This adds support for CONFIG_COMPAT_VDSO. As this will certainly raise
questions, I left in the code needed for an alternative approach (which
requires mode C code, but less build script changes).
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
Index: head-2007-02-27/arch/i386/Kconfig
===================================================================
--- head-2007-02-27.orig/arch/i386/Kconfig 2007-03-05 10:00:18.000000000
+0100
+++ head-2007-02-27/arch/i386/Kconfig 2007-02-27 16:27:37.000000000 +0100
@@ -819,7 +819,6 @@ config HOTPLUG_CPU
config COMPAT_VDSO
bool "Compat VDSO support"
- depends on !X86_XEN
default y
help
Map the VDSO to the predictable old-style address too.
Index: head-2007-02-27/arch/i386/kernel/Makefile
===================================================================
--- head-2007-02-27.orig/arch/i386/kernel/Makefile 2007-03-05
10:00:18.000000000 +0100
+++ head-2007-02-27/arch/i386/kernel/Makefile 2007-02-27 16:27:37.000000000
+0100
@@ -74,6 +74,52 @@ $(obj)/vsyscall-%.so: $(src)/vsyscall.ld
$(obj)/vsyscall-%.o $(obj)/$(vsyscall_note) FORCE
$(call if_changed,syscall)
+ifeq ($(CONFIG_XEN)$(CONFIG_COMPAT_VDSO),yy)
+
+# vsyscall.o also contains the vsyscall DSO relocation info as __initdata.
+# We must build both alternative images before we can assemble it.
+# Note: kbuild does not track this dependency due to usage of .include
+$(obj)/vsyscall.o: $(obj)/vsyscall-int80.rel $(obj)/vsyscall-sysenter.rel
+targets += $(foreach F,int80 sysenter,vsyscall-$F.so.alt vsyscall-$F.rel)
+targets += vsyscall.lds.alt
+
+# The alternative DSO images are built using an alternate base address.
+quiet_cmd_syscall_alt = REBASE $@
+ cmd_syscall_alt = sed
's,^\([[:space:]]*\.[[:space:]]*=[[:space:]]*\),\1-0x55AA0000 + ,' $< >$@
+
+quiet_cmd_syscall_rel = COMPARE $@
+ cmd_syscall_rel = set -e; \
+ cmp -l $(basename $<) $< \
+ | { read off1 old1 new1; \
+ read off2 old2 new2; \
+ test $$(expr $$off1 + 1) = $$off2; \
+ echo " .long $$(expr $$off1 - 3)"; \
+ while read off1 old3 new3; do \
+ read off2 old4 new4; \
+ test $$(expr $$off1 + 1) = $$off2; \
+ test $$old1 = $$old3 -a $$new1 = $$new3; \
+ test $$old2 = $$old4 -a $$new2 = $$new4; \
+ echo " .long $$(expr $$off1 - 3)"; \
+ done; \
+ } >$@
+
+SYSCFLAGS_vsyscall-sysenter.so.alt = $(vsyscall-flags)
+SYSCFLAGS_vsyscall-int80.so.alt = $(vsyscall-flags)
+
+$(obj)/vsyscall.lds.alt: $(obj)/vsyscall.lds FORCE
+ $(call if_changed,syscall_alt)
+
+$(obj)/vsyscall-int80.so.alt $(obj)/vsyscall-sysenter.so.alt: \
+$(obj)/vsyscall-%.so.alt: $(obj)/vsyscall.lds.alt \
+ $(obj)/vsyscall-%.o $(obj)/$(vsyscall_note) FORCE
+ $(call if_changed,syscall)
+
+$(obj)/vsyscall-int80.rel $(obj)/vsyscall-sysenter.rel: \
+$(obj)/vsyscall-%.rel: $(obj)/vsyscall-%.so.alt FORCE
+ $(call if_changed,syscall_rel)
