Date: Sun, 14 May 2023 22:57:55 +0100 From: Jessica Clarke <jrtc27@freebsd.org> To: Dmitry Chagin <dchagin@FreeBSD.org> Cc: "src-committers@freebsd.org" <src-committers@FreeBSD.org>, "dev-commits-src-all@freebsd.org" <dev-commits-src-all@FreeBSD.org>, "dev-commits-src-main@freebsd.org" <dev-commits-src-main@FreeBSD.org> Subject: Re: git: d957343f8713 - main - linux(4): Rework signal trampoline on Aarch64 Message-ID: <BDF5B900-C28B-4F0A-B21D-7BA56856070A@freebsd.org> In-Reply-To: <202305142131.34ELV9OX074101@gitrepo.freebsd.org> References: <202305142131.34ELV9OX074101@gitrepo.freebsd.org>
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On 14 May 2023, at 22:31, Dmitry Chagin <dchagin@FreeBSD.org> wrote: >=20 > The branch main has been updated by dchagin: >=20 > URL: = https://cgit.FreeBSD.org/src/commit/?id=3Dd957343f8713a312442a0140b7a7752e= d7b2d870 >=20 > commit d957343f8713a312442a0140b7a7752ed7b2d870 > Author: Dmitry Chagin <dchagin@FreeBSD.org> > AuthorDate: 2023-05-14 21:27:31 +0000 > Commit: Dmitry Chagin <dchagin@FreeBSD.org> > CommitDate: 2023-05-14 21:27:31 +0000 >=20 > linux(4): Rework signal trampoline on Aarch64 >=20 > To avoid clobbering of any registers by the trampoline code use = Linux > way to call signal handlers. I.e., we are out from the kernel right = into > the signal handler, put return address from the signal handler into = the > link register. > The mysterious NOP is required for some unwinders (e.g. libc++) = that > unconditionally subtract one from the result of _Unwind_GetIP() in = order > to identify the calling function. >=20 > MFC after: 1 week So this is basically a revert of c56480a83235 "linux(4): Implement = signal trampoline for arm64 in a FreeBSD-way=E2=80=9D? Not a huge fan of this = flip-flopping without much justification and with no review. Jess > --- > sys/arm64/linux/linux_locore.asm | 5 +++-- > sys/arm64/linux/linux_sysvec.c | 6 +++--- > sys/arm64/linux/linux_vdso.lds.s | 1 + > 3 files changed, 7 insertions(+), 5 deletions(-) >=20 > diff --git a/sys/arm64/linux/linux_locore.asm = b/sys/arm64/linux/linux_locore.asm > index 6ebecef51b39..de3e5dd52a00 100644 > --- a/sys/arm64/linux/linux_locore.asm > +++ b/sys/arm64/linux/linux_locore.asm > @@ -45,10 +45,11 @@ linux_platform: >=20 > .text >=20 > - nop /* This is what Linux calls a "Mysterious NOP". */ > EENTRY(__kernel_rt_sigreturn) > - blr x8 > + nop /* This is what Linux calls a "Mysterious NOP". */ >=20 > + .globl __user_rt_sigreturn > +__user_rt_sigreturn: > mov x8, #LINUX_SYS_linux_rt_sigreturn > svc #0 > EEND(__kernel_rt_sigreturn) > diff --git a/sys/arm64/linux/linux_sysvec.c = b/sys/arm64/linux/linux_sysvec.c > index 299586e1c7b6..bb9ff25893eb 100644 > --- a/sys/arm64/linux/linux_sysvec.c > +++ b/sys/arm64/linux/linux_sysvec.c > @@ -118,7 +118,7 @@ LIN_SDT_PROBE_DEFINE0(sysvec, linux_exec_setregs, = todo); >=20 > LINUX_VDSO_SYM_CHAR(linux_platform); > LINUX_VDSO_SYM_INTPTR(kern_timekeep_base); > -LINUX_VDSO_SYM_INTPTR(__kernel_rt_sigreturn); > +LINUX_VDSO_SYM_INTPTR(__user_rt_sigreturn); >=20 > static int > linux_fetch_syscall_args(struct thread *td) > @@ -353,9 +353,9 @@ linux_rt_sendsig(sig_t catcher, ksiginfo_t *ksi, = sigset_t *mask) > tf->tf_x[2] =3D 0; > } > tf->tf_x[29] =3D (register_t)&fp->fp; > - tf->tf_x[8] =3D (register_t)catcher; > + tf->tf_elr =3D (register_t)catcher; > tf->tf_sp =3D (register_t)fp; > - tf->tf_elr =3D (register_t)__kernel_rt_sigreturn; > + tf->tf_lr =3D (register_t)__user_rt_sigreturn; >=20 > CTR3(KTR_SIG, "sendsig: return td=3D%p pc=3D%#x sp=3D%#x", td, = tf->tf_elr, > tf->tf_sp); > diff --git a/sys/arm64/linux/linux_vdso.lds.s = b/sys/arm64/linux/linux_vdso.lds.s > index 652b99545069..3f6b70c09176 100644 > --- a/sys/arm64/linux/linux_vdso.lds.s > +++ b/sys/arm64/linux/linux_vdso.lds.s > @@ -70,6 +70,7 @@ VERSION > global: > linux_platform; > kern_timekeep_base; > + __user_rt_sigreturn; > local: *; > }; > } Jess
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