* [PATCH] aarch64: Handle fewer relocations for RTLD_BOOTSTRAP
@ 2022-06-06 4:37 Fangrui Song
2022-06-11 2:32 ` Fangrui Song
0 siblings, 1 reply; 7+ messages in thread
From: Fangrui Song @ 2022-06-06 4:37 UTC (permalink / raw)
To: libc-alpha
The RTLD_BOOTSTRAP branch is used to relocate ld.so itself. It only
needs to handle RELATIVE, GLOB_DAT, and JUMP_SLOT.
Tested on aarch64-linux-gnu.
---
sysdeps/aarch64/dl-machine.h | 33 +++++++++++++++------------------
1 file changed, 15 insertions(+), 18 deletions(-)
diff --git a/sysdeps/aarch64/dl-machine.h b/sysdeps/aarch64/dl-machine.h
index 292abe5152..ae8b14425a 100644
--- a/sysdeps/aarch64/dl-machine.h
+++ b/sysdeps/aarch64/dl-machine.h
@@ -178,7 +178,9 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
return;
else
{
+# ifndef RTLD_BOOTSTRAP
const ElfW(Sym) *const refsym = sym;
+# endif
struct link_map *sym_map = RESOLVE_MAP (map, scope, &sym, version,
r_type);
ElfW(Addr) value = SYMBOL_ADDRESS (sym_map, sym, true);
@@ -191,6 +193,18 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
switch (r_type)
{
+ case AARCH64_R(GLOB_DAT):
+ case AARCH64_R(JUMP_SLOT):
+ *reloc_addr = value + reloc->r_addend;
+ break;
+
+# ifndef RTLD_BOOTSTRAP
+ case AARCH64_R(ABS32):
+# ifdef __LP64__
+ case AARCH64_R(ABS64):
+# endif
+ *reloc_addr = value + reloc->r_addend;
+ break;
case AARCH64_R(COPY):
if (sym == NULL)
break;
@@ -210,30 +224,17 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
? sym->st_size : refsym->st_size);
break;
- case AARCH64_R(RELATIVE):
- case AARCH64_R(GLOB_DAT):
- case AARCH64_R(JUMP_SLOT):
- case AARCH64_R(ABS32):
-#ifdef __LP64__
- case AARCH64_R(ABS64):
-#endif
- *reloc_addr = value + reloc->r_addend;
- break;
-
case AARCH64_R(TLSDESC):
{
struct tlsdesc volatile *td =
(struct tlsdesc volatile *)reloc_addr;
-#ifndef RTLD_BOOTSTRAP
if (! sym)
{
td->arg = (void*)reloc->r_addend;
td->entry = _dl_tlsdesc_undefweak;
}
else
-#endif
{
-#ifndef RTLD_BOOTSTRAP
# ifndef SHARED
CHECK_STATIC_TLS (map, sym_map);
# else
@@ -245,7 +246,6 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
}
else
# endif
-#endif
{
td->arg = (void*)(sym->st_value + sym_map->l_tls_offset
+ reloc->r_addend);
@@ -256,14 +256,10 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
}
case AARCH64_R(TLS_DTPMOD):
-#ifdef RTLD_BOOTSTRAP
- *reloc_addr = 1;
-#else
if (sym_map != NULL)
{
*reloc_addr = sym_map->l_tls_modid;
}
-#endif
break;
case AARCH64_R(TLS_DTPREL):
@@ -286,6 +282,7 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
value = elf_ifunc_invoke (value);
*reloc_addr = value;
break;
+# endif /* !RTLD_BOOTSTRAP */
default:
_dl_reloc_bad_type (map, r_type, 0);
--
2.36.1.255.ge46751e96f-goog
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] aarch64: Handle fewer relocations for RTLD_BOOTSTRAP
2022-06-06 4:37 [PATCH] aarch64: Handle fewer relocations for RTLD_BOOTSTRAP Fangrui Song
@ 2022-06-11 2:32 ` Fangrui Song
2022-06-13 8:33 ` Szabolcs Nagy
0 siblings, 1 reply; 7+ messages in thread
From: Fangrui Song @ 2022-06-11 2:32 UTC (permalink / raw)
To: Marcus Shawcroft, Szabolcs Nagy; +Cc: libc-alpha
On 2022-06-05, Fangrui Song wrote:
>The RTLD_BOOTSTRAP branch is used to relocate ld.so itself. It only
>needs to handle RELATIVE, GLOB_DAT, and JUMP_SLOT.
