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Re: Re: [PATCH] linux-user/i386: Properly align signal frame
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From: |
fanwj |
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Subject: |
Re: Re: [PATCH] linux-user/i386: Properly align signal frame |
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Date: |
Fri, 26 May 2023 10:56:33 +0800 (GMT+08:00) |
"The beginning of the structure, with pretaddr, should be just below 16-byte
alignment."
It is incorrect! The beginning of the structure, with pretaddr not aligned as
16-byte!
On x86-64, It aligned as (16n - sizeof(void*)) because of instruction "call" !
> -----原始邮件-----
> 发件人: "Richard Henderson" <richard.henderson@linaro.org>
> 发送时间: 2023-05-24 13:50:43 (星期三)
> 收件人: qemu-devel@nongnu.org
> 抄送: fanwj@mail.ustc.edu.cn, laurent@vivier.eu
> 主题: Re: [PATCH] linux-user/i386: Properly align signal frame
>
> On 5/23/23 22:46, Richard Henderson wrote:
> > The beginning of the structure, with pretaddr, should be just below
> > 16-byte alignment. Disconnect fpstate from sigframe, just like the
> > kernel does.
> >
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> > linux-user/i386/signal.c | 104 +++++++++++++++++--------------
> > tests/tcg/x86_64/sigstack.c | 33 ++++++++++
> > tests/tcg/x86_64/Makefile.target | 1 +
> > 3 files changed, 90 insertions(+), 48 deletions(-)
> > create mode 100644 tests/tcg/x86_64/sigstack.c
>
> Oops, meant to add
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1648
>
> r~
>
> >
> > diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c
> > index 60fa07d6f9..c49467de78 100644
> > --- a/linux-user/i386/signal.c
> > +++ b/linux-user/i386/signal.c
> > @@ -191,16 +191,7 @@ struct sigframe {
> > struct target_fpstate fpstate_unused;
> > abi_ulong extramask[TARGET_NSIG_WORDS-1];
> > char retcode[8];
> > -
> > - /*
> > - * This field will be 16-byte aligned in memory. Applying QEMU_ALIGNED
> > - * to it ensures that the base of the frame has an appropriate
> > alignment
> > - * too.
> > - */
> > - struct target_fpstate fpstate QEMU_ALIGNED(8);
> > };
> > -#define TARGET_SIGFRAME_FXSAVE_OFFSET (
> > \
> > - offsetof(struct sigframe, fpstate) + TARGET_FPSTATE_FXSAVE_OFFSET)
> >
> > struct rt_sigframe {
> > abi_ulong pretcode;
> > @@ -210,27 +201,21 @@ struct rt_sigframe {
> > struct target_siginfo info;
> > struct target_ucontext uc;
> > char retcode[8];
> > - struct target_fpstate fpstate QEMU_ALIGNED(8);
> > };
> > -#define TARGET_RT_SIGFRAME_FXSAVE_OFFSET (
> > \
> > - offsetof(struct rt_sigframe, fpstate) + TARGET_FPSTATE_FXSAVE_OFFSET)
> > #else
> > -
> > struct rt_sigframe {
> > abi_ulong pretcode;
> > struct target_ucontext uc;
> > struct target_siginfo info;
> > - struct target_fpstate fpstate QEMU_ALIGNED(16);
> > };
> > -#define TARGET_RT_SIGFRAME_FXSAVE_OFFSET (
> > \
> > - offsetof(struct rt_sigframe, fpstate) + TARGET_FPSTATE_FXSAVE_OFFSET)
> > #endif
> >
> > /*
> > * Set up a signal frame.
> > */
> >
> > -static void xsave_sigcontext(CPUX86State *env, struct
> > target_fpstate_fxsave *fxsave,
> > +static void xsave_sigcontext(CPUX86State *env,
> > + struct target_fpstate_fxsave *fxsave,
> > abi_ulong fxsave_addr)
> > {
> > if (!(env->features[FEAT_1_ECX] & CPUID_EXT_XSAVE)) {
> > @@ -266,8 +251,9 @@ static void xsave_sigcontext(CPUX86State *env, struct
> > target_fpstate_fxsave *fxs
> > }
> >
> > static void setup_sigcontext(struct target_sigcontext *sc,
> > - struct target_fpstate *fpstate, CPUX86State *env, abi_ulong mask,
> > - abi_ulong fpstate_addr)
> > + struct target_fpstate *fpstate,
> > + CPUX86State *env, abi_ulong mask,
> > + abi_ulong fpstate_addr)
> > {
> > CPUState *cs = env_cpu(env);
> > #ifndef TARGET_X86_64
> > @@ -347,10 +333,11 @@ static void setup_sigcontext(struct target_sigcontext
> > *sc,
> > * Determine which stack to use..
