Re: [PATCH 07/13] kexec: Implementation of new syscall kexec_file_load

Vivek Goyal
2014-06-11T17:05:09Z

On Wed, Jun 11, 2014 at 04:13:20PM +0200, Borislav Petkov wrote:
> On Fri, Jun 06, 2014 at 02:02:14PM -0400, Vivek Goyal wrote:
> > > If you want to make it more explicit, you could do
> > >
> > > #define RES_OK 0
> > > #define RES_ERR 1
> > > #define RES_STOP 2
> >
> > You are saying that called back function should return this to walk_*
> > functions? But then we lose the actual error code which should be
> > passed to parent function which actually called walk_* function.
>
> Well, RES_STOP could implicitly mean stop and no error. Also, if
> you really want to return back the retval, you could slice it into
> bitfields:
>
> retval = [ ... 8 | 7 ... 0]
>
> where [7:0] is the return value and bits from 8 onwards contain
> different flags like RES_STOP. I did it just for the fun of it and it
> looks like below. I honestly can't say that I'm crazy about it though.

You are doing the same thing as I am doing. The only difference is that
I am using separate bool variable and you are trying to use upper bits
of return code to carry that extra information.

I personally think that using separate bool variable is simpler as
compared to using upper bits in return code.

Thanks
Vivek

>
> --
> Index: b/kernel/resource.c
> ===================================================================
> --- a/kernel/resource.c 2014-06-11 14:49:35.865426300 +0200
> +++ b/kernel/resource.c 2014-06-11 15:37:50.050299684 +0200
> @@ -371,7 +371,7 @@ static int find_next_iomem_res(struct re
> }
>
> int walk_ram_res(char *name, unsigned long flags, u64 start, u64 end,
> - void *arg, int (*func)(u64, u64, void *))
> + void *arg, int (*func)(u64, u64, void *))
> {
> struct resource res;
> u64 orig_end;
> @@ -384,12 +384,12 @@ int walk_ram_res(char *name, unsigned lo
> while ((res.start < res.end) &&
> (find_next_iomem_res(&res, name) >= 0)) {
> ret = (*func)(res.start, res.end, arg);
> - if (ret)
> + if (ret & RES_STOP)
> break;
> res.start = res.end + 1;
> res.end = orig_end;
> }
> - return ret;
> + return RETVAL(ret);
> }
>
> /*
> @@ -441,7 +441,7 @@ static int find_next_system_ram(struct r
> * with pfn can truncate ranges.
> */
> int walk_system_ram_res(u64 start, u64 end, void *arg,
> - int (*func)(u64, u64, void *))
> + int (*func)(u64, u64, void *))
> {
> struct resource res;
> u64 orig_end;
> @@ -454,12 +454,13 @@ int walk_system_ram_res(u64 start, u64 e
> while ((res.start < res.end) &&
> (find_next_system_ram(&res, "System RAM") >= 0)) {
> ret = (*func)(res.start, res.end, arg);
> - if (ret)
> + if (ret & RES_STOP)
> break;
> res.start = res.end + 1;
> res.end = orig_end;
> }
> - return ret;
> +
> + return RETVAL(ret);
> }
>
> #if !defined(CONFIG_ARCH_HAS_WALK_MEMORY)
> Index: b/kernel/kexec.c
> ===================================================================
> --- a/kernel/kexec.c 2014-06-11 14:49:35.865426300 +0200
> +++ b/kernel/kexec.c 2014-06-11 16:03:26.264232477 +0200
> @@ -2063,8 +2063,9 @@ static int __kexec_add_segment(struct ki
> }
>
> static int locate_mem_hole_top_down(unsigned long start, unsigned long end,
> - struct kexec_buf *kbuf)
> + struct kexec_buf *kbuf)
> {
> + int ret = 0;
> struct kimage *image = kbuf->image;
> unsigned long temp_start, temp_end;
>
> @@ -2076,7 +2077,7 @@ static int locate_mem_hole_top_down(unsi
> temp_start = temp_start & (~(kbuf->buf_align - 1));
>
> if (temp_start < start || temp_start < kbuf->buf_min)
> - return 0;
> + return EADDRNOTAVAIL;
>
> temp_end = temp_start + kbuf->memsz - 1;
>
> @@ -2098,12 +2099,15 @@ static int locate_mem_hole_top_down(unsi
> kbuf->memsz);
>
> /* Stop navigating through remaining System RAM ranges */
