[Buildroot] [PATCH 1/2] toolchain: introduce BR2_TOOLCHAIN_HAS_GCC_BUG_104820

[Buildroot] [PATCH 1/2] toolchain: introduce BR2_TOOLCHAIN_HAS_GCC_BUG_104820

[Yegor Yefremov]

-fzero-call-used-regs is broken on MIPS before R6, which still has the
hi/lo registers: gcc either rejects -fzero-call-used-regs=used for
functions using them:

  sorry, unimplemented: argument 'used' is not supported for '-fzero-call-used-regs' on this target

or, depending on the code, the ABI and the optimization level, ICEs:

  during RTL pass: zero_call_used_regs
  channels.c:437:1: internal compiler error: in int_mode_for_mode, at stor-layout.cc:408

This has been reported upstream, and is still present in gcc 15.3.0:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104820
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104817

MIPS R6 doesn't have hi/lo and is not affected.

Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
---
 toolchain/Config.in | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/toolchain/Config.in b/toolchain/Config.in
index 4e6a8d7927..5f4c5f5fb7 100644
--- a/toolchain/Config.in
+++ b/toolchain/Config.in
@@ -210,6 +210,16 @@ config BR2_TOOLCHAIN_HAS_GCC_BUG_104028
 	bool
 	default y if BR2_m68k
 
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104820
+# ICE: on MIPS: in int_mode_for_mode, at stor-layout.cc:408 during
+# RTL pass: zero_call_used_regs. MIPS before R6 also rejects
+# -fzero-call-used-regs=used in functions using the hi/lo registers.
+# This bug still exists in gcc = 15.3.0
+config BR2_TOOLCHAIN_HAS_GCC_BUG_104820
+	bool
+	default y if (BR2_mips || BR2_mipsel || BR2_mips64 || BR2_mips64el) \
+		&& !BR2_MIPS_CPU_MIPS32R6 && !BR2_MIPS_CPU_MIPS64R6
+
 # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107728
 # https://sourceware.org/bugzilla/show_bug.cgi?id=29621
 config BR2_TOOLCHAIN_HAS_GCC_BUG_107728
-- 
2.34.1

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[Buildroot] [PATCH 2/2] package/openssh: fix build on MIPS before R6 at -O0

[Yegor Yefremov]

openssh fails to build on MIPS64 (n32/n64 ABI) before R6 with
BR2_OPTIMIZE_0:

  during RTL pass: zero_call_used_regs
  channels.c: In function 'channel_set_xtype':
  channels.c:437:1: internal compiler error: in int_mode_for_mode, at stor-layout.cc:408

Since version 9.6p1, openssh builds with -fzero-call-used-regs=used if
the compiler supports it. On MIPS before R6, gcc rejects this option or
ICEs on functions using the hi/lo registers (gcc bug 104820). The
configure check usually catches this, but at -O0 its test program
builds fine with n32/n64, so the option ends up being used.

Disable -fzero-call-used-regs on MIPS before R6, through the configure
cache variable already used for powerpc64le. This doesn't lose anything,
as the option is never usable there.

This issue has been present since commit 3c047ea463e2
("package/openssh: security bump to version 9.6p1"), which switched
from -fzero-call-used-regs=all (always rejected by the configure check
on MIPS before R6) to -fzero-call-used-regs=used. It therefore affects
2024.02 and later, including all maintained branches. The cache
variable only exists since openssh 10.1, so for branches with an older
openssh, --without-hardening would be needed instead.

Fixes:
https://autobuild.buildroot.org/results/68d260341341afb0dfb7244f641f5196df3649a8

Fixes: 3c047ea463e27ceaafde76d64406862c3322daa0 ("package/openssh: security bump to version 9.6p1")
Assisted-by: Claude:claude-opus-5-5
Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
---
 package/openssh/openssh.mk | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/package/openssh/openssh.mk b/package/openssh/openssh.mk
index 6808db9962..a0cd3168e0 100644
--- a/package/openssh/openssh.mk
+++ b/package/openssh/openssh.mk
@@ -36,7 +36,9 @@ define OPENSSH_PERMISSIONS
 	/var/empty d 755 root root - - - - -
 endef
 
-ifeq ($(BR2_powerpc64le),y)
+# -fzero-call-used-regs=used is not supported on powerpc64le and makes
+# gcc ICE on MIPS before R6
+ifneq ($(BR2_powerpc64le)$(BR2_TOOLCHAIN_HAS_GCC_BUG_104820),)
 OPENSSH_CONF_ENV += ossh_cv_cflag__fzero_call_used_regs_used=no
 endif
 
-- 
2.34.1

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Re: [Buildroot] [PATCH 1/2] toolchain: introduce BR2_TOOLCHAIN_HAS_GCC_BUG_104820

[Thomas Petazzoni via buildroot]

On Sat, Oct 24, 2026 at 11:50:08PM +0200, Yegor Yefremov wrote:
> -fzero-call-used-regs is broken on MIPS before R6, which still has the
> hi/lo registers: gcc either rejects -fzero-call-used-regs=used for
> functions using them:
> 
>   sorry, unimplemented: argument 'used' is not supported for '-fzero-call-used-regs' on this target
> 
> or, depending on the code, the ABI and the optimization level, ICEs:
> 
>   during RTL pass: zero_call_used_regs
>   channels.c:437:1: internal compiler error: in int_mode_for_mode, at stor-layout.cc:408
> 
> This has been reported upstream, and is still present in gcc 15.3.0:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104820
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104817
> 
> MIPS R6 doesn't have hi/lo and is not affected.
> 
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>

Series applied to master, thanks!

Best regards,

Thomas Petazzoni
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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