This patch adds the top level perfmon system calls.
Signed-off-by: Stephane Eranian <[email protected]>
--
Index: o3/perfmon/perfmon_syscalls.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ o3/perfmon/perfmon_syscalls.c 2008-11-25 17:55:04.000000000 +0100
@@ -0,0 +1,741 @@
+/*
+ * perfmon_syscalls.c: perfmon2 system call interface
+ *
+ * This file implements the perfmon2 interface which
+ * provides access to the hardware performance counters
+ * of the host processor.
+ *
+ * The initial version of perfmon.c was written by
+ * Ganesh Venkitachalam, IBM Corp.
+ *
+ * Then it was modified for perfmon-1.x by Stephane Eranian and
+ * David Mosberger, Hewlett Packard Co.
+ *
+ * Version Perfmon-2.x is a complete rewrite of perfmon-1.x
+ * by Stephane Eranian, Hewlett Packard Co.
+ *
+ * Copyright (c) 1999-2006 Hewlett-Packard Development Company, L.P.
+ * Contributed by Stephane Eranian <[email protected]>
+ * David Mosberger-Tang <[email protected]>
+ *
+ * More information about perfmon available at:
+ * http://perfmon2.sf.net
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of version 2 of the GNU General Public
+ * License as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ * 02111-1307 USA
+ */
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/ptrace.h>
+#include <linux/perfmon_kern.h>
+#include <linux/uaccess.h>
+#include "perfmon_priv.h"
+
+/*
+ * Context locking rules:
+ * ---------------------
+ * - any thread with access to the file descriptor of a context can
+ * potentially issue perfmon calls
+ *
+ * - calls must be serialized to guarantee correctness
+ *
+ * - as soon as a context is attached to a thread or CPU, it may be
+ * actively monitoring. On some architectures, such as IA-64, this
+ * is true even though the pfm_start() call has not been made. This
+ * comes from the fact that on some architectures, it is possible to
+ * start/stop monitoring from userland.
+ *
+ * - If monitoring is active, then there can PMU interrupts. Because
+ * context accesses must be serialized, the perfmon system calls
+ * must mask interrupts as soon as the context is attached.
+ *
+ * - perfmon system calls that operate with the context unloaded cannot
+ * assume it is actually unloaded when they are called. They first need
+ * to check and for that they need interrupts masked. Then, if the
+ * context is actually unloaded, they can unmask interrupts.
+ *
+ * - interrupt masking holds true for other internal perfmon functions as
+ * well. Except for PMU interrupt handler because those interrupts
+ * cannot be nested.
+ *
+ * - we mask ALL interrupts instead of just the PMU interrupt because we
+ * also need to protect against timer interrupts which could trigger
+ * a set switch.
+ */
+
+struct pfm_syscall_cookie {
+ struct file *filp;
+ int fput_needed;
+};
+
+/*
+ * cannot attach if :
+ * - kernel task
+ * - task not owned by caller (checked by ptrace_may_attach())
+ * - task is dead or zombie
+ * - cannot use blocking notification when self-monitoring
+ */
+static int pfm_task_incompatible(struct pfm_context *ctx,
+ struct task_struct *task)
+{
+ /*
+ * cannot attach to a kernel thread
+ */
+ if (!task->mm) {
+ PFM_DBG("cannot attach to kernel thread [%d]", task->pid);
+ return -EPERM;
+ }
+
+ /*
+ * cannot attach to a zombie task
+ */
+ if (task->exit_state == EXIT_ZOMBIE || task->exit_state == EXIT_DEAD) {
+ PFM_DBG("cannot attach to zombie/dead task [%d]", task->pid);
+ return -EBUSY;
+ }
+ return 0;
+}
+
+/**
+ * pfm_get_task -- check permission and acquire task to monitor
+ * @ctx: perfmon context
+ * @pid: identification of the task to check
+ * @task: upon return, a pointer to the task to monitor
+ *
+ * This function is used in per-thread mode only AND when not
+ * self-monitoring. It finds the task to monitor and checks
+ * that the caller has permissions to attach. It also checks
+ * that the task is stopped via ptrace so that we can safely
+ * modify its state.
