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SubjectRe: [PATCH] BUG preserve registers
Andrew Morton wrote:
>
> I think I'm done with this now.

Famous last words. There's a slightly updated version at
http://www.zip.com.au/~akpm/linux/2.4/2.4.18-pre9/

CONFIG_DEBUG_BUGVEROSE has been retained - it's now used to enable
BUG() in a couple of bloaty places. But BUG() now always
reports file-and-line.

Also, here's the kill-BUG-in-headers patch. With this, the
kernel image is in fact a few kbytes smaller than stock
2.4.18-pre9 with CONFIG_DEBUG_BUGVERBOSE=n, and we get full
file-and-line and the registers aren't trashed, so everyone's
happy.

It's interesting to run

strings -n16 vmlinux | sort
and look at the output. There are still quite a lot of printk's
in inline functions which could be tidied up. NFS blows about
3k and reiserfs with extra debug checking enabled is pretty gross.

I guess I'll propose these patches for 2.4.19-pre. There isn't
anything really critical here. Total saving in my build is
120 kbytes, or 5% of the kernel size.




--- linux-2.4.18-pre9/include/asm-i386/mmu_context.h Tue Oct 23 21:59:06 2001
+++ linux-akpm/include/asm-i386/mmu_context.h Sun Feb 10 00:42:25 2002
@@ -48,7 +48,7 @@ static inline void switch_mm(struct mm_s
else {
cpu_tlbstate[cpu].state = TLBSTATE_OK;
if(cpu_tlbstate[cpu].active_mm != next)
- BUG();
+ VERBOSE_BUG();
if(!test_and_set_bit(cpu, &next->cpu_vm_mask)) {
/* We were in lazy tlb mode and leave_mm disabled
* tlb flush IPI delivery. We must flush our tlb.
--- linux-2.4.18-pre9/include/linux/kernel.h Thu Feb 7 13:04:22 2002
+++ linux-akpm/include/linux/kernel.h Sun Feb 10 00:07:18 2002
@@ -181,4 +181,7 @@ struct sysinfo {
char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding: libc5 uses this.. */
};

+extern void bug_in_interrupt(void);
+extern void out_of_line_bug(void);
+
#endif
--- linux-2.4.18-pre9/include/asm-i386/pci.h Thu Feb 7 13:04:22 2002
+++ linux-akpm/include/asm-i386/pci.h Sun Feb 10 00:42:35 2002
@@ -73,7 +73,7 @@ static inline dma_addr_t pci_map_single(
size_t size, int direction)
{
if (direction == PCI_DMA_NONE)
- BUG();
+ VERBOSE_BUG();
flush_write_buffers();
return virt_to_bus(ptr);
}
@@ -89,7 +89,7 @@ static inline void pci_unmap_single(stru
size_t size, int direction)
{
if (direction == PCI_DMA_NONE)
- BUG();
+ VERBOSE_BUG();
/* Nothing to do */
}

@@ -101,7 +101,7 @@ static inline dma_addr_t pci_map_page(st
unsigned long offset, size_t size, int direction)
{
if (direction == PCI_DMA_NONE)
- BUG();
+ VERBOSE_BUG();

return (page - mem_map) * PAGE_SIZE + offset;
}
@@ -110,7 +110,7 @@ static inline void pci_unmap_page(struct
size_t size, int direction)
{
if (direction == PCI_DMA_NONE)
- BUG();
+ VERBOSE_BUG();
/* Nothing to do */
}

@@ -143,16 +143,16 @@ static inline int pci_map_sg(struct pci_
int i;

if (direction == PCI_DMA_NONE)
- BUG();
+ VERBOSE_BUG();

/*
* temporary 2.4 hack
*/
for (i = 0; i < nents; i++ ) {
if (sg[i].address && sg[i].page)
- BUG();
+ VERBOSE_BUG();
else if (!sg[i].address && !sg[i].page)
- BUG();
+ VERBOSE_BUG();

if (sg[i].address)
sg[i].dma_address = virt_to_bus(sg[i].address);
@@ -172,7 +172,7 @@ static inline void pci_unmap_sg(struct p
int nents, int direction)
{
if (direction == PCI_DMA_NONE)
- BUG();
+ VERBOSE_BUG();
/* Nothing to do */
}

