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linux/arch/x86/um/signal.c
Benjamin Berg 3f17fed214 um: switch to regset API and depend on XSTATE 
The PTRACE_GETREGSET API has now existed since Linux 2.6.33. The XSAVE
CPU feature should also be sufficiently common to be able to rely on it.

With this, define our internal FP state to be the hosts XSAVE data. Add
discovery for the hosts XSAVE size and place the FP registers at the end
of task_struct so that we can adjust the size at runtime.

Next we can implement the regset API on top and update the signal
handling as well as ptrace APIs to use them. Also switch coredump
creation to use the regset API and finally set HAVE_ARCH_TRACEHOOK.

This considerably improves the signal frames. Previously they might not
have contained all the registers (i386) and also did not have the
sizes and magic values set to the correct values to permit userspace to
decode the frame.

As a side effect, this will permit UML to run on hosts with newer CPU
extensions (such as AMX) that need even more register state.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241023094120.4083426-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2024-10-23 12:13:16 +02:00

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/*
* Copyright (C) 2003 PathScale, Inc.
* Copyright (C) 2003 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <linux/personality.h>
#include <linux/ptrace.h>
#include <linux/kernel.h>
#include <linux/syscalls.h>
#include <asm/unistd.h>
#include <linux/uaccess.h>
#include <asm/ucontext.h>
#include <frame_kern.h>
#include <registers.h>
#include <skas.h>
#include <linux/regset.h>
#include <asm/sigframe.h>
#ifdef CONFIG_X86_32
struct _xstate_64 {
struct _fpstate_64 fpstate;
struct _header xstate_hdr;
struct _ymmh_state ymmh;
/* New processor state extensions go here: */
};
#else
#define _xstate_64 _xstate
#endif
static int copy_sc_from_user(struct pt_regs *regs,
struct sigcontext __user *from)
{
struct _xstate_64 __user *from_fp64;
struct sigcontext sc;
int err;
/* Always make any pending restarted system calls return -EINTR */
current->restart_block.fn = do_no_restart_syscall;
err = copy_from_user(&sc, from, sizeof(sc));
if (err)
return err;
#define GETREG(regno, regname) regs->regs.gp[HOST_##regno] = sc.regname
#ifdef CONFIG_X86_32
GETREG(GS, gs);
GETREG(FS, fs);
GETREG(ES, es);
GETREG(DS, ds);
#endif
GETREG(DI, di);
GETREG(SI, si);
GETREG(BP, bp);
GETREG(SP, sp);
GETREG(BX, bx);
GETREG(DX, dx);
GETREG(CX, cx);
GETREG(AX, ax);
GETREG(IP, ip);
#ifdef CONFIG_X86_64
GETREG(R8, r8);
GETREG(R9, r9);
GETREG(R10, r10);
GETREG(R11, r11);
GETREG(R12, r12);
GETREG(R13, r13);
GETREG(R14, r14);
GETREG(R15, r15);
#endif
GETREG(CS, cs);
GETREG(EFLAGS, flags);
#ifdef CONFIG_X86_32
GETREG(SS, ss);
#endif
#undef GETREG
#ifdef CONFIG_X86_32
from_fp64 = ((void *)sc.fpstate) + offsetof(struct _fpstate_32, _fxsr_env);
#else
from_fp64 = (void *)sc.fpstate;
#endif
err = copy_from_user(regs->regs.fp, from_fp64, host_fp_size);
if (err)
return 1;
#ifdef CONFIG_X86_32
/* Data is duplicated and this copy is the important one */
err = copy_regset_from_user(current,
task_user_regset_view(current),
REGSET_FP_LEGACY, 0,
sizeof(struct user_i387_struct),
(void *)sc.fpstate);
if (err < 0)
return err;
#endif
return 0;
}
static int copy_sc_to_user(struct sigcontext __user *to,
struct _xstate __user *to_fp, struct pt_regs *regs,
unsigned long mask)
{
struct _xstate_64 __user *to_fp64;
struct sigcontext sc;
struct faultinfo * fi = &current->thread.arch.faultinfo;
int err;
memset(&sc, 0, sizeof(struct sigcontext));
#define PUTREG(regno, regname) sc.regname = regs->regs.gp[HOST_##regno]
