Re: [PATCH v5 23/27] x86/modules: Adapt module loading for PIE support
On Mon, Jun 25, 2018 at 4:51 PM Randy Dunlap wrote: > > On 06/25/18 15:39, Thomas Garnier wrote: > > Adapt module loading to support PIE relocations. Generate dynamic GOT if > > a symbol requires it but no entry exists in the kernel GOT. > > Hi, > > This patch description (and a few others with the same sentence) is a little > confusing to me: > > > Position Independent Executable (PIE) support will allow to extend the > > KASLR randomization range 0x8000. > > Is there a word missing after "range"? May "below"? > As is, it seems to imply "range by 0x8000." Yes, below. I will fix this on all patch descriptions on next iteration. Thanks! > > > thanks. > > > > > Signed-off-by: Thomas Garnier > > --- > > arch/x86/Makefile | 4 + > > arch/x86/include/asm/module.h | 11 ++ > > arch/x86/include/asm/sections.h | 4 + > > arch/x86/kernel/module.c| 181 +++- > > arch/x86/kernel/module.lds | 3 + > > 5 files changed, 198 insertions(+), 5 deletions(-) > > create mode 100644 arch/x86/kernel/module.lds > > > -- > ~Randy -- Thomas
Re: [PATCH v5 23/27] x86/modules: Adapt module loading for PIE support
On Mon, Jun 25, 2018 at 4:51 PM Randy Dunlap wrote: > > On 06/25/18 15:39, Thomas Garnier wrote: > > Adapt module loading to support PIE relocations. Generate dynamic GOT if > > a symbol requires it but no entry exists in the kernel GOT. > > Hi, > > This patch description (and a few others with the same sentence) is a little > confusing to me: > > > Position Independent Executable (PIE) support will allow to extend the > > KASLR randomization range 0x8000. > > Is there a word missing after "range"? May "below"? > As is, it seems to imply "range by 0x8000." Yes, below. I will fix this on all patch descriptions on next iteration. Thanks! > > > thanks. > > > > > Signed-off-by: Thomas Garnier > > --- > > arch/x86/Makefile | 4 + > > arch/x86/include/asm/module.h | 11 ++ > > arch/x86/include/asm/sections.h | 4 + > > arch/x86/kernel/module.c| 181 +++- > > arch/x86/kernel/module.lds | 3 + > > 5 files changed, 198 insertions(+), 5 deletions(-) > > create mode 100644 arch/x86/kernel/module.lds > > > -- > ~Randy -- Thomas
Re: [PATCH v5 23/27] x86/modules: Adapt module loading for PIE support
On 06/25/18 15:39, Thomas Garnier wrote: > Adapt module loading to support PIE relocations. Generate dynamic GOT if > a symbol requires it but no entry exists in the kernel GOT. Hi, This patch description (and a few others with the same sentence) is a little confusing to me: > Position Independent Executable (PIE) support will allow to extend the > KASLR randomization range 0x8000. Is there a word missing after "range"? May "below"? As is, it seems to imply "range by 0x8000." thanks. > > Signed-off-by: Thomas Garnier > --- > arch/x86/Makefile | 4 + > arch/x86/include/asm/module.h | 11 ++ > arch/x86/include/asm/sections.h | 4 + > arch/x86/kernel/module.c| 181 +++- > arch/x86/kernel/module.lds | 3 + > 5 files changed, 198 insertions(+), 5 deletions(-) > create mode 100644 arch/x86/kernel/module.lds -- ~Randy
Re: [PATCH v5 23/27] x86/modules: Adapt module loading for PIE support
On 06/25/18 15:39, Thomas Garnier wrote: > Adapt module loading to support PIE relocations. Generate dynamic GOT if > a symbol requires it but no entry exists in the kernel GOT. Hi, This patch description (and a few others with the same sentence) is a little confusing to me: > Position Independent Executable (PIE) support will allow to extend the > KASLR randomization range 0x8000. Is there a word missing after "range"? May "below"? As is, it seems to imply "range by 0x8000." thanks. > > Signed-off-by: Thomas Garnier > --- > arch/x86/Makefile | 4 + > arch/x86/include/asm/module.h | 11 ++ > arch/x86/include/asm/sections.h | 4 + > arch/x86/kernel/module.c| 181 +++- > arch/x86/kernel/module.lds | 3 + > 5 files changed, 198 insertions(+), 5 deletions(-) > create mode 100644 arch/x86/kernel/module.lds -- ~Randy
[PATCH v5 23/27] x86/modules: Adapt module loading for PIE support
Adapt module loading to support PIE relocations. Generate dynamic GOT if
a symbol requires it but no entry exists in the kernel GOT.
