rtld: Add new hook to initialize dp register on hppa
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Patch applied to master at the time it was sent
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| dj/TryBot-32bit |
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Build for i686
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Commit Message
The test elf/tst-audit2 fails on hppa with a segmentation fault in the
long branch stub used to call malloc from calloc. This occur because
the test is not a PIC executable and calloc is called from the dynamic
linker before the dp register is initialized in _dl_start_user.
The fix is to add a new hook, ELF_MACHINE_AFTER_RTLD_RELOC, in dl_main
to allow initialization of the dp register just after relocation is
completed.
Okay?
Dave
---
Comments
* John David Anglin:
> @@ -338,16 +350,6 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
> its return value is the user program's entry point. */
>
> #define RTLD_START \
> -/* Set up dp for any non-PIC lib constructors that may be called. */ \
> -static struct link_map * __attribute__((used)) \
> -set_dp (struct link_map *map) \
> -{ \
> - register Elf32_Addr dp asm ("%r27"); \
> - dp = D_PTR (map, l_info[DT_PLTGOT]); \
> - asm volatile ("" : : "r" (dp)); \
> - return map; \
> -} \
> - \
> asm ( \
> " .text\n" \
> " .globl _start\n" \
> @@ -447,14 +449,11 @@ asm ( \
> " stw %r24,-44(%sp)\n" \
> \
> ".Lnofix:\n" \
> + /* Call _dl_init(main_map, argc, argv, envp). */ \
> " addil LT'_rtld_local,%r19\n" \
> " ldw RT'_rtld_local(%r1),%r26\n" \
> -" bl set_dp, %r2\n" \
> " ldw 0(%r26),%r26\n" \
> \
> - /* Call _dl_init(_dl_loaded, argc, argv, envp). */ \
> -" copy %r28,%r26\n" \
> - \
> /* envp = argv + argc + 1 */ \
> " sh2add %r25,%r24,%r23\n" \
> " bl _dl_init,%r2\n" \
Can't you compute the PLTGOT address using a relocation that is filled
in by the link editor, before calling _dl_start? The link editor should
know the offset between the current code access and the start of the
PLTGOT.
Thanks,
Florian
On Fri, Feb 11, 2022 at 9:30 AM John David Anglin <dave.anglin@bell.net> wrote:
>
> The test elf/tst-audit2 fails on hppa with a segmentation fault in the
> long branch stub used to call malloc from calloc. This occur because
> the test is not a PIC executable and calloc is called from the dynamic
> linker before the dp register is initialized in _dl_start_user.
>
> The fix is to add a new hook, ELF_MACHINE_AFTER_RTLD_RELOC, in dl_main
> to allow initialization of the dp register just after relocation is
> completed.
>
> Okay?
>
> Dave
> ---
>
> diff --git a/elf/rtld.c b/elf/rtld.c
> index 19e328f89e..fcea41cb86 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -2333,6 +2333,10 @@ dl_main (const ElfW(Phdr) *phdr,
> /* Make sure no new search directories have been added. */
> assert (GLRO(dl_init_all_dirs) == GL(dl_all_dirs));
>
> +#ifdef ELF_MACHINE_AFTER_RTLD_RELOC
> + ELF_MACHINE_AFTER_RTLD_RELOC (main_map);
> +#endif
We should avoid macro Please use an inline function instead.
> if (rtld_multiple_ref)
> {
> /* There was an explicit ref to the dynamic linker as a shared lib.
