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Subject[PATCH 4/7] Fix places where using %gs changes the usermode ABI.
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There are a few places where the change in struct pt_regs and the use
of %gs affect the userspace ABI. These are primarily debugging
interfaces where thread state can be inspected or extracted.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Chuck Ebbert <76306.1226@compuserve.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

Index: ak-pda-gs/arch/i386/kernel/process.c
===================================================================
--- ak-pda-gs.orig/arch/i386/kernel/process.c 2006-09-20 16:40:18.000000000 +1000
+++ ak-pda-gs/arch/i386/kernel/process.c 2006-09-20 16:46:40.000000000 +1000
@@ -304,8 +304,8 @@
regs->eax,regs->ebx,regs->ecx,regs->edx);
printk("ESI: %08lx EDI: %08lx EBP: %08lx",
regs->esi, regs->edi, regs->ebp);
- printk(" DS: %04x ES: %04x\n",
- 0xffff & regs->xds,0xffff & regs->xes);
+ printk(" DS: %04x ES: %04x GS: %04x\n",
+ 0xffff & regs->xds,0xffff & regs->xes, 0xffff & regs->xgs);

cr0 = read_cr0();
cr2 = read_cr2();
@@ -499,7 +499,7 @@
dump->regs.ds = regs->xds;
dump->regs.es = regs->xes;
savesegment(fs,dump->regs.fs);
- savesegment(gs,dump->regs.gs);
+ dump->regs.gs = regs->xgs;
dump->regs.orig_eax = regs->orig_eax;
dump->regs.eip = regs->eip;
dump->regs.cs = regs->xcs;
Index: ak-pda-gs/arch/i386/kernel/ptrace.c
===================================================================
--- ak-pda-gs.orig/arch/i386/kernel/ptrace.c 2006-09-20 15:33:57.000000000 +1000
+++ ak-pda-gs/arch/i386/kernel/ptrace.c 2006-09-20 16:46:40.000000000 +1000
@@ -94,13 +94,9 @@
return -EIO;
child->thread.fs = value;
return 0;
- case GS:
- if (value && (value & 3) != 3)
- return -EIO;
- child->thread.gs = value;
- return 0;
case DS:
case ES:
+ case GS:
if (value && (value & 3) != 3)
return -EIO;
value &= 0xffff;
@@ -116,8 +112,8 @@
value |= get_stack_long(child, EFL_OFFSET) & ~FLAG_MASK;
break;
}
- if (regno > GS*4)
- regno -= 2*4;
+ if (regno > ES*4)
+ regno -= 1*4;
put_stack_long(child, regno - sizeof(struct pt_regs), value);
return 0;
}
@@ -131,18 +127,16 @@
case FS:
retval = child->thread.fs;
break;
- case GS:
- retval = child->thread.gs;
- break;
case DS:
case ES:
+ case GS:
case SS:
case CS:
retval = 0xffff;
/* fall through */
default:
- if (regno > GS*4)
- regno -= 2*4;
+ if (regno > ES*4)
+ regno -= 1*4;
regno = regno - sizeof(struct pt_regs);
retval &= get_stack_long(child, regno);
}
Index: ak-pda-gs/include/asm-i386/elf.h
===================================================================
--- ak-pda-gs.orig/include/asm-i386/elf.h 2006-09-20 15:33:57.000000000 +1000
+++ ak-pda-gs/include/asm-i386/elf.h 2006-09-20 16:46:40.000000000 +1000
@@ -91,7 +91,7 @@
pr_reg[7] = regs->xds; \
pr_reg[8] = regs->xes; \
savesegment(fs,pr_reg[9]); \
- savesegment(gs,pr_reg[10]); \
+ pr_reg[10] = regs->xgs; \
pr_reg[11] = regs->orig_eax; \
pr_reg[12] = regs->eip; \
pr_reg[13] = regs->xcs; \
--
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