> > */
> >
> > -static inline abi_ulong
> > -get_sigframe(struct target_sigaction *ka, CPUX86State *env, size_t
> > fxsave_offset)
> > +static abi_ulong get_sigframe(struct target_sigaction *ka, CPUX86State
> > *env,
> > + size_t *frame_size, abi_ulong *fpsave_addr)
> > {
> > - unsigned long esp;
> > + abi_ulong esp, orig;
> > + size_t fpsave_size;
> >
> > /* Default to using normal stack */
> > esp = get_sp_from_cpustate(env);
> > @@ -371,16 +358,23 @@ get_sigframe(struct target_sigaction *ka, CPUX86State
> > *env, size_t fxsave_offset
> > }
> > #endif
> > }
> > + orig = esp;
> >
> > - if (!(env->features[FEAT_1_EDX] & CPUID_FXSR)) {
> > - return (esp - (fxsave_offset + TARGET_FXSAVE_SIZE)) & -8ul;
> > - } else if (!(env->features[FEAT_1_ECX] & CPUID_EXT_XSAVE)) {
> > - return ((esp - TARGET_FXSAVE_SIZE) & -16ul) - fxsave_offset;
> > + if (!(env->features[FEAT_1_ECX] & CPUID_EXT_XSAVE)) {
> > + fpsave_size = TARGET_FXSAVE_SIZE;
> > + esp = ROUND_DOWN(esp - fpsave_size, 16);
> > } else {
> > - size_t xstate_size =
> > - xsave_area_size(env->xcr0, false) +
> > TARGET_FP_XSTATE_MAGIC2_SIZE;
> > - return ((esp - xstate_size) & -64ul) - fxsave_offset;
> > + fpsave_size = xsave_area_size(env->xcr0, false)
> > + + TARGET_FP_XSTATE_MAGIC2_SIZE;
> > + esp = ROUND_DOWN(esp - fpsave_size, 64);
> > }
> > + *fpsave_addr = esp;
> > +
> > + esp = esp - *frame_size + sizeof(abi_ulong);
> > + esp = ROUND_DOWN(esp, 16) - sizeof(abi_ulong);
> > +
> > + *frame_size = orig - esp;
> > + return esp;
> > }
> >
> > #ifndef TARGET_X86_64
> > @@ -405,26 +399,34 @@ void setup_frame(int sig, struct target_sigaction *ka,
> > target_sigset_t *set, CPUX86State *env)
> > {
> > abi_ulong frame_addr;
> > + abi_ulong fpstate_addr;
> > + size_t frame_size;
> > struct sigframe *frame;
> > + struct target_fpstate *fpstate;
> > int i;
> >
> > - frame_addr = get_sigframe(ka, env, TARGET_SIGFRAME_FXSAVE_OFFSET);
> > + frame_size = sizeof(struct sigframe);
> > + frame_addr = get_sigframe(ka, env, &frame_size, &fpstate_addr);
> > trace_user_setup_frame(env, frame_addr);
> >
> > - if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0))
> > + frame = lock_user(VERIFY_WRITE, frame_addr, frame_size, false);
> > + if (!frame) {
> > goto give_sigsegv;
> > + }
> > + fpstate = (void *)frame + (fpstate_addr - frame_addr);
> >
> > __put_user(sig, &frame->sig);
> >
> > - setup_sigcontext(&frame->sc, &frame->fpstate, env, set->sig[0],
> > - frame_addr + offsetof(struct sigframe, fpstate));
> > + setup_sigcontext(&frame->sc, fpstate, env, set->sig[0], fpstate_addr);
> >
> > - for(i = 1; i < TARGET_NSIG_WORDS; i++) {
> > + for (i = 1; i < TARGET_NSIG_WORDS; i++) {
> > __put_user(set->sig[i], &frame->extramask[i - 1]);
> > }
> >
> > - /* Set up to return from userspace. If provided, use a stub
> > - already in userspace. */
> > + /*
> > + * Set up to return from userspace.
> > + * If provided, use a stub already in userspace.
> > + */
> > if (ka->sa_flags & TARGET_SA_RESTORER) {
> > __put_user(ka->sa_restorer, &frame->pretcode);
> > } else {
> > @@ -443,11 +445,10 @@ void setup_frame(int sig, struct target_sigaction *ka,
> > cpu_x86_load_seg(env, R_CS, __USER_CS);
> > env->eflags &= ~TF_MASK;
> >
> > - unlock_user_struct(frame, frame_addr, 1);
> > -
> > + unlock_user(frame, frame_addr, frame_size);
> > return;
> >
> > -give_sigsegv:
> > + give_sigsegv:
> > force_sigsegv(sig);
> > }
> > #endif
> > @@ -458,17 +459,24 @@ void setup_rt_frame(int sig, struct target_sigaction
> > *ka,
> > target_sigset_t *set, CPUX86State *env)
> > {
> > abi_ulong frame_addr;
> > + abi_ulong fpstate_addr;
> > + size_t frame_size;
> > #ifndef TARGET_X86_64
> > abi_ulong addr;
> > #endif
> > struct rt_sigframe *frame;
> > + struct target_fpstate *fpstate;
> > int i;
> >
> > - frame_addr = get_sigframe(ka, env, TARGET_RT_SIGFRAME_FXSAVE_OFFSET);
> > + frame_size = sizeof(struct rt_sigframe);
> > + frame_addr = get_sigframe(ka, env, &frame_size, &fpstate_addr);
> > trace_user_setup_rt_frame(env, frame_addr);
> >
> > - if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0))
> > + frame = lock_user(VERIFY_WRITE, frame_addr, frame_size, false);
> > + if (!frame) {
> > goto give_sigsegv;
> > + }
> > + fpstate = (void *)frame + (fpstate_addr - frame_addr);
> >
> > /* These fields are only in rt_sigframe on 32 bit */
> > #ifndef TARGET_X86_64
> > @@ -490,10 +498,10 @@ void setup_rt_frame(int sig, struct target_sigaction
> > *ka,
> > }
> > __put_user(0, &frame->uc.tuc_link);
> > target_save_altstack(&frame->uc.tuc_stack, env);
> > - setup_sigcontext(&frame->uc.tuc_mcontext, &frame->fpstate, env,
> > - set->sig[0], frame_addr + offsetof(struct rt_sigframe,
> > fpstate));
> > + setup_sigcontext(&frame->uc.tuc_mcontext, fpstate, env,
> > + set->sig[0], fpstate_addr);
> >
> > - for(i = 0; i < TARGET_NSIG_WORDS; i++) {
> > + for (i = 0; i < TARGET_NSIG_WORDS; i++) {
> > __put_user(set->sig[i], &frame->uc.tuc_sigmask.sig[i]);
> > }
> >
> > @@ -533,15 +541,15 @@ void setup_rt_frame(int sig, struct target_sigaction
> > *ka,
> > cpu_x86_load_seg(env, R_SS, __USER_DS);
> > env->eflags &= ~TF_MASK;
> >
> > - unlock_user_struct(frame, frame_addr, 1);
> > -
> > + unlock_user(frame, frame_addr, frame_size);
> > return;
> >
> > -give_sigsegv:
> > + give_sigsegv:
> > force_sigsegv(sig);
> > }
> >
> > -static int xrstor_sigcontext(CPUX86State *env, struct
> > target_fpstate_fxsave *fxsave,
> > +static int xrstor_sigcontext(CPUX86State *env,
> > + struct target_fpstate_fxsave *fxsave,
> > abi_ulong fxsave_addr)
> > {
> > if (env->features[FEAT_1_ECX] & CPUID_EXT_XSAVE) {
> > diff --git a/tests/tcg/x86_64/sigstack.c b/tests/tcg/x86_64/sigstack.c
> > new file mode 100644
> > index 0000000000..06cb847569
> > --- /dev/null
> > +++ b/tests/tcg/x86_64/sigstack.c
> > @@ -0,0 +1,33 @@
> > +#include <stdlib.h>
> > +#include <assert.h>
> > +#include <signal.h>
> > +#include <stdint.h>
> > +
> > +void __attribute__((noinline)) bar(void)
> > +{
> > + exit(EXIT_SUCCESS);
> > +}
> > +
> > +void __attribute__((noinline, ms_abi)) foo(void)
> > +{
> > + /*
> > + * With ms_abi, there are call-saved xmm registers, which are forced
> > + * to the stack around the call to sysv_abi bar(). If the signal
> > + * stack frame is not properly aligned, movaps will raise #GP.
> > + */
> > + bar();
> > +}
> > +
> > +void sighandler(int num)
> > +{
> > + void* sp = __builtin_dwarf_cfa();
> > + assert((uintptr_t)sp % 16 == 0);
> > + foo();
> > +}
> > +
> > +int main(void)
> > +{
> > + signal(SIGUSR1, sighandler);
> > + raise(SIGUSR1);
> > + abort();
> > +}
> > diff --git a/tests/tcg/x86_64/Makefile.target
> > b/tests/tcg/x86_64/Makefile.target
> > index e64aab1b81..d961599f64 100644
> > --- a/tests/tcg/x86_64/Makefile.target
> > +++ b/tests/tcg/x86_64/Makefile.target
> > @@ -13,6 +13,7 @@ X86_64_TESTS += vsyscall
> > X86_64_TESTS += noexec
> > X86_64_TESTS += cmpxchg
> > X86_64_TESTS += adox
> > +X86_64_TESTS += sigstack
> > TESTS=$(MULTIARCH_TESTS) $(X86_64_TESTS) test-x86_64
> > else
> > TESTS=$(MULTIARCH_TESTS)
>