> - return 1;
> + ret |= RES_STOP;
> +
> + return ret;
> }
>
> static int locate_mem_hole_bottom_up(unsigned long start, unsigned long end,
> - struct kexec_buf *kbuf)
> + struct kexec_buf *kbuf)
> {
> + int ret = 0;
> struct kimage *image = kbuf->image;
> unsigned long temp_start, temp_end;
>
> @@ -2114,7 +2118,7 @@ static int locate_mem_hole_bottom_up(uns
> temp_end = temp_start + kbuf->memsz - 1;
>
> if (temp_end > end || temp_end > kbuf->buf_max)
> - return 0;
> + return EADDRNOTAVAIL;
> /*
> * Make sure this does not conflict with any of existing
> * segments
> @@ -2133,7 +2137,9 @@ static int locate_mem_hole_bottom_up(uns
> kbuf->memsz);
>
> /* Stop navigating through remaining System RAM ranges */
> - return 1;
> + ret |= RES_STOP;
> +
> + return ret;
> }
>
> static int walk_ram_range_callback(u64 start, u64 end, void *arg)
> @@ -2141,12 +2147,11 @@ static int walk_ram_range_callback(u64 s
> struct kexec_buf *kbuf = (struct kexec_buf *)arg;
> unsigned long sz = end - start + 1;
>
> - /* Returning 0 will take to next memory range */
> if (sz < kbuf->memsz)
> - return 0;
> + return EADDRNOTAVAIL;
>
> if (end < kbuf->buf_min || start > kbuf->buf_max)
> - return 0;
> + return EADDRNOTAVAIL;
>
> /*
> * Allocate memory top down with-in ram range. Otherwise bottom up
> @@ -2168,15 +2173,15 @@ int kexec_add_buffer(struct kimage *imag
> unsigned long buf_max, bool top_down, unsigned long *load_addr)
> {
>
> - unsigned long nr_segments = image->nr_segments, new_nr_segments;
> struct kexec_segment *ksegment;
> struct kexec_buf buf, *kbuf;
> + int ret;
>
> /* Currently adding segment this way is allowed only in file mode */
> if (!image->file_mode)
> return -EINVAL;
>
> - if (nr_segments >= KEXEC_SEGMENT_MAX)
> + if (image->nr_segments >= KEXEC_SEGMENT_MAX)
> return -EINVAL;
>
> /*
> @@ -2208,25 +2213,18 @@ int kexec_add_buffer(struct kimage *imag
>
> /* Walk the RAM ranges and allocate a suitable range for the buffer */
> if (image->type == KEXEC_TYPE_CRASH)
> - walk_ram_res("Crash kernel", IORESOURCE_MEM | IORESOURCE_BUSY,
> - crashk_res.start, crashk_res.end, kbuf,
> - walk_ram_range_callback);
> + ret = walk_ram_res("Crash kernel",
> + IORESOURCE_MEM | IORESOURCE_BUSY,
> + crashk_res.start, crashk_res.end, kbuf,
> + walk_ram_range_callback);
> else
> - walk_system_ram_res(0, -1, kbuf, walk_ram_range_callback);
> -
> - /*
> - * If range could be found successfully, it would have incremented
> - * the nr_segments value.
> - */
> - new_nr_segments = image->nr_segments;
> + ret = walk_system_ram_res(0, -1, kbuf, walk_ram_range_callback);
>
> - /* A suitable memory range could not be found for buffer */
> - if (new_nr_segments == nr_segments)
> + if (ret)
> return -EADDRNOTAVAIL;
>
> /* Found a suitable memory range */
> -
> - ksegment = &image->segment[new_nr_segments - 1];
> + ksegment = &image->segment[image->nr_segments - 1];
> *load_addr = ksegment->mem;
> return 0;
> }
> Index: b/include/linux/ioport.h
> ===================================================================
> --- a/include/linux/ioport.h 2014-06-11 14:49:35.865426300 +0200
> +++ b/include/linux/ioport.h 2014-06-11 16:02:12.775235692 +0200
> @@ -237,6 +237,16 @@ extern int iomem_is_exclusive(u64 addr);
> extern int
> walk_system_ram_range(unsigned long start_pfn, unsigned long nr_pages,
> void *arg, int (*func)(unsigned long, unsigned long, void *));
> +
> +#define RET_BITS 8
> +#define RET_MASK ((1U << RET_BITS) - 1)
> +#define RETVAL(r) (-((r) & RET_MASK))
> +
> +#define RET_OK 0
> +#define RET_ERR 1
> +
> +#define RES_STOP BIT(0 + RET_BITS)
> +
> extern int
> walk_system_ram_res(u64 start, u64 end, void *arg,
> int (*func)(u64, u64, void *));