> diff --git a/sysdeps/hppa/dl-machine.h b/sysdeps/hppa/dl-machine.h
> index da4d57d2e4..74a81dc1f7 100644
> --- a/sysdeps/hppa/dl-machine.h
> +++ b/sysdeps/hppa/dl-machine.h
> @@ -70,6 +70,18 @@ __hppa_init_bootstrap_fdesc_table (struct link_map *map)
> map->l_mach.fptr_table = boot_table;
> }
>
> +/* Set up dp for any non-PIC lib functions that may be called. */
> +static inline void
> +set_dp (struct link_map *map)
> +{
> + register Elf32_Addr dp asm ("%r27");
> + dp = D_PTR (map, l_info[DT_PLTGOT]);
> + asm volatile ("" : : "r" (dp));
> +}
> +
> +#define ELF_MACHINE_AFTER_RTLD_RELOC(map) \
> + set_dp (map);
> +
> #define ELF_MACHINE_BEFORE_RTLD_RELOC(map, dynamic_info) \
> __hppa_init_bootstrap_fdesc_table (map); \
> _dl_fptr_init();
> @@ -338,16 +350,6 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
> its return value is the user program's entry point. */
>
> #define RTLD_START \
> -/* Set up dp for any non-PIC lib constructors that may be called. */ \
> -static struct link_map * __attribute__((used)) \
> -set_dp (struct link_map *map) \
> -{ \
> - register Elf32_Addr dp asm ("%r27"); \
> - dp = D_PTR (map, l_info[DT_PLTGOT]); \
> - asm volatile ("" : : "r" (dp)); \
> - return map; \
> -} \
> - \
> asm ( \
> " .text\n" \
> " .globl _start\n" \
> @@ -447,14 +449,11 @@ asm ( \
> " stw %r24,-44(%sp)\n" \
> \
> ".Lnofix:\n" \
> + /* Call _dl_init(main_map, argc, argv, envp). */ \
> " addil LT'_rtld_local,%r19\n" \
> " ldw RT'_rtld_local(%r1),%r26\n" \
> -" bl set_dp, %r2\n" \
> " ldw 0(%r26),%r26\n" \
> \
> - /* Call _dl_init(_dl_loaded, argc, argv, envp). */ \
> -" copy %r28,%r26\n" \
> - \
> /* envp = argv + argc + 1 */ \
> " sh2add %r25,%r24,%r23\n" \
> " bl _dl_init,%r2\n" \
>
On 2022-02-11 12:51 p.m., Florian Weimer wrote:
> * John David Anglin:
>
>> @@ -338,16 +350,6 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
>> its return value is the user program's entry point. */
>>
>> #define RTLD_START \
>> -/* Set up dp for any non-PIC lib constructors that may be called. */ \
>> -static struct link_map * __attribute__((used)) \
>> -set_dp (struct link_map *map) \
>> -{ \
>> - register Elf32_Addr dp asm ("%r27"); \
>> - dp = D_PTR (map, l_info[DT_PLTGOT]); \
>> - asm volatile ("" : : "r" (dp)); \
>> - return map; \
>> -} \
>> - \
>> asm ( \
>> " .text\n" \
>> " .globl _start\n" \
>> @@ -447,14 +449,11 @@ asm ( \
>> " stw %r24,-44(%sp)\n" \
>> \
>> ".Lnofix:\n" \
>> + /* Call _dl_init(main_map, argc, argv, envp). */ \
>> " addil LT'_rtld_local,%r19\n" \
>> " ldw RT'_rtld_local(%r1),%r26\n" \
>> -" bl set_dp, %r2\n" \
>> " ldw 0(%r26),%r26\n" \
>> \
>> - /* Call _dl_init(_dl_loaded, argc, argv, envp). */ \
>> -" copy %r28,%r26\n" \
>> - \
>> /* envp = argv + argc + 1 */ \
>> " sh2add %r25,%r24,%r23\n" \
>> " bl _dl_init,%r2\n" \
> Can't you compute the PLTGOT address using a relocation that is filled
> in by the link editor, before calling _dl_start? The link editor should
> know the offset between the current code access and the start of the
> PLTGOT.
I'm not sure I like this at all. What relocation? Even if there was a relocation, it appears this
would make the behavior dependent on the link editor and thousands of applications would
need relinking.
