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

Borislav Petkov
2014-06-11T14:13:24Z

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.

--
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 *));