+ *
+ * task refcount is incremented when succesful.
+ */
+static int pfm_get_task(struct pfm_context *ctx, pid_t pid,
+ struct task_struct **task)
+{
+ struct task_struct *p;
+ int ret = 0, ret1 = 0;
+
+ /*
+ * When attaching to another thread we must ensure
+ * that the thread is actually stopped. Just like with
+ * perfmon system calls, we enforce that the thread
+ * be ptraced and STOPPED by using ptrace_check_attach().
+ *
+ * As a consequence, only the ptracing parent can actually
+ * attach a context to a thread. Obviously, this constraint
+ * does not exist for self-monitoring threads.
+ *
+ * We use ptrace_may_access() to check for permission.
+ */
+ read_lock(&tasklist_lock);
+
+ p = find_task_by_vpid(pid);
+ if (p)
+ get_task_struct(p);
+
+ read_unlock(&tasklist_lock);
+
+ if (!p) {
+ PFM_DBG("task not found %d", pid);
+ return -ESRCH;
+ }
+
+ ret = -EPERM;
+
+ /*
+ * returns 0 if cannot attach
+ */
+ ret1 = ptrace_may_access(p, PTRACE_MODE_ATTACH);
+ if (ret1)
+ ret = ptrace_check_attach(p, 0);
+
+ PFM_DBG("may_attach=%d check_attach=%d", ret1, ret);
+
+ if (ret || !ret1)
+ goto error;
+
+ ret = pfm_task_incompatible(ctx, p);
+ if (ret)
+ goto error;
+
+ *task = p;
+
+ return 0;
+error:
+ if (!(ret1 || ret))
+ ret = -EPERM;
+
+ put_task_struct(p);
+
+ return ret;
+}
+
+/*
+ * context must be locked when calling this function
+ */
+int __pfm_check_task_state(struct pfm_context *ctx, int check_mask,
+ unsigned long *flags)
+{
+ struct task_struct *task;
+ unsigned long local_flags, new_flags;
+ int state, ret;
+
+recheck:
+ /*
+ * task is NULL for system-wide context
+ */
+ task = ctx->task;
+ state = ctx->state;
+ local_flags = *flags;
+
+ PFM_DBG("state=%d check_mask=0x%x task=[%d]",
+ state, check_mask, task ? task->pid:-1);
+ /*
+ * if the context is detached, then we do not touch
+ * hardware, therefore there is not restriction on when we can
+ * access it.
+ */
+ if (state == PFM_CTX_UNLOADED)
+ return 0;
+ /*
+ * no command can operate on a zombie context.
+ * A context becomes zombie when the file that identifies
+ * it is closed while the context is still attached to the
+ * thread it monitors.
+ */
+ if (state == PFM_CTX_ZOMBIE)
+ return -EINVAL;
+
+ /*
+ * at this point, state is PFM_CTX_LOADED
+ */
+
+ /*
+ * some commands require the context to be unloaded to operate
+ */
+ if (check_mask & PFM_CMD_UNLOADED) {
+ PFM_DBG("state=%d, cmd needs context unloaded", state);
+ return -EBUSY;
+ }
+
+ /*
+ * self-monitoring always ok.
+ */
+ if (task == current)
+ return 0;
+
+ /*
+ * at this point, monitoring another thread
+ */
+
+ /*
+ * When we operate on another thread, we must wait for it to be
+ * stopped and completely off any CPU as we need to access the
+ * PMU state (or machine state).
+ *
+ * A thread can be put in the STOPPED state in various ways
+ * including PTRACE_ATTACH, or when it receives a SIGSTOP signal.
+ * We enforce that the thread must be ptraced, so it is stopped
+ * AND it CANNOT wake up while we operate on it because this
+ * would require an action from the ptracing parent which is the
+ * thread that is calling this function.
+ *
+ * The dependency on ptrace, imposes that only the ptracing
+ * parent can issue command on a thread. This is unfortunate
+ * but we do not know of a better way of doing this.
+ */
+ if (check_mask & PFM_CMD_STOPPED) {
+
+ spin_unlock_irqrestore(&ctx->lock, local_flags);
+
+ /*
+ * check that the thread is ptraced AND STOPPED
+ */
+ ret = ptrace_check_attach(task, 0);
+
+ spin_lock_irqsave(&ctx->lock, new_flags);
+
+ /*
+ * flags may be different than when we released the lock
+ */
+ *flags = new_flags;
+
+ if (ret)
+ return ret;
+ /*
+ * we must recheck to verify if state has changed
+ */
+ if (unlikely(ctx->state != state)) {
+ PFM_DBG("old_state=%d new_state=%d",
+ state,
+ ctx->state);
+ goto recheck;
+ }
+ }
+ return 0;
+}
+
+int pfm_check_task_state(struct pfm_context *ctx, int check_mask,
+ unsigned long *flags)
+{
+ int ret;
+ ret = __pfm_check_task_state(ctx, check_mask, flags);
+ PFM_DBG("ret=%d",ret);
+ return ret;
+}
+
+/**
+ * pfm_get_args - Function used to copy the syscall argument into kernel memory
+ * @ureq: user argument
+ * @sz: user argument size
+ * @lsz: size of stack buffer
+ * @laddr: stack buffer address
+ * @req: point to start of kernel copy of the argument
+ * @ptr_free: address of kernel copy to free
+ *
+ * There are two options:
+ * - use a stack buffer described by laddr (addresses) and lsz (size)
+ * - allocate memory
+ *
+ * return:
+ * < 0 : in case of error (ptr_free may not be updated)
+ * 0 : success
+ * - req: points to base of kernel copy of arguments
+ * - ptr_free: address of buffer to free by caller on exit.
+ * NULL if using the stack buffer
+ *
+ * when ptr_free is not NULL upon return, the caller must kfree()
+ */
+int pfm_get_args(void __user *ureq, size_t sz, size_t lsz, void *laddr,
+ void **req, void **ptr_free)
+{
+ void *addr;
+
+ /*
+ * check syadmin argument limit
+ */
+ if (unlikely(sz > pfm_controls.arg_mem_max)) {
+ PFM_DBG("argument too big %zu max=%zu",
+ sz,
+ pfm_controls.arg_mem_max);
+ return -E2BIG;
+ }
+
+ /*
+ * check if vector fits on stack buffer
+ */
+ if (sz > lsz) {
+ addr = kmalloc(sz, GFP_KERNEL);
+ if (unlikely(addr == NULL))
+ return -ENOMEM;
+ *ptr_free = addr;
+ } else {
+ addr = laddr;
+ *req = laddr;
+ *ptr_free = NULL;
+ }
+
+ /*
+ * bring the data in
+ */
+ if (unlikely(copy_from_user(addr, ureq, sz))) {
+ if (addr != laddr)
+ kfree(addr);
+ return -EFAULT;
+ }
+
+ /*
+ * base address of kernel buffer
+ */
+ *req = addr;
+
+ return 0;
+}
+
+/**
+ * pfm_acquire_ctx_from_fd -- get ctx from file descriptor
+ * @fd: file descriptor
+ * @ctx: pointer to pointer of context updated on return
+ * @cookie: opaque structure to use for release
+ *
+ * This helper function extracts the ctx from the file descriptor.
+ * It also increments the refcount of the file structure. Thus
+ * it updates the cookie so the refcount can be decreased when
+ * leaving the perfmon syscall via pfm_release_ctx_from_fd
+ */
+static int pfm_acquire_ctx_from_fd(int fd, struct pfm_context **ctx,
+ struct pfm_syscall_cookie *cookie)
+{
+ struct file *filp;
+ int fput_needed;
+
+ filp = fget_light(fd, &fput_needed);
+ if (unlikely(filp == NULL)) {
+ PFM_DBG("invalid fd %d", fd);
+ return -EBADF;
+ }
+
+ *ctx = filp->private_data;
+
+ if (unlikely(!*ctx || filp->f_op != &pfm_file_ops)) {
+ PFM_DBG("fd %d not related to perfmon", fd);
+ return -EBADF;
+ }
+ cookie->filp = filp;
+ cookie->fput_needed = fput_needed;
+
+ return 0;
+}
+
+/**
+ * pfm_release_ctx_from_fd -- decrease refcount of file associated with context
+ * @cookie: the cookie structure initialized by pfm_acquire_ctx_from_fd
+ */
+static inline void pfm_release_ctx_from_fd(struct pfm_syscall_cookie *cookie)
+{
+ fput_light(cookie->filp, cookie->fput_needed);
+}
+
+/**
+ * pfm_validate_type_sz -- validate sz based on type
+ * @type : PFM_RW_XX type passed to pfm_write or pfm_read
+ * @sz : vector size in bytes
+ *
+ * return:
+ * the number of elements in the vector, 0 if error
+ */
+static size_t pfm_validate_type_sz(int type, size_t sz)
+{
+ size_t count, sz_type;
+
+ switch(type) {
+ case PFM_RW_PMD:
+ case PFM_RW_PMC:
+ sz_type = sizeof(struct pfarg_pmr);
+ break;
+ default:
+ PFM_DBG("invalid type=%d", type);
+ return 0;
+ }
+
+ count = sz / sz_type;
+
+ if ((count * sz_type) != sz) {
+ PFM_DBG("invalid size=%zu for type=%d", sz, type);
+ return 0;
+ }
+
+ PFM_DBG("sz=%zu sz_type=%zu count=%zu",
+ sz,
+ sz_type,
+ count);
+
+ return count;
+}
+
+/*
+ * unlike the other perfmon system calls, this one returns a file descriptor
+ * or a value < 0 in case of error, very much like open() or socket()
+ */
+asmlinkage long sys_pfm_create(int flags, struct pfarg_sinfo __user *ureq)
+{
+ struct pfm_context *new_ctx;
+ struct pfarg_sinfo sif;
+ int ret;
+
+ PFM_DBG("flags=0x%x sif=%p", flags, ureq);
+
+ if (perfmon_disabled)
+ return -ENOSYS;
+
+ if (flags) {
+ PFM_DBG("no flags accepted yet");
+ return -EINVAL;
+ }
+ ret = __pfm_create_context(flags, &sif, &new_ctx);
+
+ /*
+ * copy sif to user level argument, if requested
+ */
+ if (ureq && copy_to_user(ureq, &sif, sizeof(sif))) {
+ pfm_undo_create(ret, new_ctx);
+ ret = -EFAULT;
+ }
+ return ret;
+}
+
+asmlinkage long sys_pfm_write(int fd, int uflags,
+ int type,
+ void __user *ureq,
+ size_t sz)
+{
+ u64 buf[PFM_STK_ARG];
+ struct pfm_context *ctx;
+ struct pfm_syscall_cookie cookie;
+ void *req, *fptr;
+ unsigned long flags;
+ size_t count;
+ int ret;
+
+ PFM_DBG("fd=%d flags=0x%x type=%d req=%p sz=%zu",
+ fd, uflags, type, ureq, sz);
+
+ if (uflags) {
+ PFM_DBG("no flags defined");
+ return -EINVAL;
+ }
+
+ count = pfm_validate_type_sz(type, sz);
+ if (!count)
+ return -EINVAL;
+
+ ret = pfm_acquire_ctx_from_fd(fd, &ctx, &cookie);
+ if (ret)
+ return ret;
+
+ ret = pfm_get_args(ureq, sz, sizeof(buf), buf, (void **)&req, &fptr);
+ if (ret)
+ goto error;
+
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ ret = pfm_check_task_state(ctx, PFM_CMD_STOPPED, &flags);
+ if (ret)
+ goto skip;
+ switch(type) {
+ case PFM_RW_PMC:
+ ret = __pfm_write_pmcs(ctx, req, count);
+ break;
+ case PFM_RW_PMD:
+ ret = __pfm_write_pmds(ctx, req, count);
+ break;
+ default:
+ PFM_DBG("invalid type=%d", type);
+ ret = -EINVAL;
+ }
+skip:
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ /*
+ * This function may be on the critical path.
