 2.17
is known to do this.
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the default
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use r3 instead to pass _dl_fini.
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Note that every arch that wants to support standalone execution needs
to align its stack pointer in crtX since ldso will adjust the stack pointer
when adjusting argc and argv in standalone mode.
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should not break ABI.
Minor cleanup as well.
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execution of ldso.
Added new asm for MIPS to be tested.
All arches should retest.
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This patch makes -fpic work for PCC and optimzes the relcation by moving the cache
flushing stuff to JMP relocs only. Actually PPCs ldso can only handle small
GOT tables(<=8192 entries)anyhow, so it makes little sense to compile PPC with -fPIC.
libuClibc shrunk from 340724 to 330780 bytes with -fpic.
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Hi
I just noticed that gcc has an "b"(Address base register) operand that
will match all "r" registers but r0. It is a better fix then adding
r0 to the clobber list.
What do you think?
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Begin converting some big ugly macros to inline functions
instead
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to be arch specific to work properly.
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to make it easier to treat it specially while not bothering the
rest of the code with the same constraints.
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The current behavior of the powerpc boot1_arch.h seems somewhat broken.
Currently room is made on the stack pointer for the link register, but the link
register is never actually pushed onto it. glibc bears the following comments:
/* Call _dl_start with one parameter pointing at argc */
mr r3,r1
/* (we have to frob the stack pointer a bit to allow room for
_dl_start to save the link register). */
followed by the -16 add to r1. Despite the fact that r1 is modified, the link
register is never actually pushed onto r1, thus the adjustment is completely
superfluous.
There's two possible fixes for this, either saving the link register in the way
that glibc does, or getting rid of the r1 adjustment. As I'm not sure if saving
the link register will actually break the _dl_boot2 callin, both options will
probably want to be played with.
The following bit of inline assembly in the attached patch builds cleanly for
me with gcc 3.3 on darwin, but I'm not able to test it any further beyond that.
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some other minor warnings.
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shared library support. This also adds some cleaner error
handling, which I (Erik) then ported over to x86 and arm.
In addition Stefan added the following fixes:
- in hash.c was the lvalue handling of global library functions wrong.
To fix this I had to change the prototype of _dl_find_hash. (==> TIS and
ELF spec. Vers. 1.2)
- in ldso.c was the order of the .init sections calls wrong. Before we call
the initialization code of a library we have to check that all dependend
libraries are already initialized. This can easily made by calling it in the
revers loading order. For this I added a previous pointer chain.
- in ldso.c the ELF magics wasn't checked fo PPC, MIPS and SH architecture
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should work now. R_PPC_JMP_SLOT correctly being lazily relocated.
hash.h: Added a field in elf_resolve to store a ppc-specific address.
boot1.c: Added debugging code. Disabled check that fails on powerpc
because the string literal requires a reloc that isn't performed.
Added check to ignore d_tag if it is out of bounds, as has been
observed with powerpc binaries.
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of debugging information is still there.
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