>
>Tested on aarch64-linux-gnu.
>---
> sysdeps/aarch64/dl-machine.h | 33 +++++++++++++++------------------
> 1 file changed, 15 insertions(+), 18 deletions(-)
>
>diff --git a/sysdeps/aarch64/dl-machine.h b/sysdeps/aarch64/dl-machine.h
>index 292abe5152..ae8b14425a 100644
>--- a/sysdeps/aarch64/dl-machine.h
>+++ b/sysdeps/aarch64/dl-machine.h
>@@ -178,7 +178,9 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
> return;
> else
> {
>+# ifndef RTLD_BOOTSTRAP
> const ElfW(Sym) *const refsym = sym;
>+# endif
> struct link_map *sym_map = RESOLVE_MAP (map, scope, &sym, version,
> r_type);
> ElfW(Addr) value = SYMBOL_ADDRESS (sym_map, sym, true);
>@@ -191,6 +193,18 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
>
> switch (r_type)
> {
>+ case AARCH64_R(GLOB_DAT):
>+ case AARCH64_R(JUMP_SLOT):
>+ *reloc_addr = value + reloc->r_addend;
>+ break;
>+
>+# ifndef RTLD_BOOTSTRAP
>+ case AARCH64_R(ABS32):
>+# ifdef __LP64__
>+ case AARCH64_R(ABS64):
>+# endif
>+ *reloc_addr = value + reloc->r_addend;
>+ break;
> case AARCH64_R(COPY):
> if (sym == NULL)
> break;
>@@ -210,30 +224,17 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
> ? sym->st_size : refsym->st_size);
> break;
>
>- case AARCH64_R(RELATIVE):
>- case AARCH64_R(GLOB_DAT):
>- case AARCH64_R(JUMP_SLOT):
>- case AARCH64_R(ABS32):
>-#ifdef __LP64__
>- case AARCH64_R(ABS64):
>-#endif
>- *reloc_addr = value + reloc->r_addend;
>- break;
>-
> case AARCH64_R(TLSDESC):
> {
> struct tlsdesc volatile *td =
> (struct tlsdesc volatile *)reloc_addr;
>-#ifndef RTLD_BOOTSTRAP
> if (! sym)
> {
> td->arg = (void*)reloc->r_addend;
> td->entry = _dl_tlsdesc_undefweak;
> }
> else
>-#endif
> {
>-#ifndef RTLD_BOOTSTRAP
> # ifndef SHARED
> CHECK_STATIC_TLS (map, sym_map);
> # else
>@@ -245,7 +246,6 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
> }
> else
> # endif
>-#endif
> {
> td->arg = (void*)(sym->st_value + sym_map->l_tls_offset
> + reloc->r_addend);
>@@ -256,14 +256,10 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
> }
>
> case AARCH64_R(TLS_DTPMOD):
>-#ifdef RTLD_BOOTSTRAP
>- *reloc_addr = 1;
>-#else
> if (sym_map != NULL)
> {
> *reloc_addr = sym_map->l_tls_modid;
> }
>-#endif
> break;
>
> case AARCH64_R(TLS_DTPREL):
>@@ -286,6 +282,7 @@ elf_machine_rela (struct link_map *map, struct r_scope_elem *scope[],
> value = elf_ifunc_invoke (value);
> *reloc_addr = value;
> break;
>+# endif /* !RTLD_BOOTSTRAP */
>
> default:
> _dl_reloc_bad_type (map, r_type, 0);
>--
>2.36.1.255.ge46751e96f-goog
Cc machine maintainers
^ permalink raw reply [flat|nested] 7+ messages in thread* Re: [PATCH] aarch64: Handle fewer relocations for RTLD_BOOTSTRAP
2022-06-11 2:32 ` Fangrui Song
@ 2022-06-13 8:33 ` Szabolcs Nagy
2022-06-14 0:02 ` Fangrui Song
0 siblings, 1 reply; 7+ messages in thread
From: Szabolcs Nagy @ 2022-06-13 8:33 UTC (permalink / raw)
To: Fangrui Song; +Cc: Marcus Shawcroft, libc-alpha
The 06/10/2022 19:32, Fangrui Song wrote:
> On 2022-06-05, Fangrui Song wrote:
> > The RTLD_BOOTSTRAP branch is used to relocate ld.so itself. It only
> > needs to handle RELATIVE, GLOB_DAT, and JUMP_SLOT.
