Hi David,
I have fixed the issues with the patch and sent an updated patch. I
was able to reproduce the issue
in a qemu sparc emulator running Debian. I checked that the VDSO
binaries pass compilation with the
new patch in that environment.
Thanks,
Nagarathnam.
On 9/10/2017 9:03 PM, David Miller wrote:
From: David Miller <davem@xxxxxxxxxxxxx>
Date: Sat, 09 Sep 2017 20:41:29 -0700 (PDT)
The arch/sparc/vdso/vdso.lds file says:
vvar_start = . -(1 << 12);
And "1 << 12" is 4096, therefore a multiple of 4096 and not 8192.
So, as requested, the object built gets:
davem@patience:~/src/GIT/sparc-next$ nm -n arch/sparc/vdso/vdso64.so.dbg
fffffffffffff000 a vvar_data
fffffffffffff000 a vvar_start
Breaking this down further, the linker scripts are written assuming
they will be built by a host compiler that generates 64-bit target
code by default.
This is not a safe assumption.
My system generates 32-bit binaries from gcc by default, and that's
why you end up with a value of PAGE_SIZE which is 4096 propagating
through all of the generated linker scripts.
x86, where it seems like were at least used as a template for the
sparc linker scripts, gets away with this because the PAGE_SIZE
is the same on 32-bit and 64-bit.
Anyways, since 8192 is hard coded into vdso2c, just use 8192 as
PAGE_SIZE in vdso-layout.lds.S and maybe put a comment above it.
The next problem with the patch is that we get a warning because
the variable 'secstrings_hdr' is set but not used in vdso2c.h, and
compiler warnings are treated as errors under arch/sparc.
This is fixed simply by:
diff --git a/arch/sparc/vdso/vdso2c.h b/arch/sparc/vdso/vdso2c.h
index 8d1b5cf..b193e3d 100644
--- a/arch/sparc/vdso/vdso2c.h
+++ b/arch/sparc/vdso/vdso2c.h
@@ -17,9 +17,8 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
unsigned long mapping_size;
int i;
unsigned long j;
- const char *secstrings;
- ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr, *secstrings_hdr;
+ ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr;
ELF(Ehdr) *hdr = (ELF(Ehdr) *)raw_addr;
ELF(Dyn) *dyn = 0, *dyn_end = 0;
INT_BITS syms[NSYMS] = {};
@@ -64,9 +63,6 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
}
/* Walk the section table */
- secstrings_hdr = raw_addr + GET_BE(&hdr->e_shoff) +
- GET_BE(&hdr->e_shentsize)*GET_BE(&hdr->e_shstrndx);
- secstrings = raw_addr + GET_BE(&secstrings_hdr->sh_offset);
for (i = 0; i < GET_BE(&hdr->e_shnum); i++) {
ELF(Shdr) *sh = raw_addr + GET_BE(&hdr->e_shoff) +
GET_BE(&hdr->e_shentsize) * i;
--
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