> > KOSAKI Motohiro wrote:
> > > > fs/binfmt_elf.c:
> > > > 77 #define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)
> > > Can do_brk() return BAD_ADDR() _and_ !IS_ERR_VALUE() value? when?
> >
> > For example, arch/mips/include/asm/processor.h has below definitions
> > which is smaller than INT_MAX
> >
> > 47 #ifdef CONFIG_32BIT
> > (...snipped...)
> > 52 #define TASK_SIZE 0x7fff8000UL
> > (...snipped...)
> > 63 #endif
> > 64
> > 65 #ifdef CONFIG_64BIT
> > (...snipped...)
> > 74 #define TASK_SIZE 0x10000000000UL
> > (...snipped...)
> > 91 #endif
> >
> > Also, several architectures define TASK_SIZE as
> >
> > #define TASK_SIZE PAGE_OFFSET
> >
> > and PAGE_OFFSET could be 0 if CONFIG_KERNEL_RAM_BASE_ADDRESS is not defined.
> >
> > include/asm-generic/page.h
> > 68 #ifdef CONFIG_KERNEL_RAM_BASE_ADDRESS
> > 69 #define PAGE_OFFSET (CONFIG_KERNEL_RAM_BASE_ADDRESS)
> > 70 #else
> > 71 #define PAGE_OFFSET (0)
> > 72 #endif
> >
> > If TASK_SIZE == 0, BAD_ADDR(x) is always true and !IS_ERR_VALUE(x) can be true.
> > Although I don't know which combination makes such environment,
> > I think "BAD_ADDR() _and_ !IS_ERR_VALUE()" can happen.
>
> I think you should read do_brk() itself. the spec is
>
> success case:
> return addr argument
>
> error case:
> return error code
>
> When does it return invalid address?
Does this makes a bit cleanups?
>From 5f5556d30ac1876ec2211a2eae77e8372183a9b1 Mon Sep 17 00:00:00 2001
From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Date: Fri, 15 Oct 2010 05:13:40 +0900
Subject: [cleanup][PATCH] elf: kill BAD_ADDR() macro
BAD_ADDR() macro is useless because 1) do_brk() and do_mmap() return
only either valid pointer or error code 2) when kernel and userland have
perfectly different address space (such as old 4G:4G separation), to
compare TASK_SIZE has no good meaning.
Then, this patch change it to use IS_ERR_VALUE instead (as other a lot
of places).
But, this is theorical issue. this patch doesn't have functional change.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
fs/binfmt_elf.c | 6 ++----
1 files changed, 2 insertions(+), 4 deletions(-)
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 535e763..ee235dd 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -74,8 +74,6 @@ static struct linux_binfmt elf_format = {
.hasvdso = 1
};
-#define BAD_ADDR(x) ((unsigned long)(x) >= TASK_SIZE)
-
static int set_brk(unsigned long start, unsigned long end)
{
start = ELF_PAGEALIGN(start);
@@ -85,7 +83,7 @@ static int set_brk(unsigned long start, unsigned long end)
down_write(¤t->mm->mmap_sem);
addr = do_brk(start, end - start);
up_write(¤t->mm->mmap_sem);
- if (BAD_ADDR(addr))
+ if (IS_ERR_VALUE(addr))
return addr;
}
current->mm->start_brk = current->mm->brk = end;
@@ -345,7 +343,7 @@ static unsigned long elf_map(struct file *filep, unsigned long addr,
if (total_size) {
total_size = ELF_PAGEALIGN(total_size);
map_addr = do_mmap(filep, addr, total_size, prot, type, off);
- if (!BAD_ADDR(map_addr))
+ if (!IS_ERR_VALUE(map_addr))
do_munmap(current->mm, map_addr+size, total_size-size);
} else
map_addr = do_mmap(filep, addr, size, prot, type, off);
--
1.6.5.2
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