From bb4322f74340de578bc61ed0cfb9690ddeb9ef76 Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Thu, 15 Jun 2017 15:03:41 +0100 Subject: arm64: signal: factor out signal frame record allocation This patch factors out the allocator for signal frame optional records into a separate function, to ensure consistency and facilitate later expansion. No overrun checking is currently done, because the allocation is in user memory and anyway the kernel never tries to allocate enough space in the signal frame yet for an overrun to occur. This behaviour will be refined in future patches. The approach taken in this patch to allocation of the terminator record is not very clean: this will also be replaced in subsequent patches. For future extension, a comment is added in sigcontext.h documenting the current static allocations in __reserved[]. This will be important for determining under what circumstances userspace may or may not see an expanded signal frame. Reviewed-by: Catalin Marinas Signed-off-by: Dave Martin Signed-off-by: Will Deacon --- arch/arm64/kernel/signal.c | 43 ++++++++++++++++++++++++++++++++++++------- 1 file changed, 36 insertions(+), 7 deletions(-) (limited to 'arch/arm64/kernel') diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index eaef530579f8..fa787e6ac7c2 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -79,6 +79,22 @@ static size_t sigframe_size(struct rt_sigframe_user_layout const *user) return round_up(max(user->size, sizeof(struct rt_sigframe)), 16); } +/* + * Allocate space for an optional record of bytes in the user + * signal frame. The offset from the signal frame base address to the + * allocated block is assigned to *offset. + */ +static int sigframe_alloc(struct rt_sigframe_user_layout *user, + unsigned long *offset, size_t size) +{ + size_t padded_size = round_up(size, 16); + + *offset = user->size; + user->size += padded_size; + + return 0; +} + static void __user *apply_user_offset( struct rt_sigframe_user_layout const *user, unsigned long offset) { @@ -287,19 +303,32 @@ badframe: /* Determine the layout of optional records in the signal frame */ static int setup_sigframe_layout(struct rt_sigframe_user_layout *user) { - user->fpsimd_offset = user->size; - user->size += round_up(sizeof(struct fpsimd_context), 16); + int err; + + err = sigframe_alloc(user, &user->fpsimd_offset, + sizeof(struct fpsimd_context)); + if (err) + return err; /* fault information, if valid */ if (current->thread.fault_code) { - user->esr_offset = user->size; - user->size += round_up(sizeof(struct esr_context), 16); + err = sigframe_alloc(user, &user->esr_offset, + sizeof(struct esr_context)); + if (err) + return err; } - /* set the "end" magic */ - user->end_offset = user->size; + /* + * Allocate space for the terminator record. + * HACK: here we undo the reservation of space for the end record. + * This bodge should be replaced with a cleaner approach later on. + */ + user->limit = offsetof(struct rt_sigframe, uc.uc_mcontext.__reserved) + + sizeof(user->sigframe->uc.uc_mcontext.__reserved); - return 0; + err = sigframe_alloc(user, &user->end_offset, + sizeof(struct _aarch64_ctx)); + return err; } -- cgit v1.2.3