X86/X86-64 linkers check code sequence while performing TLS optimization
like:
/* IE->LE transition:
Originally it can be one of:
movq [EMAIL PROTECTED](%rip), %reg
addq [EMAIL PROTECTED](%rip), %reg
We change it into:
movq $foo, %reg
leaq foo(%reg), %reg
addq $foo, %reg. */
BFD_ASSERT (rel->r_offset >= 3);
val = bfd_get_8 (input_bfd, contents + rel->r_offset - 3);
BFD_ASSERT (val == 0x48 || val == 0x4c);
type = bfd_get_8 (input_bfd, contents + rel->r_offset - 2);
BFD_ASSERT (type == 0x8b || type == 0x03);
reg = bfd_get_8 (input_bfd, contents + rel->r_offset - 1);
BFD_ASSERT ((reg & 0xc7) == 5);
reg >>= 3; BFD_ASSERT (rel->r_offset + 4 <=
input_section->size);
But not all TLS code sequences generated by all compilers follow the same
sequence. In many cases, such optimization is dangerous and wrong. We
should check the code sequence before performing such optimization.
--
Summary: Linker should check code sequence before TLS
optimization
Product: binutils
Version: 2.19 (HEAD)
Status: NEW
Severity: normal
Priority: P2
Component: ld
AssignedTo: unassigned at sources dot redhat dot com
ReportedBy: hjl at lucon dot org
CC: bug-binutils at gnu dot org,jakub at redhat dot com
http://sourceware.org/bugzilla/show_bug.cgi?id=4928
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