#ifdef CONFIG_X86_32
PUTREG(GS, gs);
PUTREG(FS, fs);
PUTREG(ES, es);
PUTREG(DS, ds);
#endif
PUTREG(DI, di);
PUTREG(SI, si);
PUTREG(BP, bp);
PUTREG(SP, sp);
PUTREG(BX, bx);
PUTREG(DX, dx);
PUTREG(CX, cx);
PUTREG(AX, ax);
#ifdef CONFIG_X86_64
PUTREG(R8, r8);
PUTREG(R9, r9);
PUTREG(R10, r10);
PUTREG(R11, r11);
PUTREG(R12, r12);
PUTREG(R13, r13);
PUTREG(R14, r14);
PUTREG(R15, r15);
#endif
sc.cr2 = fi->cr2;
sc.err = fi->error_code;
sc.trapno = fi->trap_no;
PUTREG(IP, ip);
PUTREG(CS, cs);
PUTREG(EFLAGS, flags);
#ifdef CONFIG_X86_32
PUTREG(SP, sp_at_signal);
PUTREG(SS, ss);
#endif
#undef PUTREG
sc.oldmask = mask;
sc.fpstate = (unsigned long)to_fp;
err = copy_to_user(to, &sc, sizeof(struct sigcontext));
if (err)
return 1;
#ifdef CONFIG_X86_32
err = copy_regset_to_user(current,
task_user_regset_view(current),
REGSET_FP_LEGACY, 0,
sizeof(struct _fpstate_32), to_fp);
if (err < 0)
return err;
__put_user(X86_FXSR_MAGIC, &to_fp->fpstate.magic);
BUILD_BUG_ON(offsetof(struct _xstate, xstate_hdr) !=
offsetof(struct _xstate_64, xstate_hdr) +
offsetof(struct _fpstate_32, _fxsr_env));
to_fp64 = (void *)to_fp + offsetof(struct _fpstate_32, _fxsr_env);
#else
to_fp64 = to_fp;
#endif /* CONFIG_X86_32 */
if (copy_to_user(to_fp64, regs->regs.fp, host_fp_size))
return 1;
/*
* Put magic/size values for userspace. We do not bother to verify them
* later on, however, userspace needs them should it try to read the
* XSTATE data. And ptrace does not fill in these parts.
*/
BUILD_BUG_ON(sizeof(int) != FP_XSTATE_MAGIC2_SIZE);
#ifdef CONFIG_X86_32
__put_user(offsetof(struct _fpstate_32, _fxsr_env) +
host_fp_size + FP_XSTATE_MAGIC2_SIZE,
&to_fp64->fpstate.sw_reserved.extended_size);
#else
__put_user(host_fp_size + FP_XSTATE_MAGIC2_SIZE,
&to_fp64->fpstate.sw_reserved.extended_size);
#endif
__put_user(host_fp_size, &to_fp64->fpstate.sw_reserved.xstate_size);
__put_user(FP_XSTATE_MAGIC1, &to_fp64->fpstate.sw_reserved.magic1);
__put_user(FP_XSTATE_MAGIC2, (int *)((void *)to_fp64 + host_fp_size));
return 0;
}
#ifdef CONFIG_X86_32
static int copy_ucontext_to_user(struct ucontext __user *uc,
struct _xstate __user *fp, sigset_t *set,
unsigned long sp)
{
int err = 0;
err |= __save_altstack(&uc->uc_stack, sp);
err |= copy_sc_to_user(&uc->uc_mcontext, fp, &current->thread.regs, 0);
err |= copy_to_user(&uc->uc_sigmask, set, sizeof(*set));
return err;
}
int setup_signal_stack_sc(unsigned long stack_top, struct ksignal *ksig,
struct pt_regs *regs, sigset_t *mask)
{
size_t math_size = offsetof(struct _fpstate_32, _fxsr_env) +
host_fp_size + FP_XSTATE_MAGIC2_SIZE;
struct sigframe __user *frame;
void __user *restorer;
int err = 0, sig = ksig->sig;
unsigned long fp_to;
/* This is the same calculation as i386 - ((sp + 4) & 15) == 0 */
stack_top = ((stack_top + 4) & -16UL) - 4;
frame = (struct sigframe __user *) stack_top - 1;
if (!access_ok(frame, sizeof(*frame)))
return 1;
/* Add required space for math frame */
frame = (struct sigframe __user *)((unsigned long)frame - math_size);
restorer = frame->retcode;
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
err |= __put_user(restorer, (void **)&frame->pretcode);
err |= __put_user(sig, &frame->sig);
fp_to = (unsigned long)frame + sizeof(*frame);
err |= copy_sc_to_user(&frame->sc,
(struct _xstate __user *)fp_to,
regs, mask->sig[0]);
if (_NSIG_WORDS > 1)
err |= __copy_to_user(&frame->extramask, &mask->sig[1],
sizeof(frame->extramask));
/*
* This is popl %eax ; movl $,%eax ; int $0x80
*
* WE DO NOT USE IT ANY MORE! It's only left here for historical
* reasons and because gdb uses it as a signature to notice
* signal handler stack frames.