+ * We want to avoid the branch if unecessary.
+ */
+ if (fptr)
+ kfree(fptr);
+error:
+ pfm_release_ctx_from_fd(&cookie);
+ return ret;
+}
+
+asmlinkage long sys_pfm_read(int fd, int uflags,
+ int type,
+ void __user *ureq,
+ size_t sz)
+{
+ u64 buf[PFM_STK_ARG];
+ struct pfm_context *ctx;
+ struct pfm_syscall_cookie cookie;
+ void *req, *fptr;
+ unsigned long flags;
+ size_t count;
+ int ret;
+
+ PFM_DBG("fd=%d flags=0x%x type=%d req=%p sz=%zu",
+ fd, uflags, type, ureq, sz);
+
+ if (uflags) {
+ PFM_DBG("no flags defined");
+ return -EINVAL;
+ }
+
+ count = pfm_validate_type_sz(type, sz);
+ if (!count)
+ return -EINVAL;
+
+ ret = pfm_acquire_ctx_from_fd(fd, &ctx, &cookie);
+ if (ret)
+ return ret;
+
+ ret = pfm_get_args(ureq, sz, sizeof(buf), buf, (void **)&req, &fptr);
+ if (ret)
+ goto error;
+
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ ret = pfm_check_task_state(ctx, PFM_CMD_STOPPED, &flags);
+ if (ret)
+ goto skip;
+
+ switch(type) {
+ case PFM_RW_PMD:
+ ret = __pfm_read_pmds(ctx, req, count);
+ break;
+ default:
+ PFM_DBG("invalid type=%d", type);
+ ret = -EINVAL;
+ }
+skip:
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ if (copy_to_user(ureq, req, sz))
+ ret = -EFAULT;
+
+ if (fptr)
+ kfree(fptr);
+error:
+ pfm_release_ctx_from_fd(&cookie);
+ return ret;
+}
+
+asmlinkage long sys_pfm_set_state(int fd, int uflags, int state)
+{
+ struct pfm_context *ctx;
+ struct pfm_syscall_cookie cookie;
+ unsigned long flags;
+ int ret;
+
+ PFM_DBG("fd=%d uflags=0x%x state=0x%x", fd, uflags, state);
+
+ if (uflags) {
+ PFM_DBG("no flags defined");
+ return -EINVAL;
+ }
+
+ switch(state) {
+ case PFM_ST_START:
+ case PFM_ST_STOP:
+ break;
+ default:
+ PFM_DBG("invalid state=0x%x", state);
+ return -EINVAL;
+ }
+
+ ret = pfm_acquire_ctx_from_fd(fd, &ctx, &cookie);
+ if (ret)
+ return ret;
+
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ ret = pfm_check_task_state(ctx, PFM_CMD_STOPPED, &flags);
+ if (!ret) {
+ if (state == PFM_ST_STOP)
+ ret = __pfm_stop(ctx);
+ else
+ ret = __pfm_start(ctx);
+ }
+
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ pfm_release_ctx_from_fd(&cookie);
+
+ return ret;
+}
+
+static long pfm_detach(int fd, int uflags)
+{
+ struct pfm_context *ctx;
+ struct pfm_syscall_cookie cookie;
+ unsigned long flags;
+ int ret;
+
+ ret = pfm_acquire_ctx_from_fd(fd, &ctx, &cookie);
+ if (ret)
+ return ret;
+
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ ret = pfm_check_task_state(ctx, PFM_CMD_STOPPED|PFM_CMD_UNLOAD, &flags);
+ if (!ret)
+ ret = __pfm_unload_context(ctx);
+
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ /*
+ * if unload was successful, then release the session
+ * must be called with interrupts enabled, thus we need
+ * to defer until are out of __pfm_unload_context()
+ */
+ if (!ret)
+ pfm_session_release();
+
+ pfm_release_ctx_from_fd(&cookie);
+
+ return ret;
+}
+
+asmlinkage long sys_pfm_attach(int fd, int uflags, int target)
+{
+ struct pfm_context *ctx;
+ struct task_struct *task;
+ struct pfm_syscall_cookie cookie;
+ unsigned long flags;
+ int ret;
+
+ PFM_DBG("fd=%d uflags=0x%x target=%d", fd, uflags, target);
+
+ if (uflags) {
+ PFM_DBG("invalid flags");
+ return -EINVAL;
+ }
+
+ /*
+ * handle detach in a separate function
+ */
+ if (target == PFM_NO_TARGET)
+ return pfm_detach(fd, uflags);
+
+ ret = pfm_acquire_ctx_from_fd(fd, &ctx, &cookie);
+ if (ret)
+ return ret;
+
+ task = current;
+
+ /*
+ * in per-thread mode (not self-monitoring), get a reference
+ * on task to monitor. This must be done with interrupts enabled
+ * Upon succesful return, refcount on task has increased.
