Date: Tue, 14 Mar 2017 20:43:04 +0000 (UTC) From: Mateusz Guzik <mjg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r315285 - in stable/11/sys: kern sys vm Message-ID: <201703142043.v2EKh4Wh038781@repo.freebsd.org>
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Author: mjg Date: Tue Mar 14 20:43:04 2017 New Revision: 315285 URL: https://svnweb.freebsd.org/changeset/base/315285 Log: MFC r312724,r312901,r312902: hwpmc: partially depessimize munmap handling if the module is not loaded HWPMC_HOOKS is enabled in GENERIC and triggers some work avoidable in the common (module not loaded) case. In particular this avoids permission checks + lock downgrade singlethreaded and in cases were an executable mapping is found the pmc sx lock is no longer bounced. Note this is a band aid. == hwpmc: partially depessimize mmap handling if the module is not loaded In particular this means the pmc sx lock is no longer taken when an executable mapping succeeds. == hwpmc: annotate pmc_hook and pmc_intr as __read_mostly Modified: stable/11/sys/kern/kern_pmc.c stable/11/sys/kern/vfs_vnops.c stable/11/sys/sys/pmckern.h stable/11/sys/vm/vm_mmap.c Directory Properties: stable/11/ (props changed) Modified: stable/11/sys/kern/kern_pmc.c ============================================================================== --- stable/11/sys/kern/kern_pmc.c Tue Mar 14 20:39:06 2017 (r315284) +++ stable/11/sys/kern/kern_pmc.c Tue Mar 14 20:43:04 2017 (r315285) @@ -59,10 +59,10 @@ MALLOC_DEFINE(M_PMCHOOKS, "pmchooks", "M const int pmc_kernel_version = PMC_KERNEL_VERSION; /* Hook variable. */ -int (*pmc_hook)(struct thread *td, int function, void *arg) = NULL; +int __read_mostly (*pmc_hook)(struct thread *td, int function, void *arg) = NULL; /* Interrupt handler */ -int (*pmc_intr)(int cpu, struct trapframe *tf) = NULL; +int __read_mostly (*pmc_intr)(int cpu, struct trapframe *tf) = NULL; /* Bitmask of CPUs requiring servicing at hardclock time */ volatile cpuset_t pmc_cpumask; Modified: stable/11/sys/kern/vfs_vnops.c ============================================================================== --- stable/11/sys/kern/vfs_vnops.c Tue Mar 14 20:39:06 2017 (r315284) +++ stable/11/sys/kern/vfs_vnops.c Tue Mar 14 20:43:04 2017 (r315285) @@ -2479,10 +2479,12 @@ vn_mmap(struct file *fp, vm_map_t map, v } #ifdef HWPMC_HOOKS /* Inform hwpmc(4) if an executable is being mapped. */ - if (error == 0 && (prot & VM_PROT_EXECUTE) != 0) { - pkm.pm_file = vp; - pkm.pm_address = (uintptr_t) *addr; - PMC_CALL_HOOK(td, PMC_FN_MMAP, (void *) &pkm); + if (PMC_HOOK_INSTALLED(PMC_FN_MMAP)) { + if ((prot & VM_PROT_EXECUTE) != 0 && error == 0) { + pkm.pm_file = vp; + pkm.pm_address = (uintptr_t) *addr; + PMC_CALL_HOOK(td, PMC_FN_MMAP, (void *) &pkm); + } } #endif return (error); Modified: stable/11/sys/sys/pmckern.h ============================================================================== --- stable/11/sys/sys/pmckern.h Tue Mar 14 20:39:06 2017 (r315284) +++ stable/11/sys/sys/pmckern.h Tue Mar 14 20:43:04 2017 (r315285) @@ -174,6 +174,9 @@ extern const int pmc_kernel_version; /* PMC soft per cpu trapframe */ extern struct trapframe pmc_tf[MAXCPU]; +/* Quick check if preparatory work is necessary */ +#define PMC_HOOK_INSTALLED(cmd) __predict_false(pmc_hook != NULL) + /* Hook invocation; for use within the kernel */ #define PMC_CALL_HOOK(t, cmd, arg) \ do { \ Modified: stable/11/sys/vm/vm_mmap.c ============================================================================== --- stable/11/sys/vm/vm_mmap.c Tue Mar 14 20:39:06 2017 (r315284) +++ stable/11/sys/vm/vm_mmap.c Tue Mar 14 20:43:04 2017 (r315285) @@ -500,6 +500,7 @@ kern_munmap(struct thread *td, uintptr_t #ifdef HWPMC_HOOKS struct pmckern_map_out pkm; vm_map_entry_t entry; + bool pmc_handled; #endif vm_offset_t addr; vm_size_t pageoff; @@ -524,20 +525,24 @@ kern_munmap(struct thread *td, uintptr_t return (EINVAL); vm_map_lock(map); #ifdef HWPMC_HOOKS - /* - * Inform hwpmc if the address range being unmapped contains - * an executable region. - */ - pkm.pm_address = (uintptr_t) NULL; - if (vm_map_lookup_entry(map, addr, &entry)) { - for (; - entry != &map->header && entry->start < addr + size; - entry = entry->next) { - if (vm_map_check_protection(map, entry->start, - entry->end, VM_PROT_EXECUTE) == TRUE) { - pkm.pm_address = (uintptr_t) addr; - pkm.pm_size = (size_t) size; - break; + pmc_handled = false; + if (PMC_HOOK_INSTALLED(PMC_FN_MUNMAP)) { + pmc_handled = true; + /* + * Inform hwpmc if the address range being unmapped contains + * an executable region. + */ + pkm.pm_address = (uintptr_t) NULL; + if (vm_map_lookup_entry(map, addr, &entry)) { + for (; + entry != &map->header && entry->start < addr + size; + entry = entry->next) { + if (vm_map_check_protection(map, entry->start, + entry->end, VM_PROT_EXECUTE) == TRUE) { + pkm.pm_address = (uintptr_t) addr; + pkm.pm_size = (size_t) size; + break; + } } } } @@ -545,14 +550,16 @@ kern_munmap(struct thread *td, uintptr_t vm_map_delete(map, addr, addr + size); #ifdef HWPMC_HOOKS - /* downgrade the lock to prevent a LOR with the pmc-sx lock */ - vm_map_lock_downgrade(map); - if (pkm.pm_address != (uintptr_t) NULL) - PMC_CALL_HOOK(td, PMC_FN_MUNMAP, (void *) &pkm); - vm_map_unlock_read(map); -#else - vm_map_unlock(map); + if (__predict_false(pmc_handled)) { + /* downgrade the lock to prevent a LOR with the pmc-sx lock */ + vm_map_lock_downgrade(map); + if (pkm.pm_address != (uintptr_t) NULL) + PMC_CALL_HOOK(td, PMC_FN_MUNMAP, (void *) &pkm); + vm_map_unlock_read(map); + } else #endif + vm_map_unlock(map); + /* vm_map_delete returns nothing but KERN_SUCCESS anyway */ return (0); }
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