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| author | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2018-08-27 16:16:43 -0300 |
|---|---|---|
| committer | Adhemerval Zanella <adhemerval.zanella@linaro.org> | 2018-09-25 16:27:50 -0300 |
| commit | b5c45e83753b27dc538dff2d55d4410c385cf3a4 (patch) | |
| tree | 7c88e09f3bcf2edbdf2a1196b50c54ab7459b0c5 /elf/dl-reloc.c | |
| parent | d62f9ec0cce26a275ec68f4564814041a33395b1 (diff) | |
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Fix ifunc support with DT_TEXTREL segments (BZ#20480)
Currently, DT_TEXTREL is incompatible with IFUNC. When DT_TEXTREL or
DF_TEXTREL is seen, the dynamic linker calls __mprotect on the segments
with PROT_READ|PROT_WRITE before applying dynamic relocations. It leads
to segfault when performing IFUNC resolution (which requires PROT_EXEC
as well for the IFUNC resolver).
This patch makes it call __mprotect with extra PROT_WRITE bit, which
will keep the PROT_EXEC bit if exists, and thus fixes the segfault.
FreeBSD rtld libexec/rtld-elf/rtld.c (reloc_textrel_prot) does the same.
Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu,
sparc64-linux-gnu, sparcv9-linux-gnu, and armv8-linux-gnueabihf.
Adam J. Richte <adam_richter2004@yahoo.com>
Adhemerval Zanella <adhemerval.zanella@linaro.org>
Fangrui Song <maskray@google.com>
[BZ #20480]
* config.h.in (CAN_TEXTREL_IFUNC): New define.
* configure.ac: Add check if linker supports textrel relocation with
ifunc.
* elf/dl-reloc.c (_dl_relocate_object): Use all required flags on
DT_TEXTREL segments, not only PROT_READ and PROT_WRITE.
* elf/Makefile (ifunc-pie-tests): Add tst-ifunc-textrel.
(CFLAGS-tst-ifunc-textrel.c): New rule.
* elf/tst-ifunc-textrel.c: New file.
Diffstat (limited to 'elf/dl-reloc.c')
| -rw-r--r-- | elf/dl-reloc.c | 20 |
1 files changed, 8 insertions, 12 deletions
diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c index 053916eeae..164f4efa10 100644 --- a/elf/dl-reloc.c +++ b/elf/dl-reloc.c @@ -200,17 +200,6 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[], newp->start = PTR_ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize)) + (caddr_t) l->l_addr; - if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0) - { - errstring = N_("cannot make segment writable for relocation"); - call_error: - _dl_signal_error (errno, l->l_name, NULL, errstring); - } - -#if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7 - newp->prot = (PF_TO_PROT - >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf; -#else newp->prot = 0; if (ph->p_flags & PF_R) newp->prot |= PROT_READ; @@ -218,7 +207,14 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[], newp->prot |= PROT_WRITE; if (ph->p_flags & PF_X) newp->prot |= PROT_EXEC; -#endif + + if (__mprotect (newp->start, newp->len, newp->prot|PROT_WRITE) < 0) + { + errstring = N_("cannot make segment writable for relocation"); + call_error: + _dl_signal_error (errno, l->l_name, NULL, errstring); + } + newp->next = textrels; textrels = newp; } |