@@ -190,7 +190,7 @@ static inline void pci_dma_sync_single(s
size_t size, int direction)
{
if (direction == PCI_DMA_NONE)
- BUG();
+ VERBOSE_BUG();
flush_write_buffers();
}

@@ -205,7 +205,7 @@ static inline void pci_dma_sync_sg(struc
int nelems, int direction)
{
if (direction == PCI_DMA_NONE)
- BUG();
+ VERBOSE_BUG();
flush_write_buffers();
}

--- linux-2.4.18-pre9/include/asm-i386/smplock.h Tue Oct 23 21:59:10 2001
+++ linux-akpm/include/asm-i386/smplock.h Sun Feb 10 00:42:26 2002
@@ -59,7 +59,7 @@ static __inline__ void lock_kernel(void)
static __inline__ void unlock_kernel(void)
{
if (current->lock_depth < 0)
- BUG();
+ VERBOSE_BUG();
#if 1
if (--current->lock_depth < 0)
spin_unlock(&kernel_flag);
--- linux-2.4.18-pre9/include/linux/dcache.h Tue Oct 23 21:59:05 2001
+++ linux-akpm/include/linux/dcache.h Sun Feb 10 00:07:18 2002
@@ -242,11 +242,8 @@ extern char * __d_path(struct dentry *,

static __inline__ struct dentry * dget(struct dentry *dentry)
{
- if (dentry) {
- if (!atomic_read(&dentry->d_count))
- BUG();
+ if (dentry)
atomic_inc(&dentry->d_count);
- }
return dentry;
}

--- linux-2.4.18-pre9/include/linux/file.h Wed Aug 23 11:22:26 2000
+++ linux-akpm/include/linux/file.h Sun Feb 10 00:07:18 2002
@@ -71,30 +71,7 @@ static inline void put_unused_fd(unsigne
write_unlock(&files->file_lock);
}

-/*
- * Install a file pointer in the fd array.
- *
- * The VFS is full of places where we drop the files lock between
- * setting the open_fds bitmap and installing the file in the file
- * array. At any such point, we are vulnerable to a dup2() race
- * installing a file in the array before us. We need to detect this and
- * fput() the struct file we are about to overwrite in this case.
- *
- * It should never happen - if we allow dup2() do it, _really_ bad things
- * will follow.
- */
-
-static inline void fd_install(unsigned int fd, struct file * file)
-{
- struct files_struct *files = current->files;
-
- write_lock(&files->file_lock);
- if (files->fd[fd])
- BUG();
- files->fd[fd] = file;
- write_unlock(&files->file_lock);
-}
-
+void fd_install(unsigned int fd, struct file * file);
void put_files_struct(struct files_struct *fs);

#endif /* __LINUX_FILE_H */
--- linux-2.4.18-pre9/include/linux/nfs_fs.h Fri Dec 21 11:19:23 2001
+++ linux-akpm/include/linux/nfs_fs.h Sun Feb 10 00:42:44 2002
@@ -168,7 +168,7 @@ nfs_file_cred(struct file *file)
struct rpc_cred *cred = (struct rpc_cred *)(file->private_data);
#ifdef RPC_DEBUG
if (cred && cred->cr_magic != RPCAUTH_CRED_MAGIC)
- BUG();
+ out_of_line_bug();
#endif
return cred;
}
--- linux-2.4.18-pre9/include/linux/quotaops.h Tue Oct 23 21:59:31 2001
+++ linux-akpm/include/linux/quotaops.h Sun Feb 10 00:42:52 2002
@@ -40,8 +40,6 @@ extern int dquot_transfer(struct inode

static __inline__ void DQUOT_INIT(struct inode *inode)
{
- if (!inode->i_sb)
- BUG();
lock_kernel();
if (sb_any_quota_enabled(inode->i_sb) && !IS_NOQUOTA(inode))
inode->i_sb->dq_op->initialize(inode, -1);
@@ -51,11 +49,8 @@ static __inline__ void DQUOT_INIT(struct
static __inline__ void DQUOT_DROP(struct inode *inode)
{
lock_kernel();
- if (IS_QUOTAINIT(inode)) {
- if (!inode->i_sb)
- BUG();
+ if (IS_QUOTAINIT(inode))
inode->i_sb->dq_op->drop(inode); /* Ops must be set when there's any quota... */
- }
unlock_kernel();
}