the motivation is not clear to me.
is there an issue with other relocations or is this just a cleanup patch?
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] aarch64: Handle fewer relocations for RTLD_BOOTSTRAP
2022-06-13 8:33 ` Szabolcs Nagy
@ 2022-06-14 0:02 ` Fangrui Song
2022-06-14 5:07 ` Florian Weimer
0 siblings, 1 reply; 7+ messages in thread
From: Fangrui Song @ 2022-06-14 0:02 UTC (permalink / raw)
To: Szabolcs Nagy; +Cc: Marcus Shawcroft, libc-alpha
On 2022-06-13, Szabolcs Nagy wrote:
>The 06/10/2022 19:32, Fangrui Song wrote:
>> On 2022-06-05, Fangrui Song wrote:
>> > The RTLD_BOOTSTRAP branch is used to relocate ld.so itself. It only
>> > needs to handle RELATIVE, GLOB_DAT, and JUMP_SLOT.
>
>the motivation is not clear to me.
>
>is there an issue with other relocations or is this just a cleanup patch?
It is a cleanup: remove dead code paths.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] aarch64: Handle fewer relocations for RTLD_BOOTSTRAP
2022-06-14 0:02 ` Fangrui Song
@ 2022-06-14 5:07 ` Florian Weimer
2022-06-14 7:49 ` Szabolcs Nagy
0 siblings, 1 reply; 7+ messages in thread
From: Florian Weimer @ 2022-06-14 5:07 UTC (permalink / raw)
To: Fangrui Song via Libc-alpha; +Cc: Szabolcs Nagy, Fangrui Song, Marcus Shawcroft
* Fangrui Song via Libc-alpha:
> On 2022-06-13, Szabolcs Nagy wrote:
>>The 06/10/2022 19:32, Fangrui Song wrote:
>>> On 2022-06-05, Fangrui Song wrote:
>>> > The RTLD_BOOTSTRAP branch is used to relocate ld.so itself. It only
>>> > needs to handle RELATIVE, GLOB_DAT, and JUMP_SLOT.
>>
>>the motivation is not clear to me.
>>
>>is there an issue with other relocations or is this just a cleanup patch?
>
> It is a cleanup: remove dead code paths.
I think it could be paired (later) with a test that checks that ld.so
uses just the relocation types implemented for self-relocation.
I do not think it's possible in general to use the same code for
self-relocation and subsequent library loading, especially on
HIDDEN_VAR_NEEDS_DYNAMIC_RELOC architectures (I like the new name, by
the way).
Thanks,
Florian
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] aarch64: Handle fewer relocations for RTLD_BOOTSTRAP
2022-06-14 5:07 ` Florian Weimer
@ 2022-06-14 7:49 ` Szabolcs Nagy
2022-06-14 8:19 ` Fangrui Song
0 siblings, 1 reply; 7+ messages in thread
From: Szabolcs Nagy @ 2022-06-14 7:49 UTC (permalink / raw)
To: Florian Weimer
Cc: Fangrui Song via Libc-alpha, Fangrui Song, Marcus Shawcroft
The 06/14/2022 07:07, Florian Weimer wrote:
> * Fangrui Song via Libc-alpha:
> > On 2022-06-13, Szabolcs Nagy wrote:
> >>The 06/10/2022 19:32, Fangrui Song wrote:
> >>> On 2022-06-05, Fangrui Song wrote:
> >>> > The RTLD_BOOTSTRAP branch is used to relocate ld.so itself. It only
> >>> > needs to handle RELATIVE, GLOB_DAT, and JUMP_SLOT.