Position Independent Executable (PIE) support will allow to extend the
KASLR randomization range 0x8000.
Signed-off-by: Thomas Garnier
---
arch/x86/Makefile | 4 +
arch/x86/include/asm/module.h | 11 ++
arch/x86/include/asm/sections.h | 4 +
arch/x86/kernel/module.c| 181 +++-
arch/x86/kernel/module.lds | 3 +
5 files changed, 198 insertions(+), 5 deletions(-)
create mode 100644 arch/x86/kernel/module.lds
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index c2c221fd20d7..112ccdc99566 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -134,7 +134,11 @@ else
KBUILD_CFLAGS += $(cflags-y)
KBUILD_CFLAGS += -mno-red-zone
+ifdef CONFIG_X86_PIE
+KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/x86/kernel/module.lds
+else
KBUILD_CFLAGS += -mcmodel=kernel
+endif
# -funit-at-a-time shrinks the kernel .text considerably
# unfortunately it makes reading oopses harder.
diff --git a/arch/x86/include/asm/module.h b/arch/x86/include/asm/module.h
index 7948a17febb4..68ff05e14288 100644
--- a/arch/x86/include/asm/module.h
+++ b/arch/x86/include/asm/module.h
@@ -5,12 +5,23 @@
#include
#include
+#ifdef CONFIG_X86_PIE
+struct mod_got_sec {
+ struct elf64_shdr *got;
+ int got_num_entries;
+ int got_max_entries;
+};
+#endif
+
struct mod_arch_specific {
#ifdef CONFIG_UNWINDER_ORC
unsigned int num_orcs;
int *orc_unwind_ip;
struct orc_entry *orc_unwind;
#endif
+#ifdef CONFIG_X86_PIE
+ struct mod_got_sec core;
+#endif
};
#ifdef CONFIG_X86_64
diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h
index 5c019d23d06b..da3d98bb2bcb 100644
--- a/arch/x86/include/asm/sections.h
+++ b/arch/x86/include/asm/sections.h
@@ -13,4 +13,8 @@ extern char __end_rodata_hpage_align[];
extern char __entry_trampoline_start[], __entry_trampoline_end[];
#endif
+#if defined(CONFIG_X86_PIE)
+extern char __start_got[], __end_got[];
+#endif
+
#endif /* _ASM_X86_SECTIONS_H */
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index f58336af095c..88895f3d474b 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -30,6 +30,7 @@
#include
#include
#include
+#include
#include
#include
@@ -77,6 +78,173 @@ static unsigned long int get_module_load_offset(void)
}
#endif
+#ifdef CONFIG_X86_PIE
+static u64 find_got_kernel_entry(Elf64_Sym *sym, const Elf64_Rela *rela)
+{
+ u64 *pos;
+
+ for (pos = (u64*)__start_got; pos < (u64*)__end_got; pos++) {
+ if (*pos == sym->st_value)
+ return (u64)pos + rela->r_addend;
+ }
+
+ return 0;
+}
+
+static u64 module_emit_got_entry(struct module *mod, void *loc,
+const Elf64_Rela *rela, Elf64_Sym *sym)
+{
+ struct mod_got_sec *gotsec = >arch.core;
+ u64 *got = (u64*)gotsec->got->sh_addr;
+ int i = gotsec->got_num_entries;
+ u64 ret;
+
+ /* Check if we can use the kernel GOT */
+ ret = find_got_kernel_entry(sym, rela);
+ if (ret)
+ return ret;
+
+ got[i] = sym->st_value;
+
+ /*
+* Check if the entry we just created is a duplicate. Given that the
+* relocations are sorted, this will be the last entry we allocated.