--- linux-2.4.18-pre9/include/linux/sched.h Fri Dec 21 11:19:23 2001
+++ linux-akpm/include/linux/sched.h Sun Feb 10 00:42:25 2002
@@ -888,7 +888,6 @@ static inline int task_on_runqueue(struc

static inline void unhash_process(struct task_struct *p)
{
- if (task_on_runqueue(p)) BUG();
write_lock_irq(&tasklist_lock);
nr_threads--;
unhash_pid(p);
--- linux-2.4.18-pre9/include/linux/highmem.h Thu Feb 7 13:04:22 2002
+++ linux-akpm/include/linux/highmem.h Sun Feb 10 00:42:28 2002
@@ -63,8 +63,6 @@ static inline void memclear_highpage_flu
{
char *kaddr;

- if (offset + size > PAGE_SIZE)
- BUG();
kaddr = kmap(page);
memset(kaddr + offset, 0, size);
flush_dcache_page(page);
--- linux-2.4.18-pre9/include/linux/skbuff.h Mon Nov 5 21:01:12 2001
+++ linux-akpm/include/linux/skbuff.h Sun Feb 10 00:42:29 2002
@@ -756,9 +756,9 @@ static inline int skb_headlen(const stru
return skb->len - skb->data_len;
}

-#define SKB_PAGE_ASSERT(skb) do { if (skb_shinfo(skb)->nr_frags) BUG(); } while (0)
-#define SKB_FRAG_ASSERT(skb) do { if (skb_shinfo(skb)->frag_list) BUG(); } while (0)
-#define SKB_LINEAR_ASSERT(skb) do { if (skb_is_nonlinear(skb)) BUG(); } while (0)
+#define SKB_PAGE_ASSERT(skb) do { if (skb_shinfo(skb)->nr_frags) out_of_line_bug(); } while (0)
+#define SKB_FRAG_ASSERT(skb) do { if (skb_shinfo(skb)->frag_list) out_of_line_bug(); } while (0)
+#define SKB_LINEAR_ASSERT(skb) do { if (skb_is_nonlinear(skb)) out_of_line_bug(); } while (0)

/*
* Add data to an sk_buff
@@ -825,8 +825,6 @@ static inline unsigned char *skb_push(st
static inline char *__skb_pull(struct sk_buff *skb, unsigned int len)
{
skb->len-=len;
- if (skb->len < skb->data_len)
- BUG();
return skb->data+=len;
}

@@ -1094,7 +1092,7 @@ static inline void *kmap_skb_frag(const
{
#ifdef CONFIG_HIGHMEM
if (in_irq())
- BUG();
+ out_of_line_bug();

local_bh_disable();
#endif
--- linux-2.4.18-pre9/include/asm-i386/highmem.h Tue Oct 23 21:59:06 2001
+++ linux-akpm/include/asm-i386/highmem.h Sun Feb 10 00:42:25 2002
@@ -62,7 +62,7 @@ extern void FASTCALL(kunmap_high(struct
static inline void *kmap(struct page *page)
{
if (in_interrupt())
- BUG();
+ bug_in_interrupt();
if (page < highmem_start_page)
return page_address(page);
return kmap_high(page);
@@ -71,7 +71,7 @@ static inline void *kmap(struct page *pa
static inline void kunmap(struct page *page)
{
if (in_interrupt())
- BUG();
+ bug_in_interrupt();
if (page < highmem_start_page)
return;
kunmap_high(page);
@@ -95,7 +95,7 @@ static inline void *kmap_atomic(struct p
vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
#if HIGHMEM_DEBUG
if (!pte_none(*(kmap_pte-idx)))
- BUG();
+ out_of_line_bug();
#endif
set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
__flush_tlb_one(vaddr);
@@ -113,7 +113,7 @@ static inline void kunmap_atomic(void *k
return;

if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx))
- BUG();
+ out_of_line_bug();

