Re: [PATCH v3] lib/bitmap: Make count and length parameters unsigned

From: Yury Norov
Date: Sun Jul 17 2022 - 00:06:27 EST

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On Thu, Jul 14, 2022 at 06:42:07PM +0200, Paul Menzel wrote:
> Counts and the length are non-negative, so make them unsigned, and adapt the
> while condition in `__bitmap_set()` and `__bitmap_clear()` accordingly.

Hi Paul,

I applied your patch on top of bitmap-for-next, and kernel failed
to boot with it on a very early stage without any logs. I attached
the target with GDB, but there's no any meaningful backtrace.
0xffffc0f6aa39541c in ?? ()
(gdb) i threads
Id Target Id Frame
* 1 Thread 1.1 (CPU#0 [running]) 0xffffc0f6aa39541c in ?? ()
2 Thread 1.2 (CPU#1 [halted ]) 0x0000000000000000 in ?? ()
3 Thread 1.3 (CPU#2 [halted ]) 0x0000000000000000 in ?? ()
4 Thread 1.4 (CPU#3 [halted ]) 0x0000000000000000 in ?? ()
(gdb) bt
#0 0xffffc0f6aa39541c in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)

Reproduced on qemu/arm64 and x86_64 with the same results. Can you
try your patch on top of bitmap-for-next and/or next-20220715?