+* (if one exists).
+*/
+ if (i > 0 && got[i] == got[i - 2]) {
+ ret = (u64)[i - 1];
+ } else {
+ gotsec->got_num_entries++;
+ BUG_ON(gotsec->got_num_entries > gotsec->got_max_entries);
+ ret = (u64)[i];
+ }
+
+ return ret + rela->r_addend;
+}
+
+#define cmp_3way(a,b) ((a) < (b) ? -1 : (a) > (b))
+
+static int cmp_rela(const void *a, const void *b)
+{
+ const Elf64_Rela *x = a, *y = b;
+ int i;
+
+ /* sort by type, symbol index and addend */
+ i = cmp_3way(ELF64_R_TYPE(x->r_info), ELF64_R_TYPE(y->r_info));
+ if (i == 0)
+ i = cmp_3way(ELF64_R_SYM(x->r_info), ELF64_R_SYM(y->r_info));
+ if (i == 0)
+ i = cmp_3way(x->r_addend, y->r_addend);
+ return i;
+}
+
+static bool duplicate_rel(const Elf64_Rela *rela, int num)
+{
+ /*
+* Entries are sorted by type, symbol index and addend. That means
+* that, if a duplicate entry exists, it must be in the preceding
+* slot.
+*/
+ return num > 0 && cmp_rela(rela + num, rela + num - 1) == 0;
+}
+
+static unsigned int count_gots(Elf64_Sym *syms, Elf64_Rela *rela, int num)
+{
+ unsigned int ret = 0;
+ Elf64_Sym *s;
+ int i;
+
+ for (i = 0; i < num; i++) {
+ switch (ELF64_R_TYPE(rela[i].r_info)) {
+ case
[PATCH v5 23/27] x86/modules: Adapt module loading for PIE support
Adapt module loading to support PIE relocations. Generate dynamic GOT if
a symbol requires it but no entry exists in the kernel GOT.
Position Independent Executable (PIE) support will allow to extend the
KASLR randomization range 0x8000.
Signed-off-by: Thomas Garnier
---
arch/x86/Makefile | 4 +
arch/x86/include/asm/module.h | 11 ++
arch/x86/include/asm/sections.h | 4 +
arch/x86/kernel/module.c| 181 +++-
arch/x86/kernel/module.lds | 3 +
5 files changed, 198 insertions(+), 5 deletions(-)
create mode 100644 arch/x86/kernel/module.lds
diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index c2c221fd20d7..112ccdc99566 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -134,7 +134,11 @@ else
KBUILD_CFLAGS += $(cflags-y)