*/
err |= __put_user(0xb858, (short __user *)(frame->retcode+0));
err |= __put_user(__NR_sigreturn, (int __user *)(frame->retcode+2));
err |= __put_user(0x80cd, (short __user *)(frame->retcode+6));
if (err)
return err;
PT_REGS_SP(regs) = (unsigned long) frame;
PT_REGS_IP(regs) = (unsigned long) ksig->ka.sa.sa_handler;
PT_REGS_AX(regs) = (unsigned long) sig;
PT_REGS_DX(regs) = (unsigned long) 0;
PT_REGS_CX(regs) = (unsigned long) 0;
return 0;
}
int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
struct pt_regs *regs, sigset_t *mask)
{
size_t math_size = offsetof(struct _fpstate_32, _fxsr_env) +
host_fp_size + FP_XSTATE_MAGIC2_SIZE;
struct rt_sigframe __user *frame;
void __user *restorer;
int err = 0, sig = ksig->sig;
unsigned long fp_to;
stack_top &= -8UL;
frame = (struct rt_sigframe __user *) stack_top - 1;
if (!access_ok(frame, sizeof(*frame)))
return 1;
/* Add required space for math frame */
frame = (struct rt_sigframe __user *)((unsigned long)frame - math_size);
restorer = frame->retcode;
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
err |= __put_user(restorer, (void **)&frame->pretcode);
err |= __put_user(sig, &frame->sig);
err |= __put_user(&frame->info, (void **)&frame->pinfo);
err |= __put_user(&frame->uc, (void **)&frame->puc);
err |= copy_siginfo_to_user(&frame->info, &ksig->info);
fp_to = (unsigned long)frame + sizeof(*frame);
err |= copy_ucontext_to_user(&frame->uc, (struct _xstate __user *)fp_to,
mask, PT_REGS_SP(regs));
/*
* This is movl $,%eax ; int $0x80
*
* WE DO NOT USE IT ANY MORE! It's only left here for historical
* reasons and because gdb uses it as a signature to notice
* signal handler stack frames.