You can find bitmap-for-next here:
https://github.com/norov/linux/

Thanks,
Yury

> For `__bitmap_set()` six less intstructions are used as a result:
>
> ```
> __bitmap_set: __bitmap_set:
> movl %esi, %eax movl %esi, %eax
> movq %rdi, %r8 <
> movl %esi, %ecx movl %esi, %ecx
> movl %edx, %edi | movl %esi, %r8d
> > movl $64, %esi
> > andl $63, %ecx
> shrl $6, %eax shrl $6, %eax
> andl $63, %esi | movl %edx, %r9d
> movq $-1, %rdx | leaq (%rdi,%rax,8), %rax
> leaq (%r8,%rax,8), %rax | subl %ecx, %esi
> leal -64(%rsi,%rdi), %r8d | movq $-1, %rdi
> salq %cl, %rdx | salq %cl, %rdi
> testl %r8d, %r8d | cmpl %edx, %esi
> js .L88 | ja .L85
> movl %r8d, %r9d <
> shrl $6, %r9d <
> leal 1(%r9), %esi <
> leaq (%rax,%rsi,8), %rsi <
> .L86: .L86:
> orq %rdx, (%rax) | subl %esi, %edx
> > orq %rdi, (%rax)
> > movl $64, %esi
> addq $8, %rax addq $8, %rax
> movq $-1, %rdx | movq $-1, %rdi
> cmpq %rsi, %rax | cmpl $63, %edx
> jne .L86 | ja .L86
> sall $6, %r9d <
> subl %r9d, %r8d <
> .L85: .L85:
> testl %r8d, %r8d | testl %edx, %edx
> je .L84 je .L84
> addl %edi, %ecx | leal (%r8,%r9), %ecx
> movq $-1, %rax | movq $-1, %rdx
> negl %ecx negl %ecx
> shrq %cl, %rax | shrq %cl, %rdx
> andq %rax, %rdx | andq %rdx, %rdi
> orq %rdx, (%rsi) | orq %rdi, (%rax)
> .L84: .L84:
> ret ret
> .L88: <
> movq %rax, %rsi <
> movl %edi, %r8d <
> jmp .L85 <
> .size __bitmap_set, .-__bitmap_set .size __bitmap_set, .-__bitmap_set
> .p2align 4 .p2align 4
> .globl __bitmap_clear .globl __bitmap_clear
> .type __bitmap_clear, @function .type __bitmap_clear, @function
> ```
>
> $ diff lib/bitmap.1.S lib/bitmap.2.S | diffstat
> unknown | 55 ++++++++++++++++++++++++-------------------------------
> 1 file changed, 24 insertions(+), 31 deletions(-)
>
> Signed-off-by: Paul Menzel <pmenzel@xxxxxxxxxxxxx>
> ---
> v2: Update signature in header file
> v3: Adapt more functions to use unsigned int
>
> include/linux/bitmap.h | 20 ++++++++++----------
> lib/bitmap.c | 26 +++++++++++++-------------
> 2 files changed, 23 insertions(+), 23 deletions(-)
>
> diff --git a/include/linux/bitmap.h b/include/linux/bitmap.h
> index 2e6cd5681040..9f1a097cd5d4 100644
> --- a/include/linux/bitmap.h
> +++ b/include/linux/bitmap.h
> @@ -164,8 +164,8 @@ bool __bitmap_intersects(const unsigned long *bitmap1,
> bool __bitmap_subset(const unsigned long *bitmap1,
> const unsigned long *bitmap2, unsigned int nbits);
> int __bitmap_weight(const unsigned long *bitmap, unsigned int nbits);
> -void __bitmap_set(unsigned long *map, unsigned int start, int len);
> -void __bitmap_clear(unsigned long *map, unsigned int start, int len);
> +void __bitmap_set(unsigned long *map, unsigned int start, unsigned int len);
> +void __bitmap_clear(unsigned long *map, unsigned int start, unsigned int len);
>
> unsigned long bitmap_find_next_zero_area_off(unsigned long *map,
> unsigned long size,
> @@ -198,17 +198,17 @@ bitmap_find_next_zero_area(unsigned long *map,
> }
>
> int bitmap_parse(const char *buf, unsigned int buflen,
> - unsigned long *dst, int nbits);
> + unsigned long *dst, unsigned int nbits);
> int bitmap_parse_user(const char __user *ubuf, unsigned int ulen,
> - unsigned long *dst, int nbits);
> + unsigned long *dst, unsigned int nbits);
> int bitmap_parselist(const char *buf, unsigned long *maskp,
> - int nmaskbits);
> + unsigned int nmaskbits);
> int bitmap_parselist_user(const char __user *ubuf, unsigned int ulen,
> - unsigned long *dst, int nbits);
> + unsigned long *dst, unsigned int nbits);
> void bitmap_remap(unsigned long *dst, const unsigned long *src,
> const unsigned long *old, const unsigned long *new, unsigned int nbits);
> int bitmap_bitremap(int oldbit,
> - const unsigned long *old, const unsigned long *new, int bits);
> + const unsigned long *old, const unsigned long *new, unsigned int bits);
> void bitmap_onto(unsigned long *dst, const unsigned long *orig,
> const unsigned long *relmap, unsigned int bits);
> void bitmap_fold(unsigned long *dst, const unsigned long *orig,
> @@ -224,13 +224,13 @@ void bitmap_copy_le(unsigned long *dst, const unsigned long *src, unsigned int n
> #endif
> unsigned int bitmap_ord_to_pos(const unsigned long *bitmap, unsigned int ord, unsigned int nbits);
> int bitmap_print_to_pagebuf(bool list, char *buf,
> - const unsigned long *maskp, int nmaskbits);
> + const unsigned long *maskp, unsigned int nmaskbits);
>
> extern int bitmap_print_bitmask_to_buf(char *buf, const unsigned long *maskp,
> - int nmaskbits, loff_t off, size_t count);
> + unsigned int nmaskbits, loff_t off, size_t count);
>
> extern int bitmap_print_list_to_buf(char *buf, const unsigned long *maskp,
> - int nmaskbits, loff_t off, size_t count);
> + unsigned int nmaskbits, loff_t off, size_t count);
>
