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SubjectRe: [PATCH] Set TIF_IRET in more places
From
Date
Jamie Lokier <lk@tantalophile.demon.co.uk> writes:

>
> It would be quite nice just to have dwarf2 unwind information, with an
> unwind handler, for the classic non-vsyscall restorer in Glibc.

A trivial routine that just calls another routine,

extern void g(void);

void f(void) { g(); asm volatile (""); }

[the asm is to prevent sibcall optimization from kicking in] produces
the assembly dump appended to this message when compiled with -O2
-fexceptions -fomit-frame-pointer. I do not know what the stuff put
in .eh_frame means, and it probably isn't exactly right for __restore
or __restore_rt, but it's a start.

> Then MD_FALLBACK_FRAME_STATE_FOR could be removed from GCC on all
> Linux targets, regardless of kernel version.

I think we'd need to keep it around for the sake of older libcs; it
shouldn't do any harm.

zw

.text
.p2align 2,,3
.globl f
.type f,@function
f:
.LFB1:
subl $12, %esp
.LCFI0:
call g
addl $12, %esp
.LCFI1:
ret
.LFE1:
.Lfe1:
.size f,.Lfe1-f
.section .eh_frame,"aw",@progbits
.Lframe1:
.long .LECIE1-.LSCIE1
.LSCIE1:
.long 0x0
.byte 0x1
.string ""
.uleb128 0x1
.sleb128 -4
.byte 0x8
.byte 0xc
.uleb128 0x4
.uleb128 0x4
.byte 0x88
.uleb128 0x1
.align 4
.LECIE1:
.LSFDE1:
.long .LEFDE1-.LASFDE1
.LASFDE1:
.long .LASFDE1-.Lframe1
.long .LFB1
.long .LFE1-.LFB1
.byte 0x4
.long .LCFI0-.LFB1
.byte 0xe
.uleb128 0x10
.byte 0x4
.long .LCFI1-.LCFI0
.byte 0xe
.uleb128 0x4
.align 4
.LEFDE1:
.ident "GCC: (GNU) 3.2.2 20021231 (Debian prerelease)"
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