[PATCH] ggc-common: Fix save PCH assertion

[PATCH] ggc-common: Fix save PCH assertion

[Jakub Jelinek]

Hi!

We are getting a gnuradio PCH ICE
/usr/include/pybind11/stl.h:447:1: internal compiler error: in gt_pch_save, at ggc-common.cc:693
0x1304e7d gt_pch_save(_IO_FILE*)
	../../gcc/ggc-common.cc:693
0x12a45fb c_common_write_pch()
	../../gcc/c-family/c-pch.cc:175
0x18ad711 c_parse_final_cleanups()
	../../gcc/cp/decl2.cc:5062
0x213988b c_common_parse_file()
	../../gcc/c-family/c-opts.cc:1319
(unfortunately it isn't reproduceable always, but often needs
up to 100 attempts, isn't reproduceable in a cross etc.).
The bug is in the assertion I've added in gt_pch_save when adding
relocation support for the PCH files in case they happen not to be
mmapped at the selected address.
addr is a relocated address which points to a location in the PCH
blob (starting at mmi.preferred_base, with mmi.size bytes) which contains
a pointer that needs to be relocated.  So the assertion is meant to
verify the address is within the PCH blob, obviously it needs to be
equal or above mmi.preferred_base, but I got the other comparison wrong
and when one is very unlucky and the last sizeof (void *) bytes of the
blob happen to be a pointer which needs to be relocated, such as on the
s390x host addr 0x8008a04ff8, mmi.preferred_base 0x8000000000 and
mmi.size 0x8a05000, addr + sizeof (void *) is equal to mmi.preferred_base +
mmi.size and that is still fine, both addresses are end of something.

Bootstrapped/regtested on x86_64-linux and i686-linux, plus tested on s390x
on the testcase which was ICEing in 1-100 iterations and there it survived
7750 attempts without ICE (forgot to stop it earlier), ok for trunk?

2024-02-03  Jakub Jelinek  <jakub@redhat.com>

	* ggc-common.cc (gt_pch_save): Allow addr to be equal to
	mmi.preferred_base + mmi.size - sizeof (void *).

--- gcc/ggc-common.cc.jj	2024-01-03 11:51:39.397622018 +0100
+++ gcc/ggc-common.cc	2024-02-02 17:33:13.106727473 +0100
@@ -692,7 +692,7 @@ gt_pch_save (FILE *f)
     {
       gcc_assert ((uintptr_t) addr >= (uintptr_t) mmi.preferred_base
 		  && ((uintptr_t) addr + sizeof (void *)
-		      < (uintptr_t) mmi.preferred_base + mmi.size));
+		      <= (uintptr_t) mmi.preferred_base + mmi.size));
       if (addr == last_addr)
 	continue;
       if (last_addr == NULL)

	Jakub

Re: [PATCH] ggc-common: Fix save PCH assertion

[Richard Biener]

> Am 03.02.2024 um 09:36 schrieb Jakub Jelinek <jakub@redhat.com>:
> 
> Hi!
> 
> We are getting a gnuradio PCH ICE
> /usr/include/pybind11/stl.h:447:1: internal compiler error: in gt_pch_save, at ggc-common.cc:693
> 0x1304e7d gt_pch_save(_IO_FILE*)
>    ../../gcc/ggc-common.cc:693
> 0x12a45fb c_common_write_pch()
>    ../../gcc/c-family/c-pch.cc:175
> 0x18ad711 c_parse_final_cleanups()
>    ../../gcc/cp/decl2.cc:5062
> 0x213988b c_common_parse_file()
>    ../../gcc/c-family/c-opts.cc:1319
> (unfortunately it isn't reproduceable always, but often needs
> up to 100 attempts, isn't reproduceable in a cross etc.).
> The bug is in the assertion I've added in gt_pch_save when adding
> relocation support for the PCH files in case they happen not to be
> mmapped at the selected address.
> addr is a relocated address which points to a location in the PCH
> blob (starting at mmi.preferred_base, with mmi.size bytes) which contains
> a pointer that needs to be relocated.  So the assertion is meant to
> verify the address is within the PCH blob, obviously it needs to be
> equal or above mmi.preferred_base, but I got the other comparison wrong
> and when one is very unlucky and the last sizeof (void *) bytes of the
> blob happen to be a pointer which needs to be relocated, such as on the
> s390x host addr 0x8008a04ff8, mmi.preferred_base 0x8000000000 and
> mmi.size 0x8a05000, addr + sizeof (void *) is equal to mmi.preferred_base +
> mmi.size and that is still fine, both addresses are end of something.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, plus tested on s390x
> on the testcase which was ICEing in 1-100 iterations and there it survived
> 7750 attempts without ICE (forgot to stop it earlier), ok for trunk?
> 

Ok

Richard 
> 2024-02-03  Jakub Jelinek  <jakub@redhat.com>
> 
>    * ggc-common.cc (gt_pch_save): Allow addr to be equal to
>    mmi.preferred_base + mmi.size - sizeof (void *).
> 
> --- gcc/ggc-common.cc.jj    2024-01-03 11:51:39.397622018 +0100
> +++ gcc/ggc-common.cc    2024-02-02 17:33:13.106727473 +0100
> @@ -692,7 +692,7 @@ gt_pch_save (FILE *f)
>     {
>       gcc_assert ((uintptr_t) addr >= (uintptr_t) mmi.preferred_base
>          && ((uintptr_t) addr + sizeof (void *)
> -              < (uintptr_t) mmi.preferred_base + mmi.size));
> +              <= (uintptr_t) mmi.preferred_base + mmi.size));
>       if (addr == last_addr)
>    continue;
>       if (last_addr == NULL)
> 
>    Jakub
>