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Commit c50842df authored by Chris Zankel's avatar Chris Zankel
Browse files

xtensa: add support for TLS 



The Xtensa architecture provides a global register called THREADPTR
for the purpose of Thread Local Storage (TLS) support. This allows us
to use a fairly simple implementation, keeping the thread pointer in
the regset and simply saving and restoring it upon entering/exiting
the from user space.

Signed-off-by: default avatarChris Zankel <chris@zankel.net>
parent b0c438e6

arch/xtensa/include/asm/elf.h

+2 −1
Original line number Diff line number Diff line
@@ -84,7 +84,8 @@ typedef struct { 
	elf_greg_t sar;

	elf_greg_t windowstart;

	elf_greg_t windowbase;

	elf_greg_t reserved[8+48];

	elf_greg_t threadptr;

	elf_greg_t reserved[7+48];

	elf_greg_t a[64];

} xtensa_gregset_t;

arch/xtensa/include/asm/ptrace.h

+2 −1
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ struct pt_regs { 
	unsigned long syscall;		/*  56 */

	unsigned long icountlevel;	/*  60 */

	unsigned long scompare1;	/*  64 */

	unsigned long threadptr;	/*  68 */



	/* Additional configurable registers that are used by the compiler. */

	xtregs_opt_t xtregs_opt;
@@ -48,7 +49,7 @@ struct pt_regs { 
	/* current register frame.

	 * Note: The ESF for kernel exceptions ends after 16 registers!

	 */

	unsigned long areg[16];		/* 128 (64) */

	unsigned long areg[16];

};



#include <variant/core.h>

arch/xtensa/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ int main(void) 
	DEFINE(PT_ICOUNTLEVEL, offsetof (struct pt_regs, icountlevel));

	DEFINE(PT_SYSCALL, offsetof (struct pt_regs, syscall));

	DEFINE(PT_SCOMPARE1, offsetof(struct pt_regs, scompare1));

	DEFINE(PT_THREADPTR, offsetof(struct pt_regs, threadptr));

	DEFINE(PT_AREG, offsetof (struct pt_regs, areg[0]));

	DEFINE(PT_AREG0, offsetof (struct pt_regs, areg[0]));

	DEFINE(PT_AREG1, offsetof (struct pt_regs, areg[1]));

arch/xtensa/kernel/entry.S

+11 −1
Original line number Diff line number Diff line
@@ -130,6 +130,11 @@ _user_exception: 
	s32i	a3, a1, PT_SAR

	s32i	a2, a1, PT_ICOUNTLEVEL



#if XCHAL_HAVE_THREADPTR

	rur	a2, threadptr

	s32i	a2, a1, PT_THREADPTR

#endif



	/* Rotate ws so that the current windowbase is at bit0. */

	/* Assume ws = xxwww1yyyy. Rotate ws right, so that a2 = yyyyxxwww1 */
@@ -510,6 +515,11 @@ user_exception_exit: 
	 *	 (if we have restored WSBITS-1 frames).

	 */



#if XCHAL_HAVE_THREADPTR

	l32i	a3, a1, PT_THREADPTR

	wur	a3, threadptr

#endif



2:	j	common_exception_exit



	/* This is the kernel exception exit.
@@ -1955,7 +1965,7 @@ ENTRY(_switch_to) 
	s32i	a6, a3, EXC_TABLE_FIXUP

	s32i	a7, a3, EXC_TABLE_KSTK



	/* restore context of the task that 'next' addresses */

	/* restore context of the task 'next' */



	l32i	a0, a13, THREAD_RA	# restore return address

	l32i	a1, a13, THREAD_SP	# restore stack pointer

arch/xtensa/kernel/process.c

+3 −2
Original line number Diff line number Diff line
@@ -259,9 +259,10 @@ int copy_thread(unsigned long clone_flags, unsigned long usp_thread_fn, 
			memcpy(&childregs->areg[XCHAL_NUM_AREGS - len/4],

			       &regs->areg[XCHAL_NUM_AREGS - len/4], len);

		}

// FIXME: we need to set THREADPTR in thread_info...



		/* The thread pointer is passed in the '4th argument' (= a5) */

		if (clone_flags & CLONE_SETTLS)

			childregs->areg[2] = childregs->areg[6];

			childregs->threadptr = childregs->areg[5];

	} else {

		p->thread.ra = MAKE_RA_FOR_CALL(

				(unsigned long)ret_from_kernel_thread, 1);