CONFIG_SPLIT_LOCK_AC_PANIC_ON_KERNEL defines how to handle split lock in kernel mode by default. But sometimes user wants to change the default behavior.
The interface /sys/kernel/debug/x86/split_lock/kernel_mode is added to allow user to do so. For example, the interface shows "[re-execute] panic" which means two behaviors: re-execute kernel faulting instruction after #AC (default) and panic in #AC. User can change the default behavior by writing "re-execute" or "panic" to the interface. Signed-off-by: Fenghua Yu <[email protected]> --- arch/x86/kernel/cpu/test_ctl.c | 89 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 89 insertions(+) diff --git a/arch/x86/kernel/cpu/test_ctl.c b/arch/x86/kernel/cpu/test_ctl.c index 6784f68af26a..0212a7979a14 100644 --- a/arch/x86/kernel/cpu/test_ctl.c +++ b/arch/x86/kernel/cpu/test_ctl.c @@ -18,6 +18,7 @@ #include <linux/reboot.h> #include <linux/syscore_ops.h> #include <linux/debugfs.h> +#include <linux/uaccess.h> #include <asm/msr.h> #define DISABLE_SPLIT_LOCK_AC 0 @@ -49,6 +50,11 @@ enum { KERNEL_MODE_LAST }; +static const char * const kernel_modes[KERNEL_MODE_LAST] = { + [KERNEL_MODE_RE_EXECUTE] = "re-execute", + [KERNEL_MODE_PANIC] = "panic", +}; + static int kernel_mode_reaction = KERNEL_MODE_RE_EXECUTE; /* Detete feature of #AC for split lock by probing bit 29 in MSR_TEST_CTL. */ @@ -361,10 +367,93 @@ static int enable_store(void *data, u64 val) DEFINE_DEBUGFS_ATTRIBUTE(enable_ops, enable_show, enable_store, "%llx\n"); +static ssize_t +mode_show(char __user *user_buf, const char * const *modes, int start_reaction, + int last_reaction, int mode_reaction, size_t count, loff_t *ppos) +{ + char buf[32], *s = buf; + int reaction, len; + + mutex_lock(&split_lock_mutex); + for (reaction = start_reaction; reaction < last_reaction; reaction++) { + if (reaction == mode_reaction) + s += sprintf(s, "[%s] ", modes[reaction]); + else + s += sprintf(s, "%s ", modes[reaction]); + } + + if (s != buf) + /* convert the last space to a newline */ + *(s - 1) = '\n'; + mutex_unlock(&split_lock_mutex); + + len = strlen(buf); + + return simple_read_from_buffer(user_buf, count, ppos, buf, len); +} + +static ssize_t +mode_store(const char __user *user_buf, size_t count, const char * const *modes, + int start_reaction, int last_reaction, int *mode_reaction) +{ + int reaction, len, ret = -EINVAL; + const char * const *s, *p; + char buf[32]; + + len = min(count, sizeof(buf) - 1); + if (copy_from_user(buf, user_buf, len)) + return -EFAULT; + + buf[len] = '\0'; + + mutex_lock(&split_lock_mutex); + p = memchr(buf, '\n', count); + len = p ? p - buf : count; + + reaction = start_reaction; + for (s = &modes[reaction]; reaction < last_reaction; s++, reaction++) { + if (*s && len == strlen(*s) && !strncmp(buf, *s, len)) { + *mode_reaction = reaction; + ret = 0; + break; + } + } + mutex_unlock(&split_lock_mutex); + + return ret; +} + +static ssize_t kernel_mode_show(struct file *file, char __user *user_buf, + size_t count, loff_t *ppos) +{ + return mode_show(user_buf, kernel_modes, KERNEL_MODE_RE_EXECUTE, + KERNEL_MODE_LAST, kernel_mode_reaction, count, ppos); +} + +static ssize_t kernel_mode_store(struct file *file, const char __user *user_buf, + size_t count, loff_t *ppos) +{ + int ret; + + ret = mode_store(user_buf, count, kernel_modes, KERNEL_MODE_RE_EXECUTE, + KERNEL_MODE_LAST, &kernel_mode_reaction); + if (ret) + return ret; + + return count; +} + +static const struct file_operations kernel_mode_ops = { + .read = kernel_mode_show, + .write = kernel_mode_store, + .llseek = default_llseek, +}; + static int __init debugfs_setup_split_lock(void) { struct debugfs_file debugfs_files[] = { {"enable", 0600, &enable_ops}, + {"kernel_mode", 0600, &kernel_mode_ops }, }; struct dentry *split_lock_dir, *fd; int i; -- 2.5.0
