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commit 558251bd8785760ad40fcbfeaaee5d27fa5b0fe4
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Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
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Date: Thu Oct 22 17:55:01 2020 +0100
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aarch64: Fix DT_AARCH64_VARIANT_PCS handling [BZ #26798]
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The variant PCS support was ineffective because in the common case
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linkmap->l_mach.plt == 0 but then the symbol table flags were ignored
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and normal lazy binding was used instead of resolving the relocs early.
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(This was a misunderstanding about how GOT[1] is setup by the linker.)
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In practice this mainly affects SVE calls when the vector length is
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more than 128 bits, then the top bits of the argument registers get
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clobbered during lazy binding.
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Fixes bug 26798.
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diff --git a/sysdeps/aarch64/dl-machine.h b/sysdeps/aarch64/dl-machine.h
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index b39eae4acf4086ee..3fd3c8a265d012b1 100644
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--- a/sysdeps/aarch64/dl-machine.h
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+++ b/sysdeps/aarch64/dl-machine.h
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@@ -391,13 +391,6 @@ elf_machine_lazy_rel (struct link_map *map,
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/* Check for unexpected PLT reloc type. */
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if (__builtin_expect (r_type == AARCH64_R(JUMP_SLOT), 1))
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{
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- if (map->l_mach.plt == 0)
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- {
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- /* Prelinking. */
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- *reloc_addr += l_addr;
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- return;
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- }
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-
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if (__glibc_unlikely (map->l_info[DT_AARCH64 (VARIANT_PCS)] != NULL))
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{
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/* Check the symbol table for variant PCS symbols. */
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@@ -421,7 +414,10 @@ elf_machine_lazy_rel (struct link_map *map,
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}
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}
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- *reloc_addr = map->l_mach.plt;
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+ if (map->l_mach.plt == 0)
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+ *reloc_addr += l_addr;
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+ else
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+ *reloc_addr = map->l_mach.plt;
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}
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else if (__builtin_expect (r_type == AARCH64_R(TLSDESC), 1))
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{
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