> >>
> >>the motivation is not clear to me.
> >>
> >>is there an issue with other relocations or is this just a cleanup patch?
> >
> > It is a cleanup: remove dead code paths.
>
> I think it could be paired (later) with a test that checks that ld.so
> uses just the relocation types implemented for self-relocation.
>
> I do not think it's possible in general to use the same code for
> self-relocation and subsequent library loading, especially on
> HIDDEN_VAR_NEEDS_DYNAMIC_RELOC architectures (I like the new name, by
> the way).
i see. cleanup is fine.
note that there is static-pie too, which requires a 3rd
way to do relocations (and ideally it would be split to
separate RELATIVE and IRELATIVE reloc processing given
that ifunc requires complex setup like dynamic allocation
for tunables handling. the split is also needed if we want
to support static-pie with HIDDEN_VAR_NEEDS_DYNAMIC_RELOC).
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] aarch64: Handle fewer relocations for RTLD_BOOTSTRAP
2022-06-14 7:49 ` Szabolcs Nagy
@ 2022-06-14 8:19 ` Fangrui Song
0 siblings, 0 replies; 7+ messages in thread
From: Fangrui Song @ 2022-06-14 8:19 UTC (permalink / raw)
To: Szabolcs Nagy
Cc: Florian Weimer, Fangrui Song via Libc-alpha, Marcus Shawcroft
On 2022-06-14, Szabolcs Nagy wrote:
>The 06/14/2022 07:07, Florian Weimer wrote:
>> * Fangrui Song via Libc-alpha:
>> > On 2022-06-13, Szabolcs Nagy wrote:
>> >>The 06/10/2022 19:32, Fangrui Song wrote:
>> >>> On 2022-06-05, Fangrui Song wrote:
>> >>> > The RTLD_BOOTSTRAP branch is used to relocate ld.so itself. It only
>> >>> > needs to handle RELATIVE, GLOB_DAT, and JUMP_SLOT.
>> >>
>> >>the motivation is not clear to me.
>> >>
>> >>is there an issue with other relocations or is this just a cleanup patch?
>> >
>> > It is a cleanup: remove dead code paths.
>>
>> I think it could be paired (later) with a test that checks that ld.so
>> uses just the relocation types implemented for self-relocation.
>>
>> I do not think it's possible in general to use the same code for
>> self-relocation and subsequent library loading, especially on
>> HIDDEN_VAR_NEEDS_DYNAMIC_RELOC architectures (I like the new name, by
>> the way).
>
>i see. cleanup is fine.
>
>note that there is static-pie too, which requires a 3rd
>way to do relocations (and ideally it would be split to
>separate RELATIVE and IRELATIVE reloc processing given
>that ifunc requires complex setup like dynamic allocation
>for tunables handling. the split is also needed if we want
>to support static-pie with HIDDEN_VAR_NEEDS_DYNAMIC_RELOC).
dl-reloc-static-pie.c uses the !RTLD_BOOTSTRAP branch, like dl-reloc.c.
I have tested that --enable-static-pie is correct.
I agree that it will be nice to have a readelf -rW test later.
For most ports, .rela?.plt and .rela?.dyn should only contain
RELATIVE|JU?MP_SLOT|GLOB_DAT.
There are a few less popular ports that I am unclear, though.
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2022-06-14 8:19 UTC | newest]
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2022-06-06 4:37 [PATCH] aarch64: Handle fewer relocations for RTLD_BOOTSTRAP Fangrui Song
2022-06-11 2:32 ` Fangrui Song
2022-06-13 8:33 ` Szabolcs Nagy
2022-06-14 0:02 ` Fangrui Song
2022-06-14 5:07 ` Florian Weimer
2022-06-14 7:49 ` Szabolcs Nagy
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