> #define BITMAP_FIRST_WORD_MASK(start) (~0UL << ((start) & (BITS_PER_LONG - 1)))
> #define BITMAP_LAST_WORD_MASK(nbits) (~0UL >> (-(nbits) & (BITS_PER_LONG - 1)))
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index b18e31ea6e66..d529f7dffc48 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -348,14 +348,14 @@ int __bitmap_weight(const unsigned long *bitmap, unsigned int bits)
> }
> EXPORT_SYMBOL(__bitmap_weight);
>
> -void __bitmap_set(unsigned long *map, unsigned int start, int len)
> +void __bitmap_set(unsigned long *map, unsigned int start, unsigned int len)
> {
> unsigned long *p = map + BIT_WORD(start);
> const unsigned int size = start + len;
> int bits_to_set = BITS_PER_LONG - (start % BITS_PER_LONG);
> unsigned long mask_to_set = BITMAP_FIRST_WORD_MASK(start);
>
> - while (len - bits_to_set >= 0) {
> + while (len >= bits_to_set) {
> *p |= mask_to_set;
> len -= bits_to_set;
> bits_to_set = BITS_PER_LONG;
> @@ -369,7 +369,7 @@ void __bitmap_set(unsigned long *map, unsigned int start, int len)
> }
> EXPORT_SYMBOL(__bitmap_set);
>
> -void __bitmap_clear(unsigned long *map, unsigned int start, int len)
> +void __bitmap_clear(unsigned long *map, unsigned int start, unsigned int len)
> {
> unsigned long *p = map + BIT_WORD(start);
> const unsigned int size = start + len;
> @@ -445,7 +445,7 @@ EXPORT_SYMBOL(bitmap_find_next_zero_area_off);
> */
> int bitmap_parse_user(const char __user *ubuf,
> unsigned int ulen, unsigned long *maskp,
> - int nmaskbits)
> + unsigned int nmaskbits)
> {
> char *buf;
> int ret;
> @@ -478,7 +478,7 @@ EXPORT_SYMBOL(bitmap_parse_user);
> * actually printed to @buf, excluding terminating '\0'.
> */
> int bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp,
> - int nmaskbits)
> + unsigned int nmaskbits)
> {
> ptrdiff_t len = PAGE_SIZE - offset_in_page(buf);
>
> @@ -499,7 +499,7 @@ EXPORT_SYMBOL(bitmap_print_to_pagebuf);
> * @count: the maximum number of bytes to print
> */
> static int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp,
> - int nmaskbits, loff_t off, size_t count)
> + unsigned int nmaskbits, loff_t off, size_t count)
> {
> const char *fmt = list ? "%*pbl\n" : "%*pb\n";
> ssize_t size;
> @@ -542,7 +542,7 @@ static int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp,
> * normal attribute with buf parameter and without offset, count::
> *
> * bitmap_print_to_pagebuf(bool list, char *buf, const unsigned long *maskp,
> - * int nmaskbits)
> + * unsigned int nmaskbits)
> * {
> * }
> *
> @@ -600,7 +600,7 @@ static int bitmap_print_to_buf(bool list, char *buf, const unsigned long *maskp,
> * Returns the number of characters actually printed to @buf
> */
> int bitmap_print_bitmask_to_buf(char *buf, const unsigned long *maskp,
> - int nmaskbits, loff_t off, size_t count)
> + unsigned int nmaskbits, loff_t off, size_t count)
> {
> return bitmap_print_to_buf(false, buf, maskp, nmaskbits, off, count);
> }
> @@ -618,7 +618,7 @@ EXPORT_SYMBOL(bitmap_print_bitmask_to_buf);
> * the print format.
> */
> int bitmap_print_list_to_buf(char *buf, const unsigned long *maskp,
> - int nmaskbits, loff_t off, size_t count)
> + unsigned int nmaskbits, loff_t off, size_t count)
> {
> return bitmap_print_to_buf(true, buf, maskp, nmaskbits, off, count);
> }
> @@ -793,7 +793,7 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
> * - ``-ERANGE``: bit number specified too large for mask
> * - ``-EOVERFLOW``: integer overflow in the input parameters
> */
> -int bitmap_parselist(const char *buf, unsigned long *maskp, int nmaskbits)
> +int bitmap_parselist(const char *buf, unsigned long *maskp, unsigned int nmaskbits)
> {
> struct region r;
> long ret;
> @@ -836,7 +836,7 @@ EXPORT_SYMBOL(bitmap_parselist);
> */
> int bitmap_parselist_user(const char __user *ubuf,
> unsigned int ulen, unsigned long *maskp,
> - int nmaskbits)
> + unsigned int nmaskbits)
> {
> char *buf;
> int ret;
> @@ -893,7 +893,7 @@ static const char *bitmap_get_x32_reverse(const char *start,
> * Leading, embedded and trailing whitespace accepted.
> */
> int bitmap_parse(const char *start, unsigned int buflen,
> - unsigned long *maskp, int nmaskbits)
> + unsigned long *maskp, unsigned int nmaskbits)
> {
> const char *end = strnchrnul(start, buflen, '\n') - 1;
> int chunks = BITS_TO_U32(nmaskbits);
> @@ -1068,7 +1068,7 @@ EXPORT_SYMBOL(bitmap_remap);
> * returns 13.
> */
> int bitmap_bitremap(int oldbit, const unsigned long *old,
> - const unsigned long *new, int bits)
> + const unsigned long *new, unsigned int bits)
> {
> int w = bitmap_weight(new, bits);
> int n = bitmap_pos_to_ord(old, oldbit, bits);
> --
> 2.36.1

Next message: Chuck Zmudzinski: "Re: [PATCH 0/3] x86: make pat and mtrr independent from each other"
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