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sh: Allow user control over misaligned fixup handling

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This patch brings the SH4 misaligned trap handler in line with what
happens on ARM:
Add a /proc/cpu/alignment which can be read from to get alignment
trap statistics and written to to influence the behaviour of the
alignment trap handling. The value to write is a bitfield, which
has the following meaning: 1 warn, 2 fixup, 4 signal
In addition, we add a /proc/cpu/kernel_alignment, to enable or
disable warnings in case of kernel code causing alignment errors.

Signed-off by: Andre Draszik <andre.draszik@st.com>
Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This commit is contained in:
Andre Draszik 2009-08-24 14:53:46 +09:00 committed by Paul Mundt
parent 9a4af027a0
commit 7436cde6b2
1 changed files with 153 additions and 0 deletions
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153
arch/sh/kernel/traps_32.c
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@ -24,6 +24,7 @@
#include <linux/kdebug.h>
#include <linux/kexec.h>
#include <linux/limits.h>
#include <linux/proc_fs.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/fpu.h>
@ -44,6 +45,87 @@
#define TRAP_ILLEGAL_SLOT_INST 13
#endif
static unsigned long se_user;
static unsigned long se_sys;
static unsigned long se_skipped;
static unsigned long se_half;
static unsigned long se_word;
static unsigned long se_dword;
static unsigned long se_multi;
/* bitfield: 1: warn 2: fixup 4: signal -> combinations 2|4 && 1|2|4 are not
valid! */
static int se_usermode = 3;
/* 0: no warning 1: print a warning message */
static int se_kernmode_warn = 1;
#ifdef CONFIG_PROC_FS
static const char *se_usermode_action[] = {
"ignored",
"warn",
"fixup",
"fixup+warn",
"signal",
"signal+warn"
};
static int
proc_alignment_read(char *page, char **start, off_t off, int count, int *eof,
void *data)
{
char *p = page;
int len;
p += sprintf(p, "User:\t\t%lu\n", se_user);
p += sprintf(p, "System:\t\t%lu\n", se_sys);
p += sprintf(p, "Skipped:\t%lu\n", se_skipped);
p += sprintf(p, "Half:\t\t%lu\n", se_half);
p += sprintf(p, "Word:\t\t%lu\n", se_word);
p += sprintf(p, "DWord:\t\t%lu\n", se_dword);
p += sprintf(p, "Multi:\t\t%lu\n", se_multi);
p += sprintf(p, "User faults:\t%i (%s)\n", se_usermode,
se_usermode_action[se_usermode]);
p += sprintf(p, "Kernel faults:\t%i (fixup%s)\n", se_kernmode_warn,
se_kernmode_warn ? "+warn" : "");
len = (p - page) - off;
if (len < 0)
len = 0;
*eof = (len <= count) ? 1 : 0;
*start = page + off;
return len;
}
static int proc_alignment_write(struct file *file, const char __user *buffer,
unsigned long count, void *data)
{
char mode;
if (count > 0) {
if (get_user(mode, buffer))
return -EFAULT;
if (mode >= '0' && mode <= '5')
se_usermode = mode - '0';
}
return count;
}
static int proc_alignment_kern_write(struct file *file, const char __user *buffer,
unsigned long count, void *data)
{
char mode;
if (count > 0) {
if (get_user(mode, buffer))
return -EFAULT;
if (mode >= '0' && mode <= '1')
se_kernmode_warn = mode - '0';
}
return count;
}
#endif
static void dump_mem(const char *str, unsigned long bottom, unsigned long top)
{
unsigned long p;
@ -194,6 +276,13 @@ static int handle_unaligned_ins(insn_size_t instruction, struct pt_regs *regs,
count = 1<<(instruction&3);
switch (count) {
case 1: se_half += 1; break;
case 2: se_word += 1; break;
case 4: se_dword += 1; break;
case 8: se_multi += 1; break; /* ??? */
}
ret = -EFAULT;
switch (instruction>>12) {
case 0: /* mov.[bwl] to/from memory via r0+rn */
@ -530,6 +619,27 @@ asmlinkage void do_address_error(struct pt_regs *regs,
local_irq_enable();
se_user += 1;
/* shout about userspace fixups */
if (se_usermode & 1)
printk(KERN_NOTICE "Unaligned userspace access "
"in \"%s\" pid=%d pc=0x%p ins=0x%04hx\n",
current->comm, current->pid, (void *)regs->pc,
instruction);
if (se_usermode & 2)
goto fixup;
if (se_usermode & 4)
goto uspace_segv;
else {
/* ignore */
trace_mark(kernel_arch_trap_exit, MARK_NOARGS);
return;
}
fixup:
/* bad PC is not something we can fix */
if (regs->pc & 1) {
si_code = BUS_ADRALN;
@ -563,6 +673,14 @@ uspace_segv:
info.si_addr = (void __user *)address;
force_sig_info(SIGBUS, &info, current);
} else {
se_sys += 1;
if (se_kernmode_warn)
printk(KERN_NOTICE "Unaligned kernel access "
"on behalf of \"%s\" pid=%d pc=0x%p ins=0x%04hx\n",
current->comm, current->pid, (void *)regs->pc,
instruction);
if (regs->pc & 1)
die("unaligned program counter", regs, error_code);
@ -872,3 +990,38 @@ void dump_stack(void)
show_stack(NULL, NULL);
}
EXPORT_SYMBOL(dump_stack);
#ifdef CONFIG_PROC_FS
/*
* This needs to be done after sysctl_init, otherwise sys/ will be
* overwritten. Actually, this shouldn't be in sys/ at all since
* it isn't a sysctl, and it doesn't contain sysctl information.
* We now locate it in /proc/cpu/alignment instead.
*/
static int __init alignment_init(void)
{
struct proc_dir_entry *dir, *res;
dir = proc_mkdir("cpu", NULL);
if (!dir)
return -ENOMEM;
res = create_proc_entry("alignment", S_IWUSR | S_IRUGO, dir);
if (!res)
return -ENOMEM;
res->read_proc = proc_alignment_read;
res->write_proc = proc_alignment_write;
res = create_proc_entry("kernel_alignment", S_IWUSR | S_IRUGO, dir);
if (!res)
return -ENOMEM;
res->read_proc = proc_alignment_read;
res->write_proc = proc_alignment_kern_write;
return 0;
}
fs_initcall(alignment_init);
#endif