diff mbox series

[v2,4/6] elf: Move note processing after l_phdr is updated

Message ID 36d457074f389740b45afc4f9c6d124046f8352b.1606319495.git.szabolcs.nagy@arm.com
State New
Headers show
Series aarch64: avoid mprotect(PROT_BTI|PROT_EXEC) [BZ #26831] | expand

Commit Message

Szabolcs Nagy Nov. 27, 2020, 1:20 p.m. UTC
Program headers are processed in two pass: after the first pass
load segments are mmapped so in the second pass target specific
note processing logic can access the notes.

The second pass is moved later so various link_map fields are
set up that may be useful for note processing such as l_phdr.
The second pass should be before the fd is closed so that is
available.
---
 elf/dl-load.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

Comments

Adhemerval Zanella Dec. 10, 2020, 6:30 p.m. UTC | #1
On 27/11/2020 10:20, Szabolcs Nagy via Libc-alpha wrote:
> Program headers are processed in two pass: after the first pass
> load segments are mmapped so in the second pass target specific
> note processing logic can access the notes.
> 
> The second pass is moved later so various link_map fields are
> set up that may be useful for note processing such as l_phdr.
> The second pass should be before the fd is closed so that is
> available.

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  elf/dl-load.c | 30 +++++++++++++++---------------
>  1 file changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/elf/dl-load.c b/elf/dl-load.c
> index 9c71b7562c..b0d65f32cc 100644
> --- a/elf/dl-load.c
> +++ b/elf/dl-load.c
> @@ -1268,21 +1268,6 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd,
>  	l->l_map_start = l->l_map_end = 0;
>  	goto call_lose;
>        }
> -
> -    /* Process program headers again after load segments are mapped in
> -       case processing requires accessing those segments.  Scan program
> -       headers backward so that PT_NOTE can be skipped if PT_GNU_PROPERTY
> -       exits.  */
> -    for (ph = &phdr[l->l_phnum]; ph != phdr; --ph)
> -      switch (ph[-1].p_type)
> -	{
> -	case PT_NOTE:
> -	  _dl_process_pt_note (l, &ph[-1]);
> -	  break;
> -	case PT_GNU_PROPERTY:
> -	  _dl_process_pt_gnu_property (l, &ph[-1]);
> -	  break;
> -	}
>    }
>  
>    if (l->l_ld == 0)
> @@ -1386,6 +1371,21 @@ cannot enable executable stack as shared object requires");
>    if (l->l_tls_initimage != NULL)
>      l->l_tls_initimage = (char *) l->l_tls_initimage + l->l_addr;
>  
> +  /* Process program headers again after load segments are mapped in
> +     case processing requires accessing those segments.  Scan program
> +     headers backward so that PT_NOTE can be skipped if PT_GNU_PROPERTY
> +     exits.  */
> +  for (ph = &l->l_phdr[l->l_phnum]; ph != l->l_phdr; --ph)
> +    switch (ph[-1].p_type)
> +      {
> +      case PT_NOTE:
> +	_dl_process_pt_note (l, &ph[-1]);
> +	break;
> +      case PT_GNU_PROPERTY:
> +	_dl_process_pt_gnu_property (l, &ph[-1]);
> +	break;
> +      }
> +
>    /* We are done mapping in the file.  We no longer need the descriptor.  */
>    if (__glibc_unlikely (__close_nocancel (fd) != 0))
>      {
>
diff mbox series

Patch

diff --git a/elf/dl-load.c b/elf/dl-load.c
index 9c71b7562c..b0d65f32cc 100644
--- a/elf/dl-load.c
+++ b/elf/dl-load.c
@@ -1268,21 +1268,6 @@  _dl_map_object_from_fd (const char *name, const char *origname, int fd,
 	l->l_map_start = l->l_map_end = 0;
 	goto call_lose;
       }
-
-    /* Process program headers again after load segments are mapped in
-       case processing requires accessing those segments.  Scan program
-       headers backward so that PT_NOTE can be skipped if PT_GNU_PROPERTY
-       exits.  */
-    for (ph = &phdr[l->l_phnum]; ph != phdr; --ph)
-      switch (ph[-1].p_type)
-	{
-	case PT_NOTE:
-	  _dl_process_pt_note (l, &ph[-1]);
-	  break;
-	case PT_GNU_PROPERTY:
-	  _dl_process_pt_gnu_property (l, &ph[-1]);
-	  break;
-	}
   }
 
   if (l->l_ld == 0)
@@ -1386,6 +1371,21 @@  cannot enable executable stack as shared object requires");
   if (l->l_tls_initimage != NULL)
     l->l_tls_initimage = (char *) l->l_tls_initimage + l->l_addr;
 
+  /* Process program headers again after load segments are mapped in
+     case processing requires accessing those segments.  Scan program
+     headers backward so that PT_NOTE can be skipped if PT_GNU_PROPERTY
+     exits.  */
+  for (ph = &l->l_phdr[l->l_phnum]; ph != l->l_phdr; --ph)
+    switch (ph[-1].p_type)
+      {
+      case PT_NOTE:
+	_dl_process_pt_note (l, &ph[-1]);
+	break;
+      case PT_GNU_PROPERTY:
+	_dl_process_pt_gnu_property (l, &ph[-1]);
+	break;
+      }
+
   /* We are done mapping in the file.  We no longer need the descriptor.  */
   if (__glibc_unlikely (__close_nocancel (fd) != 0))
     {