Messages in this thread | | | From | Thomas Meyer <> | Subject | Re: [PATCH v2] um: Allow building and running on older hosts | Date | Thu, 25 May 2017 21:51:53 +0200 |
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> Am 25.05.2017 um 20:36 schrieb Florian Fainelli <f.fainelli@gmail.com>: > > Commit a78ff1112263 ("um: add extended processor state save/restore > support") and b6024b21fec8 ("um: extend fpstate to _xstate to support > YMM registers") forced the use of the x86 FP _xstate and > PTRACE_GETREGSET/SETREGSET. On older hosts, we would neither be able to > build UML nor run it anymore with these two commits applied because we > don't have definitions for struct _xstate nor these two ptrace requests.
Btw. what soy you mean with older host? I need to revert two commits to make an UML kernel work again on a Fedora 25 installation.
> > We can determine at build time which fp context structure to check > against, just like we can keep using the old i387 fp save/restore if > PTRACE_GETRESET/SETREGSET are not defined. > > Fixes: a78ff1112263 ("um: add extended processor state save/restore support") > Fixes: b6024b21fec8 ("um: extend fpstate to _xstate to support YMM registers") > Signed-off-by: Florian Fainelli <f.fainelli@gmail.com> > --- > Changes in v2: > > - re-arrange the #ifdef/curly braces to not take the branch > > arch/x86/um/os-Linux/registers.c | 12 ++++++++---- > arch/x86/um/user-offsets.c | 4 ++++ > 2 files changed, 12 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/um/os-Linux/registers.c b/arch/x86/um/os-Linux/registers.c > index 00f54a91bb4b..28775f55bde2 100644 > --- a/arch/x86/um/os-Linux/registers.c > +++ b/arch/x86/um/os-Linux/registers.c > @@ -26,6 +26,7 @@ int save_i387_registers(int pid, unsigned long *fp_regs) > > int save_fp_registers(int pid, unsigned long *fp_regs) > { > +#ifdef PTRACE_GETREGSET > struct iovec iov; > > if (have_xstate_support) { > @@ -34,9 +35,9 @@ int save_fp_registers(int pid, unsigned long *fp_regs) > if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0) > return -errno; > return 0; > - } else { > + } else > +#endif > return save_i387_registers(pid, fp_regs); > - } > } > > int restore_i387_registers(int pid, unsigned long *fp_regs) > @@ -48,6 +49,7 @@ int restore_i387_registers(int pid, unsigned long *fp_regs) > > int restore_fp_registers(int pid, unsigned long *fp_regs) > { > +#ifdef PTRACE_SETREGSET > struct iovec iov; > > if (have_xstate_support) { > @@ -56,9 +58,9 @@ int restore_fp_registers(int pid, unsigned long *fp_regs) > if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0) > return -errno; > return 0; > - } else { > + } else > +#endif > return restore_i387_registers(pid, fp_regs); > - } > } > > #ifdef __i386__ > @@ -122,6 +124,7 @@ int put_fp_registers(int pid, unsigned long *regs) > > void arch_init_registers(int pid) > { > +#ifdef PTRACE_GETREGSET > struct _xstate fp_regs; > struct iovec iov; > > @@ -129,6 +132,7 @@ void arch_init_registers(int pid) > iov.iov_len = sizeof(struct _xstate); > if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) == 0) > have_xstate_support = 1;
In my setup above call works correctly and so have_xstate_support will be set, but save_fp_registers fails with errno 4 or so...
> +#endif > } > #endif > > diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c > index cb3c22370cf5..8af0fb5d2780 100644 > --- a/arch/x86/um/user-offsets.c > +++ b/arch/x86/um/user-offsets.c > @@ -50,7 +50,11 @@ void foo(void) > DEFINE(HOST_GS, GS); > DEFINE(HOST_ORIG_AX, ORIG_EAX); > #else > +#if defined(PTRACE_GETREGSET) && defined(PTRACE_SETREGSET) > DEFINE(HOST_FP_SIZE, sizeof(struct _xstate) / sizeof(unsigned long)); > +#else > + DEFINE(HOST_FP_SIZE, sizeof(struct _fpstate) / sizeof(unsigned long)); > +#endif > DEFINE_LONGS(HOST_BX, RBX); > DEFINE_LONGS(HOST_CX, RCX); > DEFINE_LONGS(HOST_DI, RDI); > -- > 2.12.2 > [unhandled content-type:application/pkcs7-signature]
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