[PATCH v2 19/19] mips/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 sigpage, kernel won't try to land on its
previous position (due to UNMAPPED_VDSO_BASE check instead of
context.vdso ?= 0 check).

Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: linux-mips@vger.kernel.org
Signed-off-by: Dmitry Safonov <dima@arista.com>
---
arch/mips/Kconfig | 1 +
arch/mips/kernel/signal.c | 11 +++++++----
arch/mips/kernel/vdso.c | 2 +-
arch/mips/vdso/genvdso.c | 8 --------
4 files changed, 9 insertions(+), 13 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 818a9b2c78f1..70424605710f 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -10,6 +10,7 @@ config MIPS
select ARCH_HAS_SETUP_ADDITIONAL_PAGES
select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
select ARCH_HAS_UBSAN_SANITIZE_ALL
+ select ARCH_HAS_VDSO_BASE
select ARCH_SUPPORTS_UPROBES
select ARCH_USE_BUILTIN_BSWAP
select ARCH_USE_CMPXCHG_LOCKREF if 64BIT
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index f1e985109da0..e0beaf2cdc0f 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -806,11 +806,13 @@ struct mips_abi mips_abi = {

static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
+ void *land = (void *)current->mm->vdso_base;
sigset_t *oldset = sigmask_to_save();
- int ret;
+ int ret = 1;
struct mips_abi *abi = current->thread.abi;
- void *vdso = current->mm->context.vdso;

+ if (land == (void *)UNMAPPED_VDSO_BASE)
+ goto err;
/*
* If we were emulating a delay slot instruction, exit that frame such
* that addresses in the sigframe are as expected for userland and we
@@ -843,12 +845,13 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
rseq_signal_deliver(ksig, regs);

if (sig_uses_siginfo(&ksig->ka, abi))
- ret = abi->setup_rt_frame(vdso + abi->vdso->off_rt_sigreturn,
+ ret = abi->setup_rt_frame(land + abi->vdso->off_rt_sigreturn,
ksig, regs, oldset);
else
- ret = abi->setup_frame(vdso + abi->vdso->off_sigreturn,
+ ret = abi->setup_frame(land + abi->vdso->off_sigreturn,
ksig, regs, oldset);

+err:
signal_setup_done(ret, ksig, 0);
}

diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
index e124c68322bb..b2b2e596f03b 100644
--- a/arch/mips/kernel/vdso.c
+++ b/arch/mips/kernel/vdso.c
@@ -183,7 +183,7 @@ int arch_setup_additional_pages(unsigned long *sysinfo_ehdr)
goto out;
}

- mm->context.vdso = (void *)vdso_addr;
+ mm->vdso_base = (void __user *)vdso_addr;
*sysinfo_ehdr = vdso_addr;
ret = 0;

diff --git a/arch/mips/vdso/genvdso.c b/arch/mips/vdso/genvdso.c
index 0303d30cde03..8f581a2c8578 100644
--- a/arch/mips/vdso/genvdso.c
+++ b/arch/mips/vdso/genvdso.c
@@ -259,13 +259,6 @@ int main(int argc, char **argv)
fprintf(out_file, "#include <linux/linkage.h>\n");
fprintf(out_file, "#include <linux/mm.h>\n");
fprintf(out_file, "#include <asm/vdso.h>\n");
- fprintf(out_file, "static void vdso_mremap(\n");
- fprintf(out_file, " const struct vm_special_mapping *sm,\n");
- fprintf(out_file, " struct vm_area_struct *new_vma)\n");
- fprintf(out_file, "{\n");
- fprintf(out_file, " current->mm->context.vdso =\n");
- fprintf(out_file, " (void *)(new_vma->vm_start);\n");
- fprintf(out_file, "}\n");

/* Write out the stripped VDSO data. */
fprintf(out_file,
@@ -290,7 +283,6 @@ int main(int argc, char **argv)
fprintf(out_file, "\t.mapping = {\n");
fprintf(out_file, "\t\t.name = \"[vdso]\",\n");
fprintf(out_file, "\t\t.pages = vdso_pages,\n");
- fprintf(out_file, "\t\t.mremap = vdso_mremap,\n");
fprintf(out_file, "\t},\n");

/* Calculate and write symbol offsets to */
--
2.29.2