From 7bceec4e58ee23be653c0dd366479d6cb64ae686 Mon Sep 17 00:00:00 2001 From: Hendrik Brueckner Date: Mon, 20 Nov 2017 11:46:13 +0100 Subject: s390/vdso: revise CFI annotations of vDSO functions Revise and add CFI CFA and register rule annotations to the vDSO functions for proper stack unwinding and debugging. Because glibc might call the vDSO in special ways, the vDSO code does not rely on a stack frame created by the caller. The TOD clock value can be therefore not stored in the pre-allocated stack area and additional stack space is required. To correctly annotate these situations with CFI, the .cfi_val_offset directive is required to create relative offsets on the value of the stack register %r15. Because the .cfi_val_offset directive is available with recent GNU assembler versions only, additional checks are necessary. Note that if the vDSO is assembled with an older assembler version, stack unwinding and debugging from within the vDSO code might not be possible. Signed-off-by: Hendrik Brueckner Reviewed-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/vdso64/clock_gettime.S | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) (limited to 'arch/s390/kernel/vdso64/clock_gettime.S') diff --git a/arch/s390/kernel/vdso64/clock_gettime.S b/arch/s390/kernel/vdso64/clock_gettime.S index deccd79..fac3ab5 100644 --- a/arch/s390/kernel/vdso64/clock_gettime.S +++ b/arch/s390/kernel/vdso64/clock_gettime.S @@ -16,8 +16,10 @@ .globl __kernel_clock_gettime .type __kernel_clock_gettime,@function __kernel_clock_gettime: - .cfi_startproc + CFI_STARTPROC aghi %r15,-16 + CFI_DEF_CFA_OFFSET 176 + CFI_VAL_OFFSET 15, -160 larl %r5,_vdso_data cghi %r2,__CLOCK_REALTIME_COARSE je 4f @@ -54,9 +56,13 @@ __kernel_clock_gettime: stg %r1,8(%r3) /* store tp->tv_nsec */ lghi %r2,0 aghi %r15,16 + CFI_DEF_CFA_OFFSET 160 + CFI_RESTORE 15 br %r14 /* CLOCK_MONOTONIC_COARSE */ + CFI_DEF_CFA_OFFSET 176 + CFI_VAL_OFFSET 15, -160 3: lg %r4,__VDSO_UPD_COUNT(%r5) /* load update counter */ tmll %r4,0x0001 /* pending update ? loop */ jnz 3b @@ -109,9 +115,13 @@ __kernel_clock_gettime: stg %r1,8(%r3) /* store tp->tv_nsec */ lghi %r2,0 aghi %r15,16 + CFI_DEF_CFA_OFFSET 160 + CFI_RESTORE 15 br %r14 /* CPUCLOCK_VIRT for this thread */ + CFI_DEF_CFA_OFFSET 176 + CFI_VAL_OFFSET 15, -160 9: lghi %r4,0 icm %r0,15,__VDSO_ECTG_OK(%r5) jz 12f @@ -132,15 +142,21 @@ __kernel_clock_gettime: stg %r4,8(%r3) lghi %r2,0 aghi %r15,16 + CFI_DEF_CFA_OFFSET 160 + CFI_RESTORE 15 br %r14 /* Fallback to system call */ + CFI_DEF_CFA_OFFSET 176 + CFI_VAL_OFFSET 15, -160 12: lghi %r1,__NR_clock_gettime svc 0 aghi %r15,16 + CFI_DEF_CFA_OFFSET 160 + CFI_RESTORE 15 br %r14 + CFI_ENDPROC 13: .quad 1000000000 14: .quad 19342813113834067 - .cfi_endproc .size __kernel_clock_gettime,.-__kernel_clock_gettime -- cgit v1.1