| Message ID | 20240731144428.5882-1-iii@linux.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | bsd-user/x86_64/target_arch_thread.h: Align stack | expand |
On 8/1/24 00:44, Ilya Leoshkevich wrote: > bsd-user qemu-x86_64 almost immediately dies with: > > qemu: 0x4002201a68: unhandled CPU exception 0xd - aborting > > on FreeBSD 14.1-RELEASE. This is an instruction that requires > alignment: > > (gdb) x/i 0x4002201a68 > 0x4002201a68: movaps %xmm0,-0x40(%rbp) > > and the argument is not aligned: > > (gdb) p/x env->regs[5] > $1 = 0x822443b58 > > A quick experiment shows that the userspace entry point expects > misaligned rsp: > > (gdb) starti > (gdb) p/x $rsp > $1 = 0x7fffffffeaa8 > > Emulate this behavior in bsd-user. > > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> > --- > bsd-user/x86_64/target_arch_thread.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/bsd-user/x86_64/target_arch_thread.h b/bsd-user/x86_64/target_arch_thread.h > index 52c28906d6d..25233443c14 100644 > --- a/bsd-user/x86_64/target_arch_thread.h > +++ b/bsd-user/x86_64/target_arch_thread.h > @@ -31,7 +31,7 @@ static inline void target_thread_init(struct target_pt_regs *regs, > struct image_info *infop) > { > regs->rax = 0; > - regs->rsp = infop->start_stack; > + regs->rsp = (infop->start_stack & ~0xfUL) - 8; The formula in sys/amd64/amd64/exec_machdep.c, exec_setregs is ((stack - 8) & ~0xful) + 8 With that, Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
Hmmm... All platforms likely need this.... Oh, they all have it except x86, both 32 and 64-bit.... but i386 is already properly aligned (at least in the FreeBSD kernel), so maybe that's not needed. On Wed, Jul 31, 2024 at 4:43 PM Richard Henderson < richard.henderson@linaro.org> wrote: > On 8/1/24 00:44, Ilya Leoshkevich wrote: > > bsd-user qemu-x86_64 almost immediately dies with: > > > > qemu: 0x4002201a68: unhandled CPU exception 0xd - aborting > > > > on FreeBSD 14.1-RELEASE. This is an instruction that requires > > alignment: > > > > (gdb) x/i 0x4002201a68 > > 0x4002201a68: movaps %xmm0,-0x40(%rbp) > > > > and the argument is not aligned: > > > > (gdb) p/x env->regs[5] > > $1 = 0x822443b58 > > > > A quick experiment shows that the userspace entry point expects > > misaligned rsp: > > > > (gdb) starti > > (gdb) p/x $rsp > > $1 = 0x7fffffffeaa8 > > > > Emulate this behavior in bsd-user. > > > > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> > > --- > > bsd-user/x86_64/target_arch_thread.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/bsd-user/x86_64/target_arch_thread.h > b/bsd-user/x86_64/target_arch_thread.h > > index 52c28906d6d..25233443c14 100644 > > --- a/bsd-user/x86_64/target_arch_thread.h > > +++ b/bsd-user/x86_64/target_arch_thread.h > > @@ -31,7 +31,7 @@ static inline void target_thread_init(struct > target_pt_regs *regs, > > struct image_info *infop) > > { > > regs->rax = 0; > > - regs->rsp = infop->start_stack; > > + regs->rsp = (infop->start_stack & ~0xfUL) - 8; > > The formula in sys/amd64/amd64/exec_machdep.c, exec_setregs is > > ((stack - 8) & ~0xful) + 8 > > With that, > Reviewed-by: Richard Henderson <richard.henderson@linaro.org> > Agreed. Reviewed-by: Warner Losh <imp@bsdimp.com> There's a *lot* that's missing on for amd64 emulation relative to the other platforms. Warner
On Wed, Jul 31, 2024 at 5:03 PM Warner Losh <imp@bsdimp.com> wrote: > Hmmm... All platforms likely need this.... > Oh, they all have it except x86, both 32 and 64-bit.... but i386 is > already properly aligned (at least in the > FreeBSD kernel), so maybe that's not needed. > > > On Wed, Jul 31, 2024 at 4:43 PM Richard Henderson < > richard.henderson@linaro.org> wrote: > >> On 8/1/24 00:44, Ilya Leoshkevich wrote: >> > bsd-user qemu-x86_64 almost immediately dies with: >> > >> > qemu: 0x4002201a68: unhandled CPU exception 0xd - aborting >> > >> > on FreeBSD 14.1-RELEASE. This is an instruction that requires >> > alignment: >> > >> > (gdb) x/i 0x4002201a68 >> > 0x4002201a68: movaps %xmm0,-0x40(%rbp) >> > >> > and the argument is not aligned: >> > >> > (gdb) p/x env->regs[5] >> > $1 = 0x822443b58 >> > >> > A quick experiment shows that the userspace entry point expects >> > misaligned rsp: >> > >> > (gdb) starti >> > (gdb) p/x $rsp >> > $1 = 0x7fffffffeaa8 >> > >> > Emulate this behavior in bsd-user. >> > >> > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> >> > --- >> > bsd-user/x86_64/target_arch_thread.h | 2 +- >> > 1 file changed, 1 insertion(+), 1 deletion(-) >> > >> > diff --git a/bsd-user/x86_64/target_arch_thread.h >> b/bsd-user/x86_64/target_arch_thread.h >> > index 52c28906d6d..25233443c14 100644 >> > --- a/bsd-user/x86_64/target_arch_thread.h >> > +++ b/bsd-user/x86_64/target_arch_thread.h >> > @@ -31,7 +31,7 @@ static inline void target_thread_init(struct >> target_pt_regs *regs, >> > struct image_info *infop) >> > { >> > regs->rax = 0; >> > - regs->rsp = infop->start_stack; >> > + regs->rsp = (infop->start_stack & ~0xfUL) - 8; >> >> The formula in sys/amd64/amd64/exec_machdep.c, exec_setregs is >> >> ((stack - 8) & ~0xful) + 8 >> >> With that, >> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> >> > > Agreed. > > Reviewed-by: Warner Losh <imp@bsdimp.com> > > There's a *lot* that's missing on for amd64 emulation relative to the > other platforms. > Forgot to mention that I've queued this change with Richard's suggested modification. Warner
diff --git a/bsd-user/x86_64/target_arch_thread.h b/bsd-user/x86_64/target_arch_thread.h index 52c28906d6d..25233443c14 100644 --- a/bsd-user/x86_64/target_arch_thread.h +++ b/bsd-user/x86_64/target_arch_thread.h @@ -31,7 +31,7 @@ static inline void target_thread_init(struct target_pt_regs *regs, struct image_info *infop) { regs->rax = 0; - regs->rsp = infop->start_stack; + regs->rsp = (infop->start_stack & ~0xfUL) - 8; regs->rip = infop->entry; regs->rdi = infop->start_stack; }
bsd-user qemu-x86_64 almost immediately dies with: qemu: 0x4002201a68: unhandled CPU exception 0xd - aborting on FreeBSD 14.1-RELEASE. This is an instruction that requires alignment: (gdb) x/i 0x4002201a68 0x4002201a68: movaps %xmm0,-0x40(%rbp) and the argument is not aligned: (gdb) p/x env->regs[5] $1 = 0x822443b58 A quick experiment shows that the userspace entry point expects misaligned rsp: (gdb) starti (gdb) p/x $rsp $1 = 0x7fffffffeaa8 Emulate this behavior in bsd-user. Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com> --- bsd-user/x86_64/target_arch_thread.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)