| Message ID | 20240411120819.56417-1-thuth@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | [for-9.0] meson.build: Disable -fzero-call-used-regs on OpenBSD | expand |
On 11/04/2024 14.08, Thomas Huth wrote: > QEMU currently does not work on OpenBSD since the -fzero-call-used-regs That should be "OpenBSD 7.5" ... older versions are fine since they are using an older version of Clang that does not have -fzero-call-used-regs yet, I think. Thomas > option that we added to meson.build recently does not work with the > "retguard" extension from OpenBSD's Clang. Thus let's disable the > -fzero-call-used-regs here until there's a better solution available. > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2278 > Signed-off-by: Thomas Huth <thuth@redhat.com> > --- > Note: Given that we're close to the release, I think the host_os check > is the best we can do ... the problem does not seem to trigger in all > functions, only if certain registers are used by the compiler, so a > more sophisticated check here seems to be too fragile to me right now. > > meson.build | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/meson.build b/meson.build > index c9c3217ba4..91a0aa64c6 100644 > --- a/meson.build > +++ b/meson.build > @@ -562,7 +562,11 @@ hardening_flags = [ > # > # NB: Clang 17 is broken and SEGVs > # https://github.com/llvm/llvm-project/issues/75168 > -if cc.compiles('extern struct { void (*cb)(void); } s; void f(void) { s.cb(); }', > +# > +# NB2: This clashes with the "retguard" extension of OpenBSD's Clang > +# https://gitlab.com/qemu-project/qemu/-/issues/2278 > +if host_os != 'openbsd' and \ > + cc.compiles('extern struct { void (*cb)(void); } s; void f(void) { s.cb(); }', > name: '-fzero-call-used-regs=used-gpr', > args: ['-O2', '-fzero-call-used-regs=used-gpr']) > hardening_flags += '-fzero-call-used-regs=used-gpr'
On 11/4/24 14:08, Thomas Huth wrote: > QEMU currently does not work on OpenBSD since the -fzero-call-used-regs > option that we added to meson.build recently does not work with the > "retguard" extension from OpenBSD's Clang. Thus let's disable the > -fzero-call-used-regs here until there's a better solution available. > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2278 > Signed-off-by: Thomas Huth <thuth@redhat.com> > --- > Note: Given that we're close to the release, I think the host_os check > is the best we can do ... the problem does not seem to trigger in all > functions, only if certain registers are used by the compiler, so a > more sophisticated check here seems to be too fragile to me right now. > > meson.build | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/meson.build b/meson.build > index c9c3217ba4..91a0aa64c6 100644 > --- a/meson.build > +++ b/meson.build > @@ -562,7 +562,11 @@ hardening_flags = [ > # > # NB: Clang 17 is broken and SEGVs > # https://github.com/llvm/llvm-project/issues/75168 > -if cc.compiles('extern struct { void (*cb)(void); } s; void f(void) { s.cb(); }', > +# > +# NB2: This clashes with the "retguard" extension of OpenBSD's Clang > +# https://gitlab.com/qemu-project/qemu/-/issues/2278 > +if host_os != 'openbsd' and \ > + cc.compiles('extern struct { void (*cb)(void); } s; void f(void) { s.cb(); }', > name: '-fzero-call-used-regs=used-gpr', > args: ['-O2', '-fzero-call-used-regs=used-gpr']) > hardening_flags += '-fzero-call-used-regs=used-gpr' Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
On 4/11/2024 8:12 AM, Thomas Huth wrote: > On 11/04/2024 14.08, Thomas Huth wrote: >> QEMU currently does not work on OpenBSD since the -fzero-call-used-regs > > That should be "OpenBSD 7.5" ... older versions are fine since they > are using an older version of Clang that does not have > -fzero-call-used-regs yet, I think. About the compiler version that is correct. Between 7.4 and 7.5 we upgraded from Clang 13 to 16. -fzero-call-used-regs was added with the 15 release. https://github.com/llvm/llvm-project/commit/deaf22bc0e306bc44c70d2503e9364b5ed312c49 Retguard is also used to mitigate ROP exploits and is enabled by default. https://www.openbsd.org/papers/asiabsdcon2019-rop-paper.pdf
Queued, thanks. Paolo
diff --git a/meson.build b/meson.build index c9c3217ba4..91a0aa64c6 100644 --- a/meson.build +++ b/meson.build @@ -562,7 +562,11 @@ hardening_flags = [ # # NB: Clang 17 is broken and SEGVs # https://github.com/llvm/llvm-project/issues/75168 -if cc.compiles('extern struct { void (*cb)(void); } s; void f(void) { s.cb(); }', +# +# NB2: This clashes with the "retguard" extension of OpenBSD's Clang +# https://gitlab.com/qemu-project/qemu/-/issues/2278 +if host_os != 'openbsd' and \ + cc.compiles('extern struct { void (*cb)(void); } s; void f(void) { s.cb(); }', name: '-fzero-call-used-regs=used-gpr', args: ['-O2', '-fzero-call-used-regs=used-gpr']) hardening_flags += '-fzero-call-used-regs=used-gpr'
QEMU currently does not work on OpenBSD since the -fzero-call-used-regs option that we added to meson.build recently does not work with the "retguard" extension from OpenBSD's Clang. Thus let's disable the -fzero-call-used-regs here until there's a better solution available. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2278 Signed-off-by: Thomas Huth <thuth@redhat.com> --- Note: Given that we're close to the release, I think the host_os check is the best we can do ... the problem does not seem to trigger in all functions, only if certain registers are used by the compiler, so a more sophisticated check here seems to be too fragile to me right now. meson.build | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)