/*
* force other mappings to Oops if they'll try to access
--- linux-2.4.18-pre9/include/net/tcp.h Tue Oct 23 21:59:58 2001
+++ linux-akpm/include/net/tcp.h Sun Feb 10 00:42:59 2002
@@ -1329,8 +1329,6 @@ static __inline__ int tcp_prequeue(struc
if (tp->ucopy.memory > sk->rcvbuf) {
struct sk_buff *skb1;

- if (sk->lock.users) BUG();
-
while ((skb1 = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) {
sk->backlog_rcv(sk, skb1);
NET_INC_STATS_BH(TCPPrequeueDropped);
--- linux-2.4.18-pre9/fs/open.c Fri Oct 12 13:48:42 2001
+++ linux-akpm/fs/open.c Sun Feb 10 00:48:33 2002
@@ -71,6 +71,30 @@ out:
return error;
}

+/*
+ * Install a file pointer in the fd array.
+ *
+ * The VFS is full of places where we drop the files lock between
+ * setting the open_fds bitmap and installing the file in the file
+ * array. At any such point, we are vulnerable to a dup2() race
+ * installing a file in the array before us. We need to detect this and
+ * fput() the struct file we are about to overwrite in this case.
+ *
+ * It should never happen - if we allow dup2() do it, _really_ bad things
+ * will follow.
+ */
+
+void fd_install(unsigned int fd, struct file * file)
+{
+ struct files_struct *files = current->files;
+
+ write_lock(&files->file_lock);
+ if (files->fd[fd])
+ BUG();
+ files->fd[fd] = file;
+ write_unlock(&files->file_lock);
+}
+
int do_truncate(struct dentry *dentry, loff_t length)
{
struct inode *inode = dentry->d_inode;
--- linux-2.4.18-pre9/kernel/ksyms.c Thu Feb 7 13:04:22 2002
+++ linux-akpm/kernel/ksyms.c Sun Feb 10 00:07:18 2002
@@ -164,6 +164,7 @@ EXPORT_SYMBOL(mark_buffer_dirty);
EXPORT_SYMBOL(set_buffer_async_io); /* for reiserfs_writepage */
EXPORT_SYMBOL(__mark_buffer_dirty);
EXPORT_SYMBOL(__mark_inode_dirty);
+EXPORT_SYMBOL(fd_install);
EXPORT_SYMBOL(get_empty_filp);
EXPORT_SYMBOL(init_private_file);
EXPORT_SYMBOL(filp_open);
@@ -452,6 +453,8 @@ EXPORT_SYMBOL(nr_running);

/* misc */
EXPORT_SYMBOL(panic);
+EXPORT_SYMBOL(out_of_line_bug);
+EXPORT_SYMBOL(bug_in_interrupt);
EXPORT_SYMBOL(sprintf);
EXPORT_SYMBOL(snprintf);
EXPORT_SYMBOL(sscanf);
--- linux-2.4.18-pre9/kernel/panic.c Sun Sep 30 12:26:08 2001
+++ linux-akpm/kernel/panic.c Sun Feb 10 00:07:18 2002
@@ -120,3 +120,25 @@ const char *print_tainted()
}

int tainted = 0;
+
+/*
+ * A BUG() call in an inline function in a header should be avoided,
+ * because it can seriously bloat the kernel. So here we have
+ * helper functions.
+ * We lose the BUG()-time file-and-line info this way, but it's
+ * usually not very useful from an inline anyway. The backtrace
+ * tells us what we want to know.
+ */
+
+void out_of_line_bug(void)
+{
+ BUG();
+}
+
+void bug_in_interrupt(void)
+{
+ if (in_interrupt()) {
+ printk("BUG: in_interrupt()\n");
+ BUG();
+ }
+}



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