Messages in this thread Patch in this message | | | Date | Sun, 12 Jun 2005 13:20:35 +0200 (MEST) | From | Mikael Pettersson <> | Subject | [PATCH 2.4.31 6/9] gcc4: fix x86_64 sys_iopl() bug |
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On x86_64 sys_iopl() becomes a no-op when compiled with gcc4. This breaks the X server, causing its PCI probing to fail.
This is caused by a bug. sys_iopl() receives a struct pt_regs as a formal parameter, and updates it expecting those updates to remain when it returns. This is incorrect as the calling convention rules say that a function's formal parameters are initialised copies that disappear when the function returns.
The fix (backport from 2.6) is to pass the pt_regs by reference.
Signed-off-by: Mikael Pettersson <mikpe@csd.uu.se>
arch/x86_64/ia32/ia32entry.S | 11 ++++++++++- arch/x86_64/kernel/entry.S | 11 ++++++++++- arch/x86_64/kernel/ioport.c | 6 +++--- 3 files changed, 23 insertions(+), 5 deletions(-)
diff -rupN linux-2.4.31/arch/x86_64/ia32/ia32entry.S linux-2.4.31.gcc4-x86_64-iopl-bug/arch/x86_64/ia32/ia32entry.S --- linux-2.4.31/arch/x86_64/ia32/ia32entry.S 2005-01-19 18:00:53.000000000 +0100 +++ linux-2.4.31.gcc4-x86_64-iopl-bug/arch/x86_64/ia32/ia32entry.S 2005-06-12 11:46:56.000000000 +0200 @@ -113,9 +113,18 @@ quiet_ni_syscall: PTREGSCALL stub32_fork, sys32_fork PTREGSCALL stub32_clone, sys32_clone PTREGSCALL stub32_vfork, sys32_vfork - PTREGSCALL stub32_iopl, sys_iopl PTREGSCALL stub32_rt_sigsuspend, sys_rt_sigsuspend + .macro PTREGSCALL3 label, func, arg + .globl \label +\label: + leaq \func(%rip),%rax + leaq -ARGOFFSET+8(%rsp),\arg /* 8 for return address */ + jmp ia32_ptregs_common + .endm + + PTREGSCALL3 stub32_iopl, sys_iopl, %rsi + ENTRY(ia32_ptregs_common) popq %r11 SAVE_REST diff -rupN linux-2.4.31/arch/x86_64/kernel/entry.S linux-2.4.31.gcc4-x86_64-iopl-bug/arch/x86_64/kernel/entry.S --- linux-2.4.31/arch/x86_64/kernel/entry.S 2003-11-29 00:28:11.000000000 +0100 +++ linux-2.4.31.gcc4-x86_64-iopl-bug/arch/x86_64/kernel/entry.S 2005-06-12 11:46:56.000000000 +0200 @@ -249,7 +249,16 @@ intret_signal_test: PTREGSCALL stub_vfork, sys_vfork PTREGSCALL stub_rt_sigsuspend, sys_rt_sigsuspend PTREGSCALL stub_sigaltstack, sys_sigaltstack - PTREGSCALL stub_iopl, sys_iopl + + .macro PTREGSCALL3 label,func,arg + .globl \label +\label: + leaq \func(%rip),%rax + leaq -ARGOFFSET+8(%rsp),\arg /* 8 for return address */ + jmp ptregscall_common + .endm + + PTREGSCALL3 stub_iopl, sys_iopl, %rsi ENTRY(ptregscall_common) popq %r11 diff -rupN linux-2.4.31/arch/x86_64/kernel/ioport.c linux-2.4.31.gcc4-x86_64-iopl-bug/arch/x86_64/kernel/ioport.c --- linux-2.4.31/arch/x86_64/kernel/ioport.c 2003-11-29 00:28:11.000000000 +0100 +++ linux-2.4.31.gcc4-x86_64-iopl-bug/arch/x86_64/kernel/ioport.c 2005-06-12 11:46:56.000000000 +0200 @@ -81,9 +81,9 @@ asmlinkage long sys_ioperm(unsigned long * code. */ -asmlinkage long sys_iopl(unsigned int level, struct pt_regs regs) +asmlinkage long sys_iopl(unsigned int level, struct pt_regs *regs) { - unsigned int old = (regs.eflags >> 12) & 3; + unsigned int old = (regs->eflags >> 12) & 3; if (level > 3) return -EINVAL; @@ -92,6 +92,6 @@ asmlinkage long sys_iopl(unsigned int le if (!capable(CAP_SYS_RAWIO)) return -EPERM; } - regs.eflags = (regs.eflags & 0xffffffffffffcfff) | (level << 12); + regs->eflags = (regs->eflags &~ 0x3000UL) | (level << 12); return 0; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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