[PATCH v2 15/19] x86/vdso: Migrate to generic vdso_base

Dmitry Safonov
2020-11-24T00:30:30Z

Generic way to track the landing vma area.
As a bonus, after unmapping vdso, kernel won't try to land on its
previous position (due to UNMAPPED_VDSO_BASE check instead of
context.vdso ?= 0 check).

Signed-off-by: Dmitry Safonov <dima@arista.com>
---
arch/x86/Kconfig | 1 +
arch/x86/entry/common.c | 2 +-
arch/x86/entry/vdso/extable.c | 4 ++--
arch/x86/entry/vdso/vma.c | 9 ++++-----
arch/x86/ia32/ia32_signal.c | 4 ++--
arch/x86/include/asm/mmu.h | 1 -
arch/x86/include/asm/vdso.h | 2 +-
arch/x86/kernel/signal.c | 4 ++--
8 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d676e0bad1f1..4f06760f849e 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -85,6 +85,7 @@ config X86
select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
select ARCH_HAS_SYSCALL_WRAPPER
select ARCH_HAS_UBSAN_SANITIZE_ALL
+ select ARCH_HAS_VDSO_BASE
select ARCH_HAS_DEBUG_WX
select ARCH_HAVE_NMI_SAFE_CMPXCHG
select ARCH_MIGHT_HAVE_ACPI_PDC if ACPI
diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index d9ab58cc765b..655b7d8fe734 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -151,7 +151,7 @@ __visible noinstr long do_fast_syscall_32(struct pt_regs *regs)
* Called using the internal vDSO SYSENTER/SYSCALL32 calling
* convention. Adjust regs so it looks like we entered using int80.
*/
- landing_pad = (unsigned long)current->mm->context.vdso +
+ landing_pad = (unsigned long)current->mm->vdso_base +
vdso_image_32.sym_int80_landing_pad;

/*
diff --git a/arch/x86/entry/vdso/extable.c b/arch/x86/entry/vdso/extable.c
index afcf5b65beef..16688c2d032c 100644
--- a/arch/x86/entry/vdso/extable.c
+++ b/arch/x86/entry/vdso/extable.c
@@ -25,10 +25,10 @@ bool fixup_vdso_exception(struct pt_regs *regs, int trapnr,
if (trapnr == X86_TRAP_DB || trapnr == X86_TRAP_BP)
return false;

- if (!current->mm->context.vdso)
+ if (current->mm->vdso_base == (void *)UNMAPPED_VDSO_BASE)
return false;

- base = (unsigned long)current->mm->context.vdso + image->extable_base;
+ base = (unsigned long)current->mm->vdso_base + image->extable_base;
nr_entries = image->extable_len / (sizeof(*extable));
extable = image->extable;

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index 65780a0164e3..29a795face9d 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -77,7 +77,7 @@ static void vdso_fix_landing(const struct vdso_image *image,
struct pt_regs *regs = current_pt_regs();
unsigned long vdso_land = image->sym_int80_landing_pad;
unsigned long old_land_addr = vdso_land +
- (unsigned long)current->mm->context.vdso;
+ (unsigned long)current->mm->vdso_base;

/* Fixing userspace landing - look at do_fast_syscall_32 */
if (regs->ip == old_land_addr)
@@ -92,7 +92,6 @@ static void vdso_mremap(const struct vm_special_mapping *sm,
const struct vdso_image *image = current->mm->context.vdso_image;

vdso_fix_landing(image, new_vma);
- current->mm->context.vdso = (void __user *)new_vma->vm_start;
}

#ifdef CONFIG_TIME_NS
@@ -287,7 +286,7 @@ static int map_vdso(const struct vdso_image *image, unsigned long addr,
ret = PTR_ERR(vma);
do_munmap(mm, text_start, image->size, NULL);
} else {
- current->mm->context.vdso = (void __user *)text_start;
+ current->mm->vdso_base = (void __user *)text_start;
current->mm->context.vdso_image = image;
*sysinfo_ehdr = text_start;
}
@@ -362,8 +361,8 @@ int map_vdso_once(const struct vdso_image *image, unsigned long addr)
* Check if we have already mapped vdso blob - fail to prevent
* abusing from userspace install_speciall_mapping, which may
* not do accounting and rlimit right.
- * We could search vma near context.vdso, but it's a slowpath,
- * so let's explicitly check all VMAs to be completely sure.
+ * It's a slowpath, let's explicitly check all VMAs to be
+ * completely sure.
*/
for (vma = mm->mmap; vma; vma = vma->vm_next) {
if (vma_is_special_mapping(vma, &vdso_mapping) ||
diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index f87ed1d53938..67204b1eeea0 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -256,7 +256,7 @@ int ia32_setup_frame(int sig, struct ksignal *ksig,
} else {
/* Return stub is in 32bit vsyscall page */
if (current_has_vdso_image_32())
- restorer = current->mm->context.vdso +
+ restorer = current->mm->vdso_base +
vdso_image_32.sym___kernel_sigreturn;
else
restorer = &frame->retcode;
@@ -337,7 +337,7 @@ int ia32_setup_rt_frame(int sig, struct ksignal *ksig,
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
else if (current_has_vdso_image_32())
- restorer = current->mm->context.vdso +
+ restorer = current->mm->vdso_base +
vdso_image_32.sym___kernel_rt_sigreturn;
else
restorer = &frame->retcode;
diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h
index 5d7494631ea9..7bd10e6b8386 100644
--- a/arch/x86/include/asm/mmu.h
+++ b/arch/x86/include/asm/mmu.h
@@ -43,7 +43,6 @@ typedef struct {
#endif

struct mutex lock;
- void __user *vdso; /* vdso base address */
const struct vdso_image *vdso_image; /* vdso image in use */

atomic_t perf_rdpmc_allowed; /* nonzero if rdpmc is allowed */
diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
index e3829c3a6149..31b5695eded4 100644
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -44,7 +44,7 @@ extern const struct vdso_image vdso_image_32;

#define current_has_vdso_image_32() \
likely(current->mm->context.vdso_image == &vdso_image_32 && \
- !!current->mm->context.vdso)
+ (unsigned long)current->mm->vdso_base != UNMAPPED_VDSO_BASE)
#endif

extern void __init init_vdso_image(const struct vdso_image *image);
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 6fed2e523e0a..85161df044f2 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -320,7 +320,7 @@ __setup_frame(int sig, struct ksignal *ksig, sigset_t *set,
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
else if (current_has_vdso_image_32())
- restorer = current->mm->context.vdso +
+ restorer = current->mm->vdso_base +
vdso_image_32.sym___kernel_sigreturn;
else
restorer = &frame->retcode;
@@ -382,7 +382,7 @@ static int __setup_rt_frame(int sig, struct ksignal *ksig,
if (ksig->ka.sa.sa_flags & SA_RESTORER)
restorer = ksig->ka.sa.sa_restorer;
else if (current_has_vdso_image_32())
- restorer = current->mm->context.vdso +
+ restorer = current->mm->vdso_base +
vdso_image_32.sym___kernel_rt_sigreturn;
else
restorer = &frame->retcode;
--
2.29.2