Loading dp using from _rtld_local doesn't work till relocations are done. Is there a way to compute main_map
earlier?
The suggested approach just moves the dp register initialization earlier and doesn't affect any applications.
Dave
* John David Anglin:
> I'm not sure I like this at all. What relocation? Even if there was
> a relocation, it appears this would make the behavior dependent on the
> link editor and thousands of applications would need relinking.
I meant to use this link-time relocation in _start of ld.so.
> Loading dp using from _rtld_local doesn't work till relocations are
> done. Is there a way to compute main_map earlier?
You shouldn't need main_map for this. The link editor computes the
DT_PLTGOT and therefore knows the correct (relative) address.
Thanks,
Florian
On 2022-02-11 2:07 p.m., Florian Weimer wrote:
>> Loading dp using from _rtld_local doesn't work till relocations are
>> done. Is there a way to compute main_map earlier?
> You shouldn't need main_map for this. The link editor computes the
> DT_PLTGOT and therefore knows the correct (relative) address.
Your are correct. The link editor does define the symbol $global$ at the start of the PLTGOT.
However, I couldn't find a way to load its address without rummaging through the symbol table
of main. This is less efficient than using the PLTGOT value from the ELF header and main_map.
I committed the attached change. It doesn't need a new hook.
Thanks,
Dave
@@ -2333,6 +2333,10 @@ dl_main (const ElfW(Phdr) *phdr,
/* Make sure no new search directories have been added. */
assert (GLRO(dl_init_all_dirs) == GL(dl_all_dirs));
+#ifdef ELF_MACHINE_AFTER_RTLD_RELOC
+ ELF_MACHINE_AFTER_RTLD_RELOC (main_map);
+#endif
+
if (rtld_multiple_ref)
{
/* There was an explicit ref to the dynamic linker as a shared lib.
@@ -70,6 +70,18 @@ __hppa_init_bootstrap_fdesc_table (struct link_map *map)
map->l_mach.fptr_table = boot_table;
}
+/* Set up dp for any non-PIC lib functions that may be called. */
+static inline void
+set_dp (struct link_map *map)
+{
+ register Elf32_Addr dp asm ("%r27");
+ dp = D_PTR (map, l_info[DT_PLTGOT]);
+ asm volatile ("" : : "r" (dp));
+}
+
+#define ELF_MACHINE_AFTER_RTLD_RELOC(map) \
+ set_dp (map);
+
#define ELF_MACHINE_BEFORE_RTLD_RELOC(map, dynamic_info) \
__hppa_init_bootstrap_fdesc_table (map); \
_dl_fptr_init();
@@ -338,16 +350,6 @@ elf_machine_runtime_setup (struct link_map *l, struct r_scope_elem *scope[],
its return value is the user program's entry point. */
#define RTLD_START \
-/* Set up dp for any non-PIC lib constructors that may be called. */ \
-static struct link_map * __attribute__((used)) \
-set_dp (struct link_map *map) \
-{ \
- register Elf32_Addr dp asm ("%r27"); \
- dp = D_PTR (map, l_info[DT_PLTGOT]); \
- asm volatile ("" : : "r" (dp)); \
- return map; \
-} \
- \
asm ( \
" .text\n" \
" .globl _start\n" \
@@ -447,14 +449,11 @@ asm ( \
" stw %r24,-44(%sp)\n" \
\
".Lnofix:\n" \
+ /* Call _dl_init(main_map, argc, argv, envp). */ \
" addil LT'_rtld_local,%r19\n" \
" ldw RT'_rtld_local(%r1),%r26\n" \
-" bl set_dp, %r2\n" \
" ldw 0(%r26),%r26\n" \
\
- /* Call _dl_init(_dl_loaded, argc, argv, envp). */ \
-" copy %r28,%r26\n" \
- \
/* envp = argv + argc + 1 */ \
" sh2add %r25,%r24,%r23\n" \
" bl _dl_init,%r2\n" \