From 18c167233413ace7a8a90b3291ccd255ba510cc4 Mon Sep 17 00:00:00 2001
From: dchagin <dchagin@FreeBSD.org>
Date: Sat, 9 Jan 2016 15:44:38 +0000
Subject: MFC r283407:

Implement vdso - virtual dynamic shared object. Through vdso Linux
exposes functions from kernel with proper DWARF CFI information so that
it becomes easier to unwind through them.
Using vdso is a mandatory for a thread cancelation && cleanup
on a modern glibc.
---
 sys/i386/linux/linux_locore.s | 154 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 133 insertions(+), 21 deletions(-)

(limited to 'sys/i386/linux/linux_locore.s')

diff --git a/sys/i386/linux/linux_locore.s b/sys/i386/linux/linux_locore.s
index a3e0e7dc..54553b5 100644
--- a/sys/i386/linux/linux_locore.s
+++ b/sys/i386/linux/linux_locore.s
@@ -5,33 +5,145 @@
 
 #include <i386/linux/linux_syscall.h>		/* system call numbers */
 
+#include "assym.s"
+
+/*
+ * To avoid excess stack frame the signal trampoline code emulates
+ * the 'call' instruction.
+ */
 NON_GPROF_ENTRY(linux_sigcode)
-	call	*LINUX_SIGF_HANDLER(%esp)
-	leal	LINUX_SIGF_SC(%esp),%ebx	/* linux scp */
-	mov	LINUX_SC_GS(%ebx),%gs
-	movl	%esp, %ebx			/* pass sigframe */
-	push	%eax				/* fake ret addr */
+	movl	%esp, %ebx			/* preserve sigframe */
+	call .getip0
+.getip0:
+	popl	%eax
+	add	$.startsigcode-.getip0, %eax	/* ret address */
+	push	%eax
+	jmp	*LINUX_SIGF_HANDLER(%ebx)
+.startsigcode:
+	popl	%eax				/* gcc unwind code need this */
 	movl	$LINUX_SYS_linux_sigreturn,%eax	/* linux_sigreturn() */
 	int	$0x80				/* enter kernel with args */
+.endsigcode:
 0:	jmp	0b
-	ALIGN_TEXT
-/* XXXXX */
-linux_rt_sigcode:
-	call	*LINUX_RT_SIGF_HANDLER(%esp)
+
+NON_GPROF_ENTRY(linux_rt_sigcode)
 	leal	LINUX_RT_SIGF_UC(%esp),%ebx	/* linux ucp */
 	leal	LINUX_RT_SIGF_SC(%ebx),%ecx	/* linux sigcontext */
-	mov	LINUX_SC_GS(%ecx),%gs
-	push	%eax				/* fake ret addr */
+	movl	%esp, %edi
+	call	.getip1
+.getip1:
+	popl	%eax
+	add	$.startrtsigcode-.getip1, %eax	/* ret address */
+	push	%eax
+	jmp	*LINUX_RT_SIGF_HANDLER(%edi)
+.startrtsigcode:
 	movl	$LINUX_SYS_linux_rt_sigreturn,%eax   /* linux_rt_sigreturn() */
 	int	$0x80				/* enter kernel with args */
+.endrtsigcode:
 0:	jmp	0b
-	ALIGN_TEXT
-/* XXXXX */
-linux_esigcode:
-
-	.data
-	.globl	linux_szsigcode, linux_sznonrtsigcode
-linux_szsigcode:
-	.long	linux_esigcode-linux_sigcode
-linux_sznonrtsigcode:
-	.long	linux_rt_sigcode-linux_sigcode
+
+NON_GPROF_ENTRY(linux_vsyscall)
+.startvsyscall:
+	int $0x80
+	ret
+.endvsyscall:
+
+
+	.section .note.Linux, "a",@note
+	.long 2f - 1f		/* namesz */
+	.balign 4
+	.long 4f - 3f		/* descsz */
+	.long 0
+1:
+	.asciz "Linux"
+2:
+	.balign 4
+3:
+	.long LINUX_VERSION_CODE
