On Fri, 10 Jul 2020 15:38:46 +0200 Peter Zijlstra <[email protected]> wrote:
> In order to use static_call() to wire up x86_pmu, we need to > initialize earlier; copy some of the tricks from jump_label to enable > this. > > Primarily we overload key->next to store a sites pointer when there > are no modules, this avoids having to use kmalloc() to initialize the > sites and allows us to run much earlier. > I'm confused. What was the need to have key->next store site pointers in order to move it up earlier? -- Steve > (arguably, this is much much earlier than needed for perf, but it > might allow other uses.) > > Signed-off-by: Peter Zijlstra (Intel) <[email protected]> > --- > arch/x86/kernel/setup.c | 2 + > arch/x86/kernel/static_call.c | 8 +++++- > include/linux/static_call.h | 15 +++++++++-- > kernel/static_call.c | 55 > +++++++++++++++++++++++++++++++++++++++--- > 4 files changed, 74 insertions(+), 6 deletions(-) > > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -19,6 +19,7 @@ > #include <linux/hugetlb.h> > #include <linux/tboot.h> > #include <linux/usb/xhci-dbgp.h> > +#include <linux/static_call.h> > > #include <uapi/linux/mount.h> > > @@ -848,6 +849,7 @@ void __init setup_arch(char **cmdline_p) > early_cpu_init(); > arch_init_ideal_nops(); > jump_label_init(); > + static_call_init(); > early_ioremap_init(); > > setup_olpc_ofw_pgd(); > --- a/arch/x86/kernel/static_call.c > +++ b/arch/x86/kernel/static_call.c > @@ -11,7 +11,7 @@ enum insn_type { > RET = 3, /* tramp / site cond-tail-call */ > }; > > -static void __static_call_transform(void *insn, enum insn_type type, void > *func) > +static void __ref __static_call_transform(void *insn, enum insn_type type, > void *func) > { > int size = CALL_INSN_SIZE; > const void *code; > @@ -33,11 +33,17 @@ static void __static_call_transform(void > code = text_gen_insn(RET_INSN_OPCODE, insn, func); > size = RET_INSN_SIZE; > break; > + > + default: /* GCC is a moron -- it figures @code can be uninitialized > below */ > + BUG(); > } > > if (memcmp(insn, code, size) == 0) > return; > > + if (unlikely(system_state == SYSTEM_BOOTING)) > + return text_poke_early(insn, code, size); > + > text_poke_bp(insn, code, size, NULL); > } > > --- a/include/linux/static_call.h > +++ b/include/linux/static_call.h > @@ -99,6 +99,8 @@ extern void arch_static_call_transform(v > > #ifdef CONFIG_HAVE_STATIC_CALL_INLINE > > +extern void __init static_call_init(void); > + > struct static_call_mod { > struct static_call_mod *next; > struct module *mod; /* for vmlinux, mod == NULL */ > @@ -107,7 +109,12 @@ struct static_call_mod { > > struct static_call_key { > void *func; > - struct static_call_mod *mods; > + union { > + /* bit 0: 0 = mods, 1 = sites */ > + unsigned long type; > + struct static_call_mod *mods; > + struct static_call_site *sites; > + }; > }; > > extern void __static_call_update(struct static_call_key *key, void *tramp, > void *func); > @@ -118,7 +125,7 @@ extern int static_call_text_reserved(voi > DECLARE_STATIC_CALL(name, _func); \ > struct static_call_key STATIC_CALL_KEY(name) = { \ > .func = _func, \ > - .mods = NULL, \ > + .type = 1, \ > }; \ > ARCH_DEFINE_STATIC_CALL_TRAMP(name, _func) > > @@ -143,6 +150,8 @@ extern int static_call_text_reserved(voi > > #elif defined(CONFIG_HAVE_STATIC_CALL) > > +static inline void static_call_init(void) { } > + > struct static_call_key { > void *func; > }; > @@ -188,6 +197,8 @@ static inline int static_call_text_reser > > #else /* Generic implementation */ > > +static inline void static_call_init(void) { } > + > struct static_call_key { > void *func; > }; > --- a/kernel/static_call.c > +++ b/kernel/static_call.c > @@ -94,10 +94,31 @@ static inline void static_call_sort_entr > static_call_site_cmp, static_call_site_swap); > } > > +static inline bool static_call_key_has_mods(struct static_call_key *key) > +{ > + return !(key->type & 1); > +} > + > +static inline struct static_call_mod *static_call_key_next(struct > static_call_key *key) > +{ > + if (!static_call_key_has_mods(key)) > + return NULL; > + > + return key->mods; > +} > + > +static inline struct static_call_site *static_call_key_sites(struct > static_call_key *key) > +{ > + if (static_call_key_has_mods(key)) > + return NULL; > + > + return (struct static_call_site *)(key->type & ~1); > +} > + > void __static_call_update(struct static_call_key *key, void *tramp, void > *func) > { > struct static_call_site *site, *stop; > - struct static_call_mod *site_mod; > + struct static_call_mod *site_mod, first; > > cpus_read_lock(); > static_call_lock(); > @@ -116,13 +137,22 @@ void __static_call_update(struct static_ > if (WARN_ON_ONCE(!static_call_initialized)) > goto done; > > - for (site_mod = key->mods; site_mod; site_mod = site_mod->next) { > + first = (struct static_call_mod){ > + .next = static_call_key_next(key), > + .mod = NULL, > + .sites = static_call_key_sites(key), > + }; > + > + for (site_mod = &first; site_mod; site_mod = site_mod->next) { > struct module *mod = site_mod->mod; > > if (!site_mod->sites) { > /* > * This can happen if the static call key is defined in > * a module which doesn't use it. > + * > + * It also happens in the has_mods case, where the > + * 'first' entry has no sites associated with it. > */ > continue; > } > @@ -192,16 +222,35 @@ static int __static_call_init(struct mod > if (key != prev_key) { > prev_key = key; > > + if (!mod) { > + key->sites = site; > + key->type |= 1; > + goto do_transform; > + } > + > site_mod = kzalloc(sizeof(*site_mod), GFP_KERNEL); > if (!site_mod) > return -ENOMEM; > > + if (!static_call_key_has_mods(key)) { > + site_mod->mod = NULL; > + site_mod->next = NULL; > + site_mod->sites = static_call_key_sites(key); > + > + key->mods = site_mod; > + > + site_mod = kzalloc(sizeof(*site_mod), > GFP_KERNEL); > + if (!site_mod) > + return -ENOMEM; > + } > + > site_mod->mod = mod; > site_mod->sites = site; > site_mod->next = key->mods; > key->mods = site_mod; > } > > +do_transform: > arch_static_call_transform(site_addr, NULL, key->func, > static_call_is_tail(site)); > } > @@ -344,7 +393,7 @@ int static_call_text_reserved(void *star > return ret; > } > > -static void __init static_call_init(void) > +void __init static_call_init(void) > { > int ret; > >
