Timeline for How does the ELF loader determine the initial stack size?
Current License: CC BY-SA 4.0
8 events
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| Jun 11, 2020 at 14:16 | history | edited | CommunityBot |
Commonmark migration
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| Jun 1, 2019 at 18:15 | vote | accept | Mario Carneiro | ||
| May 31, 2019 at 18:30 | comment | added | Johan Myréen |
@MarioCarneiro Yes, you are right, even the manual says so. It is not an error to just store the non-canonical address in rsp, you have to reference memory using the invalid address to trigger the exception. I don't know why they mention the non-canonical addresses separately, because they are illegal anyway.
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| May 31, 2019 at 16:34 | comment | added | Mario Carneiro |
I was unable to demonstrate any side effects of, for example, setting R10 <- RSP, RSP <- 0xbababa, RSP <- R10 where the bad value of RSP is never used before it is restored to a reasonable value. This probably isn't a very good test, but I have a hard time believing that this would ever cause a fault on its own without significant performance overhead in the hardware.
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| May 31, 2019 at 12:12 | comment | added | Johan Myréen | I guess they still call it Stack Fault Exception, since they mention the Violation Exception in the manual. One thing is for sure: you'll get an exception of you tread outside the allowed memory region. | |
| May 31, 2019 at 11:27 | comment | added | Philip Couling |
@JohanMyréen Thanks that's pretty close to what I thought. The one detail I couldn't find was what this change has done to the Stack Fault Exception. Has the loss of SP removed the exception entirely or can it now be triggered by rsp?
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| May 31, 2019 at 11:22 | comment | added | Johan Myréen |
The old SP register has become just RSP, and SS has effectively vanished. The x86-64 in long mode, which is the "normal" mode in 64-bit Linux, does not really use segmentation anymore. Only "the FS and GS segments are retained in vestigial form for use as extra-base pointers to operating system structures". WIkipedia. Loading the rsp with a non-canonical address can cause an exception, where a non-canonical means an address that does not contain all ones or all zeroes in (typically) the upper 16 bits of the 64-bit virtual address.
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| May 31, 2019 at 11:00 | history | answered | Philip Couling | CC BY-SA 4.0 |