+
+endif
+
# We also create a special relocatable object that should mirror the symbol
# table and layout of the linked DSO. With ld -R we can then refer to
# these symbols in the kernel code rather than hand-coded addresses.
Index: head-2007-02-27/arch/i386/kernel/sysenter.c
===================================================================
--- head-2007-02-27.orig/arch/i386/kernel/sysenter.c 2007-03-05
10:00:18.000000000 +0100
+++ head-2007-02-27/arch/i386/kernel/sysenter.c 2007-02-27 16:27:37.000000000
+0100
@@ -25,6 +25,8 @@
#ifdef CONFIG_XEN
#include <xen/interface/callback.h>
+extern const unsigned long vdso_rel_int80_start[], vdso_rel_int80_end[];
+extern const unsigned long vdso_rel_sysenter_start[], vdso_rel_sysenter_end[];
#endif
/*
@@ -66,6 +68,142 @@ void enable_sep_cpu(void)
#endif
}
+#if defined(CONFIG_XEN) && defined(CONFIG_COMPAT_VDSO)
+static void __init relocate_vdso(Elf32_Ehdr *ehdr, unsigned long old_base,
unsigned long new_base,
+ const unsigned long *reloc_start, const
unsigned long *reloc_end)
+{
+#if 1
+ const unsigned long *reloc;
+
+ for (reloc = reloc_start; reloc < reloc_end; ++reloc) {
+ unsigned long *ptr = (void *)((unsigned long)ehdr + *reloc);
+
+ *ptr += new_base - old_base;
+ }
+#else
+ unsigned i, ndynsym = 0, szdynsym = 0;
+ unsigned long dynsym = 0;
+
+ BUG_ON(ehdr->e_ident[EI_MAG0] != ELFMAG0);
+ BUG_ON(ehdr->e_ident[EI_MAG1] != ELFMAG1);
+ BUG_ON(ehdr->e_ident[EI_MAG2] != ELFMAG2);
+ BUG_ON(ehdr->e_ident[EI_MAG3] != ELFMAG3);
+ BUG_ON(ehdr->e_ident[EI_CLASS] != ELFCLASS32);
+ BUG_ON(ehdr->e_ident[EI_DATA] != ELFDATA2LSB);
+ BUG_ON(ehdr->e_ehsize < sizeof(*ehdr));
+ ehdr->e_entry += new_base - old_base;
+ BUG_ON(ehdr->e_phentsize < sizeof(Elf32_Phdr));
+ for (i = 0; i < ehdr->e_phnum; ++i) {
+ Elf32_Phdr *phdr = (void *)((unsigned long)ehdr + ehdr->e_phoff
+ i * ehdr->e_phentsize);
+
+ phdr->p_vaddr += new_base - old_base;
+ switch(phdr->p_type) {
+ case PT_LOAD:
+ case PT_NOTE:
+ break;
+ case PT_DYNAMIC: {
+ Elf32_Dyn *dyn = (void *)(phdr->p_vaddr -
new_base + (unsigned long)ehdr);
+ unsigned j;
+
+ for(j = 0; dyn[j].d_tag != DT_NULL; ++j) {
+ switch(dyn[j].d_tag) {
+ case DT_HASH:
+ case DT_STRTAB:
+ case DT_SYMTAB:
+ case 0x6ffffff0: /* DT_VERSYM */
+ case 0x6ffffffc: /* DT_VERDEF */
+ break;
+ case DT_SONAME:
+ case DT_STRSZ:
+ case 0x6ffffffd: /* DT_VERDEFNUM */
+ continue;
+ case DT_SYMENT:
+ szdynsym = dyn[j].d_un.d_val;
+ continue;
+ default:
+ if (dyn[j].d_tag >= 0x60000000
/* OLD_DT_LOOS */
+ || dyn[j].d_tag < 31 /*
DT_ENCODING */
+ || !(dyn[j].d_tag & 1)) {
+ printk(KERN_WARNING
"vDSO dynamic info %u has unsupported tag
%08X\n", j, dyn[j].d_tag);
+ WARN_ON(1);
+ continue;
+ }
+ break;
+ }
+ dyn[j].d_un.d_ptr += new_base -
old_base;
+ switch(dyn[j].d_tag) {
+ case DT_HASH:
+ ndynsym = ((Elf32_Word
*)dyn[j].d_un.d_ptr)[1];
+ break;
+ case DT_SYMTAB:
+ dynsym = dyn[j].d_un.d_ptr;
+ break;
+ }
+ }
+ }
+ break;
+ case PT_GNU_EH_FRAME:
+ /* XXX */
+ break;
+ default:
+ printk(KERN_WARNING "vDSO program header %u has
unsupported type %08X\n", i, phdr->p_type);
+ WARN_ON(1);
+ break;
+ }
+ }
+ BUG_ON(ehdr->e_shentsize < sizeof(Elf32_Shdr));
+ BUG_ON(ehdr->e_shnum >= SHN_LORESERVE);
+ for (i = 1; i < ehdr->e_shnum; ++i) {
+ Elf32_Shdr *shdr = (void *)((unsigned long)ehdr + ehdr->e_shoff