+4:
+	.balign 4
+	.previous
+
+
+#define do_cfa_expr(offset)                                             \
+	.byte 0x0f;			/* DW_CFA_def_cfa_expression */ \
+	.uleb128 11f-10f;		/*   length */                  \
+10:	.byte 0x74;			/*     DW_OP_breg4 */           \
+	.sleb128 offset;		/*      offset */               \
+	.byte 0x06;			/*     DW_OP_deref */           \
+11:
+
+
+	/* CIE */
+	.section .eh_frame,"a",@progbits
+.LSTARTFRAMEDLSI1:
+	.long .LENDCIEDLSI1-.LSTARTCIEDLSI1
+.LSTARTCIEDLSI1:
+	.long 0					/* CIE ID */
+	.byte 1					/* Version number */
+	.string "zRS"				/* NULL-terminated
+						 * augmentation string
+						 */
+	.uleb128 1				/* Code alignment factor */
+	.sleb128 -4				/* Data alignment factor */
+	.byte 8					/* Return address
+						 * register column
+						 */
+	.uleb128 1				/* Augmentation value length */
+	.byte 0x1b				/* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */
+	.byte 0					/* DW_CFA_nop */
+	.align 4
+.LENDCIEDLSI1:
+
+	/* FDE */
+	.long .LENDFDEDLSI1-.LSTARTFDEDLSI1	/* Length FDE */
+.LSTARTFDEDLSI1:
+	.long .LSTARTFDEDLSI1-.LSTARTFRAMEDLSI1 /* CIE pointer */
+	.long .startsigcode-.			/* PC-relative start address */
+	.long .endsigcode-.startsigcode
+	.uleb128 0				/* Augmentation */
+	do_cfa_expr(LINUX_SIGF_SC-8)
+	.align 4
+.LENDFDEDLSI1:
+
+	.long .LENDFDEDLSI2-.LSTARTFDEDLSI2	/* Length FDE */
+.LSTARTFDEDLSI2:
+	.long .LSTARTFDEDLSI2-.LSTARTFRAMEDLSI1	/* CIE pointer */
+	.long .startrtsigcode-.			/* PC-relative start address */
+	.long .endrtsigcode-.startrtsigcode
+	.uleb128 0				/* Augmentation */
+	do_cfa_expr(LINUX_RT_SIGF_SC-4+LINUX_SC_ESP)
+	.align 4
+.LENDFDEDLSI2:
+	.previous
+
+	.section .eh_frame,"a",@progbits
+.LSTARTFRAMEDLSI2:
+	.long .LENDCIEDLSI2-.LSTARTCIEDLSI2
+.LSTARTCIEDLSI2:
+	.long 0					/* CIE ID */
+	.byte 1					/* Version number */
+	.string "zR"				/* NULL-terminated
+						 * augmentation string
+						 */
+	.uleb128 1				/* Code alignment factor */
+	.sleb128 -4				/* Data alignment factor */
+	.byte 8					/* Return address register column */
+	.uleb128 1				/* Augmentation value length */
+	.byte 0x1b				/* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */
+	.byte 0x0c				/* DW_CFA_def_cfa */
+	.uleb128 4
+	.uleb128 4
+	.byte 0x88				/* DW_CFA_offset, column 0x8 */
+	.uleb128 1
+	.align 4
+.LENDCIEDLSI2:
+	.long .LENDFDEDLSI3-.LSTARTFDEDLSI3 /* Length FDE */
+.LSTARTFDEDLSI3:
+	.long .LSTARTFDEDLSI3-.LSTARTFRAMEDLSI2 /* CIE pointer */
+	.long .startvsyscall-.			/* PC-relative start address */
+	.long .endvsyscall-.startvsyscall
+	.uleb128 0
+	.align 4
+.LENDFDEDLSI3:
+	.previous
-- 
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