+ *
+ * fget_light() is protecting the context.
+ */
+ if (target != current->pid) {
+ ret = pfm_get_task(ctx, target, &task);
+ if (ret)
+ goto error;
+ }
+
+ /*
+ * irqsave is required to avoid race in case context is already
+ * loaded or with switch timeout in the case of self-monitoring
+ */
+ spin_lock_irqsave(&ctx->lock, flags);
+
+ ret = pfm_check_task_state(ctx, PFM_CMD_UNLOADED, &flags);
+ if (!ret)
+ ret = __pfm_load_context(ctx, task);
+
+ spin_unlock_irqrestore(&ctx->lock, flags);
+
+ /*
+ * in per-thread mode (not self-monitoring), we need
+ * to decrease refcount on task to monitor:
+ * - attach successful: we have a reference in ctx->task
+ * - attach failed : undo the effect of pfm_get_task()
+ */
+ if (task != current)
+ put_task_struct(task);
+error:
+ pfm_release_ctx_from_fd(&cookie);
+ return ret;
+}
Index: o3/include/linux/perfmon.h
===================================================================
--- o3.orig/include/linux/perfmon.h 2008-11-25 17:54:59.000000000 +0100
+++ o3/include/linux/perfmon.h 2008-11-25 17:55:04.000000000 +0100
@@ -72,6 +72,17 @@
#define PFM_RW_PMC 0x02 /* accessing PMC registers */
/*
+ * pfm_set_state state:
+ */
+#define PFM_ST_START 0x01 /* start monitoring */
+#define PFM_ST_STOP 0x02 /* stop monitoring */
+
+/*
+ * pfm_attach special target to trigger detach
+ */
+#define PFM_NO_TARGET -1 /* detach session target */
+
+/*
* default value for the user and group security parameters in
* /proc/sys/kernel/perfmon/sys_group
* /proc/sys/kernel/perfmon/task_group
Index: o3/include/linux/syscalls.h
===================================================================
--- o3.orig/include/linux/syscalls.h 2008-11-25 18:10:58.000000000 +0100
+++ o3/include/linux/syscalls.h 2008-11-25 18:11:06.000000000 +0100
@@ -624,4 +624,15 @@
int kernel_execve(const char *filename, char *const argv[], char *const envp[]);
+#ifdef CONFIG_PERFMON
+struct pfarg_sinfo;
+asmlinkage long sys_pfm_create(int flags, struct pfarg_sinfo *s,
+ char __user *f, void __user *uarg, size_t uarg_size);
+
+asmlinkage long sys_pfm_write(int fd, int flags, int type, void __user *arg, size_t s);
+asmlinkage long sys_pfm_read(int fd, int flags, int type, void __user *arg, size_t s);
+asmlinkage long sys_pfm_attach(int fd, int flags, int target);
+asmlinkage long sys_pfm_set_state(int fd, int flags, int state);
+#endif /* CONFIG_PERFMON */
+
#endif
--