+ i * ehdr->e_shentsize);
+
+ if (!(shdr->sh_flags & SHF_ALLOC))
+ continue;
+ shdr->sh_addr += new_base - old_base;
+ switch(shdr->sh_type) {
+ case SHT_DYNAMIC:
+ case SHT_HASH:
+ case SHT_NOBITS:
+ case SHT_NOTE:
+ case SHT_PROGBITS:
+ case SHT_STRTAB:
+ case 0x6ffffffd: /* SHT_GNU_verdef */
+ case 0x6fffffff: /* SHT_GNU_versym */
+ break;
+ case SHT_DYNSYM:
+ BUG_ON(shdr->sh_entsize < sizeof(Elf32_Sym));
+ if (!szdynsym)
+ szdynsym = shdr->sh_entsize;
+ else
+ WARN_ON(szdynsym != shdr->sh_entsize);
+ if (!ndynsym)
+ ndynsym = shdr->sh_size / szdynsym;
+ else
+ WARN_ON(ndynsym != shdr->sh_size / szdynsym);
+ if (!dynsym)
+ dynsym = shdr->sh_addr;
+ else
+ WARN_ON(dynsym != shdr->sh_addr);
+ break;
+ default:
+ printk(KERN_WARNING "vDSO section %u has unsupported
type %08X\n", i, shdr->sh_type);
+ WARN_ON(shdr->sh_size);
+ break;
+ }
+ }
+ dynsym += (unsigned long)ehdr - new_base;
+ for(i = 1; i < ndynsym; ++i) {
+ Elf32_Sym *sym = (void *)(dynsym + i * szdynsym);
+
+ if (sym->st_shndx == SHN_ABS)
+ continue;
+ sym->st_value += new_base - old_base;
+ }
+#endif
+}
+#else
+#define relocate_vdso(ehdr, old, new, start, end) ((void)0)
+#endif
+
/*
* These symbols are defined by vsyscall.o to mark the bounds
* of the ELF DSO images included therein.
@@ -104,12 +245,16 @@ int __init sysenter_setup(void)
memcpy(syscall_page,
&vsyscall_int80_start,
&vsyscall_int80_end - &vsyscall_int80_start);
+ relocate_vdso(syscall_page, VDSO_PRELINK,
__fix_to_virt(FIX_VDSO),
+ vdso_rel_int80_start, vdso_rel_int80_end);
return 0;
}
memcpy(syscall_page,
&vsyscall_sysenter_start,
&vsyscall_sysenter_end - &vsyscall_sysenter_start);
+ relocate_vdso(syscall_page, VDSO_PRELINK, __fix_to_virt(FIX_VDSO),
+ vdso_rel_sysenter_start, vdso_rel_sysenter_end);
return 0;
}
Index: head-2007-02-27/arch/i386/kernel/vsyscall.S
===================================================================
--- head-2007-02-27.orig/arch/i386/kernel/vsyscall.S 2007-03-05
10:00:18.000000000 +0100
+++ head-2007-02-27/arch/i386/kernel/vsyscall.S 2007-02-27 16:27:37.000000000
+0100
@@ -12,4 +12,20 @@ vsyscall_sysenter_start:
.incbin "arch/i386/kernel/vsyscall-sysenter.so"
vsyscall_sysenter_end:
+#if defined(CONFIG_XEN) && defined(CONFIG_COMPAT_VDSO)
+
+ .align 4
+
+ .globl vdso_rel_int80_start, vdso_rel_int80_end
+vdso_rel_int80_start:
+ .include "arch/i386/kernel/vsyscall-int80.rel"
+vdso_rel_int80_end:
+
+ .globl vdso_rel_sysenter_start, vdso_rel_sysenter_end
+vdso_rel_sysenter_start:
+ .include "arch/i386/kernel/vsyscall-sysenter.rel"
+vdso_rel_sysenter_end:
+
+#endif
+
__FINIT
Index: head-2007-02-27/include/asm-i386/elf.h
===================================================================
--- head-2007-02-27.orig/include/asm-i386/elf.h 2007-03-05 10:00:18.000000000
+0100
+++ head-2007-02-27/include/asm-i386/elf.h 2007-02-27 16:27:37.000000000
+0100
@@ -137,7 +137,11 @@ extern int dump_task_extended_fpu (struc
#ifdef CONFIG_COMPAT_VDSO
# define VDSO_COMPAT_BASE VDSO_HIGH_BASE
-# define VDSO_PRELINK VDSO_HIGH_BASE
+# ifndef CONFIG_XEN
+# define VDSO_PRELINK VDSO_HIGH_BASE
+# else
+# define VDSO_PRELINK (0UL - FIX_VDSO * PAGE_SIZE)
+# endif
#else
# define VDSO_COMPAT_BASE VDSO_BASE
# define VDSO_PRELINK 0
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