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kernel/x86: Rework handling of %edx in syscall handler (again.)

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The previous change to this logic (9921f44462)
apparently caused intermittent crashes with various applications. It
seems that EDX is not expected to be clobbered by functions that do not have 64-bit return values, and if it is, crashes result, like #19024.

This commit reworks the logic to not change %edx in the iframe at all
if we don't have a 64-bit return value, and then adjusts the debug logic
to clear %edx before invoking the post-syscall debugger hook. This means
we have to run the post-syscall debugger hook before clearing the
flags, but that should be fine (and perhaps even useful.)

Fixes #19024, and possibly other crashes that have cropped up on
32-bit x86 in the last few weeks, at least.

Change-Id: I3280033bc2dd05aca254555d6ee3b173a270ebf9
Reviewed-on: https://review.haiku-os.org/c/haiku/+/8158
Haiku-Format: Haiku-format Bot <[email protected]>
Reviewed-by: Michael Lotz <[email protected]>
This commit is contained in:
Augustin Cavalier
2024-08-30 20:50:07 +00:00
committed by waddlesplash
parent d8df56379c
commit 07cfddfa0c
1 changed files with 28 additions and 22 deletions
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src/system/kernel/arch/x86/32/interrupts.S
+28 -22
View File
@@ -172,6 +172,10 @@
addl $8, %esp;
# define TRACE_POST_SYSCALL() \
testl $THREAD_FLAGS_64_BIT_SYSCALL_RETURN, THREAD_flags(%edi); \
jnz 1f; \
xor %edx, %edx; \
1: \
push %edx; /* syscall return value */ \
push %eax; \
movl IFRAME_orig_eax(%ebp), %eax; /* syscall number */ \
@@ -642,13 +646,11 @@ STATIC_FUNCTION(handle_syscall):
// call the syscall function
call *SYSCALL_INFO_function(%esi)
testl $THREAD_FLAGS_64_BIT_SYSCALL_RETURN, THREAD_flags(%edi)
jnz 1f
xor %edx, %edx
1:
// overwrite the values of %eax and %edx on the stack (the syscall return value)
testl $THREAD_FLAGS_64_BIT_SYSCALL_RETURN, THREAD_flags(%edi)
jz 1f
movl %edx, IFRAME_dx(%ebp)
1:
movl %eax, IFRAME_ax(%ebp)
TRACE_POST_SYSCALL()
@@ -682,6 +684,27 @@ FUNCTION_END(handle_syscall)
FUNCTION_END(do_pre_syscall_debug)
STATIC_FUNCTION(post_syscall_work):
// post syscall debugging
testl $THREAD_FLAGS_DEBUGGER_INSTALLED, THREAD_flags(%edi)
jz 2f
pushl -8(%ebp) // syscall start time
pushl -12(%ebp)
xor %edx, %edx
testl $THREAD_FLAGS_64_BIT_SYSCALL_RETURN, THREAD_flags(%edi)
jz 1f
movl IFRAME_dx(%ebp), %edx // syscall return value
1:
movl IFRAME_ax(%ebp), %eax
push %edx
push %eax
lea 16(%esp), %eax // syscall parameters
push %eax
movl IFRAME_orig_eax(%ebp), %eax // syscall number
push %eax
call user_debug_post_syscall
addl $24, %esp
2:
// clear the 64 bit return value and syscall restarted bits
testl $(THREAD_FLAGS_64_BIT_SYSCALL_RETURN \
| THREAD_FLAGS_SYSCALL_RESTARTED), THREAD_flags(%edi)
@@ -695,23 +718,6 @@ FUNCTION_END(handle_syscall)
cmpxchgl %edx, THREAD_flags(%edi)
jnz 1b
2:
// post syscall debugging
testl $THREAD_FLAGS_DEBUGGER_INSTALLED, THREAD_flags(%edi)
jz 1f
pushl -8(%ebp) // syscall start time
pushl -12(%ebp)
movl IFRAME_dx(%ebp), %edx // syscall return value
movl IFRAME_ax(%ebp), %eax
push %edx
push %eax
lea 16(%esp), %eax // syscall parameters
push %eax
movl IFRAME_orig_eax(%ebp), %eax // syscall number
push %eax
call user_debug_post_syscall
addl $24, %esp
1:
FUNCTION_END(post_syscall_work)
bad_syscall_number: