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SubjectRe: [PATCH] m68k: add missing SOFTIRQENTRY_TEXT linker section
Hi Greg,

CC mingo, Hiramatsu-san, linux-arch, lkml

On Tue, Nov 14, 2017 at 7:04 AM, Greg Ungerer <gerg@linux-m68k.org> wrote:
> Commit be7635e7287e ("arch, ftrace: for KASAN put hard/soft IRQ entries
> into separate sections") added a new linker section, SOFTIRQENTRY_TEXT,
> to the linker scripts for most architectures. It didn't add it to any of
> the linker scripts for the m68k architecture. This was not really a problem
> because it is only defined if either of CONFIG_FUNCTION_GRAPH_TRACER or
> CONFIG_KASAN are enabled - which can never be true for m68k.
>
> However commit 229a71860547 ("irq: Make the irqentry text section
> unconditional") means that SOFTIRQENTRY_TEXT is now always defined. So on
> m68k we now end up with a separate ELF section for .softirqentry.text
> instead of it being part of the .text section. On some m68k targets in some

Nice catch!

+10 other architectures also don't have the section.

> configurations this can also cause a fatal link error:
>
> LD vmlinux
> /usr/local/bin/../m68k-uclinux/bin/ld.real: section .softirqentry.text loaded at [0000000010de10c0,0000000010de12dd] overlaps section .rodata loaded at [0000000010de10c0,0000000010e0fd67]

How does it cause the overlap?

For me, "readelf -S vmlinux" gives:

There are 21 section headers, starting at offset 0x524850:

Section Headers:
[Nr] Name Type Addr Off Size ES Flg Lk Inf Al
[ 0] NULL 00000000 000000 000000 00 0 0 0
[ 1] .text PROGBITS 00001000 001000 2dacb4 00 AX 0 0 4
[ 2] .softirqentry.tex PROGBITS 002dbcb4 2dbcb4 0001a0 00 AX 0 0 2
[ 3] __ex_table PROGBITS 002dbe60 2dbe60 0027f0 00 A 0 0 4
[ 4] .rodata PROGBITS 002df000 2df000 09ee20 00 WA 0 0 16
[ 5] __ksymtab PROGBITS 0037de20 37de20 006538 00 A 0 0 2
[ 6] __ksymtab_gpl PROGBITS 00384358 384358 003f08 00 A 0 0 2
[ 7] __ksymtab_strings PROGBITS 00388260 388260 01747d 00 A 0 0 1
[ 8] __param PROGBITS 0039f6e0 39f6e0 000924 00 A 0 0 4
[ 9] __modver PROGBITS 003a0004 3a0004 000ffc 00 A 0 0 2
[10] .data PROGBITS 003a1000 3a1000 021c20 00 WA 0 0 32
[11] .bss NOBITS 003c2c20 3c2c20 02b2fc 00 WA 0 0 16
[12] .init.text PROGBITS 003ee000 3c4000 01a4b2 00 AX 0 0 4
[13] .init.data PROGBITS 004084b4 3de4b4 008180 00 WA 0 0 4
[14] .m68k_fixup PROGBITS 00410634 3e6634 001140 00 WA 0 0 1
[15] .notes NOTE 00411774 3e7774 000024 00 A 0 0 4
[16] .init_end NOBITS 00411798 3e7798 000868 00 WA 0 0 1
[17] .comment PROGBITS 00000000 3e7798 000039 01 MS 0 0 1
[18] .shstrtab STRTAB 00000000 524791 0000bd 00 0 0 1
[19] .symtab SYMTAB 00000000 3e77d4 0a66e0 10
20 32238 4
[20] .strtab STRTAB 00000000 48deb4 0968dd 00 0 0 1
Key to Flags:
W (write), A (alloc), X (execute), M (merge), S (strings)
I (info), L (link order), G (group), T (TLS), E (exclude), x (unknown)
O (extra OS processing required) o (OS specific), p (processor specific)

> To fix add in the missing SOFTIRQENTRY_TEXT section into the m68k linker
> scripts. I noticed that m68k is also missing the IRQENTRY_TEXT section,
> so this patch also adds an entry for that too.
>
> Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
> ---
> arch/m68k/kernel/vmlinux-nommu.lds | 2 ++
> arch/m68k/kernel/vmlinux-std.lds | 2 ++
> arch/m68k/kernel/vmlinux-sun3.lds | 2 ++
> 3 files changed, 6 insertions(+)
>
> diff --git a/arch/m68k/kernel/vmlinux-nommu.lds b/arch/m68k/kernel/vmlinux-nommu.lds
> index 3aa571a..cf6edda 100644
> --- a/arch/m68k/kernel/vmlinux-nommu.lds
> +++ b/arch/m68k/kernel/vmlinux-nommu.lds
> @@ -45,6 +45,8 @@ SECTIONS {
> .text : {
> HEAD_TEXT
> TEXT_TEXT
> + IRQENTRY_TEXT
> + SOFTIRQENTRY_TEXT
> SCHED_TEXT
> CPUIDLE_TEXT
> LOCK_TEXT
> diff --git a/arch/m68k/kernel/vmlinux-std.lds b/arch/m68k/kernel/vmlinux-std.lds
> index 89172b8..625a578 100644
> --- a/arch/m68k/kernel/vmlinux-std.lds
> +++ b/arch/m68k/kernel/vmlinux-std.lds
> @@ -16,6 +16,8 @@ SECTIONS
> .text : {
> HEAD_TEXT
> TEXT_TEXT
> + IRQENTRY_TEXT
> + SOFTIRQENTRY_TEXT
> SCHED_TEXT
> CPUIDLE_TEXT
> LOCK_TEXT
> diff --git a/arch/m68k/kernel/vmlinux-sun3.lds b/arch/m68k/kernel/vmlinux-sun3.lds
> index 293990e..9868270 100644
> --- a/arch/m68k/kernel/vmlinux-sun3.lds
> +++ b/arch/m68k/kernel/vmlinux-sun3.lds
> @@ -16,6 +16,8 @@ SECTIONS
> .text : {
> HEAD_TEXT
> TEXT_TEXT
> + IRQENTRY_TEXT
> + SOFTIRQENTRY_TEXT
> SCHED_TEXT
> CPUIDLE_TEXT
> LOCK_TEXT

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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