Commit 62b672c4 authored by Heiko Carstens's avatar Heiko Carstens Committed by Alexander Gordeev
Browse files

s390/stackstrace: Detect vdso stack frames 



Clear the backchain of the extra stack frame added by the vdso user wrapper
code. This allows the user stack walker to detect and skip the non-standard
stack frame. Without this an incorrect instruction pointer would be added
to stack traces, and stack frame walking would be continued with a more or
less random back chain.

Fixes: aa44433a ("s390: add USER_STACKTRACE support")
Reviewed-by: default avatarJens Remus <jremus@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
parent be72ea09

arch/s390/include/asm/processor.h

+1 −0
Original line number Diff line number Diff line
@@ -98,6 +98,7 @@ void cpu_detect_mhz_feature(void); 


extern const struct seq_operations cpuinfo_op;

extern void execve_tail(void);

unsigned long vdso_text_size(void);

unsigned long vdso_size(void);



/*

arch/s390/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -66,6 +66,7 @@ int main(void) 
	OFFSET(__SF_SIE_CONTROL_PHYS, stack_frame, sie_control_block_phys);

	DEFINE(STACK_FRAME_OVERHEAD, sizeof(struct stack_frame));

	BLANK();

	OFFSET(__SFUSER_BACKCHAIN, stack_frame_user, back_chain);

	DEFINE(STACK_FRAME_USER_OVERHEAD, sizeof(struct stack_frame_user));

	OFFSET(__SFVDSO_RETURN_ADDRESS, stack_frame_vdso_wrapper, return_address);

	DEFINE(STACK_FRAME_VDSO_OVERHEAD, sizeof(struct stack_frame_vdso_wrapper));

arch/s390/kernel/stacktrace.c

+24 −4
Original line number Diff line number Diff line
@@ -92,10 +92,16 @@ static inline bool ip_invalid(unsigned long ip) 
	return false;

}



static inline bool ip_within_vdso(unsigned long ip)

{

	return in_range(ip, current->mm->context.vdso_base, vdso_text_size());

}



void arch_stack_walk_user_common(stack_trace_consume_fn consume_entry, void *cookie,

				 struct perf_callchain_entry_ctx *entry,

				 const struct pt_regs *regs, bool perf)

{

	struct stack_frame_vdso_wrapper __user *sf_vdso;

	struct stack_frame_user __user *sf;

	unsigned long ip, sp;

	bool first = true;
@@ -112,12 +118,26 @@ void arch_stack_walk_user_common(stack_trace_consume_fn consume_entry, void *coo 
	while (1) {

		if (__get_user(sp, &sf->back_chain))

			break;

		/* Sanity check: ABI requires SP to be 8 byte aligned. */

		if (!sp || sp & 0x7)

		/*

		 * VDSO entry code has a non-standard stack frame layout.

		 * See VDSO user wrapper code for details.

		 */

		if (!sp && ip_within_vdso(ip)) {

			sf_vdso = (void __user *)sf;

			if (__get_user(ip, &sf_vdso->return_address))

				break;

			sp = (unsigned long)sf + STACK_FRAME_VDSO_OVERHEAD;

			sf = (void __user *)sp;

			if (__get_user(sp, &sf->back_chain))

				break;

		} else {

			sf = (void __user *)sp;

			if (__get_user(ip, &sf->gprs[8]))

				break;

		}

		/* Sanity check: ABI requires SP to be 8 byte aligned. */

		if (sp & 0x7)

			break;

		if (ip_invalid(ip)) {

			/*

			 * If the instruction address is invalid, and this

arch/s390/kernel/vdso.c

+9 −4
Original line number Diff line number Diff line
@@ -210,17 +210,22 @@ static unsigned long vdso_addr(unsigned long start, unsigned long len) 
	return addr;

}



unsigned long vdso_size(void)

unsigned long vdso_text_size(void)

{

	unsigned long size = VVAR_NR_PAGES * PAGE_SIZE;

	unsigned long size;



	if (is_compat_task())

		size += vdso32_end - vdso32_start;

		size = vdso32_end - vdso32_start;

	else

		size += vdso64_end - vdso64_start;

		size = vdso64_end - vdso64_start;

	return PAGE_ALIGN(size);

}



unsigned long vdso_size(void)

{

	return vdso_text_size() + VVAR_NR_PAGES * PAGE_SIZE;

}



int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)

{

	unsigned long addr = VDSO_BASE;

arch/s390/kernel/vdso64/vdso_user_wrapper.S

+1 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ __kernel_\func: 
	CFI_VAL_OFFSET 15,-STACK_FRAME_USER_OVERHEAD

	stg	%r14,__SFVDSO_RETURN_ADDRESS(%r15)

	CFI_REL_OFFSET 14,__SFVDSO_RETURN_ADDRESS

	xc	__SFUSER_BACKCHAIN(8,%r15),__SFUSER_BACKCHAIN(%r15)

	brasl	%r14,__s390_vdso_\func

	lg	%r14,__SFVDSO_RETURN_ADDRESS(%r15)

	CFI_RESTORE 14