| Message ID | 20230515083323.1358039-4-bugaevc@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | x86_64-gnu signal fixes | expand |
Applied, thanks! Sergey Bugaev, le lun. 15 mai 2023 11:33:22 +0300, a ecrit: > The real i386_thread_state Mach structure has an alignment of 8 on > x86_64. However, in struct sigcontext, the compiler was packing sc_gs > (which is the first member of sc_i386_thread_state) into the same 8-byte > slot as sc_error; this resulted in the rest of sc_i386_thread_state > members having wrong offsets relative to each other, and the overall > sc_i386_thread_state layout mismatching that of i386_thread_state. > > Fix this by explicitly adding the required padding members, and > statically asserting that this results in the desired alignment. > > The same goes for sc_i386_float_state. > > Checked on x86_64-gnu. > > Signed-off-by: Sergey Bugaev <bugaevc@gmail.com> > --- > sysdeps/mach/hurd/x86/trampoline.c | 6 ++++++ > sysdeps/mach/hurd/x86_64/bits/sigcontext.h | 8 ++++++++ > 2 files changed, 14 insertions(+) > > diff --git a/sysdeps/mach/hurd/x86/trampoline.c b/sysdeps/mach/hurd/x86/trampoline.c > index 1f92064e..6318c952 100644 > --- a/sysdeps/mach/hurd/x86/trampoline.c > +++ b/sysdeps/mach/hurd/x86/trampoline.c > @@ -242,11 +242,17 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, const struct sigaction *action > > /* struct sigcontext is laid out so that starting at sc_gs mimics a > struct i386_thread_state. */ > + _Static_assert (offsetof (struct sigcontext, sc_i386_thread_state) > + % __alignof__ (struct i386_thread_state) == 0, > + "sc_i386_thread_state layout mismatch"); > memcpy (&scp->sc_i386_thread_state, > &state->basic, sizeof (state->basic)); > > /* struct sigcontext is laid out so that starting at sc_fpkind mimics > a struct i386_float_state. */ > + _Static_assert (offsetof (struct sigcontext, sc_i386_float_state) > + % __alignof__ (struct i386_float_state) == 0, > + "sc_i386_float_state layout mismatch"); > ok = machine_get_state (ss->thread, state, i386_FLOAT_STATE, > &state->fpu, &scp->sc_i386_float_state, > sizeof (state->fpu)); > diff --git a/sysdeps/mach/hurd/x86_64/bits/sigcontext.h b/sysdeps/mach/hurd/x86_64/bits/sigcontext.h > index 3a3b34bc..63960544 100644 > --- a/sysdeps/mach/hurd/x86_64/bits/sigcontext.h > +++ b/sysdeps/mach/hurd/x86_64/bits/sigcontext.h > @@ -46,6 +46,11 @@ struct sigcontext > /* Error code associated with this signal (interpreted as `error_t'). */ > int sc_error; > > + /* Make sure the below members are properly aligned, and not packed > + together with sc_error -- otherwise the layout won't match that of > + i386_thread_state. */ > + int sc_pad1; > + > /* All following members are machine-dependent. The rest of this > structure is written to be laid out identically to: > { > @@ -86,6 +91,9 @@ struct sigcontext > long sc_ursp; /* This stack pointer is used. */ > int sc_ss; /* Stack segment register. */ > > + /* Make sure the below has the same layout as i386_float_state. */ > + int sc_pad2; > + > /* Following mimics struct i386_float_state. Structures and symbolic > values can be found in <mach/i386/fp_reg.h>. */ > #define sc_i386_float_state sc_fpkind > -- > 2.40.1 > >
diff --git a/sysdeps/mach/hurd/x86/trampoline.c b/sysdeps/mach/hurd/x86/trampoline.c index 1f92064e..6318c952 100644 --- a/sysdeps/mach/hurd/x86/trampoline.c +++ b/sysdeps/mach/hurd/x86/trampoline.c @@ -242,11 +242,17 @@ _hurd_setup_sighandler (struct hurd_sigstate *ss, const struct sigaction *action /* struct sigcontext is laid out so that starting at sc_gs mimics a struct i386_thread_state. */ + _Static_assert (offsetof (struct sigcontext, sc_i386_thread_state) + % __alignof__ (struct i386_thread_state) == 0, + "sc_i386_thread_state layout mismatch"); memcpy (&scp->sc_i386_thread_state, &state->basic, sizeof (state->basic)); /* struct sigcontext is laid out so that starting at sc_fpkind mimics a struct i386_float_state. */ + _Static_assert (offsetof (struct sigcontext, sc_i386_float_state) + % __alignof__ (struct i386_float_state) == 0, + "sc_i386_float_state layout mismatch"); ok = machine_get_state (ss->thread, state, i386_FLOAT_STATE, &state->fpu, &scp->sc_i386_float_state, sizeof (state->fpu)); diff --git a/sysdeps/mach/hurd/x86_64/bits/sigcontext.h b/sysdeps/mach/hurd/x86_64/bits/sigcontext.h index 3a3b34bc..63960544 100644 --- a/sysdeps/mach/hurd/x86_64/bits/sigcontext.h +++ b/sysdeps/mach/hurd/x86_64/bits/sigcontext.h @@ -46,6 +46,11 @@ struct sigcontext /* Error code associated with this signal (interpreted as `error_t'). */ int sc_error; + /* Make sure the below members are properly aligned, and not packed + together with sc_error -- otherwise the layout won't match that of + i386_thread_state. */ + int sc_pad1; + /* All following members are machine-dependent. The rest of this structure is written to be laid out identically to: { @@ -86,6 +91,9 @@ struct sigcontext long sc_ursp; /* This stack pointer is used. */ int sc_ss; /* Stack segment register. */ + /* Make sure the below has the same layout as i386_float_state. */ + int sc_pad2; + /* Following mimics struct i386_float_state. Structures and symbolic values can be found in <mach/i386/fp_reg.h>. */ #define sc_i386_float_state sc_fpkind
The real i386_thread_state Mach structure has an alignment of 8 on x86_64. However, in struct sigcontext, the compiler was packing sc_gs (which is the first member of sc_i386_thread_state) into the same 8-byte slot as sc_error; this resulted in the rest of sc_i386_thread_state members having wrong offsets relative to each other, and the overall sc_i386_thread_state layout mismatching that of i386_thread_state. Fix this by explicitly adding the required padding members, and statically asserting that this results in the desired alignment. The same goes for sc_i386_float_state. Checked on x86_64-gnu. Signed-off-by: Sergey Bugaev <bugaevc@gmail.com> --- sysdeps/mach/hurd/x86/trampoline.c | 6 ++++++ sysdeps/mach/hurd/x86_64/bits/sigcontext.h | 8 ++++++++ 2 files changed, 14 insertions(+)