John Paul Adrian Glaubitz
132c5f769c
- add dosemu-LTO-fix.patch (bnc#1160098) OBS-URL: https://build.opensuse.org/request/show/766316 OBS-URL: https://build.opensuse.org/package/show/Emulators/dosemu?expand=0&rev=29
87 lines
3.0 KiB
Diff
87 lines
3.0 KiB
Diff
From: Jiri Slaby <jslaby@suse.cz>
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Subject: remove undefined behaviour/fix LTO build
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References: bnc#1160098
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The code defines two const pointers:
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unsigned char * const mem_base;
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char * const lowmem_base;
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They are set during setup.
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But the C standard clearly states:
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If an attempt is made to modify an object defined with a
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const-qualified type through use of an lvalue with non-const-qualified
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type, the behavior is undefined.
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This pretty nicely breaks when using modern gcc with LTO enabled. Gcc
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thinks the point is always NULL, as was initialized.
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This was fixed in dosemu2 by:
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https://github.com/stsp/dosemu2/commit/d36496646b31891ce952f3e9b63946a2ff2371b3
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https://github.com/stsp/dosemu2/commit/bb4437f93912d4d47961d2cbb0f13c737f8295c2
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---
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src/arch/linux/mapping/mapping.c | 6 +++---
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src/base/init/init.c | 2 +-
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src/include/memory.h | 9 +++++----
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3 files changed, 9 insertions(+), 8 deletions(-)
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--- a/src/arch/linux/mapping/mapping.c
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+++ b/src/arch/linux/mapping/mapping.c
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@@ -57,8 +57,8 @@ static int kmem_mappings = 0;
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static struct mem_map_struct kmem_map[MAX_KMEM_MAPPINGS];
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static int init_done = 0;
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-unsigned char * const mem_base;
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-char * const lowmem_base;
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+unsigned char *mem_base;
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+char *lowmem_base;
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#ifndef HAVE_MREMAP_FIXED
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int have_mremap_fixed = 1;
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#endif
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@@ -427,7 +427,7 @@ void *alloc_mapping(int cap, size_t maps
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if (cap & MAPPING_INIT_LOWRAM) {
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PRIV_SAVE_AREA
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Q__printf("MAPPING: LOWRAM_INIT, cap=%s, base=%p\n", cap, addr);
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- *(char **)(&lowmem_base) = addr;
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+ lowmem_base = addr;
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/* we may need root to mmap address 0 */
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enter_priv_on();
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addr = alias_mapping(MAPPING_INIT_LOWRAM, 0,
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--- a/src/base/init/init.c
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+++ b/src/base/init/init.c
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@@ -310,7 +310,7 @@ void low_mem_init(void)
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"WARN: as root, or by changing the vm.mmap_min_addr setting in\n"
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"WARN: /etc/sysctl.conf or a file in /etc/sysctl.d/ to 0.\n",
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result);
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- *(unsigned char **)&mem_base = result;
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+ mem_base = result;
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#endif
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}
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--- a/src/include/memory.h
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+++ b/src/include/memory.h
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@@ -233,7 +233,7 @@ void *lowmemp(const void *ptr);
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restrictions it can be non-zero. Non-zero values block vm86 but at least
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give NULL pointer protection.
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*/
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-extern unsigned char * const mem_base;
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+extern unsigned char *mem_base;
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/* lowmem_base points to a shared memory image of the area 0--1MB+64K.
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It does not have any holes or mapping for video RAM etc.
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@@ -242,10 +242,11 @@ extern unsigned char * const mem_base;
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simx86, NULL page protection, and removal of the VGA protected memory
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access hack.
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- It is set "const" to help GCC optimize accesses. In reality it is set only
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- once, at startup
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+ It is not set "const" as it is set once, at startup. Making it const
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+ would violate the C standard and would cause crashes and/or weird
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+ behaviour.
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*/
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-extern char * const lowmem_base;
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+extern char *lowmem_base;
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#define UNIX_READ_BYTE(addr) (*(Bit8u *) (addr))
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#define UNIX_WRITE_BYTE(addr, val) (*(Bit8u *) (addr) = (val) )
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