KBUILD_CFLAGS += -mno-red-zone
+ifdef CONFIG_X86_PIE
+KBUILD_LDFLAGS_MODULE += -T $(srctree)/arch/x86/kernel/module.lds
+else
KBUILD_CFLAGS += -mcmodel=kernel
+endif
# -funit-at-a-time shrinks the kernel .text considerably
# unfortunately it makes reading oopses harder.
diff --git a/arch/x86/include/asm/module.h b/arch/x86/include/asm/module.h
index 7948a17febb4..68ff05e14288 100644
--- a/arch/x86/include/asm/module.h
+++ b/arch/x86/include/asm/module.h
@@ -5,12 +5,23 @@
#include
#include
+#ifdef CONFIG_X86_PIE
+struct mod_got_sec {
+ struct elf64_shdr *got;
+ int got_num_entries;
+ int got_max_entries;
+};
+#endif
+
struct mod_arch_specific {
#ifdef CONFIG_UNWINDER_ORC
unsigned int num_orcs;
int *orc_unwind_ip;
struct orc_entry *orc_unwind;
#endif
+#ifdef CONFIG_X86_PIE
+ struct mod_got_sec core;
+#endif
};
#ifdef CONFIG_X86_64
diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h
index 5c019d23d06b..da3d98bb2bcb 100644
--- a/arch/x86/include/asm/sections.h
+++ b/arch/x86/include/asm/sections.h
@@ -13,4 +13,8 @@ extern char __end_rodata_hpage_align[];
extern char __entry_trampoline_start[], __entry_trampoline_end[];
#endif
+#if defined(CONFIG_X86_PIE)
+extern char __start_got[], __end_got[];
+#endif
+
#endif /* _ASM_X86_SECTIONS_H */
diff --git a/arch/x86/kernel/module.c b/arch/x86/kernel/module.c
index f58336af095c..88895f3d474b 100644
--- a/arch/x86/kernel/module.c
+++ b/arch/x86/kernel/module.c
@@ -30,6 +30,7 @@
#include
#include
#include
+#include
#include
#include
@@ -77,6 +78,173 @@ static unsigned long int get_module_load_offset(void)
}
#endif
+#ifdef CONFIG_X86_PIE
+static u64 find_got_kernel_entry(Elf64_Sym *sym, const Elf64_Rela *rela)
+{
+ u64 *pos;
+
+ for (pos = (u64*)__start_got; pos < (u64*)__end_got; pos++) {
+ if (*pos == sym->st_value)
+ return (u64)pos + rela->r_addend;
+ }
+
+ return 0;
+}
+
+static u64 module_emit_got_entry(struct module *mod, void *loc,
+const Elf64_Rela *rela, Elf64_Sym *sym)
+{
+ struct mod_got_sec *gotsec = >arch.core;
+ u64 *got = (u64*)gotsec->got->sh_addr;
+ int i = gotsec->got_num_entries;
+ u64 ret;
+
+ /* Check if we can use the kernel GOT */
+ ret = find_got_kernel_entry(sym, rela);
+ if (ret)
+ return ret;
+
+ got[i] = sym->st_value;
+
+ /*
+* Check if the entry we just created is a duplicate. Given that the
+* relocations are sorted, this will be the last entry we allocated.
+* (if one exists).
+*/
+ if (i > 0 && got[i] == got[i - 2]) {
+ ret = (u64)[i - 1];
+ } else {
+ gotsec->got_num_entries++;
+ BUG_ON(gotsec->got_num_entries > gotsec->got_max_entries);
+ ret = (u64)[i];
+ }
+
+ return ret + rela->r_addend;
+}
+
+#define cmp_3way(a,b) ((a) < (b) ? -1 : (a) > (b))
+
+static int cmp_rela(const void *a, const void *b)
+{
+ const Elf64_Rela *x = a, *y = b;
+ int i;
+
+ /* sort by type, symbol index and addend */
+ i = cmp_3way(ELF64_R_TYPE(x->r_info), ELF64_R_TYPE(y->r_info));
+ if (i == 0)
+ i = cmp_3way(ELF64_R_SYM(x->r_info), ELF64_R_SYM(y->r_info));
+ if (i == 0)
+ i = cmp_3way(x->r_addend, y->r_addend);
+ return i;
+}
+
+static bool duplicate_rel(const Elf64_Rela *rela, int num)
+{
+ /*
+* Entries are sorted by type, symbol index and addend. That means
+* that, if a duplicate entry exists, it must be in the preceding
+* slot.
+*/
+ return num > 0 && cmp_rela(rela + num, rela + num - 1) == 0;
+}
+
+static unsigned int count_gots(Elf64_Sym *syms, Elf64_Rela *rela, int num)
+{
+ unsigned int ret = 0;
+ Elf64_Sym *s;
+ int i;
+
+ for (i = 0; i < num; i++) {
+ switch (ELF64_R_TYPE(rela[i].r_info)) {
+ case