*/
err |= __put_user(0xb8, (char __user *)(frame->retcode+0));
err |= __put_user(__NR_rt_sigreturn, (int __user *)(frame->retcode+1));
err |= __put_user(0x80cd, (short __user *)(frame->retcode+5));
if (err)
return err;
PT_REGS_SP(regs) = (unsigned long) frame;
PT_REGS_IP(regs) = (unsigned long) ksig->ka.sa.sa_handler;
PT_REGS_AX(regs) = (unsigned long) sig;
PT_REGS_DX(regs) = (unsigned long) &frame->info;
PT_REGS_CX(regs) = (unsigned long) &frame->uc;
return 0;
}
SYSCALL_DEFINE0(sigreturn)
{
unsigned long sp = PT_REGS_SP(&current->thread.regs);
struct sigframe __user *frame = (struct sigframe __user *)(sp - 8);
sigset_t set;
struct sigcontext __user *sc = &frame->sc;
int sig_size = (_NSIG_WORDS - 1) * sizeof(unsigned long);
if (copy_from_user(&set.sig[0], &sc->oldmask, sizeof(set.sig[0])) ||
copy_from_user(&set.sig[1], frame->extramask, sig_size))
goto segfault;
set_current_blocked(&set);
if (copy_sc_from_user(&current->thread.regs, sc))
goto segfault;
/* Avoid ERESTART handling */
PT_REGS_SYSCALL_NR(&current->thread.regs) = -1;
return PT_REGS_SYSCALL_RET(&current->thread.regs);
segfault:
force_sig(SIGSEGV);
return 0;
}
#else
int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
struct pt_regs *regs, sigset_t *set)
{
unsigned long math_size = host_fp_size + FP_XSTATE_MAGIC2_SIZE;
struct rt_sigframe __user *frame;
int err = 0, sig = ksig->sig;
unsigned long fp_to;
frame = (struct rt_sigframe __user *)
round_down(stack_top - sizeof(struct rt_sigframe), 16);
/* Add required space for math frame */
frame = (struct rt_sigframe __user *)((unsigned long)frame - math_size);
/* Subtract 128 for a red zone and 8 for proper alignment */
frame = (struct rt_sigframe __user *) ((unsigned long) frame - 128 - 8);
if (!access_ok(frame, sizeof(*frame) + math_size))
goto out;
if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
err |= copy_siginfo_to_user(&frame->info, &ksig->info);
if (err)
goto out;
}
/* Create the ucontext. */
err |= __put_user(0, &frame->uc.uc_flags);
err |= __put_user(0, &frame->uc.uc_link);
err |= __save_altstack(&frame->uc.uc_stack, PT_REGS_SP(regs));
fp_to = (unsigned long)frame + sizeof(*frame);
err |= copy_sc_to_user(&frame->uc.uc_mcontext,
(struct _xstate __user *)fp_to,
regs, set->sig[0]);
err |= __put_user(fp_to, &frame->uc.uc_mcontext.fpstate);
if (sizeof(*set) == 16) {
err |= __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
err |= __put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]);
}
else
err |= __copy_to_user(&frame->uc.uc_sigmask, set,
sizeof(*set));
/*
* Set up to return from userspace. If provided, use a stub
* already in userspace.
*/
/* x86-64 should always use SA_RESTORER. */
if (ksig->ka.sa.sa_flags & SA_RESTORER)
err |= __put_user((void *)ksig->ka.sa.sa_restorer,
&frame->pretcode);
else
/* could use a vstub here */
return err;
if (err)
return err;
PT_REGS_SP(regs) = (unsigned long) frame;
PT_REGS_DI(regs) = sig;
/* In case the signal handler was declared without prototypes */
PT_REGS_AX(regs) = 0;
/*
* This also works for non SA_SIGINFO handlers because they expect the
* next argument after the signal number on the stack.
*/
PT_REGS_SI(regs) = (unsigned long) &frame->info;
PT_REGS_DX(regs) = (unsigned long) &frame->uc;
PT_REGS_IP(regs) = (unsigned long) ksig->ka.sa.sa_handler;
out:
return err;
}
#endif
SYSCALL_DEFINE0(rt_sigreturn)
{
unsigned long sp = PT_REGS_SP(&current->thread.regs);
struct rt_sigframe __user *frame =
(struct rt_sigframe __user *)(sp - sizeof(long));
struct ucontext __user *uc = &frame->uc;
sigset_t set;
if (copy_from_user(&set, &uc->uc_sigmask, sizeof(set)))
goto segfault;
set_current_blocked(&set);
if (copy_sc_from_user(&current->thread.regs, &uc->uc_mcontext))
goto segfault;
/* Avoid ERESTART handling */
PT_REGS_SYSCALL_NR(&current->thread.regs) = -1;
return PT_REGS_SYSCALL_RET(&current->thread.regs);
segfault:
force_sig(SIGSEGV);
return 0;
}
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