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authorDave Martin <Dave.Martin@arm.com>2017-06-15 15:03:38 +0100
committerWill Deacon <will.deacon@arm.com>2017-06-20 12:42:58 +0100
commit20987de3c2c45c314e0386f724aa85f55d984ef2 (patch)
treee4239945bd5c53c4d7d7865e76d7683858bda8ff /arch
parent8f36094802e4e6de180b36bcac4cfd9d319e1b64 (diff)
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arm64: signal: split frame link record from sigcontext structure
In order to be able to increase the amount of the data currently written to the __reserved[] array in the signal frame, it is necessary to overwrite the locations currently occupied by the {fp,lr} frame link record pushed at the top of the signal stack. In order for this to work, this patch detaches the frame link record from struct rt_sigframe and places it separately at the top of the signal stack. This will allow subsequent patches to insert data between it and __reserved[]. This change relies on the non-ABI status of the placement of the frame record with respect to struct sigframe: this status is undocumented, but the placement is not declared or described in the user headers, and known unwinder implementations (libgcc, libunwind, gdb) appear not to rely on it. Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Dave Martin <Dave.Martin@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm64/kernel/signal.c50
1 files changed, 32 insertions, 18 deletions
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index c7b6de62f9d3..1e5ed3be78ed 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -19,6 +19,7 @@
#include <linux/compat.h>
#include <linux/errno.h>
+#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/personality.h>
#include <linux/freezer.h>
@@ -41,10 +42,18 @@
struct rt_sigframe {
struct siginfo info;
struct ucontext uc;
+};
+
+struct frame_record {
u64 fp;
u64 lr;
};
+struct rt_sigframe_user_layout {
+ struct rt_sigframe __user *sigframe;
+ struct frame_record __user *next_frame;
+};
+
static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
{
struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
@@ -162,16 +171,17 @@ badframe:
return 0;
}
-static int setup_sigframe(struct rt_sigframe __user *sf,
+static int setup_sigframe(struct rt_sigframe_user_layout *user,
struct pt_regs *regs, sigset_t *set)
{
int i, err = 0;
+ struct rt_sigframe __user *sf = user->sigframe;
void *aux = sf->uc.uc_mcontext.__reserved;
struct _aarch64_ctx *end;
/* set up the stack frame for unwinding */
- __put_user_error(regs->regs[29], &sf->fp, err);
- __put_user_error(regs->regs[30], &sf->lr, err);
+ __put_user_error(regs->regs[29], &user->next_frame->fp, err);
+ __put_user_error(regs->regs[30], &user->next_frame->lr, err);
for (i = 0; i < 31; i++)
__put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
@@ -209,34 +219,36 @@ static int setup_sigframe(struct rt_sigframe __user *sf,
return err;
}
-static struct rt_sigframe __user *get_sigframe(struct ksignal *ksig,
- struct pt_regs *regs)
+static int get_sigframe(struct rt_sigframe_user_layout *user,
+ struct ksignal *ksig, struct pt_regs *regs)
{
unsigned long sp, sp_top;
- struct rt_sigframe __user *frame;
sp = sp_top = sigsp(regs->sp, ksig);
- sp = (sp - sizeof(struct rt_sigframe)) & ~15;
- frame = (struct rt_sigframe __user *)sp;
+ sp = round_down(sp - sizeof(struct frame_record), 16);
+ user->next_frame = (struct frame_record __user *)sp;
+
+ sp = round_down(sp - sizeof(struct rt_sigframe), 16);
+ user->sigframe = (struct rt_sigframe __user *)sp;
/*
* Check that we can actually write to the signal frame.
*/
- if (!access_ok(VERIFY_WRITE, frame, sp_top - sp))
- frame = NULL;
+ if (!access_ok(VERIFY_WRITE, user->sigframe, sp_top - sp))
+ return -EFAULT;
- return frame;
+ return 0;
}
static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
- void __user *frame, int usig)
+ struct rt_sigframe_user_layout *user, int usig)
{
__sigrestore_t sigtramp;
regs->regs[0] = usig;
- regs->sp = (unsigned long)frame;
- regs->regs[29] = regs->sp + offsetof(struct rt_sigframe, fp);
+ regs->sp = (unsigned long)user->sigframe;
+ regs->regs[29] = (unsigned long)&user->next_frame->fp;
regs->pc = (unsigned long)ka->sa.sa_handler;
if (ka->sa.sa_flags & SA_RESTORER)
@@ -250,20 +262,22 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
static int setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
struct pt_regs *regs)
{
+ struct rt_sigframe_user_layout user;
struct rt_sigframe __user *frame;
int err = 0;
- frame = get_sigframe(ksig, regs);
- if (!frame)
+ if (get_sigframe(&user, ksig, regs))
return 1;
+ frame = user.sigframe;
+
__put_user_error(0, &frame->uc.uc_flags, err);
__put_user_error(NULL, &frame->uc.uc_link, err);
err |= __save_altstack(&frame->uc.uc_stack, regs->sp);
- err |= setup_sigframe(frame, regs, set);
+ err |= setup_sigframe(&user, regs, set);
if (err == 0) {
- setup_return(regs, &ksig->ka, frame, usig);
+ setup_return(regs, &ksig->ka, &user, usig);
if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
err |= copy_siginfo_to_user(&frame->info, &ksig->info);
regs->regs[1] = (unsigned long)&frame->info;